Feasibility Study of Centrifuge Modeling of SAGD Caprock Integrity

  • Author / Creator
    Wu, Jingyu
  • The Joslyn steam release incident in 2006 has significantly influenced the approval process for steam assisted gravity drainage (SAGD) projects, which now require rigorous caprock integrity assessment to be conducted. In the past, most of the research efforts have been devoted to reservoir geomechanical simulation studies of caprock integrity. Physical modeling is conducted to a lesser extent, as it is difficult to carry out physical modeling of prototypes at such a scale as SAGD projects. Within the Geotechnical Centrifuge Experimental Research Facility (GeoCERF) at University of Alberta, research is ongoing to utilize the newly built 50g-ton beam centrifuge for physical modeling study of caprock failure mechanisms at high gravitational fields. The centrifuge model will be spun at 100g. According to the scaling law, a 20m thick caprock formation can be simulated using only 20cm thick test material, which makes scaled physical modeling of caprock failure possible. Prototype, reservoir geomechanical simulation and centrifuge modeling are closely integrated in this research. Caprock is deemed as homogeneous material without any pre-existing faults or weak planes. Thus, shear failure and tensile failure are the two major failure modes of caprock to be explored. In reservoir geomechanical simulations, caprock behaviour is described using the elasto-perfectly plastic model with Mohr-Coulomb failure criterion. The development of shearing zones in caprock is analyzed along with displacement profile evolutions at the base of caprock. According to parametric analysis, caprock shearing failure is commonly observed for caprock with different mechanical properties and the shearing patterns of caprock at failure are the same with the vertical displacement at the base of caprock being the main driving force regardless of material property differences. In addition, the vertical displacement profiles at caprock shearing failure also share the same characteristics. A custom-designed electromechanical device named Geomechanical Caprock Deflection Mechanism (GeoCDM) was successfully built and commissioned within GeoCERF to fail the caprock at 100g. In this research, over-consolidated Speswhite kaolin with consistent properties is employed to mimic the caprock in the centrifuge models for the purpose of eliminating the influences of property variability of in-situ materials. Consolidated-drained triaxial tests are conducted on samples cored from the kaolin block and the test results reveal that there are significant property differences between the caprock shale and the over-consolidated Speswhite kaolin in terms of material stiffness, strength and dilation behaviour after shearing. This research is focused on the feasibility study of centrifuge modeling of caprock integrity; however, for future studies, creating synthetic materials with close properties to caprock shale should be a research focus. Through an image-based displacement measurement technique of particle image velocimetry (PIV), the deformation of the kaolin block can be directly captured. Two Kulite miniature pore pressure transducers are installed inside the overconsolidated Speswhite kaolin block for observation of the internal pore pressure changes and an external pore pressure transducer is connected to the base of the kaolin block. Mariotte Bottle is employed to maintain the hydrostatic pressure inside the centrifuge model. Two preliminary tests were conducted to test the GeoCDM setup. Pore pressure transducers are proven to be working well within the GeoCDM setup and the PIV system can effectively track the soil deformation during centrifuge spinning. However, the PIV analysis results had been compromised due to the faulty hydro-mechanical sealing at the base of the kaolin block, which are now being modified for future tests. For future studies, the results of the centrifuge testing should be compared to those of numerical simulations to verify and modify the numerical tools for SAGD caprock integrity study.

  • Subjects / Keywords
  • Graduation date
    Spring 2016
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.