A new evaluation method of gel’s dynamic sealing characteristic in porous media

Abstract

Water shutoff through injection wells is one of the most important techniques used for water injection profile control and modification in severely heterogeneous reservoirs, aiming at stabilizing oil production. It has been widely reported that the effectiveness and efficiency of water shutoff using gel is mostly dependent on the gel dynamic sealing properties in the porous media. Firstly the gelation strength and gelation time of polymer gel were evaluated. Then, core flowing experiments were conducted before and after gelation in a 32 m long sand pack. In addition, water flooding core experiments were also carried out in a long core of 80 cm before and after injecting gel system to check the reliability of this evaluation method. The experimental results show that moderate-strength gel can be formed at 65 °C. According to the integrated evaluation of the plugging coefficient, plugging strength and water breakthrough time, the gel particles are capable of migrating to a distance of 7.47 m from the injection point of the 32 m long sand pack during the water injection process after gelation. Based on sands gelation status and effluent analyses, the effective migration distance of the gel particles is 4–14 m. Through the core flooding experiments using the 80 cm heterogeneous core, it is evidenced that the gel can be formed in the deep reservoir (40.63% of total length) with the plugging strength as high as 6.33 MPa/m, which leads to extra oil recovery of 10.55% of original oil in place (OOIP) by water flooding after gel treatment.