Platform jacket marine growth measurement
Overview
Our customer, a global energy company, had previously been carrying out marine growth surveys of jacket structures using ROV video and simple thickness probes. Whilst this method gives a gross estimate of the marine growth on the jacket, it is insufficient to quantify surface roughness, increase in diameter, volume of growth and other parameters.
To derive these parameters, Ashtead Technology was approached to carry out a survey to help collect data for generating an accurate 3D model of certain members of the North face of the jacket, from the splash zone to the base of the jacket, in 370ft water depth.
Solution
Ashtead Technology is a leader in subsea 3D imaging and metrology with a long history of utilising advanced laser, sonar and photogrammetry techniques to construct high resolution digital representations of subsea assets and infrastructure with sub-millimetric accuracy.
Specifically for this challenge, we provided a solution to survey the entire face of the jacket using the customer’s work class ROV on their light construction vessel. Ashtead Technology proposed using its ROV3D real-time 3D modelling system to generate models of select jacket members below 50ft water depth. The ROV could not go higher than 50ft water depth so a solution for modelling the section from that elevation to the waterline and above-water splash zone had to be found. Ashtead Technology used a high-resolution NORBIT Winghead Multibeam sonar and vessel mounted NORBIT Lidar for modelling that section.
Benefits and value
- All sections of the jacket that the customer needed surveyed were successfully completed
- Fast data collection time; approximately 24 hours
- Real-time model generation via ROV3D provides coverage mapping; system allows for higher accuracy modelling using digital stills, if needed
- 3D models allowed comprehensive measurements of marine growth, including average thickness and local maxima using surface elevation heat maps
Results
Ashtead Technology provided a comprehensive report detailing the results and analysis of the marine growth distribution, surface roughness and thickness. The customer was delighted with the solution which provided optimal results.
