Abstract
Inflow control devices (ICDs) are designed to provide an even inflow across production zones by adjusting the completion pressure differential in order to balance reservoir drawdown. This helps to delay production of unwanted fluids whilst enhancing oil production. Newer designs also permit a degree of autonomous control. Although able to function without intervention, they can, in some circumstances, detect if the inflowing fluid is desirable, and act to restrict the flow if it is not. Several designs for these autonomous inflow control devices (AICDs) are available from service companies. One forces inflowing fluids to enter gates depending on inertial and viscous forces of the various fluids. Another is an autonomous valve in the shape of a free floating disc that restricts the flow rate of low viscosity fluids and is primarily used to choke gas and water inflow. Recently, a device with water swellable rubber inside the nozzle has been proposed, but is not yet commercially available.
This paper is divided into three parts. First, AICD published performance data from two commercially available devices is fitted with a generalized Bernoulli equation with adjustable parameters. Second, an optimization study is carried out where AICD device strengths and calibration parameters are specified as optimization control variables for all production wells in a detailed simulation study of a North Sea reservoir. Located in the northern part, the Ivar Aasen field (formerly Draupne Field) is a sandstone oil field where oil viscosity is low, similar to that of water. Wells in this setting can exhibit significant GOR and water cut at various times. Optimized parameters from this study, with a Net Present Value objective function, are compared to parameters from the fitted devices to determine whether commercially available devices have the performance of optimum devices, for this field. Third, to compare oil production and water control of the two commercially available devices and a third proposed device with water swellable rubber in the nozzle, a comparison of recoveries is made between a base case with open-hole completions and cases where wells are equipped with these three AICD designs. Discussions focus on (i) properties of these various devices in order to design an improved AICD for recovery operations in this field, (ii) a comparison of these devices against standard nozzle ICDs where it is shown that, for this field, the standard nozzle ICDs perform as well as the AICDs.
