Lecture Notes: Hydraulic Fracturing Operations and Earth Modeling
Introduction
- Presenter: Dr. Ahmed Rari
- Experience: 20+ years in energy and petroleum industry
- Specialties: Acidizing, hydraulic fracturing, geomechanics, geothermal energy, carbon capture, storage, hydrogen technologies
- Current Position: Research manager at Milit Research Hub
- Academic Background: PhD and Masters in petroleum engineering from Texas Tech University
- Publications: 30+ research papers
- Awards: Distinguished Achievement Award from SP International (2021)
Key Points from Previous Lecture
- Importance of keeping the injection rate constant for accurate mathematical modeling in hydraulic fracturing
- Question from previous lecture addressed: Keeping injection rate constant ensures that mathematical models for closure pressure and leak-off coefficient are valid
- Detailed explanation planned for upcoming lecture on Tuesday
Today's Topics
- Hydraulic Fracturing Operations
- Mechanical Modeling in Hydraulic Fracturing
- Equipment Used in Hydraulic Fracturing
- Fracturing Fluids and Materials
- Principle Stresses and Mechanical Properties
Hydraulic Fracturing Operations
Conventional Hydraulic Fracturing
- Used for conventional reservoirs (e.g. Sandstone)
- Fluid used can be cross-linked gel (Jello-like consistency)
Equipment for Hydraulic Fracturing
- Pumps: 2000 horsepower on average; job size can vary based on the number of pumps and total horsepower utilized
- Manifold: Connects pumps to the wellhead; has low pressure and high-pressure sections
- Blender: Mixes Frack fluid with chemicals and propant
- Monitoring Truck: Supervises and controls operations, including job supervisor, Frack engineer, fluid technician
- Tree Saver/Isolator: Protects the Christmas tree (wellhead) by inserting a tube that can handle pressure above the wellhead’s rating
Fracturing Fluids and Materials
- Types: Fresh water, KCl, gu (similar to beans, used in food industry)
- Proppant: Sand-like material to keep fractures open, varies in size (40/70, 30/50, 20/40, 16/30)
- Chemicals: Cross-linkers, breakers, friction reducers, biocides, etc.
- Alternative Fluid: Slick water (used in hydraulic fracturing of shale; consists of fresh water and friction reducer)
Importance of Fresh Water
- Hydraulic fracturing activities require a substantial amount of fresh water
- Challenges faced in regions with limited fresh water resources
Principle Stresses in Hydraulic Fracturing
Principal Stresses in Earth
- Overburden Stress: Weight of rock points to the center of the Earth; measured by integrating density logs
- Horizontal Stresses: Maximum and minimum horizontal stresses; orientation and magnitude affect hydraulic fracturing and wellbore design
- Normal Fault System: Overburden stress is the greatest stress
- Thrust Fault System: Overburden stress is the smallest stress
- Strike-slip Fault System: Overburden is between maximum and minimum horizontal stresses
Measuring and Modeling Stresses
- Dynamic vs Static Young’s Modulus: Dynamic from Sonic log; static from lab testing on cores
- Poisson Ratio: Ratio of lateral strain to longitudinal strain, should be between 0.0 and 0.5
- Calculating Stresses: Using equations involving Poisson’s ratio, Young’s modulus, overburden stress, pore pressure
- Max Horizontal Stress: Difficult to measure accurately; uses wellbore failure analysis
Quiz and Questions
- Conducted a quiz to reinforce learning on formation damage, hydraulic fracturing goals, acid types, and proper methods to mitigate formation damage
- Main takeaways from the quiz: Hydraulic fracturing aims to enhance oil and gas recovery by creating fractures that increase formation conductivity; common formation damage is due to drilling and completion operations
Summary
- Complex nature of hydraulic fracturing operations and the need for precise measurements and equipment
- Importance of selecting proper fracturing fluids and materials
- Understanding principal stresses and their implications for well design and hydraulic fracturing
Next Session
- Upcoming lecture on Tuesday for further discussion on mechanical modeling and more detailed explanations
Questions and Answers
- Addressed importance of converting dynamic Young’s modulus to static Young’s modulus for accurate modeling
- Encouraged posting further questions under YouTube video if not answered during the session
For any further questions, post under the video on YouTube.
Next lecture: Tuesday