Quantitative Characterization Method for Remaining Oil Distribution in Heavy Oil After Multi-Cycle Steam Huff and Puff Based on CT Scanning

Abstract

Steam huff and puff is an important development method for heavy oil reservoirs. An accurate description of the remaining oil distribution after steam huff and puff is crucial for reservoir development. In this study, an experimental setup is used to simulate the multi-cycle steam huff and puff process more realistically. The occurrence state and distribution of remaining oil after different cycles of steam huff and puff are investigated. CT scanning is conducted after the first, fourth, and seventh cycles. Based on characterization parameters such as shape factor, contact ratio, and Euler number, the microscopic remaining oil is classified into network remaining oil, cluster remaining oil, film remaining oil, and isolated droplet remaining oil. The volume proportions of different types of remaining oil of different cycles of steam huff and puff are compared. The viscosity of the heavy oil used in the experiment is 560 mPa·s (25°C). The results indicate that as the number of cycles increases, the volume proportion of network remaining oil decreases, while the volume proportions of cluster, film, and isolated droplet remaining oil increase. From the first to the seventh cycle, the volume proportion of network remaining oil decreases by 34.11%, while the volume proportions of cluster, film, and isolated droplet remaining oil increase by 12.87%, 14.48%, and 6.76% respectively. The oil phase transitions from a continuous distribution to a discontinuous distribution. With an increase in the number of cycles, the water saturation increases, and the distribution of remaining oil becomes more dispersed. The results of this research guide the subsequent production of heavy oil.