The Grain Beach Distribution Of Qixia Formation In Middle-Wetern Sichuan Basin And Its Affect On Reservior

This paper with carbonate sedimentary,reservoir geology and log interpretation as guide,samples were collected and observed,while log and rock core data was used to indicate the relationship between grain beaches and reservoir.Several conclusions are obtained:(1)Lower Permian strata is divided into SQ1,SQ2,SQ3 orderly.Qixia belongs to SQ1,SQ1 can be divided into 2 parts: the transgressive system tractand(TST,QI 1st member),high system tract(HST,QI 2nd member.).Qixia formation in Lower Permian strata mainly consists of marine carbonate,while the environment is gentle incline carbonate sedimentary.The facies include inside gentle slope,middle gentle slope,outside gentle slope and basin-gentle slope.(2)Grain beach is mainly composed of biodetritus beach while rocks consist of Leopard print dolomitic limestone,micrite limestone,augen limestone and grain dolomite.Compared to Qi 1st member,grain beach can be easily found in Qi 2nd,which is continuous and thick.In this study,the range of grain beach in western is larger than middle Sichuan basin.Besides,it is under control of sea-level change and palaeo-geomorphology,where high frequency sealevel changes and high level of palaeo-geomorphology is helpful to the growth of grain beach.(3)Reserving spaces in reservoir mainly including intercrystal pores,intercrystal solution pores,and fractures etc.while the reservoir includes tow types : pore-fracture and porous-fracture.That can be impacted on sedimentation,tectonism,dolomitization.The reservoirs in the region of Jiange-Ya'an and Moxi-Shehong promise a bright prospect and log arrangement in the basin exploration.