Using a well-to-well interplay during the CO2 huff-n-puff process for enhanced oil recovery in an inclined oil reservoir: Experiments, simulations, and pilot tests

• Published in: Frontiers in energy research Vol. 10
• Main Authors: Hao, Hongda, Hou, Jirui, Qu, Ming, Guo, Wenmin, Deng, Song, Liu, Huaizhu
• Format: Journal Article
• Language: English
• Published: Frontiers Media S.A 24.01.2023
• Subjects: CO2 huff-n-puff; enhanced oil recovery; inclined reservoir; interwell remaining oil; well-to-well interplay
• ISSN: 2296-598X; 2296-598X
• DOI: 10.3389/fenrg.2022.1002053

A well-to-well interplay of CO 2 huff-n-puff is proposed as a novel gas injection strategy for displacing interwell-remaining oil in a well pair in an inclined oil reservoir. The well-to-well interplay mechanisms for enhanced oil recovery (EOR) are first studied in the laboratory using a three-dimensional (3D) physical model. Different CO 2 injection schemes are designed according to different well locations, and the production performance including oil, water, and gas rates is used for the EOR evaluation. A sensitivity analysis of the well-to-well interplay is then studied using a numerical model, and geological, developmental and fluidic factors are considered in the simulations. The experimental results show that, when CO 2 is injected into a lower well, a higher well always benefits with an oil increment. Under the effects of gravity segregation and edge-water driving, the injected CO 2 at the lower position can move upward to a higher position, where a large proportion of crude oil remains between wells after natural edge-water flooding. Oil recovery from the well-to-well interplay is 2.30% higher than conventional CO 2 huff-n-puff in the laboratory. Numerical results show that CO 2 injection mass, stratigraphic dip, horizontal permeability, and interwell spacing are the factors that most influence the well-to-well interplay; an application criterion for the well-to-well interplay is then proposed based on the simulations. Pilot tests using the well-to-well interplay of CO 2 huff-n-puff have been widely applied in C2-1 Block, Jidong Oilfield, China, since 2010. A total of 2.27 × 10 4  m 3 crude oil was recovered to the end of 2018, and the oil/CO 2 exchange ratio was as high as 3.92. The well-to-well interplay not only effectively extracted the interwell-remaining oil but also achieved higher CO 2 utilization efficiency. The findings of this study can lead to a better understanding of the EOR mechanisms used in the well-to-well interplay during the CO 2 huff-n-puff process in an inclined oil reservoir.