Shows Bi-directional Impact forces acquired from the bottomhole assembly during fishing operations in a 310 well bore. (Images of IGS)

Advances in technology have greatly increased the success rate of coiled tubing (CT) operations in most regions of the world. One of the biggest advances in CT in recent years is the development of high-powered sensors that record forces on the tubing string more accurately. Real-time tools often rely on crystal-based sensors, which are capable of reading temperature and pressure within a range of .003% accuracy. While the sensitivity of crystal-based sensors is well established, they are typically more expensive and can lead to increased operating costs. In addition, crystal-based sensors are not robust and can be easily damaged in operations where heavy impacts are commonplace.

Impact Guidance Systems’ DataCoil is a new memory-based CT logging tool that offers more data and increased reliability downhole for most types of operations. Whilst memory based, the system has the ability to record multiple parameters such as wellbore and bottomhole assembly (BHA) information simultaneously when placed within the coiled tubing string or as part of the BHA.

The tool uses strain-gauge technology, which provides more durability in virtually all CT operations over that of crystal type sensors. Historically, strain gauge sensors are less accurate and less reliable than crystal based sensors. However several companies including IGS are now able to develop strain gauge technology that offers increased accuracy with more longevity and flexibility than ever before.

Once each tool is assembled, it is pressure and temperature calibrated within a 70-point test matrix up to 10,000 psi. As a result, the unit’s sensors record data at a range of up to .07% accuracy with many tools verified to as low as .02%.

Vital statistics

Traditional CT logging tools provide measurements of two parameters: pressure and temperature. The new tool, due to its improved sensors, can read new parameters in coiled tubing applications that previously could not be measured.

The tool can measure temperatures up to 300°F (150ºC) and pressures of up to 10,000 psi both internally and externally to the coil. DataCoil records compression and tensile forces for use in applications where CT drilling on plugs, packers etc can benefit from this data. Inclination of the well bore is also recorded, which has proven to provide critical data when entering multilaterals for detection. In addition to these sensors the tool also records mechanical and hydraulic impact forces on the BHA. Designed with a true bi-directional sensor, the tool delineates upward impacts from any recoil in the string affected by the impact force with a sensitivity ranging from 200–150,000 lbs.

The tool records these parameters during setting and recovery applications for thru-tubing, inflatable, permanent or straddle packers. It is also designed for use with retrievable bridge plugs, lock mandrels, side pocket mandrels, side sliding doors, tractor operations and intelligent completion technology.

By analyzing the wellbore environment along with forces and stress acting on the coil, operators can better determine alternate solutions to thru-tubing operations and BHA configuration. Enhancing operator awareness of the dynamic forces acting on the coil at depth drastically enhances the efficiency of thru-tubing processes.

Proving ground

In October 2007, a major operator first applied the technology in its field on Alaska’s North Slope. The project scope was to perform a fishing operation for a stuck toolstring.

The well had a slickline toolstring stuck since 1991. The fish was at 8,000 ft (2,440 m) at 27º deviation. CT was deployed to impact and push the toolstring to bottom using a vibratory hammer.

The operator programmed the tool to record pressure, temperature, impact (up and down) and inclination. Using the vibratory hammer the fish was jarred downward for a period of 20 minutes with a total of 24,000 impacts to move the fish to bottom. The DataCoil system had been placed between the fish and the vibratory hammer in order to capture all wellbore and BHA samples. Expected impact loads from the vibratory hammer were to be approximately 10,000 lbs. Once recovered the system delivered data that showed impact forces of 9,450 lbs were applied to the fish.

Upon its recovery, the operator was able to use the custom software package to download accurately captured pressure, temperature and inclination data. The inclination sensor captured both a wellbore angle of 27º and an actual jarring angle of 31º showing that the toolstring was leaning to the high side of the tubing during impacting. It should be noted that the compression/tensile sensor had been turned off for this application.

The digital view of the CT’s performance gave the operator a better understanding of the dynamic forces within the CT BHA and wellbore environment. Currently the only available option to acquire such data was from real time data acquisition which is both costly and difficult to obtain.

In the eyes of the Alaskan field operator the ability for any sensor module to be deployed and undergo such extremes from both the wellbore environment and the punishing impact regime would seem an unlikely candidate for survival. The DataCoil system that was deployed on the fishing operation has since been deployed in nine other well bore, scale cleaning, wellbore analysis and fishing operations.

In the wings

Due to the tool’s continued use in more than a dozen other projects in Alaska and the Gulf of Mexico, the company is currently adding a torque sensor and Casing Collar Locator to its arsenal of logging parameters. A real-time version (developed jointly with a US operator) is currently under development with an expected release date of November 2008.

The addition of real time technology is intended to give operators the ability to change flow rates, tension or compression on the coil with actual BHA and wellbore information supplied topside, which eliminates guess work and the chances of costly miss-runs.

Since its development the technology has transcended from CT operations and is now being developed and implemented into drilling systems.

CAPTION: Figure 1. Shows Bi-directional Impact forces acquired from the bottomhole assembly during fishing operations in a 310 well bore. (Images of IGS)