Geomechanics

Reservoir Engineering
By OgbonLab

Measure the stress, respect the friction: the well stays open, the frac goes where you send it, and the fault stays asleep.

The earth as a structure carrying load: the stress tensor and the Mohr circle, effective stress, rock strength, pore-pressure prediction, the stress polygon, the Kirsch equations and the mud-weight window, fracturing, fault reactivation, and depletion, calibrated into a full mechanical earth model on the Ogbon-1 well and ending in a Geomechanics Lab.

13 parts 73 sections Free, browser-native
Start reading → First up: Why Geomechanics? The Loaded Earth

Table of contents

Every section is a working session: text, math, code, interactive widgets. Click any title to jump in.

Part 0: Part 0: The Bridge

  1. Why Geomechanics? The Loaded Earth
  2. From Force to Traction to Stress
  3. The Three Pressures
  4. Four Failures That Built a Discipline
  5. The Toolkit Map

Part 1: Part 1: Stress, the Tensor and the Circle

  1. The Stress Tensor
  2. Principal Stresses and Rotation
  3. The Mohr Circle
  4. Three Circles: Mohr in 3D
  5. Effective Stress Moves the Circle
  6. The Vertical Stress from a Density Log

Part 2: Part 2: Strain, Elasticity, and the Poroelastic Rock

  1. Strain and the Small-Strain Tensor
  2. Hooke's Law and the Moduli
  3. Uniaxial Strain and the Resting Earth
  4. Biot and the Effective-Stress Coefficient
  5. Skempton's B and Undrained Response
  6. Injection, Depletion, and the Stress They Leave

Part 3: Part 3: Rock Strength and Failure

  1. Strength in the Lab
  2. The Coulomb Criterion
  3. Byerlee's Law: Friction Without a Rock Name
  4. Tensile Failure and the Griffith Tail
  5. Hoek-Brown and Curved Envelopes
  6. Compaction and the End Cap

Part 4: Part 4: Pore Pressure

  1. Normal Pressure and the Ladder
  2. Undercompaction: Pressure from Burial
  3. Unloading and the Centroid
  4. The Normal Compaction Trend
  5. Eaton's Method
  6. Bowers and the Unloading Limb
  7. Smectite to Illite: A Thermal Clock
  8. The Smectite-Illite Transformation
  9. Seeing It Before the Bit

Part 5: Part 5: In-Situ Stress, The Polygon

  1. Anderson's Three Worlds
  2. Frictional Equilibrium: The Crust at Its Limit
  3. The Stress Polygon
  4. Measuring Shmin: LOT, XLOT, Minifrac
  5. SHmax: The Hardest Number
  6. The World Stress Map

Part 6: Part 6: The Wellbore, Kirsch and the Window

  1. The Kirsch Equations
  2. Breakouts
  3. Drilling-Induced Tensile Fractures
  4. The Mud-Weight Window
  5. Deviated Wells
  6. Reading the Well: Images and Calipers

Part 7: Part 7: Fracturing the Rock

  1. The Fracture Gradient
  2. Breakdown and Propagation
  3. Minifrac and DFIT
  4. Hydraulic Fracturing at Scale
  5. Brittleness and Frac-ability

Part 8: Part 8: Calibration, The Ogbon-1 Mechanical Earth Model

  1. The Mechanical Earth Model
  2. Sv and Pp on Ogbon-1
  3. Strength from Logs
  4. Shmin from the LOT Ledger
  5. SHmax from the Wellbore
  6. The Ogbon-1 Stress Model

Part 9: Part 9: Faults and Induced Seismicity

  1. Stress on a Fault
  2. Slip Tendency
  3. The Reactivation Pressure
  4. Induced Seismicity
  5. Seal or Leak

Part 10: Part 10: The Producing Field

  1. The Stress Path
  2. Compaction and Subsidence
  3. Wells in a Compacting Field
  4. 4D Geomechanics
  5. Capstone: The Sand That Fails
  6. Capstone: The Frac Hit

Part 11: Part 11: Review and Final Exam

  1. Review Question Bank
  2. Final Examination

Part 12: Part 12: The Geomechanics Lab

  1. The Lab
  2. The Model Reference Card
  3. Python Presets
  4. Which Model? An Advisor
  5. From the Lab to the Field

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