Relationship Between Tectonic, Sedimentation Characteristics And Distribution Of Gas Hydrate In Muli Coalfield Of Qilian Mountain, China

As a new emerging potential alternative sources of energy in 21stcentury, gashydrate (GH) has been studied widly on gas hydrate occurrence, lithology particle size,porosity, permeability of sediment bearing GH and the relation between gas hydratereservoir and thickness of permafrost layer in permafrost regions, previously. Withfurther research, scientists have realized the importance of tectonic activities andsedimentation controlling to gas hydrate distribution, recently. However, the researchstill remain rather weak.In this article, the effect of tectonic activities and sedimentation on gas hydrate isfirst studied on gas hydrate exploration of permafrost area in China, based on thesystematic and detailed stratum description of five cores bearing gas hydrate, andcomprehensive analysis of particle size, minerals, elements, fault fracture zone andpermafrost properties. Listed below are several results and acknowledgements whichare acquired:(1) With cores analysing, faults and broken zones identifying, three results wasobtained: (a) gas hydrate reservoir are principally controlled by regional main faultswhich are flow conduits for deep gas source; (b) other small faults and broken zonesprovide fluids partly and storage space for gas hydrate; (c) the source of gas mainlyconsists of deeper thermogenic gas.(2) The stratigraphic characteristics and special ditribution of stratigraphic unitsdistribution are clarified. Meanwhile, the sedimentary environment was analyzed.Two results was obtained: (a) gas hydrate is mainly existed in Jiangcang Formation(J2j2), where the depositional environment is lake. It is suggested that JiangcangFormation (J2j2) may have some controlling effect on hydrate reservoir (faciescontrolling); (b) the main particle size fraction bearing gas hydrate is different invaried sedimentation. And local coarse sediments provide beneficial storage space forgas hydrate.(3) Gas hydrate reservoir, found in the permafrost regions of Qilian Mountain, isnot only controlled by permafrost thickness, but also related with permafrost lithology,such as particularly coal-bearing and low permeability stratum in DK-2 and DK-3exploration area being beneficial"craprock".(4) With core profile of integration and contrasting with lithology, sedimentary facies and faults, We get some new identification marks of private formationboundaries of the middle Jurassic.(5) Based on analysis and compared with permafrost regions bearing gas hydrate inCanada, we summarize the special aspects of Qilian Mountain gas hydrate strata,including sorts of permafrost, permafrost thickness, permafrost lithology, gas hydrateoccurrence and sedimentary faces. We systematically acquire structural featurescontrol function on gas hydrate. It firstly provides new acknowledgements ofstratigraphic and sedimentary environment for gas hydrate exploration, in addition, itprovides new reference materials for coal geological exploration.