Patent ID: 7708839
Filing Date: 2010-05-04
Classification: F16L

Abstract:
1. A method for dewatering a pipeline having at least one end near the seafloor comprising: attaching a compressed gas source to a first end of a pipeline having a dewatering pig disposed within; attaching a pig receiver to a second end of the pipeline located subsea, said pig receiver including a gas-fluid separator adapted to separate gas from fluid being pulled through the pig receiver; attaching a subsea dewatering pump in fluid communication with the gas-fluid separator; releasing the compressed gas behind the dewatering pig to push the pig toward the second end of the pipeline; operating the subsea dewatering pump with a submersible vehicle (SV) to draw fluid and the pig towards the second end of the pipeline; separating gas arriving at the pig receiver via the gas-fluid separator and collecting the gas that enters said pig receiver in a gas chamber; and sensing gas in a water outlet line of said pig receiver and, upon said sensing, shutting off said dewatering pump, wherein gas collected in the gas chamber is vented when the dewatering pump is shut off and the dewatering pump is restarted after venting of the gas to prevent gas locking of the subsea dewatering pump, thereby drawing essentially all the water out of said pipeline with a subsea pump operated by a submersible vehicle (SV) at said end near the seafloor.