Comprehensive Evaluation Of Reservoirs And Optimum Selection Of Favorable Blocks In Chang 6 Area Of Hujianshan

Hujianshan area is located in the Midwest of Ordos Basin.Yanchang Formation in this area is divided into ten intervals,and Chang-6 interval is an important layer for oil and gas exploration in this area.Through some previous studies,we have had some understanding of the study area,but the understanding of reservoir characteristics and sedimentary facies is not clear.Through the previous studies,we have some knowledge of the study area,but the understanding of reservoir and sedimentary facies characteristics is not clear.Moreover,reservoir 6 is a low porosity and low permeability reservoir with complex spatial structure and various diagenetic types,which hinder the exploration and development of the oilfield.In order to make clear the distribution characteristics of the reservoir,it is very important for the next exploration and development of the oil field to make a comprehensive evaluation of the Chang 6 reservoir and select the favorable blockIn this paper,the Chang 6 reservoir group is taken as the research object,referring to the K2 and K4 marker layers,and according to the principle of sedimentary cycle and formation thickness,the Chang 6 reservoir group is divided into five small layers.The structure of the target layer is relatively simple,which is high in the East and low in the West as a whole.Some nose like uplifts with little fluctuation are developed in some areas.Based on the study of sedimentary characteristics,it is determined that there are delta front and delta plain subfacies in Chang 6 reservoir.Underwater distributary channel microfacies,branch channel microfacies,distributary Bay microfacies and Hekou dam are relatively developed in the study area.On the plane,the sand body develops along the river channel,and on the longitudinal,the multi-stage river channel overlaps.According to the core sampling data,the reservoir in the study area is determined to be low porosity and low permeability reservoir.From the top to the bottom,from the south to the north,the development of reservoir physical properties gradually becomes poor.On the basis of the above research results,the reservoir is comprehensively evaluated.Five representative parameters such as oil saturation,porosity,reservoir thickness,permeability and shale content are selected.The weight value of parameters is calculated by AHP.Two kinds of reservoir comprehensive evaluation models,comprehensive quantitative evaluation method and fuzzy mathematics method,are established.The accuracy of the two evaluation results is verified by the oil test data Finally,the fuzzy evaluation method is selected as the comprehensive evaluation method of the reservoir.Based on the results of fuzzy evaluation,Chang 6 reservoir is divided into four types,i.e.class ?(good),class ?(good),class ?(general)and class ?(poor),and the distribution range of each type of reservoir is defined.Based on the results of reservoir comprehensive evaluation,combined with production performance data,three types of favorable blocks are finally selected,i.e.class A(priority production area),class B(reserve production area)and class C(potential replacement area),and their distribution range in each small layer is determined,providing reliable basis for the next exploration and development of the oilfield.