Flexibility in equipment layout reduces
rig-up time and improves CT operations. Conventional offshore CT units typically involve 54 crane lifts during rig-up; the new unit cuts this number to 36. CT SEAS components travel to the wellsite preassembled and pretested on skids to reduce the number of crane lifts and the amount of manual equipment handling. The injector head is transported with the connector installed. A self-folding gooseneck and partially automated process for stabbing coiled tubing into the injector head limits personnel exposure to hazards. To simplify hookups and pressure testing, the improved skid designs have fewer valves and some piping is connected and tested in advance as modular components. Distributed electric control of valves in place of centralized hydraulic control reduces the number of hydraulic connections. The CT SEAS system has 36 hydraulic connections instead of the usual 84 of older units.
> A Valhall platform, North Sea Norwegian sector. The new CT SEAS unit performs perforating and wellbore cleanout operations before and after proppant fracturing treatments in the BP Valhall eld offshore Norway.
Wellsite Efficiency
A feasibility study in 2001 and subsequent engineering efforts resulted in a new offshore CT unit, which was launched in 2003. The auto- mated, modular CT SEAS Coiled Tubing Safer, Efficient Automated Solutions system was first installed on a BP Valhall field platform in the North Sea Norwegian sector (above).3 A typical Valhall fi eld horizontal well requires 5 to 12 separate fracture stimulations. To save time, BP performs drilling and completion operations simultaneously on the platform. After well-completion equipment is installed, the drilling rig skids to the next wellhead slot. A large CT unit and a stimulation vessel complete the wells. The fi rst CT run performs wellbore cleanout
and perforating. The stimulation vessel then pumps a proppant fracturing treatment. The next CT run cleans out excess proppant, but leaves a sand plug to isolate the preceding fracture. The next interval is perforated, and this cycle continues until all zones are stimulated.
In the past, conventional CT units operated
with a 13-member crew. The equipment spread consisted of a control unit, reel and power pack, well-control equipment, two high-pressure posi- tive displacement pumps, mud shakers, flow valves and chokes, and an injector-head stand. Recent extended-reach wells with 2,000-m
-in. coiled tubing would increase operational efficiency and allow completion of additional intervals, but required a redesigned CT unit. An evaluation of platform operations and requirements, and local regulations helped engi- neers develop the new CT SEAS unit. The new design targeted decreases in rig-up and overall operational cycle times to achieve a 15% effi- ciency increase and a 30% reduction in CT personnel. The resulting CT SEAS unit consists of modular components that are easy to deliver and assemble, produce zero discharge and optimize space utilization offshore (next page, top).
[6,562-ft] horizontal sections drilled to tap outer areas of the field are more challenging than previous wells. The ability to use larger, heavier 27
⁄ 8
Control cabin ergonomics allow operators to react quickly and efficiently to any situation (next page, bottom). Automated process and equipment control reduces crew requirements from 13 to 9 members and allows the unit opera- tor to focus on well-intervention efficiency. Process-control software incorporates automated safety features that reduce risk exposure in set- tings prone to human errors.
During CT operations, job parameters are
monitored, recorded and plotted by the CoilCAT coiled tubing computer-aided treatment system for real-time data acquisition. The InterACT real- time monitoring and data delivery system provides secure Web-based, two-way communica- tion that makes fi eld data available at all stages of a CT operation.4
Authorized client and Schlumberger personnel have access to data and can monitor jobs remotely. Streaming data transfer facilitates real-time evaluation of operations to help fine-tune job procedures and speed up decision-making.
The CT SEAS unit has improved wellbore cleanout efficiency and allowed completion of more diffi cult fl ank wells. The capability of run- ning up to 6,000 m [1,829 ft] of 27
⁄ 8
3. Andreassen T, Langeteig B, Amaravadi S, Mallalieu R and Polsky Y: “ Field Launch of a Safer, More-Ef cient Coiled-Tubing Unit in North Sea for Valhall Stimulations,” paper SPE 89604, presented at the SPE/ICoTA Coiled Tubing Conference and Exhibition, Houston, Texas, USA, March 23– 24, 2004.
4. Cabanzo LE and Zhou W: “ Real-Time Data Delivery in Coiled-Tubing Well Interventions,” paper SPE 89528, presented at the SPE/ICoTA Coiled Tubing Conference and Exhibition, Houston, Texas, USA, March 23– 24, 2004.
-in. coiled
40
Oilfi eld Review
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