The Numerical Simulation Study Of Viscoelastic Polymer Displacement

At present, Polymer displacement has been widely applied in oilfield, and the economic benefit is good. The mechanism of polymer flooding has been acknowledged clearly after many years of lab test and field application. At the same time, polymer flooding numerical simulation technique is becoming mature. But the physical and chemical behaviors of polymer solution in the multi-pore media are not well described in the current polymer flooding numerical simulation software, for example, the viscoelasticity of polymer solution. According to the acknowledgement of polymer flooding microscopic mechanism and the analysis of application in oilfield, current mathematic model need to be improved in following aspects: The effects of three viscosities, bulk viscosity, extensional viscosity and interfacial viscosity, on polymer displacement effect, especially the viscoelasticity of polymer solution, dead end pore effect and creep effect when polymer solution passing the multi-pore media should be improved when we do the mechanism analysis, mathematic-physical description and software developing etc. Demonstrating on polymer solution can improve the mobility ratio, enlarge the sweep volume in macroscopic aspect and can enhance the sweep effect by its viscoelasticity in microscopic aspect, the viscoelastic polymer flooding mathematic model is built. It considers the polymer solution rheology and physical-chemical effects in the multi-pore media. The extensional viscosity when polymer solution passing the size-varing pores is considered into Darcy viscosity, rebuilding the effective viscosity model in the Darcy Law. By limited difference method, two dimensional, two phase polymer flooding numerical model is built. Then the model is solved by IMPES method, and the dynamic indexes in every oil layer, for example, the injection and production in every layer are calculated using dynamic division method. Using the polymer displacement numerical simulation software researched, polymer solutions of different concentrations and molecule weights are studied in west party of Middle block in Daqing Oilfield. By comparing forecasting dynamic index results, the best polymer solution concentration and molecule weight are chosen.