Comprehensive Evaluation and Application of a Hybrid Gel System for Conformance Control in Shinan Reservoir

Abstract

After long-term production, most mature reservoirs have severe conformance issues, which are extremely difficult to solve by deploying solely gel systems. In this work, we developed a hybrid gel technology for the Shinan oil reservoir, which involves the sequential injection of in situ gel and microgel, with in situ gel aimed at plugging the primary high conductivity zones such as fractures and high permeability highly water-washed zones and microgel targeted at other highly water-washed zones that were not plugged by in situ gel. We systematically studied factors affecting the gelation time, thermal stability, and plugging performance of in situ gels and microgels. Results showed that shearing in the rock matrix is the key factor affecting the gelation behavior and gel strength. The plugging performance decreases as the permeability contrast increases. The core flooding test using artificial two-layer core showed that the stable water flooding pressure gradient after in situ gel treatment could be further increased by 0.25 MPa/m by tailing microgel. The field application of this new technology showed that the average water injection pressure was increased by 1.8 MPa, the daily liquid production was increased by 92.3 t, and the water cut was reduced by 6.5%.