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It is difficult to predict the oil and gas productivity when multiple production sections are used to produce multiple reservoirs at the same time. To solve this problem, a semi-analytical productivity prediction model of double-step horizontal wells is established. Reservoir anisotropy, properties, seepage interference, wellbore pressure drop are considered in this model. The discretization method is applied to divide the double-step horizontal well into several sections for the coupling of reservoir model and wellbore model based on some relevant theories of seepage mechanics, fluid mechanics and numerical analysis. Two double-step horizontal wells in the Minghuazhen Formation and Dongying Formation in Caofeidian Oilfield are used for instance verification to analyze the production of each micro-element in the wellbore and the distribution of cumulative production along the wellbore. The results show that the distribution of the micro-element sections of the upper and lower horizontal sections of the double-step horizontal well presents a typical "U"-shaped distribution. The heel and toe sections of the horizontal section have a larger production, while the middle section has a smaller production. Comparing the productivity predicted by the model of the double-step horizontal well built in this paper with the actual well productivity, it can be seen that the relative error of the well D is 4.47% and the relative error of the well F is 5.8%. The prediction error is controlled within 10%, the model established in this paper has good prediction accuracy. This paper proposes a wellbore-reservoir coupled double-step horizontal well productivity model. This model can effectively predict the prediction distribution, pressure distribution and cumulative production distribution along each micro-element section of the wellbore and the model has good applicability in the actual oil field.
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