Practical Approach to Caprock Analysis

Abstract

The issues of caprock integrity have been thrust into the forefront of consideration and regulation. There have been several documented steam and bitumen leaks to surface and recently the AER has placed a moratorium on the licensing of shallow thermal in-situ oilsand projects. They have also sent out a series of draft requirements. In the interim, the draft letters are a good indicator of future requirements.A brief description will be made of the main technical issues in determining caprock integrity. A detailed discussion will also be made of the 5 separate documents issued by the AER. A practical approach to deal with these technical and regulatory requirements will be outlined. The foundation of all of this analysis is a good understanding of the conditions in the ground. The paper will concentrate on core acquisition, storage, analysis and preservation from the drill site to the laboratory. This is the starting point for laboratory testing, MOP determination, geomechanical modelling and thermal reservoir simulation.Failure to properly quantify the geomechanical properties and in-situ stress can increase the potential for failure. This could end a project, tie up capital, produce environmental liabilities and risk public safety. Responsible development of thermal projects requires that caprock integrity be quantified. Geomechanical Processes in SAGDThere are numerous processes that occur in a SAGD operation, which affects the geomechanical response of caprock. Figure-1 illustrates the influence of the SAGD operation on the geomechanical processes in the subsurface and at the ground surface. Geological and mechanical properties of the strata also influence the geomechanical processes in a system.The main forces that will be discussed include:• Thermal expansion -which increases stresses in the heated zone.