This course provides an introduction of topics related to drilling geomechanics. It is recommended for reservoir, production, drilling and completion engineers, earth scientists, asset team managers and other oilfield professionals who want to understand the basic principles of rock mechanics as it applies to drilling wells safely. It is especially useful for people who do not have a geomechanics background or hands-on experience in determining rock properties from the lab/log data or in designing mud weights for vertical or inclined wellbores. The course describes the step-by-step procedure for developing a 1-D mechanical earth model starting from log data and integrating available lab and drilling data for calibration.
The course will focus on the following topics:
- Fundamentals of Rock Mechanics and its Applications: normal and shear stresses on a plane, 1-D, 2-D and 3-D stresses, Mohr’s circle for calculating stresses on a plane, principal stresses, and effective stresses. Review of various rock mechanics applications in the petroleum industry.
- Earth Stresses: in-situ vertical and horizontal stresses, their estimation from logs and calibration with field data; different stress faulting regimes, and geological evidences.
- Rock Strength Parameters: unconfined compressive strength, cohesion and friction angle, Young’s modulus, Poisson’s ratio, and their estimation from log and lab-based methods; static vs. dynamic properties, etc.
- Laboratory Testing: characterization of rock mechanical properties from lab tests, such as load and deformation measurements, elastic and failure parameter determination from triaxial tests, and other tests (hydrostatic, uniaxial, pore volume compressibility).
- Log Based Parameters: estimating elastic rock mechanical properties from standard sonic and density log measurements, dynamic vs. static rock properties and calibration with lab data.
- Wellbore Stresses: induced stresses due to drilling a hole – hoop (tangential or circumferential) and radial stresses; mechanisms of borehole failure such as breakouts or shear failure, drilling induced fractures, lost circulation problems, breathing and ballooning; LOT/FIT/Mini-frac, closure stress determination, field data calibration; failure types and models, Mohr’s circle to explain rock failure types and effect of mud weight and other parameters on rock failure.
- Mud Window: collapse and tensile failure limits, frac gradient, failure criteria, mud weight window, tight holes, lost circulation, etc.
If time permits, the following additional topics may be covered:
- Well Inclination and Depletion Effects: effect of well inclination and depletion on collapse mud weight and frac gradient, and on mud weight window; narrow mud weight window, enhancing mud weight window with stress caging or wellbore strengthening, etc.
- Case Studies: appropriate case studies to demonstrate the various aspects of the course.