T.D. Williamson (TDW) was contracted by an operator in the Gulf of Mexico to replace two flexible joints connecting two steel catenary risers on a tension leg platform 120km (75mi) off the coast of Louisiana.
TDW performed simultaneous isolations on the operator’s platform’s 10in oil pipeline and 14in natural gas pipeline using the SmartPlug double block and monitor isolations. As a result, a low volume of product needed to be evacuated before the inline joint replacement.
Prior to the project execution, TDW performed communication and pull-tests in a test rig to test the efficacy of the tool.
The 10in oil pipeline was first isolated using a combination of high friction and high sealing pigs that traveled a total distance of 84m (276ft). After the pipeline section was depressurized, it was partially lifted out of the seawater to allow access to the flexible joint. Once the new joint was in place, the pipeline was re-pressurized. The SmartPlug tool was then lowered by cable into the riser—below the new flexible joint—where it was used, along with a ported blind flange, to create an isolation barrier for hydrotesting the new welds.
The 14in natural gas line isolation followed a similar, yet more intricate, course: A three-module SmartPlug tool traveled a total distance of 72m (250ft) to perform a DNV GL-certified, double block and monitor isolation and provide an additional barrier to enable a hydrotest after the flexible joint was replaced. Prior to execution, however, concern was placed on the tools ability to pass through the platform’s inline-check valve. As a result, the line was first inspected using a high resolution deformation inspection tool. The inline inspection (ILI) data was utilized in the SmartPlug tool piggability report during the engineering phase, giving both TDW and the operator the confidence that the tool would make it through the check valve.
“The ILI information and engineering studies provided a high level of assurance that the line was acceptable for SmartPlug tool operations,” said Jay Knudsen, TDW project manager. “Data from the ILI run was useful to the [operator’s] process engineers and may be applicable to additional projects.”
According to the operator, the replacement project required close collaboration among multiple service companies, and it was completed ahead of schedule and under budget.
Image: SmartPlug installation/TDW
Subscribe
