The Toolkit Map
Learning objectives
- Lay out the course as a machine: tensor to strength to pressure to polygon to wellbore to calibration to faults and the producing field
- Recognize the one self-consistent canon state that every part of the course computes on
- Preview the anchor numbers, 3.12, 27.9 degrees, two-thirds, that will each get a section of their own
- Know where the Geomechanics Lab sits and what it will hand you at the end
The Machine, Assembled
Here is the whole course on one page. Part 1 builds the stress tensor and its picture, the Mohr circle, then subtracts pore pressure to get the effective stress the rock actually feels. Part 2 adds the poroelastic rock: how stiffness, Biot's coefficient, and the resting earth's connect stress to strain and pressure. Part 3 supplies strength: the Coulomb line, Byerlee's universal friction, tensile and compactive limits. Part 4 predicts pore pressure before the bit finds it. Part 5 is the summit of the theory half: Anderson's regimes and the stress polygon, the map of every stress state friction permits. Parts 6 and 7 take the machine to the wellbore: the Kirsch equations turn breakouts and tensile fractures into stress measurements, the mud-weight window turns them into drilling decisions, and fracturing pushes past the window's ceiling on purpose.
Part 8 is where the course stops being hypothetical: every method calibrates on the Ogbon-1 well, the same well the Petrophysics and Rock Physics courses share, and the pieces assemble into a mechanical earth model. Parts 9 and 10 spend that model on the biggest questions: which faults are one pressure change from slipping, and what depletion does to stress, compaction, subsidence, and the 4D seismic signal. Part 11 is review and a final examination; Part 12 is the Geomechanics Lab, where the polygon, the Mohr diagram, the wellbore, and the window share one live state, with runnable Python and a model advisor to take home.
One State, Carried All the Way
A course design choice worth naming: almost every number in this book is computed on one self-consistent stress state, the Ogbon-1 canon at 3000 m that Part 8 will justify: overburden 67.7 MPa, pore pressure 35.3, minimum horizontal stress 46, maximum 62. Touch any node in the map above and you will see the anchor that state produces there, from the friction limit 3.12 to the 27.9 degree breakout to the two-thirds depletion rule. When you meet each number again in its own section, it will already be familiar; by Part 12 the whole set will feel like one object seen from twelve directions, which is exactly what it is. Now, to work: Part 1 opens with the machine that eats planes.
References
- Zoback, M. D. (2007). Reservoir Geomechanics. Cambridge University Press.
- Jaeger, J. C., Cook, N. G. W., & Zimmerman, R. W. (2007). Fundamentals of Rock Mechanics (4th ed.). Blackwell.
- Fjaer, E., Holt, R. M., Horsrud, P., Raaen, A. M., & Risnes, R. (2008). Petroleum Related Rock Mechanics (2nd ed.). Elsevier.