The Research, Development And Application Of Reservoir Simulator Based On PEBI Grid

After long time development of Chinese reservoir, the well density is very large and the distribution of oil and water is more complex than before. The old reservoir's potential synergistic object turns to residual oil that is highly dispersed but relatively concentrated in local. Therefore, the technique of numerical simulation considering multi-layer and multi-pahse situation of reservoir has been researched in this dissertation, which is based on unstructured grid. By using the simulator that has been developed, the water injection process has been investigated. The main works of the dissertation are as follows:1. The numerical simulator based on unstructured grid:On the basis of black oil model, the discretization has been implemented by using FVM on unstructured grids (PEBI and Radial grid mainly). The problem of variable bubble points has been considered in this simulator. In the process of changing bubble points, four different situations have been proposed:gas exists, gas dissolved in oil, gas does not exist and gas released from oil. The method to simulate the process is variable substitution. When gas saturation is above zero, the variables are pressure, gas saturation and water saturation; when gas saturation equals zero, the variables are pressure, gas-oil ratio and water saturation. According to these four different situations and variables, the linearization of seepage equation has been analyzed. An in result, the discrete format has been obtained.2. According to various well type, the inner boundary well treatment methods have been proposed:After the introduction of Peaceman well treatment and Van Pollen well treatment, the inner boundary well treatment consiedering vertical well and horizontal well has been proposed. According to various well type and production control model, the implicit well treatment has been deduced by usint Darcy rule, including BHP, Flow Rate and VFP control model.3. The method of pressure calculation considering gravity has been given. The method is applicable to the pressure calculation in well case perforated and the initialization of numerical simuation. Under the hydrostatic hypothesis, the initial pressure, oil/gas/water saturation and gas-oil ratio can be obtained.4. The well treatment considering water injector has been build up to predict the process of water injection more precisely:According to the engineering of water injection, the selection of water separator greatly influences the water injection processes of oil field. To analyze the influences of water separator to bottom hole pressure(BHP) and injection rate in the injection process, a new well treatment model has been proposed on the basis of conventional inner boundary of well treatment. By this means, the response of BHP and flow rate in the process of water injection has been surveyed by the coupled solution of BHP, injection rate and reservoir fluids dynamics. The computational results indicated that the water injection can not either be regarded as constant pressure nor constant flow process. Through using different nozzles, simulations under same reservoir conditions showed that when initializing injection flow rate is constant, smaller nozzles have better smoothing effect on injection flow rate than larger nozzles. When the diameter of nozzle is constant, permeability is the main factor which will influence the response of injection flow rate and the oil-water saturation is the minor one.