Coiled Tubing conveyed Electrical Submersible Pump completions (CT-ESP) have now been established as a costeffective means of improving production in pressure depleted reservoirs, with low installation and work over costs. However, due to max lift limitations, and crane down grading practices associated with offshore platforms, the use of CTESP's in many cases cannot be considered, because it is simply impossible to lift a CT-ESP reel of the required length on board the platform. This paper describes a worked solution
for a conventional CT reel that exceeded the platform crane lift capacity. A worked solution
for a CT-ESP recompletion, followed by a proposal
for a complete CT-ESP solution, with a focus on overcoming the max crane lift issue, thereby allowing deeper CT deployed ESP completions in the future.
The reservoir parameters that normally trigger the need for CT-ESP completions are low flowing bottom hole pressures (FBHP), gas lift no longer effective, water injection causing unacceptable water production, and a need for increased drawdown capability. These parameters typically exist in wells that have produced over a long period of time. Here is where the conflict of interest exists for the CT-ESP solution. If a well has been producing for twenty years then the offshore platform has been operational for even longer. This means that the platform crane will either have had a low max lift capacity to begin with (as is the case in marginal fields with small platforms) or will have gone through a down grade program as the platform has aged. The scenario is simple, how do you get a CT-ESP reel in excess of 30 Tons onto a platform with a max crane lift of 20 Tons? For example a 10,000ft CT-ESP string, outside diameter (OD) 2 3/8", with 0.204" wall thickness, including lifting arrangement and transport base weights 34.5 Tons. The present solutions of boat spooling or crane barge are prohibitively expensive. The solution described here is to transport the required length of CT on two separate reels and use a split reel spooler system. The challenge then is to join the CT sections together on the platform. This will be achieved using a specially designed tube / tube connector. This not only enables the pipe to be joined together, but also allows access to enable the splicing of the electrical cables and hydraulic control lines inside. From an engineering perspective, the joining of two conventional CT strings offshore presents a number of challenges if field welding is not an option. However, existing methods, tools and equipment can be used in innovative ways to overcome these challenges. The added complexities associated with joining electrical cables and hydraulic flow lines will involve new design concepts for the connector and some inventive methods being applied to ensure a successful connection offshore. It is clear that the problem with crane lift capacities must be overcome, as it is safe to say that the CT-ESP completion solution will always be faced with platform crane lift limitations.