| 摘要 |
Thruster pig for sending through a pipe from an entrance facility to a receiving location, for servicing or monitoring, by pumping a thrusting fluid into the pipe to force the pig forwards into the pipe, said thruster pig comprising: a body having a front end and a back end, which back end includes a reaction surface to which said thrusting fluid applies a motive force, said body having a diameter slightly smaller than the inner diameter of the pipe, a seal circumferentially arranged on the pig to seal between said body and said pipe, a connector for releasable connection of a return flow line to the pig, said connector including a shifting mandrel that is activated to open the connector by pumping a ball through the return flow line, said ball being retained in the return flow line after opening the connector, a blanking device arranged to blank a bore left as the return flow line is disconnected; such that said thruster pig and any connected servicing or monitoring equipment is operable by pumping a fluid into the annulus between the pipe and the return flow line while returning fluid through said return flow line as required to maintain a differential pressure over said pig to urge said pig forwards through the pipe, while at any point said return flow line can be disconnected from the pig and retrieved to the entrance end and the blanked pig can be urged forwards to a pig receiving location by pumping or directing fluid into the pipe. A thruster pig system for hydrate removal is an embodiment of the invention. |
