Static Performance Evaluation of the Sealing System and Its Sealing Effect in CO2 Flooding

CCUS is an important technical means to achieve oil displacement and carbon sequestration in the oil and gas field. However, due to the influence of geological characteristics and fluid physical properties, CO2 flooding is easy to gas channeling, which seriously restricts the effect of enhanced oil recovery and carbon sequestration. Therefore, long-term channeling technology research is urgently needed. In order to meet the needs of channeling agent injection and long-term stability, three existing systems of CO2 response thickening fluid (R-A, R-B, R-C) and acid-resistant foam (F-A, F-B, F-C) were selected in the experiment, respectively evaluating and optimizing the strong response thickening fluid (R-A) and the strongest acid resistant foam (F-A) in CO2 environment. The core displacement device was constructed in the laboratory to study the channeling effect of F-A, R-A and their combination slug. The results show that the response of R-B and R-C is no chop in the CO2 environment (up to 2.5 mpa·s), while the maximum thickening of R-A is 496 mpa·s. The foaming volume (520 mL), defoaming half-life (122 min), and drainage half-life (9 min) of 0.30 vol% of F-A are the best acid resistant foam. The optimal displacement results of 0.30 vol% F-A and 1.50 vol% R-A show that compared with single system blocking channeling, the combined control channeling gas reduction rate is still as high as 94%, and the blocking channeling rate increases about 39.9–48.7%, and the blocking rate reaches 60.4%, which plays a strong plugging and conformance control effect. In this study, the system and control process suitable for CO2 flooding long-term channeling under the condition of meeting the injectivity are screened, which has certain reference significance for the current research on CO2 flooding and channeling technology in oil fields at home and abroad.