Abstract

Steam assisted gravity drainage (SAGD) is one of two commercial in situ recovery technologies (the other is cyclic steam stimulation, CSS) being deployed for bitumen recovery within the vast oilsands reserves in Northern Alberta, Canada. However, to ensure the safe operation of SAGD, caprock integrity has to be maintained. In the past, most of the research efforts have been devoted to reservoir geomechanical simulation studies of SAGD caprock integrity. Physical modeling studies are conducted to a lesser extent. This paper describes a newly developed testing program of SAGD caprock integrity using the 50g-ton beam centrifuge, the first of its kind in Western Canada, at Geotechnical Centrifuge Experimental Research Facility (GeoCERF) at University of Alberta. Initial studies have utilized over-consolidated Speswhite kaolin block samples to mimic the caprock in centrifuge models instead of using in-situ caprock material for the purpose of eliminating the influences of property variability. At 100g centrifuge spinning, a 20cm thick test material can simulate a caprock formation of 20m, while stress profile in the centrifuge model is still similar to that in the prototype. In order to fail the caprock at 100g, a custom-designed electromechanical device named Geomechanical Caprock Deflection Mechanism (GeoCDM) is successfully manufactured and commissioned. Image-based displacement measurement technique of Particle Image Velocimetry (PIV) is employed to measure the soil deformation.

1. INTRODUCTION

Steam Assisted Gravity Drainage (SAGD) is a widely used thermal recovery process for extracting bitumen from the oilsands reservoirs in Northern Alberta. Because of the continuous injection of high pressure and high temperature steam into the oilsands reservoir, the stress and strain fields in the reservoir and its surrounding formations are significantly altered, which may lead to the failure of the caprock overlying the reservoir. The 2006 Joslyn steam release incident has been a bitter lesson learnt from losing the caprock integrity [1]. Since then, tremendous efforts have been devoted to reservoir geomechanical simulation studies of SAGD caprock integrity. Physical modeling studies have been conducted to a lesser extent, as it is difficult to carry out physical modeling of prototypes at such a scale as SAGD projects.

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