The Lab
Learning objectives
- Assemble the whole course into one four-tab workbench sharing a single stress state
- Load the Ogbon-1 canon or its depleted twin and drive the pore pressure and mud weight
- Watch the polygon, Mohr circle, wellbore, and mud window respond together to one change
- Read the four verdicts at once: regime, mobilized friction, breakout, and the safe mud band
One State, Four Instruments
Part 12 is the Lab, where the models stop being chapters and become a working kit. This first section is the workbench itself: a single stress state, viewed through four tabs at once. The Polygon classifies the state and tells you whether it is what friction allows. The Mohr circle reads the mobilized friction, how close the rock sits to slipping. The Wellbore shows the breakout the state and the mud weight produce. The Window shows the safe mud band. Change one thing, the pore pressure or the mud weight, and all four respond together, because they are four faces of one stress state.
Load the Ogbon-1 canon and read the field you calibrated in Part 8: Sv 67.7, Pp 35.3, Shmin 46, SHmax 62, normal-faulting, mobilized friction 0.58, breakouts about 28 degrees, a narrow mud window. Then load the depleted Ogbon-1 and watch the whole picture shift as the stress path of Part 10 drops the pressure and the horizontal stresses: the polygon moves, the fracture gradient falls, and the mud window narrows from the top. The Lab makes the couplings visceral, that a pore-pressure change is not one number but a shift in the regime, the friction margin, the borehole, and the drilling window all at once, which is exactly the systems thinking a mechanical earth model demands.
How to Use It
Drive the two sliders and read the four verdicts under the figure, which update no matter which tab is showing. Push the pore pressure up toward Shmin and watch the mobilized friction climb and the window close; drop the mud weight and watch the breakout grow on the Wellbore tab; raise it and watch it cross the loss line on the Window tab. The Lab is not a new idea, it is every idea of the course wired together, and the point is to feel how tightly the pieces are coupled. The remaining sections of Part 12 give you the tools to take that coupling home: a reference deck of every model, a set of Python programs that reproduce the canon exactly, and an advisor that tells you which model to reach for.
References
- Zoback, M. D. (2007). Reservoir Geomechanics. Cambridge University Press.
- Plumb, R., Edwards, S., Pidcock, G., Lee, D., & Stacey, B. (2000). The mechanical earth model concept. IADC/SPE Drilling Conference, SPE 59128.