Hydraulic Fracturing Operations and Earth Modeling

Jul 29, 2024

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

  1. Hydraulic Fracturing Operations
  2. Mechanical Modeling in Hydraulic Fracturing
  3. Equipment Used in Hydraulic Fracturing
  4. Fracturing Fluids and Materials
  5. 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