Study On The Characteristics Of The K₁g₁ Dolomite Reservoir In The Xiagou Formation Of Long 101 Block, Qingxi Oilfield, Jiuquan Basin

Affected by the thrust of the northern margin of Qilian Mountains,a large thrust fault zone has been formed in the southern part of the Qingxi Sag,which extends northwest.Guided by sedimentary petrology,development geology,petroleum geol-ogy and reservoir geology,this paper utilizes regional geological background,core analysis,logging,seismic and production dynamics.Based on the datas,the charac-teristics,distribution and fractures of K1g1 reservoir of Xiagou Formation in block Long 101 of Qingxi Oilfield,Qingxi Sag,Jiuquan Basin are studied by means of mul-ti-disciplinary and multi-means comprehensive research methods.Finally,the main controlling factors of dolomite reservoir development are analyzed from four aspects:lithology,sedimentary facies,fracture and tectonism.The main reservoir of Qingxi Oilfield is the Lower Cretaceous Xiagou Formation,with an average buried depth of about 3500m.According to the research,it is believed that the dolomite reservoirs in the Lower Ditch Group are mainly layered dolomitic mudstone,argillaceous dolomite and dolomite.The main layer is the dissolution space of dolomite and argillaceous dolomite reservoirs in the study area,which are mainly dissolution pores,intercrystalline pores and cracks.The core analysis porosity distri-bution interval is mainly concentrated in 1%to 7%,with an average of 4.7%.The carbonate sedimentary facies are mainly lacustrine sediments and delta deposits;on the basis of core,well logging and test analysis,The relationship between lithology,physical properties,hydrocarbon-bearing properties and electrical properties of dolo-mite reservoirs in the study area is analyzed.It is concluded that the fine-grained do-lomite in the study area has relatively good physical properties;the oil and gas display level is mainly oil trace;The distribution characteristics of dolomite,the thickness of reservoir and the characteristics of effective thickness provide strong evidence for the evaluation of reservoirs in the later stage.Finally,based on the research results of res-ervoir characteristics and the classification criteria of carbonate reservoirs,the study area The rock reservoir was comprehensively evaluated.A large number of coring and oil test data have confirmed that the tectonic fracture formed by the tectonic action is not only an important type of reservoir space,but also provides a favorable channel for the later diagenetic fluid and hydrocarbon migration,and improves the permeabil-ity and storage of the reservoir.Set performance plays an important role.Combined with the comprehensive comparison of cracks and reservoirs,the cracks were com-prehensively evaluatedThe development of dolomite reservoir is mainly controlled by lithology,sedi-mentary facies,diagenesis and tectonism.Reservoir development is closely related to lithology,reservoir porosity and permeability of different lithologies have obvious differences;sedimentary facies control the rock type and rock structure of reservoir,which is the basic condition for primary pore preservation and secondary pore devel-opment;tectonism is the key to the formation of high-quality reservoir.Therefore,sedimentation,diagenesis and structure are the main controlling factors in the study.