Aiming at the subtle gas reservoirs characteristic of low pore, low permeability, low abundance and large area's distribution of the upper Paleozoic in Ordos basin, in the way of studying typical gas reservoirs, in the clue of the gas migration and on the emphasis of high permeability reservoir generation and accumulation regulation, the paper is based on the existing research data , combined with the new theory and progress of the sedimentology, fluid chemistry, petroleum geology, etc, and analyzes systema...