This paper is the result of oil and gas geological survey engineering.

Objective The Lower Carboniferous Luzhai Formation in the Central Guangxi (Guizhong) Depression exhibits significant shale gas resource potential and has recently witnessed breakthroughs in shale gas exploration. However, systematic research on its hydrocarbon generation potential and organic-inorganic pore structure characteristics is still lacking.

Methods This study focuses on the Sub-member 1 of the Luzhai Formation, based on a systematic classification of shale lithofacies types, the hydrocarbon generation potential and organic-inorganic pore structure of different lithofacies were quantitatively characterized, using methods including rock pyrolysis analysis, scanning electron microscopy (SEM) pore extraction and quantitative identification, nitrogen/carbon dioxide adsorption, and high-pressure mercury intrusion (MIP). This clarified the types of high-quality shale reservoirs in the Luzhai Formation.

Results The results indicate that the organic-rich siliceous shale lithofacies within the Luzhai Formation possesses good hydrocarbon generation potential, followed by the organic-bearing siliceous shale lithofacies. The reservoir space of the shale is dominated by micropores and mesopores, with pore types mainly comprising organic pores, intergranular pores, intragranular pores, and dissolution pores. Inorganic pores are the primary contributors to the pore space in the Luzhai Formation shale reservoirs. The organic-rich siliceous shale, developing numerous inorganic pores, micro-fractures, and some organic pores, exhibits the optimal storage capacity. The organic-bearing siliceous shale, with well-developed inorganic pores and a small number of organic pores, shows strong storage potential. In contrast, the organic-bearing calcareous shale and organic-bearing siliceous mixed shale have poorer pore connectivity and relatively lower storage capacity.

Conclusion Comprehensive analysis suggests that the organic-rich siliceous shale in the Luzhai Formation of the Central Guangxi Depression has high hydrocarbon generation potential and good storage capacity, making it the most favorable reservoir lithofacies type and the preferred target for shale gas exploration and development. These results provide theoretical support for the efficient exploration and development of shale gas in the Luzhai Formation within the Central Guangxi Depression.