Study On The Characteristics And Comprehensive Evaluation Technology Of Chang 7 Tight Sandstone Reservoir In Longdong Area

Chang 7 reservoir in X block in southwest Ordos Basin is a typical tight sandstone reservoir,and horizontal well volume fracturing is used as the main development technology.After years of development,there are many problems in horizontal Wells,such as large production differences and severe stable production situation.Therefore,it is necessary to conduct in-depth research on reservoir characteristics and comprehensive evaluation of reservoirs.The result of reservoir comprehensive evaluation will directly affect the effect of reservoir development.The X area as the research object,the principle of reservoir geology,sedimentology and logging geology as theoretical guidance,using the basic geological data,logging data,production data and fluid data,focus on the petrological types,reservoir physical property and heterogeneity,pore structure,brittle and oil content,such as reservoir characteristics research,Combined with the characteristics of reservoir seepage,reservoir fluid properties and source rock distribution characteristics,the reservoir is classified and evaluated.Through the above research and analysis methods,the following main understandings and achievements have been obtained:(1)In the study block,semi-deep lake-deep turbidity current deposits are developed in Chang 71 and Chang 72 tight oil reservoirs,among which,turbidity channel sand bodies in the southeast area of Block X are relatively developed and have better connectivity.(2)The content of quartz minerals in X area is high,but the content of feldspar in minerals is low,and the primary pores are not developed.The pore types are mainly feldspar dissolved pores,and micro-cracks are developed at the same time.By comparison,it is found that the north of X area is denser than the southeast.The displacement pressure of Chang 7reservoir in X area is high,but the median throat radius is small,the pore throat sorting is poor,and the pore structure basically belongs to small pore throat type.Compared with the southeast area,the pore structure in the north of X area is worse.(3)By using the normalized Young’s modulus and Poisson’s ratio,an accurate quantitative prediction model for the brittleness value of tight sandstone reservoir is established.It is found that the brittleness index has a great influence on the artificial fracture and network,thus affecting the production of single well.The apparent energy storage coefficient is used to comprehensively evaluate the hydrocarbon enrichment degree of the reservoir.The apparent energy storage coefficient in the southeast of X block is slightly lower than that in the north.According to lithology,TOC and logging response characteristics,the source rocks can be divided into three types.The high quality source rocks in X area are concentrated in the northwest,southeast and central part(4)To establish a comprehensive classification and evaluation standard for Chang 7 tight oil reservoir in the study area by using mathematical statistics method;High-quality reservoirs are overlapped in Zhongchang 71 and Chang 72 in the northern part of X area.Horizontal Wells are mainly located in Ⅰ and the type of reservoirs.High-quality reservoirs are relatively developed in the northern part of the southeast area,and horizontal Wells are mainly concentrated in the type of reservoirs.The development area of high-quality reservoirs in the southeast of X block is smaller than that in the north.Statistical analysis of the production performance curves of horizontal Wells with different reservoir types shows that the higher the quality reservoir development,the higher the initial production of horizontal Wells.