Free Span Rectification of Subsea Pipelines-A Case Study from Kharg Island and Asaluyeh Port, Iran

Iranian Oil Terminals Company (IOTC) contracted Dulam International Ltd to carry out free span anomaly rectificationof four (4) 56 Crude Oil pipelines Azarpad shore to Pier (PL1, PL2, and PL5 & PL6) at Kharg Sea Island and one (1)30 pipeline between Asaluyeh Port and SBM No. 1. The operations were carried out between 3rd November 2009 and27th November 2009. This paper describes the free span rectification of the installation of grout bag supports under theabove mentioned pipelines by the Dulam International Ltd Diving Team from the DPII DSV Team Muscat.Free span rectification on pipelines was carried out by using Air Diving technique with the Diver being deployedand recovered using a wet bell. A Remotely Operated Vehicle (ROV) Sea Eye was utilized to identify and observe thefree span along each pipeline. Horizon Survey Company provided services for positioning vessel, ROV and providedassistance in final positioning of the grout bags for the correction of free spans. As per engineering calculation 10 m offree span is allowed for the rectification of this 4 x 56 P/L &1 x 30 P/L. The Subsea pipeline rectification task wascarried out on 24hrs basis.

Keywords:

free span , remotely operated vehicle (ROV) , dynamic positioning (DP) , high flow excavator (HIFLEX)