A Mechanical earth model for the weyburn CO₂ monitoring and storage project and its relevance to long-term performance assessment

The ultimate goal of performance assessment for geological storage is to determine the integrity of the reservoir and its bounding seals. The injection of CO₂ gives rise to a variety of coupled physical and chemical processes, which may affect the hydraulic integrity of caprocks and the transport properties within the reservoir. Likewise, when CO₂ is stored as a component of Enhanced Oil Recovery (EOR) projects, the initial depletion of the reservoir and all the influences associated with exploitation, production, and EOR processes may affect the integrity of bounding seals. To understand the evolution of the Weyburn system under EOR-CO₂ storage conditions, a mechanical earth model was developed over the stratigraphic column for the Weyburn system. A mechanical earth model is a logical compilation of relevant information about earth stresses and rock mechanical properties based on geomechanical studies and geological, geophysical, and reservoir engineering models. This chapter reviews the construction of the earth model from the project data and presents an example of its use in evaluating the effect of historical production and injection in Phase lA, as well as the scenario where pressures are modified to maximize CO₂ stored.