Experimental Study on In-Situ Combustion and Pyrolysis Characteristics of Low-Mature Shale -- A Case Study of the Songliao Basin

Low-mature shale (Ro = 0.5% ~ 1.0%) is an important strategic alternative in China’s oil and gas resource replenishment and production enhancement. In situ conversion technology is considered the key to efficient development. As one of the main methods of in situ conversion, in situ combustion heating technology has advantages such as low cost and high thermal efficiency. However, its combustion characteristics and pyrolysis mechanism in low-mature shale are not yet clear. This study focuses on low-mature shale from the Songliao Basin, using thermogravimetric analysis (TG), total organic carbon (TOC) testing, and one-dimensional physical simulation experiments to systematically explore its in situ combustion and pyrolysis behavior. The results show that the pyrolysis process of low-mature shale can be divided into three stages: low-temperature volatilization (<250°C), organic matter pyrolysis (250-550°C), and inorganic mineral decomposition (>550°C). The optimal temperature range for in situ combustion modification is between 450 and 500°C, where the organic matter pyrolysis conversion rate exceeds 80%, and the produced oil exhibits significant lightening characteristics. The research findings provide important theoretical support for the optimization and field application of in situ combustion technology for low-mature shale and are of great significance for promoting the sustainable development of shale oil resources in China.