TDW Offshore complete subsea flex-joint installation on Independence Trail

Safe and timely repairs were essential on the leaking subsea flex-joint due to the important role of this natural gas export riser. The Enterprise Independence Hub platform has the capability to handle more than 10% of the natural gas transported from the Gulf of Mexico. Located approximately 85 feet (26 m) below sea level, the flex-joint allows the riser to withstand the movements of the platform. In order to facilitate the riser repair, Enterprise engaged TDW to isolate this flex-joint assembly, with its piggable, tetherless, SmartPlug® isolation tool.

The platform riser had previously been assessed by TDW for possible isolation with its remote-controlled SmartPlug high pressure pipeline isolation tool. This assessment allowed TDW to quickly mobilize a double block module 20-inch SmartPlug tool to the platform where it was temporarily installed in early May. The tool was launched and pigged (pumped by water) into the riser just below the flex joint. This allowed Enterprise to maintain pipeline pressure downstream of the flex-joint. With ambient pressure above the flex-joint, divers then replaced the o-ring gasket subsea and then after resealing, the entire riser was successfully pressure tested. Consequently, Enterprise was able to resume the gas flow from its production fields through the riser. The entire isolation operation was completed in just 10 days.

“This was a challenging situation for Enterprise, especially in view of the 134-mile length of the pipeline and the fact that the Steel Catenary Riser (SCR) is operating in a depth of 8,000 feet of water,” said Mark Roberts, General Manager Americas for TDW Offshore Services. “The flex-joint repair was achieved without degassing and flooding the riser, and recommissioning it post repair, which would have been far more costly in terms of production downtime and marine spread cost.” he added.