Abstract: Based on the studies of favorable geological conditions and key control factors of tight sandstone gas reservoirs in the piedmont in northern Tuha basin, it is suggested that these reservoirs are characterized by the same source rocks, self generation and self reservoir. The coal measure strata of Shuixigou group of Middle-Lower Jurassic are a set of quality source rocks and the dominant contributors to natural gas enrichment in the studied area. In the sedimentary period of Shuixigou group, the source materials supplied from the piedmont zone was abundant in the north, so underwater channel sand bodies developed at front of braided river delta, becoming the main site of the tight sandstone gas accumulation. In structural highs, fractures and fissures commonly occurred under the strong folded process, raising the percolation capability of the sand bodies; while in the flat slope area, the following tectonic movement was faint and favorable to large-scale original tight sandstone gas accumulation. And the source rocks of Shuixigou group entered into great amount of gas-generating stages in Neogene and Quaternary period, characterized by late gas accumulation, being favorable to preservation of the tight sandstone gas reservoirs.

Key words: Tuha basin, piedmont, tight sandstone gas, source rock, control factor, Shuixigou group