Modeling Improved Recovery Methods in an Unstructured Grid Simulator

摘要

Many improved recovery processes involve injection of a fluid whose properties are different than water. The fluidhydrocarbon- rock interactions lead to improved recovery. An example of an improved recovery process is polymer flooding. In this method, polymer, a water-soluble chemical, is added to improve the phase mobility ratio, which leads to improved sweep efficiency. This paper describes the modeling of some improved oil recovery processes using tracers in an unstructured grid simulator. The flow of chemicals, such as polymers, is modeled as the flow of a negligible tracer. Depending on the process, the tracer can flow either in the oil phase, the water phase, or both. Negligible tracers can also be used to model the effect of salinity on improving oil recovery for processes such as enhanced waterflooding. Another application of the tracer approach is to model single-well chemical tracer tests, which are used to determine the residual oil saturation before and after applying an improved recovery method. Other phenomena that can be modeled using this approach include mixing oils of different API gravity, mixing of waters with different salinities and vaporization of oil in a black-oil model. A major advantage of using tracers to model improved oil recovery processes is the decoupling of the tracer equations from the other component equations and solving the equations in a sequential form. This paper will also describe the system of equations, and the numerical methods used to solve the system. Several numerical simulations of the recovery processes mentioned earlier are described in this paper to demonstrate the application of modeling improved recovery processes through tracers