1,000 1,200
Gooseneck Injector head
200 400 600 800
0 1965 1972 1978 1987 1988 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004
Blowout preventer stack
Control cabin
Tubing reel
> Coiled tubing activity— 1965 to the present. Development of continuous tubulars began in World War II with project PLUTO (Pipe Lines Under The Ocean) in 1944. In the 1960s, coiled tubing (CT) was used to wash out sand, retrieve subsurface safety valves and lift uids out of wells with nitrogen. Later, CT applications expanded to include acid and fracturing treatments, tool conveyance, tubing replacement, drilling, arti cial lift and well completions. As a result, the number of CT units operating worldwide increased from a few in 1965 to more than 1,000 in 2004.
These capabilities are especially useful in wellbore cleanouts, jetting with inert gases or light fluids, perforation acid washes, acid or fracture stimulations and sand-consolidation treatments, cementing, fishing and milling, underreaming and underbalanced drilling. Adding an electric line, data or power cables inside coiled tubing strings facilitates well logging, downhole monitoring or control, directional drilling and electrical submersible pump (ESP) installations.
Deeper high-angle wellbores are increasingly common and many are beginning to require remedial interventions. Going into deeper wells
increases coiled tubing weight, requiring stronger pipe and injector heads plus improved fl uids.2
1. Ackert D, Beardsell M, Corrigan M and Newman K:
CT is a viable option for these demanding remedial operations, but detailed planning is required to ensure job safety and effi ciency. Better tubular manufacturing and quality control had a significant positive impact, but equipment optimization and improved opera- tional techniques and procedures have been equally important in improving CT performance and reliability. This article reviews the latest developments in CT wellsite effi ciency, wellbore and reservoir remediation applications, new downhole tools, reentry and underbalanced drilling operations and artifi cial lift.
“ The Coiled Tubing Revolution,” Oil eld Rev iew 1, no. 3 (October 1989): 4– 16.
Bigio D, Rike A, Christensen A, Collins J, Hardman D, Doremus D, Tracy P, Glass G, Joergensen NB and Stephens D: “ Coiled Tubing Takes Center Stage,” Oil eld Rev iew 6, no. 4 (October 1994): 9– 23.
2. Hodder M, Michel C, Kelligray D and Bailey L:
“ Investigation of Polymeric and Mixed Metal Oxide Fluids for Use in Well Intervention Operations,” paper SPE 89637, presented at the SPE/ICoTA Coiled Tubing Conference and Exhibition, Houston, Texas, USA, March 23– 24, 2004.
Spring 2004
39
Worldwide CT unit count
Well cleanouts Fishing
Jetting fluids Acidizing
Better injector heads 1,500-ft steel stock Improved manufacturing 1 1⁄ 4-in. tube HSLA steels 1 1⁄ 2-in. tube 1 3⁄ 4-in. tube
3,000-ft steel stock Bias welding 2-in. tube
Logging and drilling 2 3⁄ 8-in. tube 2 5⁄ 8-in. tube HPHT services 2 7⁄ 8-in. tube 3 1⁄ 2-in. tube 4 1⁄ 2-in. tube Scale removal
Selective stimulation Multilateral access Advanced onshore units HPHT inflatable packers Wireless depth control Advanced offshore units Optimized cleanouts
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