Geo Oceans were recently contracted to complete a scope of work for a notable Oil and Gas company on their offshore FPSO facility. The facility featured a turret mooring system with one of the world’s largest swivel stacks that have been engineered to date. This feature was implemented to allow the Facility to remain in operation during cyclone conditions, which seasonally occur within the surrounding waters.
The primary challenge here being that the facility’s turret had a large, submerged section that was situated below the facility’s mean sea level. This area was permanently flooded with seawater due to an opening in the base of the turret. This essentially limited the client’s ability to conduct inspections while the facility was in operation. Luckily, however, Geo Oceans were able to utilise our mini-ROV Inspection Technology to perform visual and NDT inspection tasks within the submerged areas of the Turret.
Overall, twelve different inspection locations were identified by the client for inspection and methodology evaluation. Of these twelve, six locations were inside the turret, with the remaining six being outside. The external locations required our ROV to fly through the annulus at the base of the turret and perform inspection tasks below the turret and hull, presenting an additional challenge due to the strong currents and water conditions surrounding the entry. The main factor impacting ROV access to the areas of interest was the space permitted for inspection within the structure due to the close proximity of equipment inside the turret, making it extremely congested. In-water surge and visibility were also considered as possible factors, which could influence ROV accessibility, but these did not present any challenges during the campaign due to our equipment’s advanced in-flight capabilities.
In total, eight different inspection techniques were used within the inspection process. These methods ranged from GVI and CVI inspections in open areas to advanced methods such as ACFM trials in very restricted access areas and external locations below the turret. In addition to this, Cathodic Protection (CP) and Ultrasonic Testing (UT) were also conducted, allowing for 3D modeling on areas such as the Mooring Chain. All the testing methodologies used were accompanied by cleaning services accomplished through using a highpressure blaster equipped on our ROV. This allowed our teams to ensure that the surface of each area to be tested was correctly prepared before testing methodology was applied, enhancing the credibility and quality of results.
Overall, the execution of the project was very successful with the primary ROV accessing all areas of interest inside and outside of the turret, including all three levels. This was an incredible outcome as it allowed our team to demonstrate the durability as well as capability of our ROVs in accessing out-of-sight, confined areas in harsher-than-usual conditions.
Written by Evan Smith
