Abstract: Deep tight gas in fault depression basins, as a kind of unconventional resources, is seldom studied. With tight glutenite gas in Shahezi Formation of Xujiaweizi fault depression, the Songliao Basin, as an example, its accumulation conditions were analyzed by using seismic, geochemistry and reservoir testing data from the aspects of structure, sediment, source rock, reservoir and reservoir-forming assemblage. In addition, resource potential of tight glutenite gas was predicted in accordance with hydrocarbon-generation kinetic theories. The results show that majority parts of the slope areas contain gentle structures, and there are few faults penetrating the Shahezi Formation and remaining in continuous activities in later stages, suggesting structural environment for hydrocarbon accumulation. The widely-distributed coal-bed source rocks with high gas-generation intensity provide excellent gas-generating conditions. Glutenites of fan delta and braided-river delta facies develop extensively, and reservoir formations are tight with secondary high-porosity and high-permeability belts in certain parts, providing preservation conditions. Source rocks and tight reservoirs are overlapped in close contact and near source rocks, presenting desirable assemblages. Drilling data indicate that this area contain gas generally. Breakthroughs have been achieved in horizontal and vertical wells. In accordance with hydrocarbon-generation kinetic theories, total resources of tight gas are estimated to be about 2395?0⁸ m³.

Key words: tight glutenite gas, source rock, reservoir, accumulation condition, resource potential, deep formation, Shahezi Formation, Xujiaweizi fault depression