A New, Accurate and Simple Model for Calculation of Productivity of Deviated and Highly Deviated Well -Part Ι: Single-Phase Incompressible and Compressible Fluid

Nowadays in the oil and gas industry, many deviated (306h660), and highly deviated (606h<90)wells are drilled to increase wellbore exposure of the reservoir and improve the productivity. A few cor-relations have been developed for productivity calculation of such wells but are only applicable to single-phase Darcy flow conditions with their extension to anisotropic formations. So far, however, no model/correlation has been proposed to predict the productivity of these wells for non-Darcy (inertia) flow conditions. Currently, for such well productivity calculations, a commercial numerical reservoir simulator is required to simulate the three-dimensional flow geometry, using a fine grid approach, which is impractical, costly and cumbersome.In this study, a three-dimensional mathematical simulator has been developed to investigate the single-phase flow behaviours around a deviated well. A large data bank of well productivity was generated,covering a wide range of variations of pertinent parameters, including the well length and angle, wellboreradius, reservoir dimensions, anisotropy, fluid properties and velocity. Using the results from the in-house simulator result, based on these results, the approach recently proposed for predicting horizontal well productivity[11]was extended to develop a general method, which can be applied to both horizontal and deviated wells placed in isotropic or anisotropic formations and flowing under either Darcy ornon-Darcy flow conditions. In this method, the complex flow behaviour around the three-dimensional(3-D) deviated/horizontal wells is replicated by an equivalent open hole. The impact of pertinent parameters is quantified in terms of a skin or, in another form, an effective wellbore radius of the equivalent open hole. This new correlation is easy to use, no numerical simulator is needed and a quite simple spreadsheet can be used to provide an accurate estimation of the horizontal/deviated well productivity in gas and oil reservoirs