Characteristics And Decline Law Of Jurassic Reservoirs In Huanjiang Oilfield,Ordos Basin

The detailed reservoir descriptions and reservoir numerical simulations are often used to study the migration laws of oil and groundwater,formulate reasonable development technology policies,and then guide the development and adjustment of oil reservoirs and improve the effects of oilfield development,which has become one of the basic and key tasks in the current oilfield development and adjustment.In this study,the Jurassic Yan'an Formation reservoir in the Huanjiang area of the Ordos Basin was selected as the research object.The Jurassic is one of the most important periods in the evolution history of the Ordos inland basin.The Jurassic reservoirs in the Huanjiang area started from the Huan 75 oil area,and production was built on a large scale from 2013 to 2015,and production continued to rise.The main development layers are Yan 10,Yan 9,Yan 8,Yan7,Yan 6,Yan 4+5,Zhiluo,etc.Compared with other Jurassic reservoirs in the Ordos Basin,this area has developed multi-layered strata systems with strong heterogeneity and complex oil-water relationship,and it has thin oil-bearing layers,low permeability,low oil saturation,and high salinity.In addition,after water injection,the production usually shows the problems of heterogeneous water flooding,rapid rise in water cut,and increasing decline.Also,it shows that the severe wellbore casing wear,the complex injection-production adjustment,and the poor development effects,especially the annual natural decline has reached more than 20%since 2016.Particularly,the decline in development of the two oil reservoirs in Luo 141 and Huan 75 is prominent,with an average decline of 25.8%,which has severely affected the further development.Therefore,this study focuses on the above-mentioned two oil areas,analyzes the main controlling factors of the rapid rise and decline of water cut in the reservoir,studies the production decline and remaining oil distribution,and proposes reasonable development and adjustment strategies to reduce the decline of the reservoir.Meantime,the research can provide a scientific case for the further exploration and development of Jurassic reservoirs in the Ordos Basin,and it can also provide reference for the development of similar oil reservoirs in China.Firstly,the paper starts with the basic geological data,establishes 20 sets of database,draws21 sets of 58 key maps such as sand body contour map,fluid production intensity and water cut contour,and systematically studies the reservoir geological characteristics.On this basis,combined with the production performance data,systematically evaluates the water injection development effect by using the methods of field statistics,reservoir engineering and numerical simulation,Based on the analysis of reservoir decline law,it is generally considered that the main factor affecting the large decline of Huanjiang Jurassic reservoir is the rapid increase of water cut caused by the high injection production intensity at the initial stage of development.Based on the above analysis,according to different reservoir types and single well contact types,this paper puts forward the technical countermeasures of fine injection production parameters control suitable for Jurassic reservoirs.The series of optimized parameters have important reference significance for the reference development of similar Jurassic reservoirs in the basin,and the Jurassic reservoirs with different reservoir characteristics can be optimized and adjusted according to the actual production performance.