Technology Update: "Smart" Technology Moves to Intervention Operations

Abstract

Intervention jobs often get into difficulty because of a lack of accurate downhole information, despite surface indications to the contrary. For example, milling assemblies are sometimes retrieved with little to no mill wear, and over-shots and spears have been pulled empty despite positive surface indications. A recent job planned for 14 runs and 30 days of rig time to recover a gravel-pack assembly from 25,000 ft, but lack of quality downhole information forced an additional 10 trips and consumed an additional 28 rig days. Without the ability to see true indications of torque, weight-on-mill, and jar-impact loads, washover shoes were pulled either untouched or junk cut, and debris was left in the well. As wells become deeper, more tortuous, and more technically challenging for intervention, it is crucial to know more about what is actually occurring at the tool face. Traditional surface-based indicators often do not reflect the actual forces being exerted at and around downhole tools. Adding "smartness" to well-intervention operations provides valuable information on downhole parameters, including weight or tension on the tool, torque, revolutions per minute (RPM), bending stress, vibration, and pressures, that have not been seen previously at surface. Even small discrete variations can be detected. The surface information, which can be viewed from both a rig-floor monitor and a remote real-time operating center, enables better understanding of what is happening downhole. It also provides the well team with a new level of process control and real-time decision-making capability while intervention work is being carried out. Armed with valuable information and improved process control, the team can operate intervention tools with greater precision and, most importantly, with consistent reliability. Fig. 1 illustrates the value that can be realized from smart intervention by improving performance and reducing risk exposure. The diagram shows that the cost of a well intervention is dominated by rig cost rather than service company charges and the operator's large exposure to cost escalation during problem jobs vs. the relatively low preventive cost to mitigate disaster. Smart intervention offers a method of reducing cost and risk in that portion of a well program in which nonproductive time (NPT) is an issue. Technology Basics Baker Oil Tools has developed a smart intervention system that integrates a modular intervention-performance sub (IPS) and a base measurement-while-drilling (MWD) tool into the bottomhole assembly (BHA). The IPS features an array of sensors, including accelerometers, strain gauges, and magnetometers (Fig. 2). All sensors are sampled at 1 kHz, and a digital signal processor inside the tool provides static parameters plus diagnostics to characterize the downhole environment. The outputs include weight on mill and mill bounce; tension at tool; torque; downhole RPM and stick/slip severity; bending stress, dogleg severity and BHA whirl; and differential pressure with equivalent circulating density. Selected parameters are transmitted uphole by means of mud-pulse telemetry. The control feedback loop complements the experienced field technician's "sense of feel" while operating the work string at surface. Capable of receiving downlink signals, the smart system provides a link for remote control of future intervention tools. Display screens present the downhole parameters in conjunction with surface-acquired data and can be linked to a remote operations center for monitoring.