Woodside Scarborough site investigation

THE CHALLENGE 

Six locations were completed adjacent to subsea infrastructure comprising two locations adjacent each side of three separate live infrastructure pipelines. Prior to completing these locations, the vessel was setup on location and completed positioning trials to assess the prevailing environmental conditions. The locations were only completed where the environmental conditions created a drift-off position, as a consequence prevention measures in the event of a complete vessel blackout and loss of station keeping. Target positions were as close as 250m to the pipelines. Benthic worked with our client to comply with all permit conditions and complete the work in a safe manner. 

Five CPT and sample locations and six (2 re-runs) box core locations were performed on seabed slopes greater than 10°. At these locations, Benthic completed risk assessments and local gradient checks using onboard survey equipment to confirm the gradient and bearing of the seabed. The PROD was then positioned over the target test location and landed, then monitored for 30 minutes prior to commencing geotechnical testing to confirm no movement of the machine was noted, and no unexpected movements occurred. The works over the steep slopes were completed without incident or damage to equipment with one test location being 18.8° and two other test locations located on a slope greater than 17°. 

THE SOLUTION & RESULT 

Benthic’s PROD was able to complete 233 individual test locations within 57 days, including one scheduled port call for crew change-out and five production days lost as a result of evasion plans for Tropical Cyclone Riley. In water depths between 70m and 1,390m, Benthic acquired 1,500m of CPT data; 550m of undisturbed samples; 25 Seismic tests intervals over 60m length and 38 box core samples within this timeframe. This testing included one CPT completed in a single push to 80m depth. PROD’s unique footing design also allowed us to collect data from the mud line.