Removing the challenges of pigging by knowing exactly where they are located.Download PDF
Locating a stuck pig
Halliburton Pipeline and Process Services successfully executed an extensive pipeline pre-commissioning campaign in the East Mediterranean. During the proceedings, a lost-pig occurrence prevented completion of the dewatering workscope of an 18” pipeline. Halliburton Pipeline and Process Services were hired by the EPC contractor to carry out an InnerVue survey to locate the lost pig and track its location during recovery.
The lost pig was located within a relatively long subsea pipeline. Surveying with an ROV was not practical due to the length of the line and associated cost. A simpler, fast and accurate method of locating the pig was required.
To locate the stuck pig, a negative pulse InnerVue survey was used. A controlled hydrodynamic wave is induced into a pressurised pipeline system, and the position of a significant flow impairment such as a blockage or pig can be determined by identifying reflexes visible in the recorded data trace. This method is suitable for use in both fluid and gas systems, though the analytical approach for either is very different. The InnerVue survey provided critical information necessary to develop a pig recovery plan after discovering that the lost pig was located 16.5km from the platform. Working closely with the EPC and Field Operator, a reverse pigging operation, involving Halliburton managing a combination of specialist services onshore, offshore, and remote deepwater, was conducted to recover the pig. A foam pig was launched from the deepwater pipeline end and travelled towards the platform over the course of five days. The propellant was nitrogen gas supplied from a membrane spread transferring N2 gas via a gathering pipeline and a crossover at a subsea manifold. Pig tracking specific InnerVue surveys were performed on board the production platform throughout the reverse pigging operations. In live conditions, pressure waves were transmitted through the system allowing real time monitoring of the now-found-pig location. Once the foam pig reached this location, both pigs in unison began moving towards the platform. Surveying continued throughout and provided a real-time location, speed, and estimated time of arrival. Upon pig receipt, a final survey was performed to confirm that all pigs had been recovered. The survey results showed that there was still a pig in the line at the subsea isolation valve location, 364m from the platform. Flow resumed until the final pig was received, allowing cessation of operations and removal of the temporary topside launcher/receiver.
Results of the InnerVue PipeSuite survey provided the information needed to evaluate and engineer an appropriate remediation plan for removal of the stuck pig. During operations to retrieve the pig, InnerVue provided live location tracking of the pig as it progressed back to the pig launcher.