Reservoir Characteristics And Comprehensive Evaluation Of He1 Member Of J72 Well Area In Hangjinqi, Northern Ordos Basin

On the basis of previous studies,this paper takes the reservoir of the Lower Shihezi Formation in J72 well area of Hangjinqi area in the Ordos Basin as the research object.According to the basic geological characteristics and combined with logging,seismic and test analysis data of the study area,the study of sedimentary facies distribution characteristics,reservoir characteristics and reservoir logging in the study area are systematically carried out from both macroscopic and microscopic aspects by using the multidisciplinary knowledges of geology,well logging,seismology and so on.The reservoir classification evaluation and the reserve calculation are finally carried out.In the study of the sedimentary facies and sand bodies plane distribution,it is considered that the Lower Shihezi Formation in the study area is a set of alluvial plain-braided river sedimentary system dominated by coarse clastic deposits.The sedimentary microfacies of the He 1 Member of the study area include lag deposit,channel bar,channel filling and floodplain.Among them,the effective reservoirs are mainly developed in lag deposit,channel bar,channel filling sedimentary microfacies.The longitudinal superposition model of sand body can be divided into scouring cutting sand body,scouring contact sand body and isolated sand body.Among them,scouring cutting sand body is an ideal place for oil and gas storage.The main distribution direction of sand body in He 1 Member is north-south direction,which is composed of two main channels superimposed and connected.In the study of the basic characteristics of the reservoir,the lithology of the reservoir rock in the He 1 Member of the Lower Shihezi Formation in J72 well area is mainly coarse-grained cuttings sandstone,and the skeleton particles include quartz,cuttings and feldspar,in which the content of quartz particles is high.The main pore types of reservoir rocks are intergranular dissolved pores and intergranular residual pores,followed by intragranular dissolved pores and intercrystalline micropores,and the main diagenesis is compaction,cementation,dissolution and so on.The main diagenesis includes compaction,cementation,dissolution and so on.In the study of the well logging of reservoir,the relationships between the “four properties”(the lithology,the physical property,the electrical property,and the gas-bearing property)of sandstone reservoir in the study area were found out,which accorded with the basic characteristics that the physical property is controlled by lithology and the gas-bearing property is controlled by physical property.Then,the calculation models of the porosity,the permeability,the shale content and the gas saturation were established.The average original gas saturation was calculated to be 55%,and the average effective thickness was calculated to be 15.5 m.Comprehensive analysis shows that the main controlling factors of reservoir development and physical property are sedimentary microfacies,clastic particle composition and size,and diagenesis.Among them,sedimentary microfacies control the scale and physical properties of the reservoir;particle size and clastic components control the physical properties of the reservoir microscopically;diagenesis is the key factor to determine the physical properties of the reservoir.Finally,according to the study of reservoir sedimentary facies,reservoir physical properties,pore structure parameters and reservoir well logging research,the reservoir in He 1 Member of the study area is divided into three types,I,II and III from good to bad,and the geological reserves were calculated.