RELATIONSHIP BETWEEN SEDIMENTARY ENVIRONMENT AND HIGH QUALITY RESERVOIRS OF CARBONIFEROUS BIOCLASTIC LIMESTONE MEMBER,WEST OF TARIM BASIN

Commencing from sedimentation,according to core,cast liquid photo,scan electron microscope etc.,combining the geology setting in the area,this study thinks that the high quality reservoirs of Carboniferous bioclastic limestone member in the western Maigaiti slope is silt crystal dolomite and clay-silt crystal dolomite;and the pore space is mostly pores(intercrystalline pore,intercrystalline emposieu,and birdeye pore) and tectonic dissolution fractures;the pore structure is chick flexure and well-sorted,with drainage pressure less than 0.5 MPa,and most pore throats of 1.5~20 μm,and with average pore throats more than 0.5 μm,most pore throats 7 μm;and the porosity is 8~29.6% with the average of 10.4%,permeability is(0.1~68.4)×10-3 μm2 with the average of 2.6×10-3 μm2,the reservoirs are of medium porosity and medium permeability to high porosity and medium permeability.Epilittoral zone dolomite of evaporation tableland and eulittoral zone limy dolomite are the primary factors controlling the development of the high quality reservoirs,and dolomitization,air fresh water dissolution,and tectonic fractures and hydrocarbon infusion of late Hercynian play the most important constructive roles in the development,connection and preservation of pores.Vertically,the high quality reservoirs are controlled by depositional setting and mostly developed in evaporation tableland on the upper and top of the bioclastic limestone member,with the thickness of 1~5 m;horizontally,they are controlled by the Qunkuqiake palaeohigh of late Early Carboniferous,and along the palaeohigh are not only favorable diagenetic facies(syngenetic dolomitization,air fresh water dissolution) of good-quality reservoir,but also important target areas for exploration.