Development of an integrated reservoir-wellbore model to examine the hydrodynamic behaviour of perforated pipes

Abstract

Perforated pipes are used widely in vertical and horizontal production wellbores. Understanding the fluid flow behaviour through perforated pipes by taking into consideration the wall inflow is crucial for determining the wellbore frictional characteristics. Accurate prediction of pressure drop along the perforated pipes is a key step in completion design of production wellbores. Many empirical and theoretical models have been reported in the literature to predict pressure drop and friction factor along perforated pipes. However, these models show contradictory findings which is resulted from variations in the wall inflow configuration and modelling assumptions. The fluid flow through the surrounding formation and its interactions with wellbore have been simplified in the previous models which limits their range of applicability.In this study, a three-dimensional integrated reservoir-wellbore model of fluid flow through a perforated pipe surrounded by porous media is developed via Computational Fluid Dynamics (CFD) simulation. The model is used to investigate the effect of perforation parameters including perforation density, diameter and phasing angle on the wall friction factor and the pressure drop along the perforated pipe. The simulations are carried out for pipe inlet velocities of 0.5, 2.5, and 5 m/s with inflow to pipe flow rate ratios of 0, 7.5, 15, 30%. The results from this study show that the friction factor varies linearly with the perforation density but does not change remarkably with the perforation diameter or phasing. The observed trends of wall friction factor with perforation parameters are further explained and confirmed by studying the local wall shear stress results. Increasing the number of perforations leads to a higher friction factor as well as a larger pressure drop along the pipe. It is also observed that for perforation phasing angle of 90°, the overall pressure drop has the highest value compared to other phasing angles due to intensified influence of mixing pressure drop. For turbulent flows with high Reynolds number, the accelerational pressure drop is more dominant than the frictional and mixing pressure drop for the same inflow to pipe flow rate ratios. The developed model provides an alternative solution to experimental studies of perforated pipes, while delivering more details on friction factor behaviour and overall pressure drop components.