Mitigation of ITA Rotation
Client: Total EP
Region: West Africa
Project: [Confidential]
Sector: Subsea Pipelines
The client approached Crondall Energy to investigate an ongoing issue with a 16-inch gas export pipeline, installed in 2007, that transports gas over 150 km from an FPSO to a platform in shallow water. The pipeline is located in West Africa in approximately 1100-1300m water depth.
The Problem
During an ROV survey performed 3 years into operation of the pipeline it was discovered that an Tn-line Tee Assembly (ITA), used for future connections, had unexpectedly rotated from its as-built position. The cause of the rotation was due to unexplained lateral buckling either side of the ITA which has not bee predicted during design. There was client concern that if left untreated, the rotation would increase and exceed what was allowable and prevent any future tie-in. Crondall Energy was tasked to match the surveyed ITA response through finite element analysis (FEA), preform integrity checks to the pipeline and and also investigate solutions to mitigate further rotation.
What We Did
Performed a muti-year survey review to investigate the changes to the pipeline over time.
Developed a FEA model of the pipeline including the ITA structure supported by its mud-mat.
Through analysis, matched the observed buckling behavior of the pipeline around the ITA resulting in rotation
Performed integrity checks of the pipeline in its buckled condition.
Determine the required restraint of the mitigation to prevent further buckling/rotation of the ITA.
Develop a concrete mattress solution and model its effectiveness through FEA
Develop an installation plan for the recommended mitigation.
Our Value
Gave confidence to the operator in continuing operation of the pipeline pre and post mitigation.
Provided a simple, cost-effective solution to a challenging problem.
Made future tie-in to the ITA possible to allow increase output of the field.
Decades of experience in subsea pipeline integrity assessments.
The Problem
During an ROV survey performed 3 years into operation of the pipeline it was discovered that an Tn-line Tee Assembly (ITA), used for future connections, had unexpectedly rotated from its as-built position. The cause of the rotation was due to unexplained lateral buckling either side of the ITA which has not bee predicted during design. There was client concern that if left untreated, the rotation would increase and exceed what was allowable and prevent any future tie-in. Crondall Energy was tasked to match the surveyed ITA response through finite element analysis (FEA), preform integrity checks to the pipeline and and also investigate solutions to mitigate further rotation.
What We Did
Performed a muti-year survey review to investigate the changes to the pipeline over time.
Developed a FEA model of the pipeline including the ITA structure supported by its mud-mat.
Through analysis, matched the observed buckling behavior of the pipeline around the ITA resulting in rotation
Performed integrity checks of the pipeline in its buckled condition.
Determine the required restraint of the mitigation to prevent further buckling/rotation of the ITA.
Develop a concrete mattress solution and model its effectiveness through FEA
Develop an installation plan for the recommended mitigation.
Our Value
Gave confidence to the operator in continuing operation of the pipeline pre and post mitigation.
Provided a simple, cost-effective solution to a challenging problem.
Made future tie-in to the ITA possible to allow increase output of the field.
Decades of experience in subsea pipeline integrity assessments.