THE EFFECT OF THERMAL CYCLING ON THE PERMEABILITY AND MECHANICAL PROPERTIES OF SHALE

Open Access
Author:
Schwartz, Brandon
Graduate Program:
Energy and Mineral Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
November 15, 2016
Committee Members:
  • Derek Elsworth, Thesis Advisor
  • Chris J Marone, Committee Member
  • Shimin Liu, Committee Member
Keywords:
  • Permeability
  • Bulk Modulus
  • Shale
  • Thermal Cycling
Abstract:
The feasibility and rate of recovery of natural gas from tight shale formations is controlled by matrix permeability and flow path length to the closest permeable conduit (fracture). The purpose of this study is to understand the evolution of transport (∂k) and mechanical (∂K) properties of shale due to applied static and cyclic thermal (∂T) stimuli. We report the evolution of permeability and bulk modulus in shales under static and cyclic thermal loading. Experiments were conducted on core samples under recreated in situ conditions. All experiments retained total stress and pore pressure constant to isolate the response of permeability and bulk modulus due to thermal stimuli, alone. Experiments were on both fractured and unfractured samples to understand the respective susceptibilities of fracture and matrix permeabilities to thermal loading. We show that before fracture coalescence permeability has a direct relationship to temperature and an inverse relationship to bulk modulus. Both permeability and bulk modulus show an hysteretic nonlinear response to thermal cycling. Permeability evolution in both fractured and unfractured samples is similar, although differences include the magnitude of permeability enhancement and the effect of matrix compaction on permeability. Deformation data suggest that thermal stress can reactivate primary consolidation. Based on experimental data, we propose a model that links permeability evolution as an inverse function of changes in bulk modulus.