The study of formation conditions and accumulation mode of biogenetic mudstone gas reservoir in Sanhu Depression is essential for understanding the accumulation mechanisms and enrichment rules of such gas reservoirs. It holds significant theoretical and practical implications for guiding the exploration and development of Quaternary mudstone gas reservoirs. This research focuses on the Quaternary mudstone in the Sanhu Depression as the main subject. To determine the reservoir formation conditions and establish the accumulation mode

various experiments were conducted

including soluble organic carbon analysis

porosity determination

and chromatography-mass spectrometry analysis. The results reveal that the presence of high levels of soluble organic carbon and herbaceous humic organic matter

along with cold and dry conditions

create favorable conditions for the generation of biogenetic mudstone gas. The Quaternary formation in Sanhu Depression has the characteristics of high porosity and low permeability with numerous micro-nano pores that provide ample space for the occurrence of biogenetic gas. Gas flow primarily occurs through Fick diffusion and slip flow. The self-sealing effect of mudstone leads to the in-situ accumulation of biogenetic gas. However

during the late Himalayan tectonic movement

the gas containment of mudstone is disrupted. As a result of buoyancy

the gas migrates upward and accumulates in high parts of the mudstone

which are adjacent to the gas-generating center

and are superimposed longitudinally with sandstone biogenetic gas reservoirs.