Study On The Sedimentary Microfacies And Predication Of Favorable Reservoir Of He-8 Segment Of Upper Palaeozoic In Sulige Area

In the west of Ordos Basin,the natural gas resources are abundant,which has large exploration potential and the natural gas exploration has made some progress.Based on predecessor's achievements,integrated use of detrital grain composition,debris composition,quartz cathodoluminescence characteristics,heavy mineral typomorphic characteristics and combination with microscopic petrology provenance analysis method,the results show that there are four provenance in study area,which are the northwest provenance,Yinshan provenance,the north Qinling provenance,the northcentral of Qilian and the west Qinling provenance in the southwest margin.Because of the supply of the terrigenous detrital material is more adequate and water power is stronger,distributary channel fast towards the lake and sediment filling quickly makes distributary channel frequent migration laterally.There is braid river delta sedimentary system of He8 member in study area,which is mainly composed of delta plain and delta front microfacies types are braided distributary channel,diara sedimentary,flood plain,underwater distributary channel and distributary bay deposit.The pore types of the sandstone of reservoir in study area comprised primary intergranular pores,intergranular corrosion pores,dissolution pores,micro-pores and cracks.The study of the reservoir diagenesis showed that the destructive diagenesis of the sandstone in study area mainly are compaction,cementation,secondary outgrowth cementation and filling of authigenic mineral.The compaction of sandstone was mainly middle to deep.The constructive diagenesis mainly comprised metasomatism,alteration,dissolution and rupture.The sand-rich region is in relation to diara,braided distributary channel and part of the development of underwater distributary channel.On account of the large thickness of sand body with coarse particle size and good physical properties,it is conducive to gas accumulation in the favorable reservoir and form the large area of gas bearing on the pattern in area.