1. Field of the Invention
The present invention relates to apparatus for making subsea interventions and more particularly for making such interventions using a spoolable compliant guide.
2. Description of the Prior Art
An operator may perform a subsea well intervention for various reasons including, for example, in response to a drop in production or some other problem in the subsea well. Such an intervention operation may involve running a monitoring tool into the subsea well to identify the problem, and depending on the type of problem encountered, the intervention may further include such steps as shutting in one or more zones, pumping a well treatment into a well, or lowering tools to actuate downhole devices (e.g., valves).
The performance of a conventional subsea intervention requires the operator to deploy a rig (such as a semi-submersible rig) or a vessel, as well as a marine riser, which is a large diameter tubing that extends from the rig or vessel to the subsea wellhead equipment. Performing intervention operations with large vessels and heavy equipment such as marine riser equipment is typically time consuming, labor intensive, and expensive. Accordingly, such conventional intervention is only performed when economics and risks are favorable. In other cases, the well performance is simply accepted without intervention. As a result, subsea wells typically produce less and for a shorter duration than platform wells.
Many subsea well operators attempt to predict future needs of the subsea wells by installing expensive completion equipment that would enable the subsea wells to fulfill these future needs without the necessity of performing a well intervention operation. Installation of such equipment substantially increases the cost to complete the subsea well. However, since the reservoir description and its dynamic behavior are usually better deciphered and understood over time, it is likely that some anticipated future needs might not materialize and some unexpected ones might appear. In other words, some of the costly completion equipment may never be utilized and equipment which turns out to be needed may not be present at the subsea wells. Nonetheless, many subsea well operators install this expensive completion equipment and accept the consequences, whatever way they may turn out, instead of performing an intervention.
A spoolable compliant guide (“SCG”) has been proposed for use in a subsea intervention operation. An SCG is constructed as a hollow tube which may be continuous or jointed, and has a first end for engagement with a floating vessel and a second end engaging a subsea wellhead. The SCG acts as a conduit between the floating vessel and the subsea wellhead for coiled tubing. Such an SCG is described in U.S. Pat. No. 6,386,290 to Headworth, which is owned by the Assignee of the present application and which is incorporated herein by reference.