SPE Members Abstract A horizontal well usually yields a high rate through its long perforation interval, resulting in a large frictional pressure drop that is believed to reduce the well productivity. Unlike conventional horizontal well methods which consider the horizontal section only, the proposed model also includes the vertical section of the well and the surface facility from the well head to the GOSP. The hydraulics model was validated stage-by-stage by various known solutions, and then applied to a high rate well. It was found that the effect of frictional pressure drop on oil rate was not as pronounced as suggested by analytical methods, or some numerical simulation studies. In summary, the pressure drop in the vertical section of the horizontal well plays an especially important role in deciding how much fluid can be produced. Therefore, it is recommended to be an integral part of horizontal well models. Introduction In models which consider the horizontal section only, frictional pressure drop was shown to reduce the productivity of horizontal wells. Dikken presented an analytical horizontal well model that combined the fluid flow in the horizontal section of a well and the reservoir flow. He concluded that the flow inside horizontal wells is either transition or turbulent in most practical situations. Furthermore, for single phase turbulent flows, he found that appreciable reduction in drawdown occurred at positions farther away from the start of the section. In a water coning example, he demonstrated that little additional production results from extending a 300 m long well with a diameter of 11.4 cm. Novy generalized Dikken's model so that it can be applied to the recovery of gas. In the process, he found that the friction factor correlation used by Dikken gives friction factors that are too high for rough tubes. Novy performed extensive sensitivity studies and he concluded that if the ratio of well-bore pressure drop to drawdown at the producing end exceeds 10%, friction is apt to reduce productivity by 10% or more. In a simulation study where the frictional pressure drop was included in the horizontal well model, Seines et al. found that by varying the effective roughness of the well, thereby changing the pressure drop, they obtained a 10% difference in cumulative production after 1 year. The well was producing at a fixed flowing bottomhole pressure (FBHP). This paper presents the work in which a complete hydraulics model for horizontal wells was developed and validated. The model was then applied to a high flowrate case. Calculated results were compared with analytical predictions. Investigation of the discrepancy in results provided some insights about the modeling of horizontal wells. P. 407
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