Petronas Carigali Sdn Bhd plans to install a Light Weight Structure platform (D28D-A) and a 8 km pipeline at D28 Field, located 90km NW of Bintulu, offshore Sarawak, in a water depth of 35m (115 ft) and are in the midst of preparing a field development plan. Preliminary hydrographic surveys indicated there may be coral outcrops present along the pipeline route and/or the structure deployment site, and require a rapid visual inspection to ascertain the accuracy of this information. It is understood that the original suggestion of the presence of corals was made through interpretation of the sidescan sonar imagery.
The objective of this study was to undertake a visual inspection of several points along the proposed pipeline route to determine if any corals were present which might warrant a realignment of the pipeline deployment.
We reviewed the sidescan sonar imagery provided by the hydrographers and PCSB to determine areas of potential coral development, based on bathymetry and seabed ‘rugosity’. On site we deployed a drop camera (UMS-7000) linked to a video recorder, and obtained SD footage of the seabed at those locations identified by the client. The camera was deployed at a number of stations along the pipeline and at points of interest to gather imagery of the seabed.
Interpretation of the imagery collected by the drop camera allowed a rapid investigation of the seabed substrate over an area far greater than that sampled by, for instance, a grab sampler, which only records the seabed at a particular small point on the seabed.