Rock and Fluid Property Changes and Environmental Risks in Heavy Oil In-Situ Combustion

作者：Shibao Yuan, Zihan Ren, Yaoli Shi, Fengxiang Yang, Haiyan Jiang, Zhibing Shen, Jianbin Liu, Tianyue Li, Adilai Kuerban, Lehong Li · 发表于：Energy & Fuels · 年份：2025 · DOI：10.1021/acs.energyfuels.5c05428 · 研究领域：Petroleum Processing and Analysis、Hydrocarbon exploration and reservoir analysis、Enhanced Oil Recovery Techniques

During the in-situ combustion process for heavy oil recovery, reservoirs, minerals, and fluids are subjected to high temperatures, making it crucial to investigate the resulting secondary changes and potential environmental risks. This study focuses on thermally induced effects during in-situ combustion, analyzing the evolution of rock porosity, permeability, mineral composition, and particularly variations in produced fluid composition. A thermal-hydraulic-mechanical coupled numerical model was established to quantitatively evaluate the effects of high temperature and thermal stress on reservoir properties and fluid flow at the field scale. Additionally, risk points at different stages of the combustion process are identified, and corresponding mitigation measures are proposed. The results demonstrate that thermal stress induces pore-throat expansion and the generation of secondary cracks, especially above 450 °C. Furthermore, it triggers multiple mineral metamorphic processes at 550 °C, including the dissolution, breakage, dehydration, and transformation of feldspar. These combined effects enhance permeability by up to 9 times after in-situ combustion. Analysis of the produced fluids reveals a significant decrease by 2.5% in the content of resins and asphaltenes in the oil, accompanied by a reduction in the molecular weight of the crude oil. Conversely, the salinity and impurity contents in the produced water increase by approximately 1.73 times. The numerical model shows t...