Reservoir characteristics and oil properties of a lacustrine shale system: Early Jurassic black shale from the Sichuan Basin, SW China

•Nanoscale clay mineral-related pores dominate the pore system of the Da’anzhai shale.•TOC content, kerogen type, clay mineral content, and porosity are key controlling factors for oil content in shales.•Real (S1-1/TOC) and maximum ((S1-1 + S1-2)/TOC) movable oil index derived from multistep pyrolysis can be used to evaluate oil mobility.•Oil mobility is mainly influenced by the thermal maturity, physical properties, mineral composition, and oil occurrence state.