Pore-scale investigation on compaction-dependent characteristics of granular packs and their impact on fluid distribution

Open Access
Author:
Torrealba, Victor Antonio
Graduate Program:
Energy and Mineral Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
March 31, 2014
Committee Members:
  • Zuleima T Karpyn, Thesis Advisor
Keywords:
  • porous media
  • compaction
  • multiphase fluids
  • pore-scale
  • drainage
  • imbibition
  • X-ray CT scanning
Abstract:
Understanding the coupled effect of rock compaction and changing stress conditions on multiphase flow in porous media is of fundamental importance for many subsurface activities including enhanced oil recovery, water drawdown from aquifers, and geologic carbon storage. Geomechanical properties of complex porous systems are dynamically linked to flow conditions, but their feedback relationship is often oversimplified due to the difficulty of representing pore-scale stress deformation and multiphase flow characteristics in high fidelity. In this work we performed pore-scale experiments of single- and multi-phase flow through bead packs at different confining pressure conditions to elucidate compaction-dependent characteristics of granular packs and their impact on fluid flow. A series of drainage and imbibition cycles was conducted on a water-wet soda-lime glass bead pack under varying confining stress conditions. Simultaneously, X-ray micro-CT was used to visualize and quantify the degree of compaction and fluid distribution corresponding with each stress condition and injection cycle. Micro-CT images were segmented using a gradient-based method to identify fluids (e.g. oil and water), and solid phase redistribution throughout the different experimental stages. Results demonstrate that the degree of compaction has a significant influence on phase trapping. It was found that an increase in confining pressure has a stabilizing effect on the displacing front during both drainage and imbibition. Alternatively, the compaction process was found to promote the disconnection of non-wetting blobs during imbibition, which in turn results into poor oil recovery by water flooding. In addition, the changes of both porosity and tortuosity were dampened as the confining pressure was increased. Finally, specific surface area was found to be more sensitive to stress conditions than porosity, which suggests that caution must be taken when considering scalability of these properties for practical modeling purposes.