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A flow is observed in the pipe for the horizontal section of slotted screen completion and inflow control device (ICD) completion, and an annulus flow exists between the pipe and the borehole wall. Based on the principles of mass conservation and momentum conservation, a model for variable mass flow in an oil reservoir to simulate wellbore–annulus–reservoir state in the horizontal section of slotted screen completion and ICD completion is proposed. Consequently, based on the newly established formation transient seepage model and wellbore and annulus variable mass flow model, an accurate prediction of the production rate of a horizontal well and optimized design parameters for slotted screen completion and inflow control device (ICD) completion are achieved. The predicted flow profiles of the established model are confirmed using the simulation software from Computer Modeling Group Ltd. When external casing packers are not considered, findings show that the predicted production rates of both slotted screen completion and ICD completion, which are obtained using the variable mass flow models without annulus flow modeling, are higher than the rates obtained using the variable mass flow models with annulus flow modeling. Both models show that the pressure profile and flow profile of the borehole wall are more uniform in wellbore–annulus–reservoir in horizontal wells. The flow model for horizontal wells with annulus flow modeling should be established to improve the accuracy of the predicted production. [ABSTRACT FROM AUTHOR]

On the basis of previous research, the true trajectory of horizontal oil wells with complex structures is considered in this study. A horizontal well is an assembly of a myriad of infinitesimal section lines along the well’s length. Hence, a method to calculate the true horizontal well trajectory potential in a top-closed reservoir with bottom water is achieved. Combined with the formula of pressure drop in a single-phase variable mass flow horizontal well, a new coupled semianalytical model for horizontal well productivity prediction is established. Using a well from an offshore oilfield in China as case study, productivity prediction via calculation and comparison of the horizontal well is conducted. Prediction results show that the new model is more accurate than other models considered. The established model for real 3D well trajectory potential converts the integral solution into even-number segments to avoid the defect of zero denominator when potential calculation is conducted for the self-infinitesimal scenario. In summary, the new coupled semianalytical calculation model of productivity prediction for horizontal wells is built by establishing a calculation model for the true trajectory potential of a horizontal well. This model is proven feasible through actual case calculation. The new model is refined and stable, and productivity prediction under true trajectory conditions can be obtained with the new model. Such productivity prediction reflects the real situation of oil wells and is conducive for the optimal design of well trajectory and parameters. [ABSTRACT FROM AUTHOR]

In the previously published studies, the calculations of critical liquid-carrying gas velocity in a horizontal well were based on conventional calculation models of a droplet in a vertical well and do not consider the influence of the inclination angle of the well on the liquid-carrying ability of gas. Horizontal wells are currently widely used in the gas fields, while the traditional critical liquid-carrying velocity models cannot be applied to evaluate gas flow characteristics in the inclined sections of horizontal wells. In this paper, based on experimental results, we established that the critical liquid-carrying conditions in an inclined well occur when the inclination angle is 55°. Considering the flow characteristics of the liquid phase in a gas well, we obtained the flow mode of the liquid film in the pipeline. The established liquid-film model provides a calculation method of the critical liquid-carrying velocity for different inclination angles. The accuracy of the new method has been verified by the field data. [ABSTRACT FROM AUTHOR]