Autonomous Underwater Vehicles Ease Deepwater-Field Integrity Management

Abstract

This article, written by Editorial Manager Adam Wilson, contains highlights of paper OTC 22438, ’The Role of Autonomous Underwater Vehicles in Deepwater Life-of- Field Integrity Management,’ by Dan McLeod and John Jacobson, Lockheed Martin, prepared for the 2011 Offshore Technology Conference Brasil, Rio de Janeiro, 4-6 October. The paper has not been peer reviewed. Integrity management of deepwater fields requires routine general visual inspections of critical infrastructure. To date, the only way to conduct general visual inspection is through the use of remotely operated vehicles (ROVs). Deepwater ROV spreads are large and heavy, requiring large support vessels and a significant number of personnel at sea. The capabilities of unmanned underwater vehicles have been enhanced through developments in autonomous technology, progressing to the point that autonomous underwater vehicles (AUVs) can now routinely conduct general visual inspection of subsea facilities. Introduction AUVs are smaller than ROVs, require less deck space, have fewer operators, and are free from precise-positioning requirements of the support vessel. Advances in autonomy, coupled with unique mission sensors, greatly reduce the human interaction required when collecting images of oil and gas underwater infra-structure. These factors dramatically reduce the operational cost of a deepwater inspection. The Marlin AUV system recently completed a series of tests in the US Gulf of Mexico, demonstrating autonomous change detection of a fixed off-shore platform. Benefits of autonomous inspection include Reduced cost of operations Faster inspection Automatic change detection Georegistered inspection data Simultaneous operations from a single support vessel Large standoff distances from the facility being inspected Increased safety of operations Reduced environmental impact Reduced specification requirements on support vessel Subsea Integrity Management A key element in any integrity-management program is regular in-service inspections. As the industry moves into deeper and harsher environments, challenges faced by operators include the high cost of subsea inspection and the limited inspection intervals available. Inspections provide a snapshot of the structural health of the system. An ROV inspection of a deepwater facility can provide visual evidence of structural degradation, impact damage, corrosion, valve damage, leaks, vibration, and other structural damage. Benchmarking the condition of subsea equipment following installation and tracking its status over time can provide a history of the deterioration rate. Deepwater Inspection Tasks Visual inspection of deepwater facilities routinely employs ROVs piloted by operators on the surface while recording high-definition video data. Video inspections include equipment that is often spread over many square kilometers, requiring the support vessel to maneuver for days. Inspection speed is totally dependent on the coordinated movement of the ROV and support vessel and on the skill of the ROV pilot.