Experimental Study on Enhanced Oil Recovery of Adaptive System after Polymer Flooding

Abstract

After polymer flooding in Daqing Oilfield, the heterogeneity of the reservoir is enhanced, leading to the development of the dominant percolation channels, a significant issue with inefficient circulation, a substantial amount of displacement agents, and elevated cost. In order to further improve oil recovery, an adaptive oil displacement system (ASP-PPG) was proposed by combining preformed particle gel (PPG) with an alkali-surfactant-polymer system (ASP). This comprehensive study aims to assess the effectiveness of the adaptive oil displacement system (ASP-PPG) in improving the recovery efficiency of heterogeneous reservoirs after polymer flooding. The evaluation encompasses various critical aspects, including static performance tests, flow experiments, microscopic experiments, profile control experiments, and flooding experiments conducted on a four-layer heterogeneous physical model. The experimental results show that the adaptive system has robust stability, enhanced mobility, effective plugging capability, and profile improvement capability. Notably, the system demonstrates the remarkable ability to successfully pass through the core and effectively block the large pores, resulting in an 18.4% recovery incremental after polymer flooding. This improvement is reflected in the reduced oil saturation values in the ultra-high permeability, high permeability, medium, and low permeability layers, which are 5.09%, 7.01%, 13.81%, and 15.45%, respectively. The adaptive system effectively recovered the remaining oil in the low and medium permeability layers, providing a promising approach for improving the recovery factors under challenging reservoir conditions.

Microscopic Remaining Oil Distribution Regularity and Enhanced Oil Recovery Methods after Polymer Flooding

“…There are only a few reports about the quantitative distribution of the remaining oil after polymer flooding. At present, there are a lot of research studies on methods and mechanisms of enhancing oil recovery after polymer flooding, such as surfactant flooding, surfactant–polymer flooding, alkaline-surfactant–polymer flooding, foam flooding, high-concentration polymer flooding, precross-link gel particle agent, heterogeneous phase composite system, modified cationic starch, adaptive system, microbial enhanced oil recovery, etc. − However, their studies lack integration with field tests correspondingly; therefore, it is incomparable due to different research conditions. The key issue lies in the absence of a systematic study on how to effectively activate and coalesce the remaining oil using chemical flooding methods after polymer flooding.…”