Feasibility and recovery efficiency of in-situ shale oil conversion in fractured reservoirs via steam heating: Based on a coupled thermo-flow-chemical model

Abstract

Shale oil is a type of liquid hydrocarbon obtained through the pyrolysis of organic matter such as kerogen in oil shale reservoirs. Effective extraction of shale oil can significantly alleviate the pressure on oil supply. Among the various methods proposed for shale oil extraction, in-situ conversion of shale oil through high-temperature steam heating is a promising technique. This study employs a newly developed thermo-flow-chemical numerical simulator to establish a heterogeneous geological model and provides a detailed description of the evolution of different components within the shale oil reservoir during the in-situ conversion process. Additionally, the study thoroughly analyzes the role of high-permeability channels, such as fractures, in fluid transport and heat transfer during this process. In comparison with homogeneous reservoirs, fractures play a controlling role in the transport of steam. After injection, steam forms a preferential transport path between the heating well and the production well through the fractures. Subsequent injected steam will preferentially travel through this path, leading to faster heating of the reservoir. However, the uneven distribution of fractures may result in incomplete pyrolysis of the organic matter within the reservoir. Additionally, we found that the producing pressure and the steam injection rate significantly affect the pyrolysis of kerogen and the production of oil and gas. Both excessively low producing pressure and excessively high steam injection rate are detrimental to shale oil extraction. Based on these findings, this study aims to develop more rational heating strategies for reservoirs with different characteristics.