A Study on the Distribution of Remaining Oil in Daqing S, P, and G Oil Layers at Different Flooding Stages

Abstract

Extensive research has been conducted on remaining oil in the Daqing Oilfield during high water cuts’ late stage, but few studies have offered multi-level analyses from both macro and micro perspectives for remaining oil under varying formation conditions and displacement methods. This article focuses on the remaining oil in the S, P, and G reservoirs of Daqing Oilfield by employing the frozen section analysis method on the cores from the S, P, and G oil layers. The research identifies patterns among them, revealing that the Micro Remaining Oil types in these cores primarily include pore surface thin film, corner, throat, cluster, intergranular adsorption, and particle adsorption. Among these, intergranular adsorption contains the highest amount of remaining oil (the highest proportion reaches 60%) and serves as the main target for development potential. The overall distribution pattern of the Micro Remaining Oil in the S, P, and G oil layers shows that as flooding intensity increases, the amount of free-state remaining oil gradually decreases, while bound-state remaining oil gradually increases. The study also examines eight typical coring wells for macroscopic remaining oil, finding four main types in the reservoir: interlayer difference, interlayer loss, interlayer interference, and injection-production imperfect types. Among these, the injection-production imperfect type has the highest remaining oil content and is the primary target for development potential. Analyzing the reservoir utilization status and oil flooding efficiency reveals that as water flooding intensifies, the oil displacement efficiency of the oil layer gradually decreases, while the efficiency of oil layer displacement improves. Strongly flooded cores exhibit less free-state remaining oil than weakly flooded cores, making displacement more challenging. This study aims to provide a foundation and support for the development of remaining oil in the S, P, and G oil layers.