Evaluation of a Riser After 10 Years of GOM Service Life

Abstract

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper OTC 28908, “Ten Years in the Water: Observation and Detailed Evaluation of a Riser After Extensive Service Life,” by Mike Tricarico, Vallourec; Chris O’Neil, Anadarko; and Thomas Peter, Vallourec, prepared for the 2018 Offshore Technology Conference, Houston, 30 April–3 May. The paper has not been peer reviewed. Copyright 2018 Offshore Technology Conference. Reproduced by permission. As part of an effort to evaluate existing riser systems, an operator launched an inspection and testing program to investigate risers retrieved following well abandonment after a service life of nearly 10 years in the Gulf of Mexico (GOM). This represented a rare opportunity to evaluate the state of the threaded and coupled risers after such a long service life and assess the remaining longevity of the riser system. Specifically, it was a chance to observe and measure the effects of actual service life as opposed to calculated service conditions on the pipe and connections. The findings provided valuable insights into the future viability of similar riser systems. Introduction The Constitution truss spar was first placed in service in 2005. The spar featured six dry tree production risers with two subsea tiebacks. It operates in the Green Canyon region of the GOM in almost 5,000 ft of water. The production risers were run in 2006. In 2015, the decision was made to abandon several of the production dry tree wells. There was a high degree of interest in investigating the risers to assess remaining life. Special attention was paid to evidence of corrosion, cracking, or wear on the outer diameter (OD) or inner diameter (ID) of the pipe, along with water ingress into the connection causing any corrosion from seawater on the bare metal of the•connection. The complete paper includes a detailed discussion of the original design, testing, and first running; this synopsis will concentrate on post-service testing and assessment. Riser Pulling, Evaluation, and Testing Pulling and Review. In late 2015, on the basis of internal evaluation, the operator pulled several of the production risers. In order to validate the remaining life of the risers and to help in-form future decisions on the longevity of threaded and coupled risers, the operator then initiated a detailed review of the risers. The stress joints, tension joints, and first connectors after those joints were kept, along with several of the risers from the middle of the string. During the pulling operations, little evaluation of the state of the risers was possible; however, photographs of several of the connections were taken as they were pulled. Most notable was the lack of corrosion on the connection.