Simulation of Turbulent Flow in Gas Wells

Abstract

Abstract A method is presented for handling near well-bore gas phase turbulence in complex reservoir systems. The method may be applied in one, two or three phase flow systems. The flow equations describing three-phase flow were modified and incorporated into a single well coning model reservoir simulator. Results are presented for two field gas wells where history matching of observed drawdowns was done to estimate reservoir parameters and turbulence coefficients. The models were then used to investigate water coning behavior in the two gas wells and develop critical rate information. Introduction It has long been recognized that to accurately describe gas well performance, in many cases, the effect of turbulence near the well-bore must be accounted for. Katz describes a treatment that may be used to account for the nondarcy flow caused by turbulence in single phase gas flow at steady or quasi-steady state conditions. This and similar methods are widely used and will give reliable results, especially when the parameters needed in the solution are "calibrated" from observed data. However, these analytical solutions are restricted to single phase gas flow and simple reservoir geometry and description. The analysis of gas well performance in complex reservoir geometries and/or in cases where multiphase flow is occurring is now feasible using reservoir simulation models. The usual approach is to study individual wells using a single-well reservoir simulator or coning model capable of handling one, two or three phase flow with complex reservoir descriptions including stratification, fractures etc. Commonly in the past, the effect of turbulence has not been included in these simulation models because the solution to the Darcy flow problem was difficult enough without further complicating the model. Recent advances in the technology of solving coning problems have now resulted in models that can problems have now resulted in models that can economically be used to study single well performance. Therefore, it is now feasible to performance. Therefore, it is now feasible to go a step further and include the effect of turbulence in these reservoir simulators. The area where this method probably has the greatest utility is in studying gas-water systems.