PDO has established a goal for well technology of being able to drill, evaluate, complete and service multilateral horizontal wells at balance or underbalanced. Reeled systems have a clear potential in this area. A project has been set in place to prove or develop technology to meet this goal. Separate trial programs are underway to investigate the drilling and completion elements required. These will be combined with the results of an underbalanceddrilling trial to allow under or at balance operations during each phase of the well's life.
The Coiled Tubing Drilling, Evaluation and Completion (CTDEC) project began in 1993 with a feasibility study outlining the potential benefits of a CT operation. Technical trials to prove the feasibility of the activities began in 1994 with a sequence of 3 drilling trials, and a single CT completion. In 1995, eight 3-1/2" CT completions were run; 4 ESP completions and 4 gas lift completions. Further trials are planned, 2-7/8" slim dual water injectors and 6 velocity strings for gas lift wells. Results so far indicate that the CT operations can be carried out technically. The next phase of the project will be to demonstrate the commercial viability of the activities in both the Drilling and Completion areas before moving to at or underbalance operations. The Drilling Engineering part of the project is continuing with a 15 well sidetracking trial to conform the economic benefits. The completion project is rounding off the technical trials before establishing further work scope. This article focuses on the Completion phase of the project.
The CTDEC project is guided by a Sponsor Steering Group (SSG) composed of the functional head of Production Technology, the Drilling Engineering manager, the head of operations in South Oman and the head of operation support in North Oman. Reporting to the SSG are 2 project managers, one for the drilling trials and one for the completion operations. With the number of issues to be addressed during the planning and operation phase, the role of the project manager is critical to the success of the project.
The CT completions project has 2 major objectives:
Demonstrate that the operations could be carried out in Oman
Provide sufficient data to allow future commercial scope to be assessed
5 completion types are addressed in the project scope:
3 1/2" gas lift completions - 4 wells. Conventional packer, sliding side door, gas lift mandrels and hanger have been selected to allow full well servicing capabilities. The alternative gas lift valves such as Halliburton'sclamp on system, or Camco's Spoolable valves do not allow the valves to beserved without retrieving the completion.
3 1/2" ESP completions - 4 wells run with the cable outside the CT. The final 2 wells were intended to be combined with the underbalanced drilling trials, however the project schedules have diverged too far for this. Alternative methods of deploying an ESP on CT - such as using annular flow withthe cable deployed inside the CT require further investigation.
The trials address current operations and are considered replacement techniques. At this stage, they do not address directly no kill or underbalanced activities.
Halliburton were selected as the completions contractor in 1994. They ordered and imported a Hydra Rig CTU for the trial program. This unit has an injector head capable of handling up to 3 1/2" CT and of generating 100,000lb. pull.