Existing industry standards do not adequately address bolting/connector performance in subsea marine applications, according to the findings of a technical review released Monday.
The review – conducted by the Quality Control-Failure Incident Team (QC-FIT) at the request of the Bureau of Safety and Environmental Enforcement (BSEE) – confirmed that hydrogen-induced stress corrosion cracking due to hydrogen embrittlement led to a fracturing of installed H4 connector bolts, causing a leak of drilling fluids in December 2012 from a rig in the U.S. Gulf of Mexico.
In light of its findings, QC-FIT has called on BSEE to encourage the oil and gas industry to develop consistent standards for connections and connection fasteners used in all offshore subsea systems, including a requirement that allows tracking connection components during their service life. Clear, consistent guidelines on material hardness, yield strength and ultimate tensile strength requirements also are needed.
BSEE should also request that ASTM International, formerly known as the American Society for Testing and Materials, further revise its standards to provide more clarity on the design and use of coatings for marine service. Additionally, BSEE should request the oil and gas industry develop an improved quality management standard for the use of subcontractors by manufacturing through multiple tiers in the manufacturing chain.
The agency should also encourage and support joint industry initiatives to evaluate connector and connection fastener design, material, maintenance, and quality specifications to identify potential requirement gaps and inconsistencies across the industry. BSEE also should encourage the development of a failure reporting system to allow BSEE and industry to identify trends and take corrective action before any incidents occur, and develop regulations to implement improved standards for connections and connection fasteners and cathodic protection systems.
QC-FIT confirmed the findings of the root cause analysis conducted by GE Oil and Gas – which manufactured the bolts – drilling contractor Transocean and Chevron Corp. following the incident in which the lower marine riser package (LMRP) of Transocean’s Discoverer India (UDW drillship) separated from the blowout prevent stack during operations.
As a result, approximately 432 barrels of synthetic-based drilling fluids were released into the Gulf of Mexico. At the time, the rig was working for Chevron at Keathley Canyon Block 736. Chevron reported to BSEE that the failure of H4 connector bolts on the LMRP – which were manufactured by GE, formerly Vetco-Gray – caused the separation and leakage of drilling fluids.
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