Optimum Control of Unwanted Water Production in Stratified Gas Reservoirs

Abstract

fax 01-972-952-9435. AbstractMinimizing production of water from gas reservoirs is one of the main strategies for enhancing primary hydrocarbon production. Advances in intelligent well technology and simulation of reservoir-production system enable optimum inflow allocation of produced fluids by controlling perforations and valve settings. However, real-time optimum control of flow is still a challenge. To this end, we have developed an advanced method for optimization of production based on a feed-back optimum control concept. The method allows optimization of inflow-control-device operation in conjunction with strategic updating of reservoir-smart well model under uncertainty.In this work, we present a hybrid optimization method for improving optimum solutions. In this method, the response of production system to control variables is mathematically described by a high-order proxy model, which is developed using Response Surface Methodology (RSM) and Design of Experiments (DOE). The validity of this method was tested for the dynamic optimum control of gas and water coning observed in a physical two-dimensional layered bead-pack model with automatic inflow control valves. The valves were actuated by distributed flow or pressure sensors. Results showed that dynamic (time-dependent valve settings) and static (fixed valve setting) control exhibited advantages one over another, depending on operational conditions. It was also found that the heterogeneity of porous media strongly influenced the control effectiveness. Field implications are discussed.

Water Production Problem in Gas Reservoirs: Concepts, Challenges, and Practical Solutions

“…After all, using a modified analytic model, it was concluded that higher values of perforation density decrease the drawdown pressure and lead to lower water-to-gas ratios during production. In water-drive gas reservoirs, although a well is typically perforated at the top of the interval and produced at a limited rate, this perforation system sometimes lowers gas production rate, and it delays water breakthrough due to water coning [28].…”

“…Yamali et al used a hybrid optimization method to optimize pressure intervals that ICVs could work with [28]. To evaluate the objective function, an approximation method was applied, called proxy model (pressure intervals are independent variables).…”

“…Approximation methods were generally more cost-effective than simulation methods. Response Surface Methodology (RSM) and experimental designs were utilized to make the proxy model for performance function [28]. Besides, other techniques were tested to ensure that the proxy model concludes a valid objective function.…”