Experimental study on the improvement of micro-pore structure in medium-low maturity continental oil shale by temperature alteration

Pore structure is the main controlling factor for oil and gas reservoir storage and migration. Recent years, in-situ high-temperature modification of pore structure has become a common method to improve permeability and enhance shale oil and gas recovery efficiency. This study aims to investigate the expansion and variation patterns of micro-pores in medium-low maturity shale under different temperatures. The medium-low maturity shale samples from Heitianchi, Liangping District, Chongqing were selected for scanning electron microscopy (SEM) experiments and gas adsorption-desorption experiments to explore the optimal reservoir modification temperature and its effect. The changes in micro-pore structure and morphology of shale under different temperatures were qualitatively and quantitatively described. The results demonstrate that an optimal temperature threshold for shale pores between 250 and 300 °C exists, where the surface area and volume of shale pores undergo significant improvement. Furthermore, under high-temperature conditions, pore morphology becomes more irregular, greatly increasing pore opening and cracks, indicating that direct heating of shale reservoirs within the range of 250-300 °C can enhance fluidity of shale oil and connectivity within the reservoir space. It not only effectively improves reservoir permeability but also reduces costs while minimizing environmental pollution, providing some fundamental guidance for large-scale in-situ extraction of shale oil.