Conformance control by a microgel in a multi-layered heterogeneous reservoir during CO2 enhanced oil recovery process

Injecting CO2 into the underground for oil displacement and shortage is an important technique for carbon capture, utilization and storage (CCUS). One of the main problems during the CO2 injection is the channeling plugging. Finding an effective method for the gas channeling plugging is a critical issue in the CO2 EOR process. In this work, an acid-resistance microgel named dispersed particle gel (DPG) was characterized and its stability was tested in the CO2 environment. The microgel size selection strategies for the homogeneous and heterogeneous reservoirs were respectively investigated using the single core flooding and three parallel core flooding experiments. Moreover, the comparison of microgel alternate CO2 (MAC) injection and water alternate CO2 (WAC) injection in the dual core flooding experiments were presented for the investigation of the role of microgel on the conformance control in CO2 flooding process. The results have shown that the microgel featured with -NH and C-N groups can keep its morphology after aging 7 days in the CO2 environment. Where, the small microgel with unobstructed migration and large microgel with good plugging efficiency for the high permeability zone were respectively featured with the higher recovery factor in homogeneous and heterogeneous conditions, which indicate they are preferred used for the oil displacement and conformance control. Compared to WAC injection, MAC injection had a higher incremental recovery factor of 12.4%. It suggests the acid-resistance microgel would be a good candidate for the conformance control during CO2 flooding process. (C) 2022 The Chemical Industry and Engineering Society of China, and Chemical Industry Press Co., Ltd. All rights reserved.

Automated summary

This study investigated the stability of an acid-resistance microgel called dispersed particle gel (DPG) in a CO2 environment and its application in CO2 flooding process. The results showed that DPG with specific functional groups can maintain stability in a CO2 environment, and DPG of different sizes have different suitability for homogeneous and heterogeneous reservoirs, achieving good migration ability and plugging efficiency. Compared to water alternate CO2 injection, microgel alternate CO2 injection can increase the recovery factor, making it suitable for conformance control in CO2 flooding process.