Improved Gridding Technique for Coupling Geomechanics to Reservoir Flow

Abstract

Abstract The application of geomechanics in reservoir flow simulation has increased substantially since it was recognized that the modeling of geomechanical effects was necessary to predict important phenomena such as compaction, subsidence, wellbore failure, etc. However, its application is strongly limited due to the use of a one-grid system for both reservoir flow and geomechanics deformation. In the case of a large field-scale simulation, the use of a one-grid system gives rise to an extremely large number of gridblocks. On one hand, for an accurate modeling of fluid flow, the gridblocks need to be reasonably small around wells and sharp fronts. Yet, these small gridblocks may not be essential for geomechanics computations. On the other hand, accurate geomechanics calculations may require many gridblocks in the overburden, underburden and sideburden (country rock) that are not necessary for fluid flow. In this work, a separate-grid technique is combined with an iterative coupling method to resolve the above problem. In this separate-grid technique, the reservoir flow grid and the geomechanics grid are distinct in order to model efficiently both fluid flow phenomena and geomechanics deformations. A method to couple the two grid systems is described. The use of this grid coupling approach reduces the simulation run time substantially with results that are very close to the one-grid method. A series of examples illustrating the application of this two-grid concept and the corresponding run-time reduction are described.