Practical EOR Reservoir Numerical Simulation Technology for Large Scale Industrial Application of Chemical Flooding

Abstract

Summary Daqing Oilfield has successfully achieved the largest scale chemical flooding industrial application in the world, the annual oil production by chemical flooding has been more than 10 million tons for 20 years. The reservoir numerical simulation technology has played an important role to ensure better oil recovery effect for chemical flooding. With the continuous expansion of chemical flooding application scale in Daqing Oilfield, the reservoir numerical simulation for chemical flooding has ever encountered a series of new challenges need to be resolved, such as mathematical characterization of oil displacement process for chemical flooding, computation speed and simulation accuracy, etc. This paper focuses on the existing difficulties in the reservoir numerical simulation for chemical flooding, developing a series of novel techniques for chemical flooding numerical simulation suitable for large scale field application of chemical flooding. Firstly, based on the new cognation of chemical flooding theory in recent years, a chemical flooding mathematical model has been developed in order to simulate the complex oil recovery process mechanism of chemical flooding more accurately, the aspect of oil displacement mechanism description, in addition to the mobility control and capillary desaturation processes, but also adds oil displacement model for chemical flooding which includes: polymer elasticity improves microscopic oil displacement efficiency, the multiple molecular weight polymers process mechanism, compound synergistic effect of chemical flooding process with low surfactant concentration, multi-surfactant compound effect, chemical competitive adsorption, reservoir wettability altering, alkali corrosion and scaling. Secondly, based on operator splitting, potential characteristics, and multi-grid method, a fast solution scheme with high stability for complex mathematical model of chemical flooding has been developed, increasing the computation speed to a large extent. Thirdly, a series of numerical simulation parameters measuring experiments have been carried out, obtaining the accurate parameters for chemical flooding numerical simulation. Finally, based on Ensemble Kalman filter algorithm, a data assimilation method has been constructed, increasing numerical simulation history matching accuracy for chemical flooding. The established reservoir numerical simulation novel method for chemical flooding has been successfully applied to chemical flooding projects in Daqing Oilfield, and an application case of the chemical flooding project in Daqing Oilfield is given in this paper, the numerical simulation results for chemical flooding demonstrate that established reservoir numerical simulation technology increases both the computation speed and simulation accuracy.