Okay, the next thing, the next example of a microbial impact on petroleum resources and geological environments that we're going to talk about is microbial enhanced oil recovery. Okay, so what is enhanced oil recovery? Well, initially, the initial phase of production of an oil reservoir is referred to as primary production. During that stage, it's very favorable. to produce oil because there's quite a lot of it there and in some cases it would have its own pressure that would help drive it out of the reservoir but we can only recover about 10% of the oil that way about 10% of the oil that's initially present okay after that starts to get a little more difficult to squeeze the oil out of the reservoir so we have to do a little bit more work this phase of production is referred to as secondary recovery or secondary production you Thank you.
Techniques that extend a field's productive life during secondary production include injecting water, gas to help displace oil and push it towards a production well. I touched on that in one of the earlier videos. And as a result of this, after this portion of production, you usually get about 20-40% of the oil that was initially present. So about 10-30% of the oil that was initially present. 30% more after primary production.
Okay, so after that there's still quite a lot of oil that's typically left, maybe up to 80% of the oil that was there initially. And this leads us to tertiary production strategies or enhanced oil recovery. And this is where we do even more work to get that oil out.
There are three major categories of enhanced oil recovery that have been commercially successful to varying degrees. This includes thermal recovery, where basically you inject steam to heat up that oil that's present and make it less viscous so it flows more easily towards the production well. Gas injection, which I guess is also involved in secondary production, but helps to also push that oil towards the production well or potentially even lower its viscosity by driving more gas into the oil.
Thank you. And then in addition to that, in some cases, people have also used chemicals to help get the oil moving more easily. And I think this is less commonly used, but basically you can inject like a solvent or something like that that would ultimately enhance the mobility of the oil.
Now, obviously, it would be great if we could use some natural processes that would be... lower costs and maybe more environmentally friendly and so because of that people have investigated using microbial processes to help enhance oil recovery and this is probably not an exhaustive list but there I've come across three examples of this that are listed in the literature so let's just walk through these the first one is using microorganisms to help remove paraffin that accumulates on the surfaces of the production infrastructure okay so paraffin is as a waxy compound one example is petroleum jelly it is found in petroleum and exists as a liquid when warm but as crude oil cools it can solidify and coat stuff basically making it harder to produce oil kind of gumming things up and apparently There are microbes that can degrade paraffin and remove it from these surfaces. And microbial paraffin removal has survived in the marketplace for many years.
And there are published results that support its effectiveness. So this is something that's apparently actually used, microbial paraffin removal. In addition to that, well stimulations.
There have been strategies that people have studied that could use microorganisms to help stimulate wells by producing compounds that could help mobilize oil, such as acid. solvents or surfactants microbial gas production can also help as the gas content of crude oil increases its viscosity decreases I alluded to that earlier when I was talking about enhanced oil recovery but if you could get microbes down there producing more gas for you that would probably be less costly than injecting the gas, depending on what you had to do to get those microbes to make gas. And another way that people have investigated using microbes is for enhanced water floods. Water flooding... is the strategy where you basically inject water to help push oil towards a production well.
Well, over time, that process becomes less efficient because that water tends to follow flow paths. that are the flow path of least resistance. So it ends up kind of following similar path every time. And as a result, less and less oil is pushed out. Well, in order to get that water to squeeze into different flow paths, the thing to do would be to clog up that preferential flow path.
So if you could get microbes growing in there, producing biofilms, that could clog up that preferential flow path and then force the water to flow. along other flow paths and maybe squeeze out more oil. So that would be an example of microbes being used for enhanced water floods.
And we'll talk a little bit more about bioclogging of porous media in a future lecture. Okay, so how do you make this happen? How would you, for example, get microbes to grow in an area in the subsurface or in pipes?
Well, there's a couple of different strategies. One of them is biostimulation. That's where you feed.
the microbes that you want to grow, providing either electron donor or electron acceptor or some nutrient that they're lacking. Another example could be bio-augmentation, where you actually introduce the microorganism that you want to grow, maybe a specific microbe that makes a surfactant that you're after or that's good at generating acid. And in some cases, bio-augmentation would be used together with biostimulation. Or where you don't want to use it. want to introduce microbial microbes or increase their abundance in the subsurface you could grow them at the subsurface and inject their products separately okay so that would be an example of injecting exit to produced microbial products down into a reservoir okay so these are the references from the portion of this lecture that examined microbial impacts on petroleum resources.
In the next portion of this lecture, I'll go into some of the roles of microorganisms in generating natural gas resources. Thank you.