Reservoir characteristics and influencing factors of multi-lithofacies shales in the Lianggaoshan Formation, Northeast Sichuan Basin

This study focuses on the shale of the Lianggaoshan Formation in the Northeast Sichuan Basin, aiming to analyze the pore structure characteristics and influencing factors of its lithofacies – critical for shale oil exploration, as the area has seen major shale oil and gas exploration breakthroughs. Fresh outcrop shale samples were collected in the field, followed by experiments including polarized-light microscope thin-section identification, X-ray diffraction, total organic carbon analysis, gas adsorption, high-pressure mercury intrusion, and scanning electron microscopy. Four lithofacies were classified. Results show the shale contains micropores, mesopores, and macropores; total organic carbon correlates positively with micropore/mesopore parameters but negatively with macropores, while quartz content shows the opposite. The Frenkel–Halsey–Hill fractal dimension correlates positively with total organic carbon, feldspar, and clay minerals, and negatively with quartz. This provides a key theoretical basis for local Lianggaoshan Formation shale oil exploration.