A new gas-accumulation theory of tight sandstone gas accumulationin Turpan-Hami Basin-proximal-generation and proximal-storage type and self-generation and self-storage type

The Turpan-Hami basin is a typical basin of Diwa-type sediments in the Jurassic Shuixigou Group. The Shuixigou Group is composed of structural movement type light to black gray,poorly sorted,poorly rounded,amalgamated,fine-to coarse-grained massive grawach sandstone and fine conglomerate rock. The coal,carbonic mudstone and dark gray-black mudstone is widely developed. The objectives of this article are to document three gas-accumulation models: “proximal-generation and proximal-storage”type,“self-generation and self-storage” type and “composite type”. The gas trap of “proximal-generation and proximal-storage” type is explained to that the gas-bearing sandstone and conglomerate rock is directly contacted with coal and consequently,the natural gas formed by coal could be easily charged into the sandstone and\\or conglomerate rock overlain on the coal; The gas trap of the "self-generation and self-storage" type is explained to that the gas-bearing sandstone and conglomerate rock has more carbonic debris and consequently,the carbonic debris could directly discharge natural gas into the sandstone and\\or conglomerate rock; And the “composite-type gas” trap is that one that has the gas-accumulation features of the above two types.Tight sandstone gas reservoir in the study area controlled by source reservoir matching of three-dimensional space in the source storage configuration accumulation time and structural trap formation,possessing “the source-reservoir-trap-hidden” perfect correspondence relationship.In the same sedimentary system,the accumulation material system transported and accumulated through the mechanism of hydrocarbon generation and expulsion by near generation and near reservoir and short distance migration. between the accumulation of material system born under the same sedimentary system through nearly close to store raw under thereservoiring mechanism of hydrocarbon expulsion and short distance migration accumulation. As a main accumulation mechanism,the “proximal-generation and proximal-storage” type developed well in flood-fan-well-developed sediment units in the north piedmont belt,which have relatively good physical properties and sometimes correspond wonderfully with coal seam thickness; whereas the “self-generation and self-storage” type is also widely distributed in those sedimentary unstable splay areas where the flood-fan-well-developed sediment units,it is a kind of supplementary accumulation mechanism; Otherwise,there is still another gas-accumulation model that is formed by overlaying of the above two gas-accumulation models. These three natural gas accumulation mechanisms are decided by the structure-sediments features of Diwa-active-type and reveals that Diwa-type gas trap has itself features of the gas-accumulation that platform-type gas trap does not have.