Loop currents impart loads and deflections onto subsea structures such as blow-out preventors (BOPs) and risers such that the ability to connect and disconnect a BOP to and from a wellhead is hampered. The current may deflect the hanging riser and BOP system away from vertical to a degree that the BOP cannot be latched to the wellhead.
If the BOP is already latched when the current loads are induced, there is no way of knowing what effect those forces will have on the BOP and riser once the connector is unlatched and the BOP is lifted off the connector. If the forces are sufficient, then the current may sweep the BOP and the riser into other equipment installed on the seafloor.
At the current time, drilling operations are halted in strong loop current conditions.
The attached figures illustrate various aspects of exemplary embodiments of the BOP Current Load Monitoring and Control System.
In its various embodiments, the subsea structure load monitoring and control system described herein below allows the running of a subsea structure, e.g. a blowout preventer (BOP), in strong loop currents or other induced loads such as current-induced loads or loads induced by lateral displacement of a vessel away from a wellhead. In the following exemplary embodiments, a system for monitoring loads in such structures, e.g. BOP connectors or risers, allows induced loads such as environmentally induced loads resulting from currents, vessel drift, and the like, or a combination thereof to be monitored and, once the loads are known, counteracted by inducing equal forces in the opposite direction.
Referring now to
Sensors 20 interface with and are read by appropriate sensor electronics 22. Sensor electronics 22 may be located on subsea structure 10, lower marine riser package 14, a remotely operated vehicle (ROV) 12, a thruster package (not shown in the figures), or the like, or a combination thereof. In any embodiment, load information obtained from sensors 20 is used to adjust the thrust output of ROV 12 or a thruster package so as to induce a load equal in force, but opposite in direction, to the induced loads such as current-induced loads.
In the operation of a preferred embodiment, referring now to
Referring now to
Once the current load and the externally applied counter-force have been applied, an operator can release subsea structure connector 11 and raise subsea structure 10 off of the wellhead without fear of subsea structure 10 or its associated riser, if any, being swept into other equipment. For example, subsea structure 10 may stay vertical during the release and raise operation.
The foregoing disclosure and description of the inventions are illustrative and explanatory. Various changes in the size, shape, and materials, as well as in the details of the illustrative construction and/or a illustrative method may be made without departing from the spirit of the invention.
The present application claims priority in part through U.S. Provisional Application 60/950,184 filed Jul. 17, 2007.
Number | Date | Country | |
---|---|---|---|
60950184 | Jul 2007 | US |