The cost of remedial work on marginal gas wells sufferingfrom water unloading problems can be prohibitive, especiallyin an offshore environment. The expected financial returnoften does not justify the rig costs associated with pulling andrunning a new completion, while the formation damage causedby many well-killing methods can reduce the productionpotential of already marginal wells.A Coiled Tubing velocity string can often prove a quick andcost-effective method of assisting in water unloading. Theability to work in live well conditions avoids damaging theformation, making it an ideal solution in many cases.However, the limited lifespan of carbon steel strings incorrosive environments calls for a different solution. The nextoption is often to run and hang off a chrome tubing string witha snubbing unit, which makes running corrosion-resistanttubing in live well conditions possible. However, the highercosts and increased time associated with a snubbing unitreduce its attractiveness.The unconventional operational procedure of runningcorrosion-resistant jointed tubing with Coiled Tubingequipment has been used on few occasions to combine thebenefits of Coiled Tubing and snubbing interventions.Although generally restricted to relatively short tailpipes, thismethod has on occasion been extended to running full velocitystrings. The limited tensile load capacity of the externallyflush threads has limited the length of the string in some cases.A solution to this problem where a complex string is run intwo independent sections has been applied in the field toincrease the total velocity string length to 4115m.The paper discusses the design and execution of the operationwhere Coiled Tubing and jointed tubing were used as a complex velocity string in order to restore production on a gaswell, while retaining the full functionality of the downholesafety valve. Particular attention will be paid to the design ofthe string, which had to be tailored to remain within theoperating envelope of the externally flush thread.
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