The Archie model is the foundation for calculating oil saturation, but limitations exist when the model is used to calculate oil saturation in water-flooded layer. In the process of water injection, the dynamic change in oil saturation will be caused by the different degrees of water flooding and the properties of the injected water. Under the dynamic condition of water flooding, the Archie model is not suitable for calculating the oil saturation of water flooded layers. By combining dynamic and static methods, a "double ratio" model of the same sedimentary facies layer in the later development stage was established: Rt =  R0− R0· f( Fw)=R0[1− f( Fw)]. Based on the parameters of rock resistivity and formation water resistivity, an improved Archie model for calculating oil saturation in water flooded layers of the same sedimentary facies was established. The interpretation of the actual data of the Zhenwu Oilfield in Jiangsu, China shows that the average relative error between the calculation result and the core analysis result is 5.46%. The calculation result is reasonable, which offers a scientific basis for predicting the remaining oil distributions. The computational results have been validated by real datasets. This improved mode can provide experience-based guidance for the calculation of the remaining oil saturation of the water flooded layer in the same sedimentary interpretation layer.

The recovery ratio is an important indicator to evaluate the effectiveness and performance of oilfield development. In order to clarify the key factors of oilfield recovery ratio in the stage of super-high water cut, 9 dynamic indicators of 12 blocks are analyzed in heavy oil reservoir of eastern China in application of reservoir engineering principles and statistical analysis methods. The results show that the four key factors of recovery are the well density, the ratio of producing wells and injecting wells, net cumulative injecting rate and the bottom hole flow pressure, and the weight of each indicator is quantified. In the horizontal contrast, comprehensive forecasting target recovery is compared with the current recovery by the dynamic method to determine according to typical block BXD. Four of important factors are discussed for the previous trend and the countermeasures of according adjustment are put forward. The proposed method and the results have a certain reference value of the theoretical research and practical application in the stage of super-high water cut oil-field.

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Archie model is the basis of calculating oil saturation, but there are some limitations when using this model to calculate oil saturation in water-flooded layer. The main reason is that the main parameters, such as rock resistivity and formation water resistivity, are constantly changing dynamic parameters in the underground with the influence of injected water. Considering that water-flooded layers changes with injection waters, influence factors of rock resistivity and formation water resistivity of primary parameters are analyzed. Considering the dynamic data of water cut is the most reactive underground fluid characteristics of real information, combined with dynamic and static, and the “double ratio” model of later development by the same sedimentary layer is established, which realizes the inversion of rock resistivity and formation water resistivity, then modified Archie model relating to water-flooded layers of the same sedimentary explaining formation. The explanation of actual data indicates that the “double ratio” model well considers the dynamic variation of production data, which makes the inversion of the flooded rock resistivity relatively accurate, besides, the modified Archie model can accurately calculate the oil saturation of water-flooded layers with a reasonable result, which offers scientific basis for the predicting of remaining oil distribution rules.