Petrophysics - Rock Physics

The Contemporary State of stress in Sedimentary Basins: Observations and Modeling

 

Instructor

  Richard A. Plumb, PhD (Plumb Geomechanics, LLC)

Duration

  1 day

Disciplines

  Petrophysics – Geomechanics, Cross Discipline

Level

  Foundation

Language

  English

EurGeol

  5 CPD points

 

Course description

The purpose of this course is to inform those geoscientists and engineers, interested in geomechanics modeling, about the variation of principal stresses in sedimentary basins and physical processes that govern them. The course starts with a review of basic concepts including: the stress tensor, total stress, effective stress, principal stress, stress regimes, and Mohr's circle. Following is a review borehole techniques used to measure earth stresses in uncased and cased wells. Next, the course explores a global data set comprising more than 1000 measurements of: the least principal stress, overburden stress, pore pressure, and lithology. Global data reveal the dependence of stress on: basin setting, pore pressure, and lithology. Detailed measurements made in tight sandstone and shale reservoirs show that bed-to-bed stress variations are associated with changes in lithology and current rock properties (coefficient of friction, Poisson's ratio, and Young's modulus). Finally, we present physical models that explain the measured stress variations and that can be used to calibrate stress models. Limits of the current technology and methodologies will be discussed and promising new developments will be identified.

 

Course objectives

Upon completion of this course, participants will be able to build more accurate geomechanical models because they will understand:

1. The spatial variability of earth stresses in sedimentary rock,
2. The relative importance that: basin setting, pore pressure, lithology, and rock mechanical properties, have on the spatial variations of stress.
3. How geological and geophysical measurements may be used to model variations of stress magnitudes,
4. Limitations of common measurement and modeling methods,
5. Why a good geological model is a prerequisite for a predictive geomechanical model.

 

Course outline

1. Overview of the geomechanics discipline and the role of earth stresses.
2. Review of fundamental concepts: stress tensor, principal stress, total stress, effective stress, and Mohr's circle.
3. Review of field methods for measuring earth stress magnitudes and direction,
4. Review the variation of the least principal stress, associated with variations in: depth, basin setting, pore pressure, overburden stress, and lithology,
5. Case studies on stratigraphic variations of the least principal stress in tight sandstone reservoirs and shale reservoirs,
6. Geological and geophysical methods for modeling horizontal stresses.
7. Limitations of existing methodologies, current challenges, and evolving technologies.

Participants' profile

The course is designed to be cross-disciplinary and is appropriate for geoscientists, exploration geologists, reservoir geologists, and petrophysicists.

 

Prerequisites

Participants should have a basic background in geoscience or reservoir geology and familiarity with geophysical measurement principles.

 

Recommended readings

Breckels, I.M., and H.A.M. van Eekelen, 1981, Relationship Between Horizontal Stress and Depth in Sedimentary Basins, paper SPE 10336, presented at the 56th Annual Fall Technical Conference and Exhibition, San Antonio, Texas, Oct. 5-7, pp. 21.

Plumb, R.A., K.F. Evans and T. Engelder, 1991, Geophysical log responses and their correlation with bed-to-bed stress contrasts in Paleozoic rocks, Appalachian Plateau, New York, J. Geophys. Res. 96(B9) 14,509-14,528.

Thiercelin, M.J., and R.A. Plumb, 1994, Core-Based Prediction of Lithologic Stress Contrasts in East Texas Formations, SPE Formation Evaluation, December, 251-258.

 

About the instructor

Richard PlumbDr. Richard A. Plumb is principal consultant at Plumb Geomechanics, LLC and a visiting scholar at Tufts University. He is a globally recognized geoscientist with over 45 years of geomechanics experience worldwide. Previously he worked 29 years for Schlumberger, where he spent 15 years in research helping to develop the science and borehole measurements used to characterize earth stress and rock mechanical properties. For the next 14 years he led the geomechanics consulting business and the geomechanics technical domain at Schlumberger.

Recent work includes: developing geomechanical models supporting planning and drilling of exploration wells in tectonically active regions of Iraq and Peru; mentoring Ph.D. students at M.I.T. and Tufts University and teaching geomechanics courses.

Current interests include: understanding how mineral composition and texture affects the rheology of mudrocks and carbonates and factors that govern the variations of contemporary stress in sedimentary basins.

Dr. Plumb holds a B.A. in Physics and Geology from Wesleyan University, a M.A. in Geology from Dartmouth and a Ph.D. in Geophysics from Columbia University. He holds 6 U.S. patents and has over 70 publications in academic and industry journals. He is an active member of the American Geophysical Union, the Society of Petroleum Engineers, the American Rock Mechanics Association and the Society of Petrophysicists and Well Log Analysts.

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