Based on the geophysical survey results, some part of the pipeline were found in free spans conditions. Interpretation from the geophysical survey shows that there were at least 181 free spans area along the pipeline with the length up to 200m and some of the pipeline was shown with span almost 3m above seabed. The ROV survey was then deployed to verify the free spans area and to check the other findings from the previous geophysical survey
Verification of freespan was conducted by setting up coordinates of the suspected area on the navigation software and ROV will start its investigation from the beginning of each free span to the end of it. Dual head scanning profilers, visual cameras which were installed on each side of the ROV and in front of vehicle were used to record pipeline condition along the suspected location. Position and depth of the ROV was overlaid to the video recording and the profile of seabed and pipeline along the inspected area were recorded in the navigation software
Information derived from the ROV inspection will then compared to the geophysical survey result and the final freespan condition were confirmed and results are tabulated for further rectification if required. Generally, there were 181 freespans locations inspected by ROV. Results of freespan from Freespan #1 at KP 3.638 to Freespan #181 at KP 233.978 are listed. There are some miss leading geophysical interpretation for the sample taken at KP 101.108 to KP 101.281, where from the geophysical survey was reported that the free span was found 150.1m but from the ROV visual inspection was found that the pipeline was set on seabed at some points with a maximum distance not more than 35m. Based on the ROV visual inspection, there were 29 freespans were found more than Maximum Allowable Span (MAS)
East Java Gas Pipeline Pipeline (EJGP) is the longest offshore gas pipeline in Indoensia. It transports gas receiving from Central Processing Plant on Pagerungan Island in Kangean Islands through the Madura Strait and onshore via Porong Sidoarjo to Surabaya with the total length of offshore part is 368km. The ROV is the first to be used to inspect this offshore gas pipeline.