Reservoir Characteristics & Comprehensive Evaluation Of Chang 4+5 Reservoir In HJS Area

The HJS area is located in the Midwest of Ordos basin,and the Chang 4+5 oil reservoir group is an important section of oil and gas exploration in the area.Some studies have been done and made certain achievements,but the understanding of sedimentary facies and reservoir characteristics is not clear.In addition,the reservoirs are low porosity and low permeability reservoirs,and the reservoir space is complicated and the diagenesis type is numerous.These characteristics restrict the exploration and development of HJS oilfield.In this paper,the Chang 4+5 reservoir is as the research object,firstly according to the principle of sedimentary cycles and stratigraphic thickness,reference K4 and K6 marker layer,the Chang 4+5 oil layer is divided into four small layers,and the structure of small layers are analyzed.On the basis of Stratigraphic classification and comparison,the sedimentary environment and sedimentary characteristics of the area are studied,and the main sedimentary environment of the research area includes Delta front and Delta plain facies sedimentary,and the facies range of Delta plain is expanding from top to bottom.The main microfacies types include branching channels,underwater distributary channels,estuarine dams,distributary bays,etc.Then,through the analysis of core,thin slice and so on,the reservoir lithology and pore characteristics are analyzed,and the fine feldspar sandstone is thinked the mian rock type of the sanstone,and the pore types are mainly intergranular pore and feldspar dissolved pore.The author think that Diagenesis includes compaction,cementation,dissolution and metasomation,and diagenesis has reached the phase A stage of diagenesis.In addition,according to the core sample data,it is clear that the reservoir is low porosity and low permeability reservoir,and the physical property is gradually worse vertically,and the southern region is better than the northern area.The influence factors of reservoir physical property are mainly sedimentary microfacies and diagenesis.Finally,this paper selects multiple evaluation parameters,and determines the importance of each parameter according to the analythic hierarchy process,obtains the judgment matrix and the weights of each parameter,and uses the comprehensive quantitative evaluation method to classify the reservoirs and clarify their distribution range.Based on the comprehensive evaluation of reservoirs,combining the production dynamic data,the author selects the priority areas,reserve building areas and potential replacement areas,and clears their distribution.These works provide the basis for further exploration and development.