Cement Evaluation: The Basics and Beyond

hello everyone good morning good afternoon and good evening to everyone who's tuning in on behalf of pio petro arab oil gas academy and sbe egypt section i'd like to welcome you to today's session my name is shahad behjat i'm a third year petroleum engineering student at knu in kurdistan iraq and i'll be your moderator for today before we start i'd like to remind you to please drop your questions in the q a section below please keep the chat box professional and ethical and please submit your quizzes before the deadline now without further ado please give a warm welcome to mr kirk harris who will be given us a short course that consists of four webinars on cement evaluation the basics and beyond mr kirk harris graduated from purdue university with a bachelor's degree in civil engineering he started his career at halliburton where he worked as a cementer operations and research engineer and technology manager he is currently the technical advisor for through bond llc which provides technical support for cementing and bond blog interpretation prior to his work at through bond mr harris was the global semantic advisor for occidental petroleum talisman energy and repsol he has been the regional cementing advisor for asia pacific the north sea europe africa the permian basin and the gulf of mexico and he is currently based in lafayette louisiana his opening session will be covering the basics of cement bond blog tool and the basic interpretation method called the five c's mr harris thank you so much for coming and the mic is yours thank you very much it is a privilege to be speaking to you this morning although i understand uh we're getting some funny connections so i ask for your patience if my voice disappears for a while uh we're getting a bit of an unstable connection for the second session i assure you it will be cleaned up and we'll make sure we don't uh run into this issue again my name is kirk harris we're going to talk about the basics of the cbl as we look at cement evaluation next week we'll look at the ultrasonic log specifically the third week we're going to look at more of advanced interpretation specifically when i receive a log how do i interpret it i receive about one a day i receive a couple few hundred a year of logs that i will interpret and we'll go through that in week three in week four we're going to shift and look at the shallower caseins and look at shoe tests in week four as we wrap up cement evaluation what i'm about to tell you you can and cannot both find it in a book what i'm doing today i'm teaching you as if i'm an audiobook but what i'm going to teach you although it is simple it is not easy it's like anything that's a little difficult for us we may be able to read about uh skiing on the slopes but to actually do it is a little more difficult and i will explain why many disciplines i guess you can read about it if you trust the author you can read about it and learn it here you're going to have to practice it but i will say there are two publications be in connection with me i can lead you to these two publications and give you more things to read but one is the api method or the api best practices for approaching cement sheath evaluation the other i i've taken a page out of the schlumberger book schlumberger writes very well about bond log interpretation or cement job evaluation so i would recommend both of those to you today the agenda we'll talk about the basics of cementing very quickly and then we'll move to the cbl cement bond log basics how to interpret the bond log and why this tool this method is controversial it's kind of funny i received a bond log about a week ago from south america in south america the manager who sent me the log said can you interpret this log for us and if so how much would the log so i said well i can look at it and i can give you my opinion for free there is no cost for my opinion but if you want in-depth explanation a full report an understanding of everything on the log then i'm going to charge you a very small amount it not much very small amount and he said that sounds great let's do it and then he called me back a day later and said we can't do that my bosses do not like the bond log the bond log is too uh difficult to understand so i will close i will finish about why this bond log is controversial why some love it why some hate it why some think it's a good tool others think it is confusing we're going to talk about the bond log and the ultrasonic both will save the ultrasonic for next week this is a combination bond log in ultrasonic bond log on the left the colorful map we'll look at next week we're going to focus on this the cbl and as you look at that i don't know if this is your first webinar on bond logs or if you've attended others but the bond log is a simple log five curves easy to understand to interpret them we'll look at is a little more tricky this is the purpose this is the reason that we're learning about bond logs someday if you're in upstream oil you will find yourself gathered around a bond log this happens to be a school i was teaching a few years ago in columbia but you will gather around the log with drilling with production with supervisors with managers engineers geologists almost every position in the oil field upstream will touch that bond log as we abandon wells i look at many bond logs to assure that we have a secure abandonment a well that has integrity as we abandon the wealth using the bond log so i hope that you get the opportunity to be gathered around the bond log and watch the dynamic that occurs because people will be arguing people will be talking it will be noisy and you may be in a position to be able to help interpret that log or even to take a leadership role in being the go-to person for your company for bond logs there's not many out there i want to be honest most of the time we allow the logging company to interpret the log if not it goes to the geologist or the petrophysicist in an oil company unfortunately cementing companies do not interpret very often and the oil company itself the drilling team often allows others to do the interpretation the cementing basics very quickly what we're trying to do when we run a bond log is to determine the success or the quality of the cement job we're going to pump with a high pressure unit cement down the casing up and around into the annulus between the hole in the casing and we want to seal that annulus with the gray cement so we'll circulate the hole with fluid we'll then pump a spacer to help clean up the mud to get a clean hole we separate the cement from the mud with a plug we pump the cement we then separate the cement from our displacing fluid which is a water or a mud and we pump it all the way to the bottom of the casing so that inside the casing there is no cement outside the casing we have the cement sealed at the bottom of the casing there is a check valve we call it float equipment to keep the cement from coming back inside the casing we can wait for the cement to set up and run a bond log so we mix the cement beautiful gray cement here we're mixing it it's being mixed on the left side of this tub being poured over into the right side of the tub where we'll then let it go to the high pressure pump and pump it down hole on top of a bottom plug b through a cementing head and we're going to pump that cement on top of that plug then drop the top plugged tee on top of the cement and displace it with liquid there we're taking returns going down the casing up the annulus what do we do next what's the next thing we do we've pumped the cement through the casing hopefully it's made it to the outside of the casing has been lifted up covering our zones to cause isolation so that the oil and gas doesn't come up to surface or come up to a previous or another formation such as a fresh water formation what do we do next part of one of my favorite things i like to do that's we sit back we relax we pour our coffee and we wait we wait we wait the cement is setting up we're then getting ready to run the bond log we're going to wait 24 to 48 hours for the bond log at the end of this session today we're going to talk about one of the disasters or some disasters that have occurred including macondo and for mcconnell we did not run a bond log because if we were going to wait 24 hours that's a half a million dollars of waiting time before we can run the bond log so the bond log costs money but the waiting costs money as well as it is on the critical path sometimes and so sometimes we have to design the cement to set up faster to be able to run a bond log sooner and at the end we have a cemented well bore we have the formation the cement and fluid which becomes part of the wellbore so let's look at the tool that we're going to run inside of this wellbore and it's kind of interesting because i don't know if you've ever thought about it sometimes i think about things with in the oil field that probably i shouldn't be thinking about or no one else thinks about i imagine going down the well does anyone ever imagine that that i'm going to take a trip down the wellbore a couple miles can you imagine how quiet it is down there if you're just sitting down there i've been inside a cave before only a hundred feet into the cave and it was dark and it was quiet well it's very quiet and we're going to run a tool down there and start making some noise and when we run that tool this is the tool we're going to make that noise with a transmitter for the bond log that is making an audible sound the sound that it makes is a clicking sound very rapid and we're listening for that sound three feet away and five feet away and we're listening for how loud that sound is and when does that those sounds arrive and after we hear the first sound what other sounds are we hearing let me take a look back here this is inside the shop of the logging company and i've kind of hidden what i want to show you here but behind this screen that you see is a test cell where we will run that tool that we just saw inside the test cell and we will measure here we go and we will measure how loud the tool is in there and different companies do it differently some companies will run it in this chamber and they will just make sure that the tool is working that it functions others will calibrate this tool and they will listen to see how loud it is in pipe that is not cemented and we get various free pipe amplitudes when we sound that tool off so here's our tool going into the wellbore we send the sound wave out it goes in all directions we're looking at one specific pathway in this case showing the arrows going down the casing which quite often is the fastest route to the receivers because sound travels through steel faster than liquids or the cement the problem with the bond log tool we go down the well it's very quiet we send out sound waves and we start listening for echoes if we're in the open hole no casing no cement open holes on the clogs the sound goes out it reflects off of the boundary which is the formation and comes back we get a nice clean sound wave coming back when we put casing into the wellbore as the sound wave goes and it hits the casing whatever's on the other side if it's a solid the sound wave passes through but if it's liquid or it's poorly bonded then it reflects back and starts to echo so when you put casein in the well it's like going into a tunnel that is made of a big piece of steel you start shouting you start getting echoes and these echoes start reflecting and make the bond log a little confusing but we're going to use snell's law to determine if we have cement the more alike these boundaries are the more the sound will travel through the more different they are the sounds will reflect so if i have my casing my casing is in air a big difference between the air and the glass i get a very loud ring because all of my energy is staying in the glass or in the casing if i cement the glass then the ring and the resonance of the ring goes away because i'm now supporting the casing with something that's like the glass a solid so when i have loud ring or high amplitude or loud sounds coming down the casing i have no cement if it's a small sound all of my energy has gone out the small sound coming down the casing means i do have cement so when i have cement i send that sound wave out it goes through the casing through the cement reflects off of the formation again the first part of the sound wave that i sent out that's going to arrive at the three foot receiver first the first part of that wave is traveling through the casing it's moving fast so it arrives first the second is going through the cement and formation and the third part of the curve is coming down alongside the tool inside the logging fluid and then we get our bond log display simple only five curves on this log you only have to know five but if it's the first time you've seen the log it looks a little confusing it doesn't necessarily show me a picture here are the curves that are on the bond log display the green curve is the gamma ray nothing to do with the bond log it's just telling us the natural radiation of the wellbore separating stands in from shales or limestones from shales the middle line there the dark line is the transit time the transit time it is telling us from when i click when i hit the transmitter to when i receive the signal this transmitter is being fed electricity through electric wire line when the electricity hits the transducer it causes the transducer to contract and sends out a pulse 20 kilohertz in frequency a sound that you can hear if you have good ears and when it goes out the time it takes to get to the three foot receiver is the transit time the casing collar locator is the hash line it tells us where the pipes are jointed together it's that extra mass of steel it's basically a magnet telling us where the large steel volume is at the joints the middle curve and i will warn you at thoroughbond we are very hesitant to spend too much time looking at the amplitude curve this is basically how loud is that sound that first sound we hear at the three foot receiver coming through the casing how loud is that and then we have the variable density log to the right that's the fifth curve that is the history of the sound wave time versus depth to when i receive it the amplitude the amplitude is the height or loudness of that first wave that arrives in this case it's fairly small the big peaks coming later those are big sounds reflecting off of the formation but that first area is coming through the casing that first peak is the amplitude i will repeat at thoroughbond we do not use amplitude specifically to interpret the log we will re-log for the cbl and we will be looking at several things on the variable density log that we will observe when we interpret the log but we take the variable density log i'll show you how we make it we cut it in half it's like being in the ocean at sea level and watching one wave go by the height of that wave is the amplitude we take that we're going to cut that wave in half eyes out of the ocean and look down on that wave and when we do it would look like this and now we'll do that as we go along the beach of the waves coming in we will mark the peaks of all of those waves and we will connect them to create the vdl again it's like flying over the ocean now looking up and down the beach that's our depth and looking at the first arrival that's hitting the receiver a history of the waves that are about to come in and be picked up on that receiver so every time you fly over the beach you're looking at a vdl i see vdls everywhere i see them when i look on the beach i see them in the clouds i see them on the lake when i throw a rock in the lake i see the waves coming in you see beautiful vdls all over the place so be watching for those videos and that's what we look at time versus depth when we look at the vdl we'll see it to the far right five curves you get the gamma the dotted line in the middle is the transit time foot receiver the hashed line is the casing collar locator the middle area we have two curves they're the same curve different scales this is measured in electrical energy it's the amplitude this particular log and it changes from log to log this particular log from 0 to 100 millivolts and then we have another curve the amplified amplitude 0 to 10 millivolts and then we have the vdl the variable density log and that's where we'll have our focus when we interpret our bond log when we look at that the first part of the wave the first wave hitting the beach is the fastest sound and that fastest path and that fastest path is traveling down the casing in this area we look for straight lines because it would be a lot of energy and since it's coming down the casing the casing is homogeneous always if our tool is centralized we get the same fluid the same casing the same fluid the wave should arrive at the same time up and down the well and we'll see straight lines in this case it's a perfectly cemented well so the lines disappear there are no straight lines and a basic rule if you see straight lines that's bad straight lines are energy coming down the casing straight lines are the same as a loud casing ring when you see no lines the energy is so small we can barely pick it up because it's very quiet sound the middle part of the curve comes through the formation big formation signals and then the last part we'll see effects coming through the fluid all of these waves coming in and the construction and deconstruct destruction of these waves as they come in show up in the video very quickly you're going to see some colored maps today and those are from radial bond logs where we have the regular cement bond log five curves we add to that a cement map that's based on eight separate receivers either at the two foot or three foot interval by the way the vdl comes from the five foot receiver that we saw earlier the cement map will come from radial receivers listening on each side of the casing at the two or three foot interval when we come to look at the bond log the key thing and i see people who have talent at this and i see people who do not and that is we have to learn to observe to observe you need to use your eyes you need to quiet the rest of your sentences i can observe and taste coffee at the same time so i think that's okay but i actually usually taste the coffee first and then observe i want you to see the eyes if you're talking it's hard to observe if you're in a hurry it's hard to observe if you don't know what to observe it's hard to observe so i want to take you through the things that we will observe there are four main things we'll observe when we look at the bond log immediately the first thing we will observe is casein ring casein ring shows up on the vdl as straight lines do you see any straight lines on the vdl the curve on the far right a lot of them matter of fact if that vdl was this glass not only do you hear a first ring you hear it resonating big ring all the way throughout there is no cement so we observe the casein ring look at these logs the log on the left do you see straight lines do you see casing ring especially first arrival casing ring we do we also see the big chevron patterns at the collars on the right by the way the log on the left has no cement in it the log on the right do you see straight lines they're not as strong but they're there and the collars do not as loudly but you can see chevron patterns here but here they're not as strong here you see the strong chevron patterns do you see straight lines here when you see straight lines first arrival that's bad at least it's going to require some interpretation if you see no straight lines then you don't worry about it or many don't maybe we should sometimes but i never receive logs that have no straight lines they don't send those to me i only see the ones with straight lines that cause bottom they go away the next thing we will look for are formation signals first of all do you see any straight lines in this log you see some to the far right those are fluid arrivals but to the left here in the vdl all of the straight lines disappear that's good but we want to make sure we're connected to the formation and they will show up as these big crooked squiggly lines so very basically straight lines are bad squiggly lines are good we're connected to the formation we're reflecting off of the formation we must be connected by cement do you see any formation signals here do you see any straight lines here no straight lines but look at all of the the crooked lines or the bending lines those are all strong formation signals it's a perfect cement job what about here straight lines do you see any just look at the vdl do you see any chevron patterns at the collars i do see straight lines i do see chevron patterns but do you see any formation signals look at them strong formation signals we must be connected to the formation that is a very good sign the third thing we'll observe the first we look for casein rings second formation signals casein ring is straight lines formation signals are crooked lines look at this log do you see straight lines a little bit in the bottom do you see formation signals i do strong crooked lines that follow the straight lines if we can apply pressure to the casing which we do here we place a thousand psi inside the casing it expands the casing it strengthens the bond and the straight lines go away so we if we do have a pressure pass then it can give us some good information here's an example where we ran a pressure pass and just look at the colored map for a second again this is a radiolog not an ultrasonic we'll look at ultrasonics next week and you don't see much change do you we tighten the bond on the one on the left it changes a little bit but there's not much change of the colored map on the right with no pressure so it tells us adding the pressure did not help we may have a big problem here more than just a bond and the final observation i will look at i get the log i look for straight lines casing ring i look for crooked lines formation signals i see if there's a pressure pass and i observe the pressure pass if anything has changed and then i look for top of cement where does it go from no straight lines to very big straight lines and i try to find the top of cement i will use that top of cement so i can compare and analyze the rest of the log results as a matter of fact we will talk in just a moment but when you cement an oil and gas well for the most part these are your only four options these are the only four things that can happen when you interpret a log they happen in different ways they happen and in different mechanisms cause it but you either have no cement did cement we might call that a micro annulus or the cement has channels in it either mud channels or gas channels or it's a good cement job perfectly tightly sealed let's look at what each of those looks like this one's pretty evident a lot of straight lines if you look at the ccl and again you'll have these charts here's our ccl our case in color locator transit time dotted in here here we have our gamma ray we actually are showing here two transit times it may be the three and five foot receiver here's our amplitude here's our vdl and this is our cement map straight lines no cement big chevron patterns this is free pipe what it will look like straight lines chevron patterns strong chevron patterns here's a microannulus poorly bonded we have straight lines they may not be as strong or they might but straight lines but the collars are dampened you see a change in the collar i look at that a lot on the vdl and we have formation signals you see the crooked lines here's what a channel might look like the unfortunate thing is that a channel often looks like de-bonded cement and on the third week we'll talk about some more advanced techniques to determine the difference between a channel and poor bonding but once again you get straight lines with the channel we get the collars they're dampened somewhat but they're pretty strong and you get formation signals where it's attached on the cement map because a cbl cannot detect channels on its own not clearly but we see the channel coming from this water zone that we know is flowing this is a big channel when we look at the ultrasonics we can we're able to see smaller channels and then we have perfect cement that's what it looks like no straight lines matter of fact it looks pretty much like the open hole sonic log everything so tightly bonded so solid that we just reflect the formation back that's what we want to see look at that beautiful cement job we can get these kind of cement jobs everywhere we we can in the most difficult of circumstances we can get a great cement job but we have to be ready to do some serious cementing sometimes we have to be aggressive we have to understand the entire wellbore but we can get these kind of results what about this one do you like this one why do you not like it i mean i don't like it because we see straight lines many will say i don't like it because the amplitude here is 72 millivolts which happens to be the free pipe amplitude for five and a half inch casing so the amplitude says i have free pipe the straight line say i have free pipe the collars start to get dampened and then we see what appears to be formation signals or are they what are those squiggly lines notice if we observe and we take our coffee and we relax and just observe if we took our time we probably could make a thousand observations about the vdl alone just look at the vdl make make some observations in your own mind what do you see simple observation do you notice that the first line is narrow the second line is bigger the third line's narrow do you notice that that's just an observation do you notice the squiggly lines to the right don't tell me what they are just do you notice them they're squiggly sometimes when we start to observe we start to interpret instead of observe to just observe here's another observation how many straight lines do you see before the squiggly lines and does it change count them one two three four five six seven there are seven straight lines before the squiggly start and notice it all happens right at the same point this is an indication and it's something we observe these are fluid arrivals coming down the casing distorting the straight lines these formations although we may be seeing some effect if the casing comes over to the side and touches the formation what we're seeing here are fluid arrivals this happens to be free pipe no cement so these are the things that we will observe now that we have kind of the basics what is the method how do we interpret bond logs we call it the five c's some of you may have joined or have seen our five c's before you will know what we're getting ready to look at we're going to construct the well first what i mean is i although i love the bond log i'm not going to trust the bond log i'm going to trust the cementing operation in other words if i pump cement and cement came all the way to surface and i saw the cement surface and the bond log says there is no cement in the well i'm going to doubt the bond log i'm going to trust the well construction first and in other words i'm going to allow the wellbore to interpret the log before the log interprets the well bore and if you're not thinking about the wellbore if you're thinking just about the log you will misinterpret the log so i'm going to kind of build the well as best i can i'm then going to look up and down and compare sections of that log when i do that i've already allowed the weld bore to interpret the log now i'm going to look up and down and i'm going to let the log interpret the log i'm not going to look for absolute numbers as much as a comparison of what parts of the log look like and i do that by just looking up and down now i have to have my coffee in hand to keep me relaxed i i promise you it's the best part of my day having coffee and just looking at the log and relaxing but knowing what to look for makes it a lot easier and a lot more enjoyable the third step is to correlate once i look up and down at points of change i look side to side i wonder what's happening here i look to see if it correlates to the wellbore so i let the wellbore interpret the log i look up and down and let the log interpret the log and then look side to side and let the log interpret the well bore that's the process we use in week three we'll look at this part much more i consider all of the things that the wellbore is doing that's trying to confuse the log and the well bore will try to do 35 things we're up to 35 things we've noticed and i'll show you a few of those and then we conclude so i construct the well i compare sections of the log i correlate side to side i consider what could be going on with the wellbore and then i conclude and it's time to interpret now here's the problem you are attending this session and you will have heard for maybe the fourth or fifth time i do not use the amplitude to interpret the problem is when you gather around this log you're going to find that it is noisy people are talking most of the time and i've done this many many times working in house at many operators but working for oxy and talisman and repsol when i walk into the room and they would know hey kirk is coming up he is focused on bond logs we respect his opinion and so let's let kirk look at this so they call me and i come up to the business unit or fly up to the location and i walk into the room and it's noisy someone might say hey hello kirk welcome come on over here and i say well what do we have here and they say oh i'm glad you showed up but we've already interpreted the log we got the answer and they got the answer by looking at the amplitude and so i try to quiet them down because they take the log and here it is and they say let's interpret this log i said okay let me get my coffee what kirk we don't have time for coffee we've already interpreted it all we did was we drew a line on the amplitude curve and you can see at the bottom it's good everything's to the left for the most part but at the top it's bad everything to the right and so we finished interpreting and i say well wait a second let's have some coffee first thank you now we can interpret and i do the interpretation by asking four questions this is how i start i ask the four questions first of all to quiet the room because someone's already got the interpretation and that interpretation is wrong and so i have to get them back to the base of hey where was the cement supposed to be by the way and then suddenly someone says oh well i don't know has anyone looked at that i guess we are talking about cement was there lead and tail did we have losses or flows maybe we put all the cement in there and it all flowed out i don't know what do we know about the construction of this do we have a weak casing to cement bond someone will say well what has that got to do with the problem and i will say it's everything the bond for a bond log interpreter is 80 thing is everything eighty percent of all logs are affected by shear bond just wanna take a quick diversion here i don't know if any of you have climbed pose recently when you get to my age your pole climbing days are long gone they're over i tried to climb a pole about 10 years ago and i jumped onto the pole but all i could do was just hang on for dear life and so if you're young and you like to climb just do it now later it's not going to be pretty when you're hanging on that pole your weight pulling you down divided by the area that your hands are holding onto that's shear bond it is the force applied to push casing out of the cement that cement surrounding cemented shear bond very important so i asked do we have a weak casing to cement bond maybe it's low shear bond and then the fourth question and if you don't know the geologist you need to get to know one because the formations have a huge effect in bond logs i asked which formation is caused in the problem so first we construct the well bore i want to know about the very simple terms i want to know where is leed cement and where is tail cement this looks like free pipe it was interpreted by a major logging company on location as free pipe when it actually was the lead cement we need to be able to interpret that we look at the cement we look at the casing we look at the formations when we construct the well sometimes you have a lot of data sometimes you don't the more data you have about the cement job the better the interpretation will be then when we compare log stations you can look and see the difference [Music] between the top and the bottom of this log and i put a there's my lead cement that was interpreted as no cement but it is lead cement and then i take that lead cement and i compare it to what is free pipe i'm comparing and you can see the difference between my thumb print on that vdl and the free pipe interval above what is below was not free although look at the amplitude the amplitude is the same and then i correlate at changes step 8 lines bad crooked lines good and i get good bad good when i correlate i just draw at the points of change i draw a line over and correlate to the bottom and to the top and now your job as an interpreter as a detective into this log is to determine why did it go from good to bad there's got to be a reason your job as an interpreter is to do that step force to consider the key factors things we're doing on location here we're running a casing or centralizer what things are we doing on location that will affect the bond log i'll give you a few examples there are 35 and we'll dive into those in week three the first is new casing some new casings this casing from argentina that was shipped and run in the middle east showing free pipe amplitude a lot of straight lines that's bad some crooked lines that's good but it's showing a bad cement job but it's brand new casing causing the problem we sandblast that casing we take off all the pretty paint and shine and you see the straight lines in those sandblasted joints disappear considering the key factors centralization you can look at log a of log and see the line in that colorful map it's because that particular casing was not centralized so we like to look for where is the casing centralized lightweight cements look at the straight lines in the upper portion of this log and watch those straight lines disappear both have crooked lines but the upper one is being hidden by the straight lines the shear bond of the cement in the upper is only 50 psi it's 200 psi below we find that we need about 150 150 psi of shear bond to get those lines to disappear so lightweight cements we must consider here's our lightweight cement in 24 hours we only get 260 psi that's that's so low it doesn't want to log very well it can provide isolation but it doesn't log another consideration pressure test when we cement the well and before we test the casing look at all of the crooked lines once again looking at the bond log we have the gamma at the transit time you can barely see case in color locator low amplitudes for the most thousand psi and we break the bonds so pressure testing we have to consider when we interpret a bond log i see this on so many logs we cement the well we wait 48 hours we pressure test the casing we break the bonds we run the bond log and we are confused a final one here is cement shrinkage when you have cement shrinkage sometimes you also have gas bubbling the cement shrinks away from the casing and the bubbles come up that's the big problem so we put expansion additive we sand blast the casing so the cement will lock into the grooves and when we add an expansion additive which tightens the bond that the cement expands and presses against that casing not only do the straight lines disappear but we find the gas percolating also disappears and finally we conclude not only do we have zonal isolation not only good or bad but why or why not why do we have zona isolation what do we see on the log or why not what's going on that's what we want to do in interpretation and when it comes to cementing you only get five choices there are two good choices we either have good cement shale we either have cement providing isolation or we have a geologic barrier that has come in and provided isolation do we have isolation or not i don't know because we may have a weak bond and that weak bond may be enough to have isolation or especially with gas wells it does not and then when it comes to no cement you only have two choices it's either no cement at all or it is a channeling issue cross flow wiping out the cement would be part of a channeling issue so these are the choices we get in concluding so we interpret the log we construct the well we compare sections we correlate side to side we consider all of the things that could be happening maybe a pressure test maybe new casing maybe a lightweight cement then we conclude and we don't conclude by saying good or bad we say it is bad because of a mud channel and here's what's going on so it gets more in depth you will understand as we begin to close here you will understand the more you're around monologues how controversial they are the controversy goes and hides some things and to look at the raw data it can lead you one way or the other and can be wrong here are the three reasons why they're a bit controversial they are simple five curves the gamma the transit time the k color locator the amplitude they are simple but they're not easy to read as soon as you put casing in and have case toll those straight lines start hiding some of the data we also have logging versus drilling and here is where logging is going to look at the logging data in this case they drilled a well and what you see through the right is what we're going to look at next week and that's the ultrasound and what we have here is a log that showed up green what does green mean for the ultrasonic tool the use it schlumberger's tool green means micro bonded it means it's kind of like a micro annulus there isn't much there but something's there the bonding is low but it's quite variable so something is there and they color it green and so they ran this log and they colored it green and we asked is there cement there and they said we're not sure but let's send it out to be processed and they sent it to be processed and they said there is cement there well we said well if there's cement there what happened here here's the bond log for it that we ran three months earlier when we knew all of our cement was pumped out the bottom of the well and there is no cement in here free pipe amplitude this is the one we just looked at with those fluid arrivals on the right so logging said we had cement drilling said we don't have cement and said the reason i know we don't have cement because we didn't pump any cement in this part of the well that's why we construct the well often logging doesn't have that data when they're running the log they don't know the history of the well and so it shows you how important it is to construct that well another reason it's controversial is because bond logs cost money now this happens to be an excerpt of the flow chart of macondo on the deepwater horizon they did not run a bond log i'm sorry they didn't run a bond log but a bond log was in the flow chart here it is way out here if they had a disaster of sorts in the cement job if all this meant had gone away they felt or if they could not easily determine where the cement might be they were going to run a bond log so since the job appeared to be okay they didn't run a bond log in the flow chart they were doing everything they could sitting it way out here to not run a bond log here's the decision did i have lost [Music] cementing no let's get on with it no bond log if and so let's not run the bond log some people say running the bond log would have cost a hundred and twenty five thousand dollars it would have that would have been the bond log alone it would have cost another three four five hundred thousand dollars of time as we waited on the cement to set without getting into my condo too much the reason it probably failed and the reason this disaster occurred and i was on the outside of my condo looking in very involved because i had worked in-house at bp i had worked for halliburton in the gulf of mexico mentoring engineers and i was working throughout afterwards with people involved with my condo i was actually in-house when we were putting the cement unit on the deepwater horizon very very important very tragic but it was going to cost a lot of monologue how do we run the bond log i think the reason there was failure is that the cement never set at least not before we started flowing well have we waited on the bond log that amount of time to run the bond log i think we would not have had that disaster we don't know but i think the cement would have been allowed to set so let's start looking at closing the session with interpreting a log and i want to show you the importance of the bond log and how we would interpret it if you've attended any of the sessions before on basic logs you may have seen a log like this how do we interpret it what's the first thing we do when the log set before us i actually just received a fresh cup of coffee so when you think about the five c's never forget the six c keeps us relaxed reminds us we're going to observe and follow a procedure for me this is not just theory i interpret logs every day and i use the fees i always have the 6c coffee with me but i use the 5cs every day this is not theory it's simple but it sets in motion the way we should interpret logs you will want to just go in and say it's bad cement there's a middle section in here that's bad cement i i know that i know at least it looks bad but is it really bad more importantly why you you have to understand the why and i'm going to show you a good reason for that as we close out today what's the first thing we do interpreting a log i already got the coffee we're going to construct the well for the purposes of this interpretation i go and i ask the questions where was the cement supposed to be in this well it's supposed to be way up the well this is just a short section at the bottom of the well is there a lead and a tail yes there is a lead and a tail but the lead should be way up the well this should all be very strong tail cement okay i then asked about things like uh did i have losses or flows i asked the drilling engineer he said no no losses no flows perfect cement job like macando quote a perfect cement job okay maybe i don't even need to run a bond log if it was a perfect cement job but we ran a bond log and i'm glad we did because we find a section in this casing that doesn't look good let me correlate first i compare i look up and down let me go back to my construction my third question is maybe there's a bonding issue my first thought if there is a bonding issue i've got good bond below good bond above it's just poor bonding in an area maybe it's new casein it's not a pressure test or that would have broken all of the bond what could it be maybe three joints of casein are new maybe there's something with the casein may i don't know and i ask that question i also ask about formations but then i compare and we look at it i compare these three sections looking up and down and at the point of change i need to correlate why does it go from good to bad i cannot just say good and bad i have to explain what's going on as an interpreter a logging engineer might say hey look it's bad i say there's not much cement there and i would say why he said that's not my job it's not my job to tell you why i'm just running the log and telling you what the log is saying i want to know what the wellbore is saying not necessarily just what the log is saying so i'm going to correlate back to the wellbore and i happen to correlate right to this point do you see the gamma spike that's our formation the casing collars are our casein the cement is all one cement so that shouldn't change but i change near a collar but i change right at the gamma there it is when you start correlating the puzzle starts to be solved next week we're going to look at this log this log is an ultrasonic log and we'll look at this in depth but look at this i'm considering things and one of the things i always consider maybe it's poor bonding maybe there are joints of casein that aren't bonding as well but when i look at this i can see that the occurrence is not happening in a collar it's happening at the gamma then go to my geologist and say what is that gamma looks like a shale my geologist says that is not a shale that's something called a hot dolomite i find out that the geologist in this infield drilling program knows more about the well than our drilling group does what we're drilling through they know the formations they know why we're doing what we're doing so i attach myself to a geologist and he says this spike is a hot dolomite as a matter of fact it's over pressured dolomite and we determine through our interpretation and every interpretation is just an interpretation it may be right it may be wrong but we determine that this hot dolomite is probably doing something that often occurs it is cross flowing into a normally pressured fractured dolomite and i've wiped my cement out of the picture and this is important because this well is an injection well i need cement across this to direct my injection into a new zone that i can flood the oil out of the well boards and all of my cement is gone guess what if i hadn't run a bond log i wouldn't know that i would inject my co2 and get no increased oil production if i didn't run a bond log because i had full returns and the job was perfect i never would have saw this so what did we do we perforated at the bottom of the bad and at the top of the bed and we were able to circulate and re-cement this well so the bond log not only told us we had a bad job it showed us the place we needed to fix and we fixed this well but it didn't only do that it also allowed us in the next 20 wells that were going to be drilled in this field it allowed us to cement them correctly you see well two we put a packer in between that flow zone and we were able to get a perfect cement job look at the vdl on well two no straight lines beautiful we did the same thing on well three we then allowed that pressure to normalize and we cemented the rest of the wells without a packer successfully so the bond log not only told us that the perfect cement job was not perfect it told us how to fix it and it told us how to cement wells in the future this tool is extremely useful the bottom log is would like to close with a few simple things in our summary first of all cement logs are simple we got the gamma transit time casing color locator those are on one side we got the amplitude in the middle and it's not that i don't like amplitude but we cannot draw a straight line and say that interpreting is just left and right of a straight line amplitudes will fool you mainly because of the poor bonding that can occur for a number of reasons and we still have isolation as an example every lightweight cement is going to fail the straight-line test the amplitude test we use the vdl not the amplitude but cement logs are simple but good interpreters must practice you must practice observation you must understand the logging tools i think if you understand the logging tools too much you'll trust them too much but you have to understand the logging tools but you have to know cementing you have to know the wellbore better have a geologist nearby the geologist is usually the go-to person because they work with logs and they know the formations but you must practice the things we talked about today you will forget in about two or three days if you don't get in front of a log in practice finally bond logs are very useful they're going to help us to fix wells help us to cement better help us to understand where production is coming from if our wellbore is the best it can be they're going to help us abandon wells and make sure that we have them properly sealed so be dedicated to your work don't give up on the bun log don't think that you have to be confused the more you work with the bun log the better it will be so be dedicated to that work with that i would like to close and i would like it to hand it back over to our moderator for any questions or comments that you might have thank you thank you mr harris for a very informative webinar i'm sure the audience benefited greatly from it in the meantime i've collected a few questions for a quick q a section um so the first question is after cementing operation is it advisable to continue drilling if we have losses when flushing or circulating yes could you repeat the question it was after drilling the wellbore after cementing operation is it advisable to continue drilling if we have losses when flushing or circulating okay i'll answer that in two questions because i'm not sure i understand the exact question but i'm working with some logs right now to where when we're drilling the well we're circulating the well without losses but when we start to circulate before some before cementing and we have losses we've questioned do we cement or do we try to cure losses before we cement and all i can say is if you have losses and you're not sure where the losses are and you cement i've got many logs before me they are the worst cement jobs you can have having the losses now if the question is we've cemented the well and everything is fine and now i drill the next whole section and i have losses should i stop or should i drill blind it's drilling blind as you we drill ahead with losses in that case it's dependent upon each wellbore but we're for the most part always always trying to heal and seal the losses so we can have full circulation if we don't for sure somewhere along the line we have a wellbore that has no integrity so i answered that in a couple ways i hope i hope that the answer was somewhere in that yeah um the second question is why channels have the same characteristics as bats meant bond on the cement blocks what is the basic idea that makes these two situations alike on the log it's a very good question if you have a channel and let's imagine it's the worst possible channel half of your wellbore half is cemented the other half has no cement so half of the well is perfect after the well is not perfect in that situation of course it's a very bad thing because all of your fluids can flow up one side of the well when you run the bond log the bond log says i'm getting formation signals from the half that is cemented but i'm getting those are the crooked lines but i'm getting straight lines from the half that is not cemented so the log looks like straight lines and crooked lines that is a classic channel but when i have poor bonding i'm fully surrounded but i'm not gripping the casing tightly this glass that i ring if i'm not gripping it enough to stop the ring so what do i get i get the same straight lines but i'm connected enough in places where i get the formation signals in both cases they're straight lines and their formation signals the channel is bad the weak bonding may or may not be bad often it is not bad so i get the same results straight lines crooked lines with two different scenarios and a talent in interpretation is looking at enough knowing your field well enough to know the difference between the two um great thank you for answering good question yes um we have a couple more questions um why the amplitude was the same in the example where vdl of lead cement was compared to another vdl which represented a free pipe what is the basic idea about the amplitude being the same where the two mentioned situations were actually different yes once again especially new case team lightweight cements the sound wave all it knows it goes out and what's directly next to the casing will determine where that sound wave goes and if it is not tightly bonded to the casing that sound wave says i'm going to reflect and stay inside the casing and i'm going to send all of my energy down the casing even though cement is present if it's not squeezing the glass if it's just barely barely touching the glass then all of the energy goes down the casing there are many other scenarios where the energy will not go out the casing it will come down here's another example if the cement is so thin that it provides no mass to grip the casing just because cement is there it will not dampen or attenuate or carry out the sound wave it will travel down as if it's free pipe so in the case i showed it is a weak cement many places around the world allow you to run cement that barely sets up so it doesn't grip the casing it has no shear bond [Music] and you must have strong shear bond to carry that sound wave out i see it more often than you can imagine lightweight cements and new casing or pressure tested casein although cement is there the sound wave is not fully connected and will travel down the casing just as if it was free pipe so the case i showed two or three cases of free pipe amplitude that was fully cemented that's uh that's part of the problem just running the bond log and part of the problem of the confusion of the bond log that's why we must construct the well and observe closely the vdo but another good question yeah uh another question is according to your experience can this process of interpretation be automated using machine learning and ai if not why yes it can be and and i some time ago i thought maybe i'm the only one thinking about this again how to make your eyes and i will show you next week next week i will show you as we look at the log where your eyes should go what they should look for and so i would i thought i was the only one thinking if i could have a computer program for my eyes to see we can automate this i believe we can but you're going to need a few little secrets on how to do that so if there's any wizards out there with ai or computers i'm talking to some people i think we can automate it and so yes i do i think there's a few secrets about how it can successfully automate it but i do believe we can oh thank you for answering mr harris thank you again for dedicating some time of your totally busy schedule to give this webinar and course in general um thank you attendees for tuning in from all around the world please stay safe wear a mask and have a great day thank you it's been my privilege thank you very much for attending

hello everyone good morning good afternoon and good evening to everyone who&#39;s tuning in on behalf of pio petro arab oil gas academy and sbe egypt section i&#39;d like to welcome you to today&#39;s session my name is shahad behjat i&#39;m a third year petroleum engineering student at knu in kurdistan iraq and i&#39;ll be your moderator for today before we start i&#39;d like to remind you to please drop your questions in the q a section below please keep the chat box professional and ethical and please submit your quizzes before the deadline now without further ado please give a warm welcome to mr kirk harris who will be given us a short course that consists of four webinars on cement evaluation the basics and beyond mr kirk harris graduated from purdue university with a bachelor&#39;s degree in civil engineering he started his career at halliburton where he worked as a cementer operations and research engineer and technology manager he is currently the technical advisor for through bond llc which provides technical support for cementing and bond blog interpretation prior to his work at through bond mr harris was the global semantic advisor for occidental petroleum talisman energy and repsol he has been the regional cementing advisor for asia pacific the north sea europe africa the permian basin and the gulf of mexico and he is currently based in lafayette louisiana his opening session will be covering the basics of cement bond blog tool and the basic interpretation method called the five c&#39;s mr harris thank you so much for coming and the mic is yours thank you very much it is a privilege to be speaking to you this morning although i understand uh we&#39;re getting some funny connections so i ask for your patience if my voice disappears for a while uh we&#39;re getting a bit of an unstable connection for the second session i assure you it will be cleaned up and we&#39;ll make sure we don&#39;t uh run into this issue again my name is kirk harris we&#39;re going to talk about the basics of the cbl as we look at cement evaluation next week we&#39;ll look at the ultrasonic log specifically the third week we&#39;re going to look at more of advanced interpretation specifically when i receive a log how do i interpret it i receive about one a day i receive a couple few hundred a year of logs that i will interpret and we&#39;ll go through that in week three in week four we&#39;re going to shift and look at the shallower caseins and look at shoe tests in week four as we wrap up cement evaluation what i&#39;m about to tell you you can and cannot both find it in a book what i&#39;m doing today i&#39;m teaching you as if i&#39;m an audiobook but what i&#39;m going to teach you although it is simple it is not easy it&#39;s like anything that&#39;s a little difficult for us we may be able to read about uh skiing on the slopes but to actually do it is a little more difficult and i will explain why many disciplines i guess you can read about it if you trust the author you can read about it and learn it here you&#39;re going to have to practice it but i will say there are two publications be in connection with me i can lead you to these two publications and give you more things to read but one is the api method or the api best practices for approaching cement sheath evaluation the other i i&#39;ve taken a page out of the schlumberger book schlumberger writes very well about bond log interpretation or cement job evaluation so i would recommend both of those to you today the agenda we&#39;ll talk about the basics of cementing very quickly and then we&#39;ll move to the cbl cement bond log basics how to interpret the bond log and why this tool this method is controversial it&#39;s kind of funny i received a bond log about a week ago from south america in south america the manager who sent me the log said can you interpret this log for us and if so how much would the log so i said well i can look at it and i can give you my opinion for free there is no cost for my opinion but if you want in-depth explanation a full report an understanding of everything on the log then i&#39;m going to charge you a very small amount it not much very small amount and he said that sounds great let&#39;s do it and then he called me back a day later and said we can&#39;t do that my bosses do not like the bond log the bond log is too uh difficult to understand so i will close i will finish about why this bond log is controversial why some love it why some hate it why some think it&#39;s a good tool others think it is confusing we&#39;re going to talk about the bond log and the ultrasonic both will save the ultrasonic for next week this is a combination bond log in ultrasonic bond log on the left the colorful map we&#39;ll look at next week we&#39;re going to focus on this the cbl and as you look at that i don&#39;t know if this is your first webinar on bond logs or if you&#39;ve attended others but the bond log is a simple log five curves easy to understand to interpret them we&#39;ll look at is a little more tricky this is the purpose this is the reason that we&#39;re learning about bond logs someday if you&#39;re in upstream oil you will find yourself gathered around a bond log this happens to be a school i was teaching a few years ago in columbia but you will gather around the log with drilling with production with supervisors with managers engineers geologists almost every position in the oil field upstream will touch that bond log as we abandon wells i look at many bond logs to assure that we have a secure abandonment a well that has integrity as we abandon the wealth using the bond log so i hope that you get the opportunity to be gathered around the bond log and watch the dynamic that occurs because people will be arguing people will be talking it will be noisy and you may be in a position to be able to help interpret that log or even to take a leadership role in being the go-to person for your company for bond logs there&#39;s not many out there i want to be honest most of the time we allow the logging company to interpret the log if not it goes to the geologist or the petrophysicist in an oil company unfortunately cementing companies do not interpret very often and the oil company itself the drilling team often allows others to do the interpretation the cementing basics very quickly what we&#39;re trying to do when we run a bond log is to determine the success or the quality of the cement job we&#39;re going to pump with a high pressure unit cement down the casing up and around into the annulus between the hole in the casing and we want to seal that annulus with the gray cement so we&#39;ll circulate the hole with fluid we&#39;ll then pump a spacer to help clean up the mud to get a clean hole we separate the cement from the mud with a plug we pump the cement we then separate the cement from our displacing fluid which is a water or a mud and we pump it all the way to the bottom of the casing so that inside the casing there is no cement outside the casing we have the cement sealed at the bottom of the casing there is a check valve we call it float equipment to keep the cement from coming back inside the casing we can wait for the cement to set up and run a bond log so we mix the cement beautiful gray cement here we&#39;re mixing it it&#39;s being mixed on the left side of this tub being poured over into the right side of the tub where we&#39;ll then let it go to the high pressure pump and pump it down hole on top of a bottom plug b through a cementing head and we&#39;re going to pump that cement on top of that plug then drop the top plugged tee on top of the cement and displace it with liquid there we&#39;re taking returns going down the casing up the annulus what do we do next what&#39;s the next thing we do we&#39;ve pumped the cement through the casing hopefully it&#39;s made it to the outside of the casing has been lifted up covering our zones to cause isolation so that the oil and gas doesn&#39;t come up to surface or come up to a previous or another formation such as a fresh water formation what do we do next part of one of my favorite things i like to do that&#39;s we sit back we relax we pour our coffee and we wait we wait we wait the cement is setting up we&#39;re then getting ready to run the bond log we&#39;re going to wait 24 to 48 hours for the bond log at the end of this session today we&#39;re going to talk about one of the disasters or some disasters that have occurred including macondo and for mcconnell we did not run a bond log because if we were going to wait 24 hours that&#39;s a half a million dollars of waiting time before we can run the bond log so the bond log costs money but the waiting costs money as well as it is on the critical path sometimes and so sometimes we have to design the cement to set up faster to be able to run a bond log sooner and at the end we have a cemented well bore we have the formation the cement and fluid which becomes part of the wellbore so let&#39;s look at the tool that we&#39;re going to run inside of this wellbore and it&#39;s kind of interesting because i don&#39;t know if you&#39;ve ever thought about it sometimes i think about things with in the oil field that probably i shouldn&#39;t be thinking about or no one else thinks about i imagine going down the well does anyone ever imagine that that i&#39;m going to take a trip down the wellbore a couple miles can you imagine how quiet it is down there if you&#39;re just sitting down there i&#39;ve been inside a cave before only a hundred feet into the cave and it was dark and it was quiet well it&#39;s very quiet and we&#39;re going to run a tool down there and start making some noise and when we run that tool this is the tool we&#39;re going to make that noise with a transmitter for the bond log that is making an audible sound the sound that it makes is a clicking sound very rapid and we&#39;re listening for that sound three feet away and five feet away and we&#39;re listening for how loud that sound is and when does that those sounds arrive and after we hear the first sound what other sounds are we hearing let me take a look back here this is inside the shop of the logging company and i&#39;ve kind of hidden what i want to show you here but behind this screen that you see is a test cell where we will run that tool that we just saw inside the test cell and we will measure here we go and we will measure how loud the tool is in there and different companies do it differently some companies will run it in this chamber and they will just make sure that the tool is working that it functions others will calibrate this tool and they will listen to see how loud it is in pipe that is not cemented and we get various free pipe amplitudes when we sound that tool off so here&#39;s our tool going into the wellbore we send the sound wave out it goes in all directions we&#39;re looking at one specific pathway in this case showing the arrows going down the casing which quite often is the fastest route to the receivers because sound travels through steel faster than liquids or the cement the problem with the bond log tool we go down the well it&#39;s very quiet we send out sound waves and we start listening for echoes if we&#39;re in the open hole no casing no cement open holes on the clogs the sound goes out it reflects off of the boundary which is the formation and comes back we get a nice clean sound wave coming back when we put casing into the wellbore as the sound wave goes and it hits the casing whatever&#39;s on the other side if it&#39;s a solid the sound wave passes through but if it&#39;s liquid or it&#39;s poorly bonded then it reflects back and starts to echo so when you put casein in the well it&#39;s like going into a tunnel that is made of a big piece of steel you start shouting you start getting echoes and these echoes start reflecting and make the bond log a little confusing but we&#39;re going to use snell&#39;s law to determine if we have cement the more alike these boundaries are the more the sound will travel through the more different they are the sounds will reflect so if i have my casing my casing is in air a big difference between the air and the glass i get a very loud ring because all of my energy is staying in the glass or in the casing if i cement the glass then the ring and the resonance of the ring goes away because i&#39;m now supporting the casing with something that&#39;s like the glass a solid so when i have loud ring or high amplitude or loud sounds coming down the casing i have no cement if it&#39;s a small sound all of my energy has gone out the small sound coming down the casing means i do have cement so when i have cement i send that sound wave out it goes through the casing through the cement reflects off of the formation again the first part of the sound wave that i sent out that&#39;s going to arrive at the three foot receiver first the first part of that wave is traveling through the casing it&#39;s moving fast so it arrives first the second is going through the cement and formation and the third part of the curve is coming down alongside the tool inside the logging fluid and then we get our bond log display simple only five curves on this log you only have to know five but if it&#39;s the first time you&#39;ve seen the log it looks a little confusing it doesn&#39;t necessarily show me a picture here are the curves that are on the bond log display the green curve is the gamma ray nothing to do with the bond log it&#39;s just telling us the natural radiation of the wellbore separating stands in from shales or limestones from shales the middle line there the dark line is the transit time the transit time it is telling us from when i click when i hit the transmitter to when i receive the signal this transmitter is being fed electricity through electric wire line when the electricity hits the transducer it causes the transducer to contract and sends out a pulse 20 kilohertz in frequency a sound that you can hear if you have good ears and when it goes out the time it takes to get to the three foot receiver is the transit time the casing collar locator is the hash line it tells us where the pipes are jointed together it&#39;s that extra mass of steel it&#39;s basically a magnet telling us where the large steel volume is at the joints the middle curve and i will warn you at thoroughbond we are very hesitant to spend too much time looking at the amplitude curve this is basically how loud is that sound that first sound we hear at the three foot receiver coming through the casing how loud is that and then we have the variable density log to the right that&#39;s the fifth curve that is the history of the sound wave time versus depth to when i receive it the amplitude the amplitude is the height or loudness of that first wave that arrives in this case it&#39;s fairly small the big peaks coming later those are big sounds reflecting off of the formation but that first area is coming through the casing that first peak is the amplitude i will repeat at thoroughbond we do not use amplitude specifically to interpret the log we will re-log for the cbl and we will be looking at several things on the variable density log that we will observe when we interpret the log but we take the variable density log i&#39;ll show you how we make it we cut it in half it&#39;s like being in the ocean at sea level and watching one wave go by the height of that wave is the amplitude we take that we&#39;re going to cut that wave in half eyes out of the ocean and look down on that wave and when we do it would look like this and now we&#39;ll do that as we go along the beach of the waves coming in we will mark the peaks of all of those waves and we will connect them to create the vdl again it&#39;s like flying over the ocean now looking up and down the beach that&#39;s our depth and looking at the first arrival that&#39;s hitting the receiver a history of the waves that are about to come in and be picked up on that receiver so every time you fly over the beach you&#39;re looking at a vdl i see vdls everywhere i see them when i look on the beach i see them in the clouds i see them on the lake when i throw a rock in the lake i see the waves coming in you see beautiful vdls all over the place so be watching for those videos and that&#39;s what we look at time versus depth when we look at the vdl we&#39;ll see it to the far right five curves you get the gamma the dotted line in the middle is the transit time foot receiver the hashed line is the casing collar locator the middle area we have two curves they&#39;re the same curve different scales this is measured in electrical energy it&#39;s the amplitude this particular log and it changes from log to log this particular log from 0 to 100 millivolts and then we have another curve the amplified amplitude 0 to 10 millivolts and then we have the vdl the variable density log and that&#39;s where we&#39;ll have our focus when we interpret our bond log when we look at that the first part of the wave the first wave hitting the beach is the fastest sound and that fastest path and that fastest path is traveling down the casing in this area we look for straight lines because it would be a lot of energy and since it&#39;s coming down the casing the casing is homogeneous always if our tool is centralized we get the same fluid the same casing the same fluid the wave should arrive at the same time up and down the well and we&#39;ll see straight lines in this case it&#39;s a perfectly cemented well so the lines disappear there are no straight lines and a basic rule if you see straight lines that&#39;s bad straight lines are energy coming down the casing straight lines are the same as a loud casing ring when you see no lines the energy is so small we can barely pick it up because it&#39;s very quiet sound the middle part of the curve comes through the formation big formation signals and then the last part we&#39;ll see effects coming through the fluid all of these waves coming in and the construction and deconstruct destruction of these waves as they come in show up in the video very quickly you&#39;re going to see some colored maps today and those are from radial bond logs where we have the regular cement bond log five curves we add to that a cement map that&#39;s based on eight separate receivers either at the two foot or three foot interval by the way the vdl comes from the five foot receiver that we saw earlier the cement map will come from radial receivers listening on each side of the casing at the two or three foot interval when we come to look at the bond log the key thing and i see people who have talent at this and i see people who do not and that is we have to learn to observe to observe you need to use your eyes you need to quiet the rest of your sentences i can observe and taste coffee at the same time so i think that&#39;s okay but i actually usually taste the coffee first and then observe i want you to see the eyes if you&#39;re talking it&#39;s hard to observe if you&#39;re in a hurry it&#39;s hard to observe if you don&#39;t know what to observe it&#39;s hard to observe so i want to take you through the things that we will observe there are four main things we&#39;ll observe when we look at the bond log immediately the first thing we will observe is casein ring casein ring shows up on the vdl as straight lines do you see any straight lines on the vdl the curve on the far right a lot of them matter of fact if that vdl was this glass not only do you hear a first ring you hear it resonating big ring all the way throughout there is no cement so we observe the casein ring look at these logs the log on the left do you see straight lines do you see casing ring especially first arrival casing ring we do we also see the big chevron patterns at the collars on the right by the way the log on the left has no cement in it the log on the right do you see straight lines they&#39;re not as strong but they&#39;re there and the collars do not as loudly but you can see chevron patterns here but here they&#39;re not as strong here you see the strong chevron patterns do you see straight lines here when you see straight lines first arrival that&#39;s bad at least it&#39;s going to require some interpretation if you see no straight lines then you don&#39;t worry about it or many don&#39;t maybe we should sometimes but i never receive logs that have no straight lines they don&#39;t send those to me i only see the ones with straight lines that cause bottom they go away the next thing we will look for are formation signals first of all do you see any straight lines in this log you see some to the far right those are fluid arrivals but to the left here in the vdl all of the straight lines disappear that&#39;s good but we want to make sure we&#39;re connected to the formation and they will show up as these big crooked squiggly lines so very basically straight lines are bad squiggly lines are good we&#39;re connected to the formation we&#39;re reflecting off of the formation we must be connected by cement do you see any formation signals here do you see any straight lines here no straight lines but look at all of the the crooked lines or the bending lines those are all strong formation signals it&#39;s a perfect cement job what about here straight lines do you see any just look at the vdl do you see any chevron patterns at the collars i do see straight lines i do see chevron patterns but do you see any formation signals look at them strong formation signals we must be connected to the formation that is a very good sign the third thing we&#39;ll observe the first we look for casein rings second formation signals casein ring is straight lines formation signals are crooked lines look at this log do you see straight lines a little bit in the bottom do you see formation signals i do strong crooked lines that follow the straight lines if we can apply pressure to the casing which we do here we place a thousand psi inside the casing it expands the casing it strengthens the bond and the straight lines go away so we if we do have a pressure pass then it can give us some good information here&#39;s an example where we ran a pressure pass and just look at the colored map for a second again this is a radiolog not an ultrasonic we&#39;ll look at ultrasonics next week and you don&#39;t see much change do you we tighten the bond on the one on the left it changes a little bit but there&#39;s not much change of the colored map on the right with no pressure so it tells us adding the pressure did not help we may have a big problem here more than just a bond and the final observation i will look at i get the log i look for straight lines casing ring i look for crooked lines formation signals i see if there&#39;s a pressure pass and i observe the pressure pass if anything has changed and then i look for top of cement where does it go from no straight lines to very big straight lines and i try to find the top of cement i will use that top of cement so i can compare and analyze the rest of the log results as a matter of fact we will talk in just a moment but when you cement an oil and gas well for the most part these are your only four options these are the only four things that can happen when you interpret a log they happen in different ways they happen and in different mechanisms cause it but you either have no cement did cement we might call that a micro annulus or the cement has channels in it either mud channels or gas channels or it&#39;s a good cement job perfectly tightly sealed let&#39;s look at what each of those looks like this one&#39;s pretty evident a lot of straight lines if you look at the ccl and again you&#39;ll have these charts here&#39;s our ccl our case in color locator transit time dotted in here here we have our gamma ray we actually are showing here two transit times it may be the three and five foot receiver here&#39;s our amplitude here&#39;s our vdl and this is our cement map straight lines no cement big chevron patterns this is free pipe what it will look like straight lines chevron patterns strong chevron patterns here&#39;s a microannulus poorly bonded we have straight lines they may not be as strong or they might but straight lines but the collars are dampened you see a change in the collar i look at that a lot on the vdl and we have formation signals you see the crooked lines here&#39;s what a channel might look like the unfortunate thing is that a channel often looks like de-bonded cement and on the third week we&#39;ll talk about some more advanced techniques to determine the difference between a channel and poor bonding but once again you get straight lines with the channel we get the collars they&#39;re dampened somewhat but they&#39;re pretty strong and you get formation signals where it&#39;s attached on the cement map because a cbl cannot detect channels on its own not clearly but we see the channel coming from this water zone that we know is flowing this is a big channel when we look at the ultrasonics we can we&#39;re able to see smaller channels and then we have perfect cement that&#39;s what it looks like no straight lines matter of fact it looks pretty much like the open hole sonic log everything so tightly bonded so solid that we just reflect the formation back that&#39;s what we want to see look at that beautiful cement job we can get these kind of cement jobs everywhere we we can in the most difficult of circumstances we can get a great cement job but we have to be ready to do some serious cementing sometimes we have to be aggressive we have to understand the entire wellbore but we can get these kind of results what about this one do you like this one why do you not like it i mean i don&#39;t like it because we see straight lines many will say i don&#39;t like it because the amplitude here is 72 millivolts which happens to be the free pipe amplitude for five and a half inch casing so the amplitude says i have free pipe the straight line say i have free pipe the collars start to get dampened and then we see what appears to be formation signals or are they what are those squiggly lines notice if we observe and we take our coffee and we relax and just observe if we took our time we probably could make a thousand observations about the vdl alone just look at the vdl make make some observations in your own mind what do you see simple observation do you notice that the first line is narrow the second line is bigger the third line&#39;s narrow do you notice that that&#39;s just an observation do you notice the squiggly lines to the right don&#39;t tell me what they are just do you notice them they&#39;re squiggly sometimes when we start to observe we start to interpret instead of observe to just observe here&#39;s another observation how many straight lines do you see before the squiggly lines and does it change count them one two three four five six seven there are seven straight lines before the squiggly start and notice it all happens right at the same point this is an indication and it&#39;s something we observe these are fluid arrivals coming down the casing distorting the straight lines these formations although we may be seeing some effect if the casing comes over to the side and touches the formation what we&#39;re seeing here are fluid arrivals this happens to be free pipe no cement so these are the things that we will observe now that we have kind of the basics what is the method how do we interpret bond logs we call it the five c&#39;s some of you may have joined or have seen our five c&#39;s before you will know what we&#39;re getting ready to look at we&#39;re going to construct the well first what i mean is i although i love the bond log i&#39;m not going to trust the bond log i&#39;m going to trust the cementing operation in other words if i pump cement and cement came all the way to surface and i saw the cement surface and the bond log says there is no cement in the well i&#39;m going to doubt the bond log i&#39;m going to trust the well construction first and in other words i&#39;m going to allow the wellbore to interpret the log before the log interprets the well bore and if you&#39;re not thinking about the wellbore if you&#39;re thinking just about the log you will misinterpret the log so i&#39;m going to kind of build the well as best i can i&#39;m then going to look up and down and compare sections of that log when i do that i&#39;ve already allowed the weld bore to interpret the log now i&#39;m going to look up and down and i&#39;m going to let the log interpret the log i&#39;m not going to look for absolute numbers as much as a comparison of what parts of the log look like and i do that by just looking up and down now i have to have my coffee in hand to keep me relaxed i i promise you it&#39;s the best part of my day having coffee and just looking at the log and relaxing but knowing what to look for makes it a lot easier and a lot more enjoyable the third step is to correlate once i look up and down at points of change i look side to side i wonder what&#39;s happening here i look to see if it correlates to the wellbore so i let the wellbore interpret the log i look up and down and let the log interpret the log and then look side to side and let the log interpret the well bore that&#39;s the process we use in week three we&#39;ll look at this part much more i consider all of the things that the wellbore is doing that&#39;s trying to confuse the log and the well bore will try to do 35 things we&#39;re up to 35 things we&#39;ve noticed and i&#39;ll show you a few of those and then we conclude so i construct the well i compare sections of the log i correlate side to side i consider what could be going on with the wellbore and then i conclude and it&#39;s time to interpret now here&#39;s the problem you are attending this session and you will have heard for maybe the fourth or fifth time i do not use the amplitude to interpret the problem is when you gather around this log you&#39;re going to find that it is noisy people are talking most of the time and i&#39;ve done this many many times working in house at many operators but working for oxy and talisman and repsol when i walk into the room and they would know hey kirk is coming up he is focused on bond logs we respect his opinion and so let&#39;s let kirk look at this so they call me and i come up to the business unit or fly up to the location and i walk into the room and it&#39;s noisy someone might say hey hello kirk welcome come on over here and i say well what do we have here and they say oh i&#39;m glad you showed up but we&#39;ve already interpreted the log we got the answer and they got the answer by looking at the amplitude and so i try to quiet them down because they take the log and here it is and they say let&#39;s interpret this log i said okay let me get my coffee what kirk we don&#39;t have time for coffee we&#39;ve already interpreted it all we did was we drew a line on the amplitude curve and you can see at the bottom it&#39;s good everything&#39;s to the left for the most part but at the top it&#39;s bad everything to the right and so we finished interpreting and i say well wait a second let&#39;s have some coffee first thank you now we can interpret and i do the interpretation by asking four questions this is how i start i ask the four questions first of all to quiet the room because someone&#39;s already got the interpretation and that interpretation is wrong and so i have to get them back to the base of hey where was the cement supposed to be by the way and then suddenly someone says oh well i don&#39;t know has anyone looked at that i guess we are talking about cement was there lead and tail did we have losses or flows maybe we put all the cement in there and it all flowed out i don&#39;t know what do we know about the construction of this do we have a weak casing to cement bond someone will say well what has that got to do with the problem and i will say it&#39;s everything the bond for a bond log interpreter is 80 thing is everything eighty percent of all logs are affected by shear bond just wanna take a quick diversion here i don&#39;t know if any of you have climbed pose recently when you get to my age your pole climbing days are long gone they&#39;re over i tried to climb a pole about 10 years ago and i jumped onto the pole but all i could do was just hang on for dear life and so if you&#39;re young and you like to climb just do it now later it&#39;s not going to be pretty when you&#39;re hanging on that pole your weight pulling you down divided by the area that your hands are holding onto that&#39;s shear bond it is the force applied to push casing out of the cement that cement surrounding cemented shear bond very important so i asked do we have a weak casing to cement bond maybe it&#39;s low shear bond and then the fourth question and if you don&#39;t know the geologist you need to get to know one because the formations have a huge effect in bond logs i asked which formation is caused in the problem so first we construct the well bore i want to know about the very simple terms i want to know where is leed cement and where is tail cement this looks like free pipe it was interpreted by a major logging company on location as free pipe when it actually was the lead cement we need to be able to interpret that we look at the cement we look at the casing we look at the formations when we construct the well sometimes you have a lot of data sometimes you don&#39;t the more data you have about the cement job the better the interpretation will be then when we compare log stations you can look and see the difference [Music] between the top and the bottom of this log and i put a there&#39;s my lead cement that was interpreted as no cement but it is lead cement and then i take that lead cement and i compare it to what is free pipe i&#39;m comparing and you can see the difference between my thumb print on that vdl and the free pipe interval above what is below was not free although look at the amplitude the amplitude is the same and then i correlate at changes step 8 lines bad crooked lines good and i get good bad good when i correlate i just draw at the points of change i draw a line over and correlate to the bottom and to the top and now your job as an interpreter as a detective into this log is to determine why did it go from good to bad there&#39;s got to be a reason your job as an interpreter is to do that step force to consider the key factors things we&#39;re doing on location here we&#39;re running a casing or centralizer what things are we doing on location that will affect the bond log i&#39;ll give you a few examples there are 35 and we&#39;ll dive into those in week three the first is new casing some new casings this casing from argentina that was shipped and run in the middle east showing free pipe amplitude a lot of straight lines that&#39;s bad some crooked lines that&#39;s good but it&#39;s showing a bad cement job but it&#39;s brand new casing causing the problem we sandblast that casing we take off all the pretty paint and shine and you see the straight lines in those sandblasted joints disappear considering the key factors centralization you can look at log a of log and see the line in that colorful map it&#39;s because that particular casing was not centralized so we like to look for where is the casing centralized lightweight cements look at the straight lines in the upper portion of this log and watch those straight lines disappear both have crooked lines but the upper one is being hidden by the straight lines the shear bond of the cement in the upper is only 50 psi it&#39;s 200 psi below we find that we need about 150 150 psi of shear bond to get those lines to disappear so lightweight cements we must consider here&#39;s our lightweight cement in 24 hours we only get 260 psi that&#39;s that&#39;s so low it doesn&#39;t want to log very well it can provide isolation but it doesn&#39;t log another consideration pressure test when we cement the well and before we test the casing look at all of the crooked lines once again looking at the bond log we have the gamma at the transit time you can barely see case in color locator low amplitudes for the most thousand psi and we break the bonds so pressure testing we have to consider when we interpret a bond log i see this on so many logs we cement the well we wait 48 hours we pressure test the casing we break the bonds we run the bond log and we are confused a final one here is cement shrinkage when you have cement shrinkage sometimes you also have gas bubbling the cement shrinks away from the casing and the bubbles come up that&#39;s the big problem so we put expansion additive we sand blast the casing so the cement will lock into the grooves and when we add an expansion additive which tightens the bond that the cement expands and presses against that casing not only do the straight lines disappear but we find the gas percolating also disappears and finally we conclude not only do we have zonal isolation not only good or bad but why or why not why do we have zona isolation what do we see on the log or why not what&#39;s going on that&#39;s what we want to do in interpretation and when it comes to cementing you only get five choices there are two good choices we either have good cement shale we either have cement providing isolation or we have a geologic barrier that has come in and provided isolation do we have isolation or not i don&#39;t know because we may have a weak bond and that weak bond may be enough to have isolation or especially with gas wells it does not and then when it comes to no cement you only have two choices it&#39;s either no cement at all or it is a channeling issue cross flow wiping out the cement would be part of a channeling issue so these are the choices we get in concluding so we interpret the log we construct the well we compare sections we correlate side to side we consider all of the things that could be happening maybe a pressure test maybe new casing maybe a lightweight cement then we conclude and we don&#39;t conclude by saying good or bad we say it is bad because of a mud channel and here&#39;s what&#39;s going on so it gets more in depth you will understand as we begin to close here you will understand the more you&#39;re around monologues how controversial they are the controversy goes and hides some things and to look at the raw data it can lead you one way or the other and can be wrong here are the three reasons why they&#39;re a bit controversial they are simple five curves the gamma the transit time the k color locator the amplitude they are simple but they&#39;re not easy to read as soon as you put casing in and have case toll those straight lines start hiding some of the data we also have logging versus drilling and here is where logging is going to look at the logging data in this case they drilled a well and what you see through the right is what we&#39;re going to look at next week and that&#39;s the ultrasound and what we have here is a log that showed up green what does green mean for the ultrasonic tool the use it schlumberger&#39;s tool green means micro bonded it means it&#39;s kind of like a micro annulus there isn&#39;t much there but something&#39;s there the bonding is low but it&#39;s quite variable so something is there and they color it green and so they ran this log and they colored it green and we asked is there cement there and they said we&#39;re not sure but let&#39;s send it out to be processed and they sent it to be processed and they said there is cement there well we said well if there&#39;s cement there what happened here here&#39;s the bond log for it that we ran three months earlier when we knew all of our cement was pumped out the bottom of the well and there is no cement in here free pipe amplitude this is the one we just looked at with those fluid arrivals on the right so logging said we had cement drilling said we don&#39;t have cement and said the reason i know we don&#39;t have cement because we didn&#39;t pump any cement in this part of the well that&#39;s why we construct the well often logging doesn&#39;t have that data when they&#39;re running the log they don&#39;t know the history of the well and so it shows you how important it is to construct that well another reason it&#39;s controversial is because bond logs cost money now this happens to be an excerpt of the flow chart of macondo on the deepwater horizon they did not run a bond log i&#39;m sorry they didn&#39;t run a bond log but a bond log was in the flow chart here it is way out here if they had a disaster of sorts in the cement job if all this meant had gone away they felt or if they could not easily determine where the cement might be they were going to run a bond log so since the job appeared to be okay they didn&#39;t run a bond log in the flow chart they were doing everything they could sitting it way out here to not run a bond log here&#39;s the decision did i have lost [Music] cementing no let&#39;s get on with it no bond log if and so let&#39;s not run the bond log some people say running the bond log would have cost a hundred and twenty five thousand dollars it would have that would have been the bond log alone it would have cost another three four five hundred thousand dollars of time as we waited on the cement to set without getting into my condo too much the reason it probably failed and the reason this disaster occurred and i was on the outside of my condo looking in very involved because i had worked in-house at bp i had worked for halliburton in the gulf of mexico mentoring engineers and i was working throughout afterwards with people involved with my condo i was actually in-house when we were putting the cement unit on the deepwater horizon very very important very tragic but it was going to cost a lot of monologue how do we run the bond log i think the reason there was failure is that the cement never set at least not before we started flowing well have we waited on the bond log that amount of time to run the bond log i think we would not have had that disaster we don&#39;t know but i think the cement would have been allowed to set so let&#39;s start looking at closing the session with interpreting a log and i want to show you the importance of the bond log and how we would interpret it if you&#39;ve attended any of the sessions before on basic logs you may have seen a log like this how do we interpret it what&#39;s the first thing we do when the log set before us i actually just received a fresh cup of coffee so when you think about the five c&#39;s never forget the six c keeps us relaxed reminds us we&#39;re going to observe and follow a procedure for me this is not just theory i interpret logs every day and i use the fees i always have the 6c coffee with me but i use the 5cs every day this is not theory it&#39;s simple but it sets in motion the way we should interpret logs you will want to just go in and say it&#39;s bad cement there&#39;s a middle section in here that&#39;s bad cement i i know that i know at least it looks bad but is it really bad more importantly why you you have to understand the why and i&#39;m going to show you a good reason for that as we close out today what&#39;s the first thing we do interpreting a log i already got the coffee we&#39;re going to construct the well for the purposes of this interpretation i go and i ask the questions where was the cement supposed to be in this well it&#39;s supposed to be way up the well this is just a short section at the bottom of the well is there a lead and a tail yes there is a lead and a tail but the lead should be way up the well this should all be very strong tail cement okay i then asked about things like uh did i have losses or flows i asked the drilling engineer he said no no losses no flows perfect cement job like macando quote a perfect cement job okay maybe i don&#39;t even need to run a bond log if it was a perfect cement job but we ran a bond log and i&#39;m glad we did because we find a section in this casing that doesn&#39;t look good let me correlate first i compare i look up and down let me go back to my construction my third question is maybe there&#39;s a bonding issue my first thought if there is a bonding issue i&#39;ve got good bond below good bond above it&#39;s just poor bonding in an area maybe it&#39;s new casein it&#39;s not a pressure test or that would have broken all of the bond what could it be maybe three joints of casein are new maybe there&#39;s something with the casein may i don&#39;t know and i ask that question i also ask about formations but then i compare and we look at it i compare these three sections looking up and down and at the point of change i need to correlate why does it go from good to bad i cannot just say good and bad i have to explain what&#39;s going on as an interpreter a logging engineer might say hey look it&#39;s bad i say there&#39;s not much cement there and i would say why he said that&#39;s not my job it&#39;s not my job to tell you why i&#39;m just running the log and telling you what the log is saying i want to know what the wellbore is saying not necessarily just what the log is saying so i&#39;m going to correlate back to the wellbore and i happen to correlate right to this point do you see the gamma spike that&#39;s our formation the casing collars are our casein the cement is all one cement so that shouldn&#39;t change but i change near a collar but i change right at the gamma there it is when you start correlating the puzzle starts to be solved next week we&#39;re going to look at this log this log is an ultrasonic log and we&#39;ll look at this in depth but look at this i&#39;m considering things and one of the things i always consider maybe it&#39;s poor bonding maybe there are joints of casein that aren&#39;t bonding as well but when i look at this i can see that the occurrence is not happening in a collar it&#39;s happening at the gamma then go to my geologist and say what is that gamma looks like a shale my geologist says that is not a shale that&#39;s something called a hot dolomite i find out that the geologist in this infield drilling program knows more about the well than our drilling group does what we&#39;re drilling through they know the formations they know why we&#39;re doing what we&#39;re doing so i attach myself to a geologist and he says this spike is a hot dolomite as a matter of fact it&#39;s over pressured dolomite and we determine through our interpretation and every interpretation is just an interpretation it may be right it may be wrong but we determine that this hot dolomite is probably doing something that often occurs it is cross flowing into a normally pressured fractured dolomite and i&#39;ve wiped my cement out of the picture and this is important because this well is an injection well i need cement across this to direct my injection into a new zone that i can flood the oil out of the well boards and all of my cement is gone guess what if i hadn&#39;t run a bond log i wouldn&#39;t know that i would inject my co2 and get no increased oil production if i didn&#39;t run a bond log because i had full returns and the job was perfect i never would have saw this so what did we do we perforated at the bottom of the bad and at the top of the bed and we were able to circulate and re-cement this well so the bond log not only told us we had a bad job it showed us the place we needed to fix and we fixed this well but it didn&#39;t only do that it also allowed us in the next 20 wells that were going to be drilled in this field it allowed us to cement them correctly you see well two we put a packer in between that flow zone and we were able to get a perfect cement job look at the vdl on well two no straight lines beautiful we did the same thing on well three we then allowed that pressure to normalize and we cemented the rest of the wells without a packer successfully so the bond log not only told us that the perfect cement job was not perfect it told us how to fix it and it told us how to cement wells in the future this tool is extremely useful the bottom log is would like to close with a few simple things in our summary first of all cement logs are simple we got the gamma transit time casing color locator those are on one side we got the amplitude in the middle and it&#39;s not that i don&#39;t like amplitude but we cannot draw a straight line and say that interpreting is just left and right of a straight line amplitudes will fool you mainly because of the poor bonding that can occur for a number of reasons and we still have isolation as an example every lightweight cement is going to fail the straight-line test the amplitude test we use the vdl not the amplitude but cement logs are simple but good interpreters must practice you must practice observation you must understand the logging tools i think if you understand the logging tools too much you&#39;ll trust them too much but you have to understand the logging tools but you have to know cementing you have to know the wellbore better have a geologist nearby the geologist is usually the go-to person because they work with logs and they know the formations but you must practice the things we talked about today you will forget in about two or three days if you don&#39;t get in front of a log in practice finally bond logs are very useful they&#39;re going to help us to fix wells help us to cement better help us to understand where production is coming from if our wellbore is the best it can be they&#39;re going to help us abandon wells and make sure that we have them properly sealed so be dedicated to your work don&#39;t give up on the bun log don&#39;t think that you have to be confused the more you work with the bun log the better it will be so be dedicated to that work with that i would like to close and i would like it to hand it back over to our moderator for any questions or comments that you might have thank you thank you mr harris for a very informative webinar i&#39;m sure the audience benefited greatly from it in the meantime i&#39;ve collected a few questions for a quick q a section um so the first question is after cementing operation is it advisable to continue drilling if we have losses when flushing or circulating yes could you repeat the question it was after drilling the wellbore after cementing operation is it advisable to continue drilling if we have losses when flushing or circulating okay i&#39;ll answer that in two questions because i&#39;m not sure i understand the exact question but i&#39;m working with some logs right now to where when we&#39;re drilling the well we&#39;re circulating the well without losses but when we start to circulate before some before cementing and we have losses we&#39;ve questioned do we cement or do we try to cure losses before we cement and all i can say is if you have losses and you&#39;re not sure where the losses are and you cement i&#39;ve got many logs before me they are the worst cement jobs you can have having the losses now if the question is we&#39;ve cemented the well and everything is fine and now i drill the next whole section and i have losses should i stop or should i drill blind it&#39;s drilling blind as you we drill ahead with losses in that case it&#39;s dependent upon each wellbore but we&#39;re for the most part always always trying to heal and seal the losses so we can have full circulation if we don&#39;t for sure somewhere along the line we have a wellbore that has no integrity so i answered that in a couple ways i hope i hope that the answer was somewhere in that yeah um the second question is why channels have the same characteristics as bats meant bond on the cement blocks what is the basic idea that makes these two situations alike on the log it&#39;s a very good question if you have a channel and let&#39;s imagine it&#39;s the worst possible channel half of your wellbore half is cemented the other half has no cement so half of the well is perfect after the well is not perfect in that situation of course it&#39;s a very bad thing because all of your fluids can flow up one side of the well when you run the bond log the bond log says i&#39;m getting formation signals from the half that is cemented but i&#39;m getting those are the crooked lines but i&#39;m getting straight lines from the half that is not cemented so the log looks like straight lines and crooked lines that is a classic channel but when i have poor bonding i&#39;m fully surrounded but i&#39;m not gripping the casing tightly this glass that i ring if i&#39;m not gripping it enough to stop the ring so what do i get i get the same straight lines but i&#39;m connected enough in places where i get the formation signals in both cases they&#39;re straight lines and their formation signals the channel is bad the weak bonding may or may not be bad often it is not bad so i get the same results straight lines crooked lines with two different scenarios and a talent in interpretation is looking at enough knowing your field well enough to know the difference between the two um great thank you for answering good question yes um we have a couple more questions um why the amplitude was the same in the example where vdl of lead cement was compared to another vdl which represented a free pipe what is the basic idea about the amplitude being the same where the two mentioned situations were actually different yes once again especially new case team lightweight cements the sound wave all it knows it goes out and what&#39;s directly next to the casing will determine where that sound wave goes and if it is not tightly bonded to the casing that sound wave says i&#39;m going to reflect and stay inside the casing and i&#39;m going to send all of my energy down the casing even though cement is present if it&#39;s not squeezing the glass if it&#39;s just barely barely touching the glass then all of the energy goes down the casing there are many other scenarios where the energy will not go out the casing it will come down here&#39;s another example if the cement is so thin that it provides no mass to grip the casing just because cement is there it will not dampen or attenuate or carry out the sound wave it will travel down as if it&#39;s free pipe so in the case i showed it is a weak cement many places around the world allow you to run cement that barely sets up so it doesn&#39;t grip the casing it has no shear bond [Music] and you must have strong shear bond to carry that sound wave out i see it more often than you can imagine lightweight cements and new casing or pressure tested casein although cement is there the sound wave is not fully connected and will travel down the casing just as if it was free pipe so the case i showed two or three cases of free pipe amplitude that was fully cemented that&#39;s uh that&#39;s part of the problem just running the bond log and part of the problem of the confusion of the bond log that&#39;s why we must construct the well and observe closely the vdo but another good question yeah uh another question is according to your experience can this process of interpretation be automated using machine learning and ai if not why yes it can be and and i some time ago i thought maybe i&#39;m the only one thinking about this again how to make your eyes and i will show you next week next week i will show you as we look at the log where your eyes should go what they should look for and so i would i thought i was the only one thinking if i could have a computer program for my eyes to see we can automate this i believe we can but you&#39;re going to need a few little secrets on how to do that so if there&#39;s any wizards out there with ai or computers i&#39;m talking to some people i think we can automate it and so yes i do i think there&#39;s a few secrets about how it can successfully automate it but i do believe we can oh thank you for answering mr harris thank you again for dedicating some time of your totally busy schedule to give this webinar and course in general um thank you attendees for tuning in from all around the world please stay safe wear a mask and have a great day thank you it&#39;s been my privilege thank you very much for attending

Transcript for:Cement Evaluation: The Basics and Beyond

Transcript for:
Cement Evaluation: The Basics and Beyond