Considering The Stress Changes Around The Borehole Reservoir - Wellbore Coupled Integrated Simulation Study

During the drilling and producing of oil/water wells, the multiphase percolation in reservoirs is closely associated with the flow in wellbores, and influences each other. Moreover, the formation pressure change causes the effective stress of rock and the pore volume change near wellbores as a result, the reservoir porosity and permeability will be redistributed. Therefore, it's necessary to synthetically study the coupling pressure system including the flow in wellbores and reservoirs and the change of rock stress near wellbores, so as to consider the system pressure transfer and loss in reason, and to provide reliable information for the decision-making of reservoir development.Based on studies of percolation in reservoirs, multiphase flow in wellbores and the stress distribution near wellbores, and using many kinds of subjects and methods, such as petroleum engineering, production engineering, rock mechanics, and computing mathematics, et al., this paper firstly established a new and rounded mathematics and numerical model coupling the multiphase flow in reservoirs and wellbores. This model can consider the multiphase flow in vertical/ slanted/horizontal well, many flow regimens of oil/water well, harmonizing calculations between reservoir and wellbores, and effects of the redistribution of rock stress near wellbores on reservoir percolation. Subsequently, a coupling reservoir-wellbores numerical simulation system (RWCS) according to the above model was successfully developed. This system has realized the true numerical reservoir simulation.Through the studies in this paper, the acquired achievements are as follows:1. Firstly established a new and rounded mathematics model coupling reservoir and wellbores, which can consider the redistribution of rock stress near wellbores.1) established a mathematics model of rock effective stress distribution near wellbores and a relationship between rock stress and permeability and porosity.2) established the production and pressure model under different flow regimen of oil/water wells, thereby realized the true well simulation and reservoir simulation.3) coupling model can compute the pressure drop in vertical / slanted/ horizontal wellbores by use of different experiential models; harmonize the calculation between reservoir and wellbores by selecting appropriate inflow performance equation.2. Established the numerical model coupling reservoir with wellbores and considering the redistribution of rock stress near wellbores by use of an associated method of the finite element and the finite difference.3. Successfully developed a multiphase flow numerical simulation system coupling reservoir-wellbores (RWCS) according to the above model.1) the RWCS realizes the multi-language development in a microcomputer, and consists of five subsystem: Picture Digitizer, Model Builder, Main Simulator, Plan Analyzer and 3D Visualizer.2) the strong functions of the RWCS enhanced the veracity of dynamic analysis, and reduced the working intension of reservoir numerical simulation.The tests and practical application of this model have proved that it is correct and reliable.