Numerical Modeling and Simulation of Mineral Dissolution in Fractured Carbonate Formation during Waterflooding Processes
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Carbonate formation usually features multi-scale fractures, cavities, and even caves residing in carbonate rocks. During a water/chemical flooding process, calcite and dolomite of carbonate rocks can be involved in various chemical reactions with the injecting fluids, which may lead to the evolution of the fracture system through dissolution process. Due to the mineral dissolution, the pre-existing natural fractures may widen and grow into large-scale wormholes and caves. Such development of natural fracture system may eventually lead to the formation of large-scale well-connected void space features that cause early breakthrough, unwanted production, and low bottom-hole pressure increase. Consequently, it is essential to develop a numerical model that can accurately describe such dynamic behavior of natural fracture system during water/chemical flooding processes in carbonate reservoirs for production forecasting and optimization. In this research, we have developed a mathematical model that combines Stokes-Brinkman and reactive-transport equations to describe the coupled processes of fluid flow, solute transport, and chemical reaction during waterflooding in fractured carbonate reservoirs. Numerical experiments have been performed on sensitivity studies using the proposed numerical solution procedure. The preliminary numerical results demonstrate that the fracture partition and spacing, flow velocity and reaction rate are the dominant factors on the fracture growth and evolution.