Simulation of oil-based mud invasion in sandstone reservoir based on a large-sized formation model

By choosing a sectorial sandstone formation module as the large-sized formation model, and a multifunctional physical simulation system of drilling mud invasion as the platform, this study carries out long-term oil-based mud invasion experiments, summarizes the variation laws of the radial resistivity of formation module, the filtration rate and invasion depth of oil-based mud filtrate, obtains the characteristics of oil-based mud invasion under different reservoir physical properties, and finally realizes the numerical simulation of oil-based mud invasion in sandstone reservoir under formation conditions. The results show that the radial resistivity of formation module increases in turn during oil-based mud invasion, and its increase rate slows down with the increasing of radial depth. At the beginning of invasion, the filtration rate decreases rapidly, the increase rate of the cumulative filtrate volume slows down, and the invasion depth is shallow. After the invasion reaches a dynamic equilibrium state, the filtration rate tends to be stable, the cumulative filtrate volume increases linearly with time, and the increase rate of the invasion depth tends to be very slow. For the low porosity and low permeability sandstone reservoir, as compared with the high porosity and high permeability sandstone reservoir, the filtration rate and cumulative filtrate volume are greater, the invasion is faster and deeper, and the radial resistivity increases earlier and faster. © 2019, Editorial Office of ACTA PETROLEI SINICA. All right reserved.