Ongoing Developments and Operations In almost every area of oil and gas activity, CT is a fi rmly established technology for remedial well interventions and the drilling and completion of new wells (previous page and right). CT allows selective placement and accurate controlled delivery of chemical, acid and fracturing treat- ments. It is also used to clean, protect or replace existing tubulars. CT versatility is especially valu- able in wellbores with questionable tubular integrity, or wells requiring fl ow conformance for water and gas control, and also for sand control. CT services can be executed effi ciently under
almost any condition, including live wells, while ensuring optimal well control. In addition, CT allows real-time communication with downhole tools conveyed to control treatments, manipulate hardware and analyze reservoir properties. This technology has proved effective for developing low-permeability, low-pressure and mature or depleted reservoirs in which conventional tech- niques fail to achieve commercial production. Upgrading existing tools and techniques while developing new technology remains a key to CT success as does improving our understand- ing of coiled tubing behavior and risk assessment. Combining multiple systems or pro- cesses yields new and unique solutions to old well-intervention challenges. For example, Schlumberger has made further advances in sys- tems for operating CT units from anchored
fl oating vessels and platforms, and recently fi eld tested a new through-tubing gravel-pack system with reentry capabilities.26 Deeper, higher pressure, higher temperature and extended-reach wells increase the complex- ity of CT operations. In 1995, Schlumberger began using simulators in training centers at Kellyville, Oklahoma, USA, and Bottesford, England,
to familiarize employees with
CT equipment, operations and contingency pro- cedures. Capitalizing on extensive simulator experience and continual improvement in portable computer capabilities, Schlumberger followed this with development of portable simulation-based training. The resulting CT Sim computer-based learn- ing resource presents concepts, equipment functionality and operating procedures. The intent was to provide prerequisite knowledge and practice in order to optimize training at the learning centers or in fi eld locations. Scheduled for release in 2004, the CT Sim program will be a key component for training and recertifi cation of CT supervisors and engineers.
> Coiled tubing pilot drilling program in Colombia’s Cusiana eld.
Schlumberger continues to develop and
refi ne equipment, procedures and techniques to extend the operating pressure ranges for CT jobs, including high-pressure applications up to 13,500 psi [93.1 MPa]. Also in development are spoolable CT connectors and completion equip- ment, including gas-lift valves, which will facilitate operations in logistically challenging areas, such as mature offshore platforms and remote or environmentally sensitive locations. However, not all well-intervention applica-
tions involve pushing the limits of CT tubular capabilities, equipment and tools. CT continues to be a workhorse for many conventional well operations and services. Petroleum Development of Oman (PDO) used CT to optimize plug and abandonment (P&A) practices.27
Rigless methods with new cement and sealant technologies minimize costs while ensur- ing long-term environmental protection in these once prolifi c oil wells.28
CT saved up to 30% com-
pared with P&A campaigns using conventional drilling and workover rigs. This represented a total savings of more than US$ 5 million in a recent 60-well program.29
As CT reliability improves, operators are reevaluating candidate wells and targeting more completions for through-tubing or concentric remedial interventions, including some wells pre- viously considered too risky for CT operations. To that end, CT equipment and string reliability con- tinue to be the focus of efforts to reduce downhole risks and decrease operational failures. Schlumberger is committed to maintaining technical leadership in CT services through cost- effective solutions that address operator needs from the most basic to the most complicated applications, with skilled personnel to imple- ment them. The goal is to assure optimal well and reservoir performance through safe and effi - cient operations.
— MET
Spring 2004
57
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