Traditionally, coiled tubing (CT) counters have been mounted above the injector and typically on a levelwind between the coiled tubing reel and the injector. This tends to expose the coiled tubing counter to vibrations, jerks and slippage as the levelwind traveling head assembly slides from side to side and the coiled tubing is run in to the well or pulled out of the well. As a result of this exposure, the depth measurement accuracy of traditional coiled tubing counters is compromised. In the shallow gas market of the Western Canadian Sedimentary Basin, the error in depth measurements associated with coiled tubing velocity strings has been found to be significant and around 6 metres. Depth confirmation is typically then carried out using slickline. As a result of the error in depth measurement and the additional depth confirmation activity during the installation of the velocity string, the overall job time, the cost of operations and exposure of personnel at the wellsite are significantly increased.
Select Energy Systems, Inc in partnership with Count-Rite Oilfield Services, Inc., has developed a length measurement tool for coiled tubing, the SelectRite coiled tubing counter. The SelectRite CT counter is installed below the injector, and field tests have shown that it eliminates the limitations of traditional coiled tubing counters highlighted previously. Data transfer from the counter to the electronic display is wireless.
Currently, four operators in Western Canada will not land their velocity strings without using Select Energy's coiled tubing counter. For all these operators, accurate surface depth measurements have been achieved using the counter, thereby eliminating the requirement for additional depth confirmation and related personnel on the jobs.
This paper discusses Select Energy's coiled tubing counter which is designed for use with CT outside diameters (OD) of 19.05 mm to 50.8 mm and is currently being used mainly for coiled tubing completions operations in Western Canada.
Select Energy Systems Inc. (SESI) was established in 1988 and was one of the first companies to offer CT completion services and related products in Alberta, Canada. Although coiled tubing was used in World War II to pipe fuel, coiled tubing technology was not applied to oil and gas operations in Canada until the 1980s.
The continuous need to reduce costs and increase production, especially in the shallow gas segment of the Western Canadian Oil and Gas industry has driven the coiled tubing service providers to move away from using the heavy-duty CT units (CTUs) to self-contained multi-purpose CTUs designed for quick rig-up and reduced personnel requirements. Often times, these low-cost CTUs have depth measuring devices that are less accurate than the more expensive CTUs with more intricate surface pipe measuring devices.