Sedimentary Facies And Reservoir Characteristics Of Cambrian Loushanguan Group In Qijiang Area

Southeastern Sichuan Basin across Sichuan,Guizhou,Chongqing,is an important part of the oil and gas exploration field.In the area,Cambrian strata as the relatively new field of exploration and development,the many research of sedimentary facies,reservoir still have many shortcomings.In recent years exploration of oil and gas of the Cambrian strata in the southeast Sichuan has got some progress.Leshan-Longnvsi and surrounding area has achieved a better exploration result.More than 10 wells of Cambrian strata in the region have been drilling in oil and gas,gas production about 10×104 m3/d,having a good exploration potential.In the future Cambrian dolomite reservoir in the region will become the key development object.Cambrian Xixiangchi Formation period,Southeast Basin Loushanguan Group deposited the thick dolomite,up to hundreds of meters.Researching the Cambrian sedimentary facies and reservoir characteristics in the region,finding out the depositional model of Loushanguan Group,reasonablely dividing the facies,and studying on reservoir control factors,have very important sense to direct production.This paper,taking the Cambrian carbonate Loushanguan Group in Qijiang region in Southeast Sichuan Basin as the research object,basing on the multidisciplinary theory,such as Sequence Stratigraphy,Petroleum Geology and Reservoir Geology,combining the field section,well logging,core and seismic data,as well as the laboratory test data,analysis,etc.,researches the stratigraphic sequence,sedimentary facies and reservoir characteristics.In this paper,achievements and understanding are as follows:(1)Through the study of field outcrops,analysis of drilling and logging data,Loushanguan Group can be divided into five three-order sequences,all composed of transgressive and highstand system tract;And established the sequence framework,realizing the matching of sequence.(2)On the basis of lithology,drilling,well logging,and the sedimentary characteristics,the restricted platform,semi-restricted platform and open platform facies were divided.The restricted platform developed mainly supratidal zone,intertidal zone,subtidal zone,barrier bar and lagoon subfacies.And set up the northwest-southeast and northeast-southwest two lattice contrast figure of sedimentary facies.Completed the model of sedimentary facies and plane distribution of facies zone.(3)Using the chips,permeability and mercury penetration data,systematically analyzed the reservoir petrologic feature,reservoir space types,pore structure and diagenesis.Lithology is mainly is given priority to powder-crystal dolomite and particle dolomite.Reservoir developed intergranular pore,intergranular dissolved pore and fracture,belongs to poor porosity permeability reservoir.Diagenesis is mainly contained compaction,pressolution,cementation filling,rupture,dissolution and dolomitization,what's more,dolomization formation stage is between penecontemporaneous and buried period.(4)Cleared the reservoir characteristics and controlling factors of Loushanguan Group.Reservoir control factors in the study area are mainly the sedimentary facies,dissolution,tectonic movement and dolomitization.Effective reservoir mainly is dolomite,but in limestone or dolomitic limestone almost has no space.And in dolomite,especially in powder-crystalline dolomite,the intergranular hole is common developed.The pores formed by the dissolution is the main reservoir space.Complex fracture from complex tectonic setting of the area,plays a constructive role on reservoir development.