Undersea LNG pipeline span investigation

Sweep survey methods such as the multibeam echo sounder and side scan sonar are used to investigate and determine the height span of an undersea liquefied natural gas (LNG) pipeline. Such methods to monitor seafloor targets have proved to be beneficial because they are more convenient, efficient, economical, and less risky than other survey equipment. Taiwan-based Chinese Petroleum Corp. (CPC) laid an LNG pipeline under the sea using side scan sonar image-forming geometry. The multibeam transducer used in the survey was Reson Inc.'s SeaBat 810 that has a full beam width of 120° and is composed of 80 beams. The results, according to the calculations, estimate the span height by comparing the side scan image with the field-investigated figures using the ROV. CPC also hired a marine company to double-check the free-span locations using a remotely-operated vehicle (ROV) equipped with robot arms to lay bags at the free-span gap.