Regular inspections are required of the pipes carrying oil and gas from rigs and subsea oil and gas installations. Greater sensitivity to environmental hazards and increasingly rigorous inspection requirements has led to a need for a rapid, regular, high quality survey capability.
Inspection of installed oil and gas pipelines is typically carried out by high frequency sonars and cameras, both of which need to be close to the pipe in order to get useful images. The inspections are especially challenging around offshore rigs and subsea installations, where safety of personnel and equipment is a major concern when carrying out boat-mounted or towed surveys. The risk of collision means that production usually needs to be halted during boat-mounted survey work. A client of NCS Survey (headquartered in Aberdeen UK, with operations worldwide) was seeking an inspection technology that would allow drilling operations to continue safely; the NCS Survey fleet of low logistics Gavia Autonomous Underwater Vehicles (AUVs) offered a solution that fitted the challenges.
The Gavia Offshore Surveyor AUV from Teledyne Gavia (manufactured in Reykjavik, Iceland) allows inspections to be carried out from a boat stationed outside the installation’s safety exclusion zone. NCS Survey now operates a fleet of four Gavia AUVs that carry a suite of survey-grade sensors to site. The Gavia’s small size and DVL-aided inertial navigation allows it to follow pipe routes right up to the rigs with no risk to the installation, and the modular mission-configurable construction enables the right set of survey sensors to be chosen for each task.
Low logistics AUVs offer benefits in terms of safety of operations, ease of deployment, and cost when compared to dedicated survey vessels, towed systems, ROV operations, or larger AUVs. Using the Gavia AUV a small team can carry out a full inspection from a vessel of opportunity located safely away from the rig, enhancing personnel and installation safety without interrupting operations.