Characterization Method and Application of Remaining Oil Dispersion Degree

Abstract

After decades of development, most oil fields have entered a period of high water cut or even extra high water cut in eastern China, and distribution of remaining oil is highly fragmented. Understanding and mastering the distribution of remaining oil is extremely important for reservoir development adjustment, and few researchers have studied the extent of remaining oil dispersion on the reservoir scale. This paper proposes a method to characterize degree of remaining oil dispersion (ROD) using the mean plaque area (MPS), plaque density (PD) and mean shape index (MSI), combined with the entropy weight method (EWM). The characterization method is evaluated by numerical simulation, and the ROD in the actual oil field is evaluated. The simulation results show that ROD curve in the typical life cycle of a reservoir development generally includes four stages: steady rise stage, rapid rise stage, fluctuating decline stage, and second steady rise stage. During the rapid rise stage, remaining oil is dispersed, PD increases, MPS decreases, and ROD increases; during the decline phase, remaining oil is produced in large quantities, PD decreases, and ROD drops. These two stages are main functional stages in which remaining oil is produced, and their changes can be used as indicators for monitoring the effectiveness of reservoir adjustment measures. The ROD curve can be used to determine the degree of dispersion of remaining oil in current reservoir, and can also be used to determine the effectiveness of adjustment measures. The characterization method of ROD proposed in this paper provides a new reference index for evaluating reservoir development status.