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Rock Properties and Mechanics

Competency Statement:

Identify rock mechanical properties from core, cuttings, and electrical logs. Use analysis to address issues related to fractures, subsurface pressures, subsidence and compaction. Illustrate an understanding of rock properties that effect seismic response.

Learning Objective:

  • Define basic rock mechanical properties, describe how they are measured.
  • Understand the differences between laboratory measurements and in-situ properties.
  • Predict formation subsurface pressure environment and principal stress directions.
  • Define rock properties and how they affect the seismic response.

Assignment Instruction:

Rock Mechanics is a very powerful approach for reservoir description and management. It provides useful and efficient links between mechanical and acoustical properties which lead to a deep understanding of the stress-strain behavior of subsurface beds. Used properly, together with geostatistical concepts, it can substantially help to elaborate an accurate picture of our geological targets.

You are a rock mechanics specialist assigned to the Exploration New Ventures team. Exploration team members come to you to gain insight and support in applying rock properties and mechanics to exploration problems. These problems may be related to tectonics, seismic evaluation, or reservoir performance. You often have a limited dataset to interpret.

In this assignment, you will calculate the elastic modulus of a reservoir target using laboratory data from well cores and well logs. Using these characterizations together with fluid substitution concepts and storage (porosity) and transport (permeability), you will be able to estimate the acoustic response to different saturation fluids.

In this sense, you will:

  • Calculate porosity and permeability from laboratory data
  • Use stress-strain relationships for linear elasticity to estimate the elastic modulus
  • Use inversion from acoustic logs and laboratory data to estimate the elastic modulus
  • Give a very educated guess for the stress state on the subsurface
  • Estimate the seismic signature of fluids and porosity

Note: Answers are used as input for subsequent questions.