The Role of Mineral Transformation due to CO2 Sequestration on the Shear Behavior of Reservoir Rock

Open Access
Author:
Sobhbidari, Farnood
Graduate Program:
Energy and Mineral Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
August 19, 2016
Committee Members:
  • Derek Elsworth, Thesis Advisor
  • Sanjay Srinivasan, Committee Member
  • Shimin Liu, Committee Member
Keywords:
  • Carbon Sequestration
  • DEM Simulation
  • Mineral Transformation
  • Shear Behavior
Abstract:
The sequestration of CO2 in subsurface formations is one feasible solution to mitigate the effects of climate change. The long-term effects of CO2-water-rock interactions are one of the important related issues in CO2 sequestration since it may have an effect of fault reactivation. Reactivation may, in turn, result in the leakage of CO2 into overlaying geological formations that contain groundwater aquifers or in triggering earthquakes in regions that had not previously experienced earthquakes. This work numerically simulates direct shear tests of reservoir rock analogs in various stages of alteration from permeation by CO2 over geologic timescales. Reservoir rock characteristics were assigned based on the Crystal Geyser site in Utah. Two different compositional end-members of the rock are used, related to unaltered and fully-altered materials. Frictional behavior of these end-member digital rocks is explored through granular mechanics modeling using the distinct element method (DEM). A linear contact model was applied to model the contact forces. A parametric study was conducted on the effect of confining stress and friction coefficient of walls on the model on the resulting predictions of friction coefficient. Confining stress was changed over the range of 10 to 50 MPa. The friction coefficient of the walls was also changed over the range of 0.2 to 0.8. There is direct effect of different friction coefficient of walls on the peak friction coefficient reservoir rock, but there is no clear effect of different friction coefficient of walls on the stable friction coefficient. The simulations on end-member behaviors demonstrated that there is no significant effect of CO2 sequestration-related mineral transformations on the shear behavior of reservoir rock for the particular mineral transformations noted here. Also, apparent is an inverse correlation between the normal stress and friction coefficient.