Geological Features And Reservoir Engineering. Isolated Oilfield Shahejie Group

Shahejie Formation is an important layer in Gudong oilfield, and it has been exploited beyond 10 years. To be further developed, on the basis of static state study, detailed dynamic analysis and fine reservoir description need to be done. and geological reserves parameters need to be made clear, which is to afford the point of reference for the study on remaining oil distribution.This paper emphasizes the combination between the static state and dynamic state. Through the systems study on structure and reservoir sedimentology, the static geology models of Shahejie Formation are constituted. Used of material balance method, the dynamic analysis is done. Based on the forecast method of production, the reserves, recovery ratios and energy status are analyzed, and the reserves are calculated and evaluated. Following conclusions are gained.Palaeogene system developed on burial hill and had been crossed by many faults. It has many beds and looks like an anticline. Gudong fault that is north and south is only a second fault in work area, and it divides the area into east part and west part. The east part arises, and the west part declines. East part has been divided into 5 blocks by some third faults, the seventh block is the highest. Equally, west part had been divided into several belts. Many fourth faults are identified through fine structural analysis.Shahejie Formation in Gudong oilfield has been detailed contrasted. It has 6 sands that are divided into 22 sediment timing cells. Through the analysis of core, well, logging and seimic data, fan delta and lacustrine deposit systems are been discerned in Shahejie Formation of Gudong oilfield. Fan delta has been developed on east of Gudong oilfield, and lacustrine deposit system has been developed on west of Gudong oilfield. The space-time distribution laws of sedimentary microfacies have been determined.Property of reservoir bed indicates that most pore is original porosity in Shahejie Formation. The oil mostly exists in biolithe, medium and fine sandstone. The heterogeneity study shows that oil is controlled by microfacies and faults in the plane, and barriers exist between the sandbodys of adjacent timing cell in the vertical. The structure of Shahejie Formation reservoir displays faulted and stratiform.The reservoir deification studies of Shapelier Formation of the blocks are done, the reservoir models are established, and the dynamic analysis are done by making use of the material balance method. The intensity of bottom water drive and the drive effectiveness are studied, and the further waterflood measure is put forward.The calculation method of recovery ratio for Shahejie Formation reservoir has been selected. The recovery reservoir of waterflooding is 747.2478×10~4t,the geological reserves is 1337.022 X 104t. The result of energy analysis in typification reservoir indicates that the effective water body is 68 times; the recovery ration of natural water drive is 31%; the pressure will drop in the condition that the production rate is l"544260m3/a and the injection-production is 0.52:1. thus injection should be strengthened, and other block like 7-block should also be strengthened.The calculation results that the geological reserves is 1496 X 104t, which is less 464X 104t than the reserves calculated on 1987, but exceeds 150X 104t than the reserves calculated on 1994. Because of building model in detail and restudy of the parameter, the result is more accurate.