Deepwater Asset Integrity: Lessons Learned

As oil and gas companies branch out further into deepwater regions in search of reserves, asset integrity becomes an even more important issue.

Such projects present a range of challenges, including the longer lifetime of the development, the severe conditions assets have to withstand and often the physical distance between the engineers and the assets.

Yet these issues are often only given the attention they deserve following a serious incident.

The Piper Alpha disaster in 1988 and the blow-out of BP's Macondo well in April 2010 both share similarities in that they were disasters which led to the death of workers and resonated with people on a global scale.

Despite the two decades between the incidents, preliminary reports into the causes of the BP incident suggest there are still many lessons which need to be learnt about deepwater asset integrity.

Monitoring and Inspection

One of the key factors in the Deepwater Horizon disaster, as identified in both BP's preliminary report on the incident and the report by the National Academy of Engineering, was the failure of the blow-out preventer (BOP) to seal the well after the hydrocarbons began leaking.

According to BP, there were a number of factors which were said to have caused this failure. BP claimed in its reports that "likely" faults within the BOP, which prevented the emergency automatic mode function of well control from being activated, were present before the incident.

A fault within the yellow pad's critical solenoid valve and insufficient battery charge in the blue pad were both said to have been part of the cause of this failure.

"Through a review of rig audit findings and maintenance records, the investigation team found indications of potential weaknesses in the testing regime and maintenance management system for the BOP," BP's report stated.

Such concerns were also raised in the report by the National Academy of Engineering, particularly surrounding the "adequacy of tests."

Similar recommendations, however, were made in the Cullen report published in 1990 into the Piper Alpha disaster.

"It is argued that more attention should and must be made to the secondary tier items such as root cause corrosion mechanisms, advanced monitoring and inspection techniques," a paper published by a group of experts, writing in Offshore magazine, explained.

It concluded "life cycle vigilance" through "diligent but limited regulatory control" was one of the key features of asset integrity - a lesson it would appear has yet to be learnt.

Original Design and Materials Selection

Regulation and monitoring, however, will only go so far if the original materials selected for the construction of the deepwater asset are neither appropriate for the task or up to standard.

Dr Binder Singhof Wood Group Integrity Management, Dr Paul Jukes of MCS Kenny, Bob Wittkower of JP Kenny Inc and Ben Poblete of Cameron highlighted in their paper that engineers are now weighing the advantages and disadvantages of two distinct material selection principles.

This debate was said to surround "whether to select carbon steel and then carefully manage the operational corrosion; or to select the corrosion resistant alloy option with minimal corrosion management."

"In other words, do we pick materials for immediate fitness for service at fabrication ("just build it") or fitness for materials life cycle performance?" they added.

BP has also been dealing with issues surrounding materials selection since it was found the cement used to seal the well may not have been suitable for the job.

The National Academy of Engineering report suggested "Questions have been raised about the strength of foam cement used in the well and whether sufficient time was allowed for the cement to set and gain strength before the negative-pressure test was conducted."

This latter point on the cement also highlights another key lesson which must be learnt surrounding deepwater asset integrity, the responsibility of contractors in the event of a disaster.

Halliburton, which supplied the cement, is disputing some of the assessments carried out to discover if the cement was at fault, and claims tests by BP could have spotted any potential issues.

With deepwater assets requiring high levels of specialist knowledge which may not be available in house, contractors and companies will be required to find ways of working together to ensure the integrity of assets and the safety of personnel.