SUMMARY: In general, geomechanical works compare evolving in-situ stress conditions with rock’s mechanical strength. Therefore, a basic geomechanical work program consists of defining the original in-situ stress condition, characterizing the rock structure and deformation/strength properties and finally, simulating the dynamical stress conditions after an engineering disturbance is introduced to rock formations which has otherwise reached equilibrium in the geological history.
In many situations, heavy oil production takes place in relatively shallow, weakly- or un-consolidated and/or geologically young rock formations. In-situ stress measurements in the field and laboratory tests on the core samples in these unique situations require special attention to principles and details. Moreover, heavy oil production often requires stimulation by injecting stimulating materials which may be at high pressures and/or high temperatures. Nonlinear coupling between the thermo-hydro-mechanical (THM) mechanisms become significant and must be adequately accounted for. All these unique challenges demand special QC/QA measures in carrying out the geomechanical works. This is the focus of the present paper. These measures are derived from experience in over 1,000 projects/tests and also after a peer review of relevant published works in the industry. Details to be covered include: use of multiple interpretation methods, real-time analysis and openhole in a mini-frac test; use of whole cores, drained condition, slow strain rates and/or heating rates in laboratory tests. It is hoped that this paper will provide a common guidance for the service providers in carrying out their geomechanical works or for the operators in managing similar projects.
Geomechanics has become increasingly important in heavy oil development. It is both a necessity to protect reservoir containment integrity and an opportunity to enhance reservoir production. Heavy oil development requires stimulation in order to achieve a high reservoir recovery factor. The stimulation is carried out by injecting steam and other stimulating materials into the reservoir. The pressure and/or temperature disturbance to the reservoir causes its deformation and impacts the caprock above the reservoir.