Fracture Assessment From Well-Centered and Reservoir Scale Coupled Geomechanical Models

Abstract An integrated and multiscale analysis has been performed to ensure safe reinjection of formation water into a sandstone saline aquifer during the lifecycle of an onshore field. The study includes well centered models to evaluate the possibility of creation and propagation of hydraulic fractures, paying special attention to vertical fracture containment within the target zone. The hydraulic fracture models are fed by geomechanical models that provide estimations of stresses and rock mechanical properties, and which include lithological and stress contrasts that replicate the drilling experience of the two injection wells. A 3D reservoir scale coupled geomechanical and fluid-flow model has been generated for integrity analysis of the target and seal formations, and faults, also analyzing the effect that injection operations could have on surface uplift. The most critical assumptions are considered in the assessment, like lower than expected fracture gradient, higher than expected injection rates, and mechanical and fluid flow parameters that favor hydraulic fracture propagation. The analyzed cases show how eventual fractures would be confined in height, only propagating laterally with a tendency of stabilizing and without affecting the integrity of nearby wells. No other type of rock failure nor fault reactivation is observed anywhere in the model. Introduction Reinjection of formation water that has been extracted along with hydrocarbons must be performed in a secure and safe manner. Geomechanics analysis can help in predicting the effect of pore-pressure increase associated to injection operations on the deformation and failure of rock (in target formation and in surrounding formations) as well as on the reactivation of faults, being both relevant aspects in ensuring safe operations during the field lifecycle.