New Closed-Loop Control System Reduces Risk in Intervention Operations

Abstract

During well construction activities, measurement-while-drilling (MWD) technology is applied to transmit sophisticated spatial and petrophysical data from downhole to surface. Used with advanced well construction tools such as rotary steerable systems, MWD technology has enabled complex, even tortuous, well profiles to be created and placed in the reservoir with great precision. However, even on these sophisticated and expensive wells, any well intervention operation process is still controlled using traditional surface-read data such as revolutions per minute (RPM), hook load, torque, etc. The ability to transmit and use downhole intervention process data in addition to surface-acquired data presents significant potential for intervention process optimization, since modern data acquisition technology close to the tool can provide not only more accurate data, but also important additional parameters not available at the surface. Examples of value-adding downhole intervention process data are bore pressure, annular pressure, weight-on-tool, tension-on-tool, torque-on-tool, RPM, workstring bending and dynamic diagnostics. Additional intervention process information on intervention hydraulics or workstring friction can be obtained by feeding existing engineering algorithms with surface- and downhole-acquired data. This paper discusses the available downhole well intervention process data and demonstrates by a number of case studies the risk reduction value of viewing these parameters in real time. Furthermore, the paper discusses factors constraining the use of the technology and gives an outlook on future developments in well intervention process optimization utilizing real-time downhole data. Introduction During the early years of the 20th century, shallow vertical wells required many months to drill. By the nineteen eighties, a 90-day well program was fairly common for an offshore well - 80 years to cut the well time by up to a third. Today, thanks to a 20-year investment in drilling optimization, a well can be drilled in thirty days. Dramatic progress has been made in target accuracy, trajectory, step-out, temperature, and even depth. The drilling optimization approach has also substantially reduced non-productive time (NPT) in the drilling arena. Well intervention, however, has not kept up; it is this sector of well operations that now has the largest potential for risk and unplanned expenditure, particularly with ambitious well trajectories and in deeper waters. A significant portion of today's unplanned NPT costs accrue during well intervention operations, de-completions, casing exits and fishing operations. Many of these costs are preventable. Currently, well intervention decisions are still based on traditional surface-acquired data such as RPM, hook load, and rotary torque. The potential for intervention process optimization and with it, the ability to substantially mitigate risk in almost any intervention operation, is significant. Optimization Essentials Much as drilling optimization has transformed the drilling industry, so, too, can real-time downhole data acquired from an intervention bottom hole assembly (BHA) - especially when combined with surface acquired data - optimize the well intervention process by facilitating decision making in real-time and enabling intervention parameter management. Creation of an intervention optimization model requires a number of essential elements.○Suitable well intervention operations○Planning and modeling○Downhole data acquisition○Data transmission○Control system○Intervention parameter management Assembling these elements and performing system integration enables real-time intervention parameter management. How can that be achieved? The concept is to utilize data very similar to that generated in MWD operations and translate the data to well intervention operations, to provide an accurate picture at surface of the energy and force distribution on the well components and well intervention tools at the end of the work string. We can now see, in real-time, what is happening downhole in well intervention operations.