Optimization of Smart Well Control

Abstract

Abstract Downhole inflow control devices allow for the flexible operation of nonconventional wells. They provide the ability to independently control each branch of a multilateral well and can therefore be used to maximize oil production or to minimize the production of unwanted water or gas. In this paper, a method for the optimization of the operation of smart wells; i.e., wells containing downhole sensors and inflow control devices, is presented and applied. The method entails the use of a conjugate gradient optimization technique applied in conjunction with a commercial reservoir simulator that contains a detailed multisegment well model. The overall optimization technique is applied to several example problems involving different types of wells and geological models as well as multiple geostatistical realizations. The improvement in predicted performance using inflow control devices, which is as high as 65% in one case, is demonstrated for all of the examples considered. There is, however, significant variation in the level of improvement attainable using these devices, so sophisticated decision-making techniques may be required when considering their use in practice. Introduction A smart (or intelligent) well is a nonconventional well with downhole instrumentation (sensors, valves and inflow control devices) installed on the production tubing. Such wells allow for the continuous in-situ monitoring of fluid flow rates and pressures and the periodic adjustment of downhole valves. Smart well technology provides great flexibility in the operation of multilateral wells, as each branch of the well can be controlled independently. In the case of a monobore well (such as a horizontal or deviated well), the downhole instrumentation essentially transforms the well into a multi-segment well, again with the ability to control each segment independently. The benefits of smart wells have been demonstrated in practical applications, especially for multiple reservoirs where commingled production is the main production strategy. In these operations, the control devices are commonly used in on/off mode (i.e., the branch is either opened or closed to production), which may not be the optimum way of operating these devices. The applicability of intelligent completions, however, is not confined to scenarios involving commingled production. Their potential benefits for production from a single reservoir have also been demonstrated.1—4 Specifically, because smart wells can be used to monitor and control flow rate and pressure, these completions can be effective for controlling the coning or cusping of water and gas. One approach for using smart well technology is to wait for problems to occur (e.g., water coning) and then reset the instrumentation to mitigate them. A better approach is to use downhole inflow control devices in conjunction with a predictive reservoir model. This allows for the optimization of reservoir performance rather than just the correction of problems that have already occurred. This latter approach — the use of inflow control devices for the optimization of well performance — is the focus of this paper. With smart completions, the objective might be to allocate the inflow rates for each branch such that the objective function (cumulative oil, net present value of the well) is maximized.