Fill cleanouts, matrix stimulation, cementing, and downhole milling are some common coiled tubing (CT) operations. The difference between the success and failure of these jobs relies heavily on the knowledge and prediction of the behavior of downhole parameters such as temperature and pressure. Another significant percentage of CT operations depends on highly accurate depth control to ensure the intended result of the operation. These depth-critical operations include setting packers, tubing patches, CT-conveyed perforating, and zonal isolation. And in virtually all CT operations, including fill cleanouts, stimulations, and cementing, the knowledge of an actual tied-in depth is advantageous to operations.

The purpose of this paper is to present a simple and reliable system that allows real-time monitoring of downhole pressure and temperature, and provides depth correlation using a casing collar locator (CCL). In this system, the downhole parameters are recorded in real time without the limitations of conventional wireline-enabled coiled tubing units.

The information presented in this paper summarizes the operations performed during the field-testing of the system at Alaska's North Slope. Twenty-seven CT operations were successfully performed using the system; this demonstrated its reliability and provided the crew with the information needed to improve the efficiency of the operations being performed.

The system comprises three main components:

  • Downhole tools capable of measuring and transmitting bottomhole pressure and temperature as well as identifying casing collars with high accuracy.

  • Fiber optic and fiber optic carrier, which provides real-time transmission of downhole data to surface.

  • Wireless bulkhead and surface interface modules to provide two-way communication between the tools and the monitoring system.

You can access this article if you purchase or spend a download.