The Performance of Perforated Completions in Gas Reservoirs

Abstract

Abstract Although investigational work has been conducted to determine the performance of perforated completions in oil wells, not much is known about the performance of perforated completions in gas reservoirs. It is the objective of this paper to help fill this gap. A finite-element program was used to study in great detail the effects of perforation geometry and formation properties in the performance of completed gas wells. More specifically, the influences of (i) shot density, (ii) perforation length, (iii) phasing angle, (iv) formation permeability, (v) formation anisotropy and (vi) turbulence factor were studied. Introduction Many studies have been conducted to determine the performance of perforated completions in oil wells, but not much is known about the performance of perforated completions in gas reservoirs. McLeod presented equations that can be used to calculate the extra pressure drop caused by turbulent flow through the rock around the wellbore. He inferred that flow convergence, low damaged zone permeability, and compacted zone around the perforation increase greatly the pressure drop from non-Darcy (turbulent) gas flow. Tariq included nonlinear effects in his evaluation of flow characteristics of perforations. He used the properties of low-viscosity liquid for his work based on Cooke's experimental results, which indicated that the turbulent factor is practically the same for liquid or gas flow. King et al. conducted a field study on oil and gas wells that showed a correlation between the underbalance pressure used in perforating and formation permeability. This correlation can be used to obtain clean perforations in sandstone.