A New Simulation Method for More Accurate Prediction of Reservoir Rock Deformation

What is it about?

Oil, gas, and carbon storage projects depend on predicting not only how fluids move underground but also how the surrounding rocks deform over time. As fluids are produced or injected, the pressure inside the reservoir changes, causing the rock to compact, expand, or even undergo permanent deformation. These changes can influence production performance, damage wells, and affect the long-term safety of underground operations. Accurately predicting these coupled processes is therefore essential for making better engineering decisions. In this work, we developed a new computational framework that allows both fluid flow and rock deformation to be simulated using the same numerical method and the same flexible computational mesh. Unlike many conventional simulators, which often rely on different numerical techniques for flow and mechanics, our approach provides a unified formulation that naturally handles complex reservoir geometries while maintaining numerical accuracy. The new model is capable of representing several types of rock behavior. In addition to ordinary elastic deformation, where the rock returns to its original shape after loading, it also captures permanent plastic deformation and time-dependent viscoplastic deformation that occur in many geological materials. These advanced mechanical models make the simulator applicable to a broader range of reservoir engineering problems. To verify the methodology, the model was tested using five different case studies, including analytical benchmarks, comparisons with a commercial reservoir simulator widely used in the petroleum industry, water-alternating-gas injection, carbon dioxide storage, and a realistic Pre-Salt reservoir model. Across these examples, the proposed method produced results that closely matched analytical solutions and commercial software while demonstrating excellent performance on flexible unstructured grids. The study also showed that accurate solutions can often be obtained using coarser meshes, reducing computational cost without significantly sacrificing accuracy. The resulting framework provides researchers and engineers with a versatile tool for studying coupled fluid flow and geomechanical behavior in challenging subsurface applications, including hydrocarbon production, enhanced oil recovery, and geological carbon storage

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Photo by Mark Ashford on Unsplash

Photo by Mark Ashford on Unsplash

Why is it important?

This study is one of the first to extend the Element-based Finite Volume Method (EbFVM) into a unified framework capable of simultaneously modeling compositional reservoir flow together with elastic, elastoplastic, and viscoplastic geomechanical behavior on fully unstructured grids. Previous implementations of EbFVM were primarily limited to linear elasticity or black-oil reservoir models. By integrating advanced constitutive models—including Mohr-Coulomb, Drucker-Prager, and Perzyna viscoplasticity—directly into a compositional simulator, this work significantly expands the range of physical processes that can be represented within a single numerical formulation. The work is particularly timely because modern energy applications increasingly require reliable geomechanical simulations. Carbon capture and storage (CCS), enhanced oil recovery, geothermal energy, and production from complex reservoirs all depend on accurately predicting how rocks deform during fluid injection and production. At the same time, industry is moving toward more complex geological models that benefit from flexible unstructured meshes. This research addresses both challenges by providing a robust, computationally efficient framework capable of handling realistic reservoir geometries while maintaining high numerical accuracy.

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