Over a few short years surface control of the reservoir by intelligent well technology has become a reality allowing improved efficiencies and economies by well documented measures. Downhole control valves have evolved from simple open/close zonal control to downhole chokes that allow metering of fluid rates from or to multiple producing zones. Complementary instrumentation of the wellbore provides real time data for pressure, temperature and flow. These capabilities along with computational and communication technologies provide the necessary ingredients to allow remote control of production in a variety of settings. In addition to remote control, the opportunity also exists to automate production even to the extent of closed loop control. As the complexity of surface controlled reservoir control valves has increased, so has the frequency of operators selecting microprocessor controlled surface hydraulic control systems to manipulate the valves. With microprocessor control in place at the well location, remote control options become the next logical step in the evolution of intelligent wells. Once remote operation has been chosen, the options for system architecture and communication are quite extensive. Successful implementation is a matter of effective interface engineering between the operator and the various service providers. A recently published article by these same authors presented a general approach to well-centric closed loop control.1 This paper explores in greater detail the process to develop and implement closed loop control for a producing well.
Much of the focus in smart fields revolves around the reservoir. In the context of closing the loop, it is important to bring focus on the well. In this paper optimizing production by closing the well-centric loop is addressed. There are multiple references to two optimization loops (see Fig. 1), the reservoir-centric slow loop and the well-centric fast loop. Closing the fast loop can be done via interventions to the well, a workover, or by operation of intelligent well equipment. In this context, intelligent well equipment is any device that allows adapting the well to its best possible operating condition without an intervention. This equipment includes well monitoring devices and intelligent well equipment. It can also include other functions like intelligent artificial lift or flow assurance but these will not be the focus of this paper.
Fig. 1. Fast Loop vs. Slow Loop (Available in full paper) Typically the justification process for the incremental expense of an intelligent well versus a conventional completion includes modeling to illustrate the potential benefits of the intelligent well. Benefit can come though increased ultimate recovery (produce more of the oil), accelerated production (produce it faster) or cost reduction (1 wells does the job of 2) or a costly intervention is avoided. Once approval for the intelligent well is given it seems only logical to compare well production against the expected performance to insure that the anticipated benefits are realized. When the value of the intelligent completion is realized from the placing adjustable downhole chokes in the well it follows that the optimum performance of the well will require changing the choke settings during the well life.