Responses to hurricanes significant, diverse, widespread

Gulf of Mexico production is of growing importance to US energy supplies, now accounting for approximately 30% of the oil and 20% of gas production in the US. Nearly 70% of the oil supply comes from deepwater facilities. The disruption to production after these hurricanes created parallel calls to action by both the industry and the government. The industry had to face the challenges of recovering from the damage and loss of assets and production. In recognition of the importance of this energy supply as a national issue, the secretary of the Interior challenged the industry to improve its recovery after severe hurricanes to minimize infrastructure damage and production disruption.

This article summarizes the initial API-led examination of the storms’ impacts and the collaborative efforts with member companies to incorporate lessons learned from these hurricanes into improved design practices and standards for the industry.

The aftermath

Some of the important observations and impacts of the hurricanes were:

• The life safety and environmental protection practices (shut down production, reduce hydrocarbon inventories, and evacuate all personnel) worked well - up to ~ 30,000 personnel were safely evacuated before each storm and pollution was minimal
• Of the more than 3,900 production platforms in the Gulf, more than 123 were destroyed
• Of the 32 deepwater production systems (tension leg platforms, spars, and semisubmersibles), theMars TLP was severely damaged in Katrina and the Typhoon TLP was destroyed in Rita. Both instances occurred near the eye of the hurricanes in severe metocean conditions
• More than 30 mobile offshore moored floating and jackup mobile offshore drilling units (MODUs) either lost station or were destroyed - a far greater number than in the previous 50 years combined. The hurricanes caused mooring lines or components to break and anchors to drag due to high loads on moored floating MODUs. Some were found miles from their pre-storm locations, causing concern about collisions and dragging anchors over pipelines. Some jackup MODUs were destroyed or set adrift as a result of wave impacts that caused them to sink or drift away until becoming grounded
• Resumption of production was severely impaired by damage or loss of offshore pipelines. The MMS reported that of the 649 damaged offshore pipeline segments, 49 were 16 in. or greater in diameter. Several major oil pipelines were also severed around compromised levees onshore
• The onshore infrastructure also was severely damaged, contributing to the slow recovery of production. Major oil and gas pipeline terminals, gas plants, and slug catcher/receiving areas were flooded, and their controlling electrical and mechanical equipment damaged or destroyed. Electric power was not restored for months in many of these areas, forcing the use of portable generators. Warehouses and manufacturing facilities that routinely support the oil industry were unable to supply parts and equipment, which required sources outside the normal channels to be located and engaged. Bridges and roadways were blocked or damaged, and waterways were clogged with debris, creating long logistical nightmares
• The human impact was catastrophic. A large percentage of the people working in the oil industry also live in the region and lost, or had major damage to, their homes, greatly impacting their ability to contribute to oil and gas production recovery.

API design standards, HEAT

Industry’s collaborative development of offshore design standards began in November 1964 when industry experts met to discuss the effects of Hurricane Hilda on offshore platforms. That meeting led to API’s Subcommittee on Offshore Structures (SC2) publishing of API RP (Recommended Practice) 2A First Edition in 1969, and laid the foundation for future collaborative efforts to develop and maintain industry design standards for offshore oil and gas production.

The design standards address the offshore environment, the performance of structures in this environment, and the design and operation of offshore structures. These standards have evolved over the years as the industry has learned from its continuing operations and exposure in the Gulf, and as it faced new challenges of operating farther offshore in deeper waters.

Figure 2 traces the history of platform design standards through three different vintages or era from 1964 through today. Each era represents major differences in the standards and reflects the inherent risks against failure or collapse relative to the latest understanding of metocean conditions and loads and structural performance. Significant updates and additions of new standards are shown along with the dates of some of the hurricanes that had important influences on the continuing evolution and improvements of the standards.

In 2005, SC2 formed the Hurricane Evaluation and Assessment Team (HEAT) to study the performance of offshore structures during hurricanes Ivan, Karina, and Rita. Recent work suggests that a new era is being entered.

The HEAT is on

The initial focus of HEAT in 2005-06 was on data gathering, analyses to better understand the metocean environment, assessing asset performance, and preparing interim guidelines for the 2006 hurricane season.

In 2007, efforts have focused on completing a revised description of the metocean conditions in severe hurricanes and developing interim guidance on the use of this information to design new structures and assess the continued safety and serviceability of existing structures. These initiatives and progress to-date are summarized below.

Following Hurricane Ivan, industry oceanographers and consultants evaluated measurements made during the storm and concluded that while Ivan generated very large waves in some areas of the Gulf, the industry’s understanding of the statistics of extreme waves for given storms was unchanged and the industry’s hindcast model worked well to characterize large intense storms like Ivan.

Similar checks were made following hurricanes Katrina and Rita, and industry experts came to the same conclusion; however concerns arose that the early (pre-1945) storms in the industry’s hindcast database (used to develop design criteria) may be biased low in terms of size and intensity, due to lack of observational data when these storms were far from land.Hindcasting refers to reconstructing the metocean conditions generated by a storm using data and numerical models to replicate the event.

Evidence that hurricanes can intensify due to interactions with the warm waters of the Loop Current and are likely more intense offshore than previously believed, led industry experts to develop a new set of hurricane metocean conditions for API using only the post-1950 portion of the hindcast database, and including a regional breakdown to capture trends in observed extremes. The new conditions are markedly more severe in the area offshore the eastern Louisiana coast, the area frequented by the Loop Current. Metocean conditions in the other three areas were largely unchanged from previous levels.

The revised metocean conditions are described in API Bulletin 2INT-MET -Interim Guidance on Hurricane Conditions in the Gulf of Mexico.

This document provides “generic” wind, wave, current, and storm surge conditions for varying water depths in each of the four areas of the Gulf, as well as guidance on performing site-specific studies.

Assessing performance

Investigations to-date have indicated that the majority of structural failures were predominately due to metocean conditions that exceeded design criteria, and not due to major deficiencies in the existing tools, practices, and standards for designing new structures or assessing existing structures.

Most existing structures fared relatively well against the onslaught of these severe hurricanes, and exhibited robustness and reserve strengths inherent in the present design practices and standards. This suggests that from a structural perspective, the procedures and design criteria may need some adjustment but wholesale changes in basic methodologies and recipes are not needed.

Floating production systems: The root cause of failure for the one TLP destroyed is still being investigated. Other deepwater floating production systems survived conditions that exceeded design criteria. This is not surprising since the design of most deepwater floating production structures include a robustness check for 100-year conditions. Some suffered significant damage to equipment on their decks due to high winds and greenwater from large waves.

Such damage required costly and time consuming repairs before production could resume. This experience is still being studied, but early results tend to validate structural design practices for the hull and mooring systems of these deepwater floating production systems. However, needed improvements in hardening the topsides to prevent wind and greenwater damage to drilling and production equipment have been identified and are being pursued.

Fixed platforms: Of the more than 3,900 fixed platforms in the Gulf, 123 were destroyed and more than 180 sustained major damage involving primary structural damage above or below water. These losses tended to occur in the areas of larger waves, and most of the destroyed or damaged platforms were older and had been designed either prior to API RP2A or to earlier editions of API RP2A, which included design criteria for waves lower than those experienced in these hurricanes.

This trend is obvious in Figure 3 which shows the vintage of the destroyed platforms (note that some destroyed platforms installed in 1990-99 were minimum consequence platforms that were designed to lower criteria because they represented no life loss or pollution threats). However, to-date, comparisons of the RP2A platform designs to observed fixed platform performance show that API recommended methods, practices, and standards predict platform performance well and will continue to provide a valid basis for the design and assessment of new and existing platforms.

Putting guidance into the hands of engineers

These studies continue and are focusing on more detailed analyses of the data and structural performance - successes as well as failures. The ongoing investigations are more complex and will take a year or more to complete and be incorporated into future recommended practices and performance standards. Any recommendations for improvements must reflect industry knowledge, experience, and best practices.

Until the more detailed ongoing studies are completed and result in updated recommended practices, bulletins have been prepared for the design of new fixed and floating structures, and the assessment of existing fixed and floating structures. These bulletins incorporate lessons learned to-date and provide guidance on how to use the updated hurricane metocean information in Bulletin 2INT-MET for the design of new fixed and floating structures and the assessment of existing fixed and floating structures. These two bulletins will be issued by June 2007 along with Bulletin 2INT-MET:

• API Bulletin 2INT-DG -Interim Guidance for Design of Offshore Structures for Hurricane Conditions
• API Bulletin 2INT-EX -Interim Guidance for Assessment of Existing Offshore Structures for Hurricane Conditions

API has scheduled workshops to introduce and overview these three Interim Bulletins to help ensure an understanding of the implications of the new metocean conditions on the design and assessment of structures. The workshops will be open to all in the offshore engineering community - company and contract personnel alike. They will be held July 17 in New Orleans and July 19 in Houston. See the API website (api.org) for more information.

Broader industry collaboration

HEAT has been the focal point and sponsor for much of this work. However, API also has worked closely with the Offshore Operators Committee and the International Association of Drilling Contractors to provide strong leadership and coordination in moving critical issues forward through hosting hurricane conferences, forming technical working groups to encourage government and industry discussions, and identifying focus areas for the industry relative to hurricane impacts on exploration and production activity.

For example, HEAT has worked with the MODU JIP to study hurricane metocean conditions and potential risks to production infrastructure from MODUs that go adrift. The MMS also has sponsored studies on mudslides, pipeline damage, and drilling rig tie-down failures, and results are being incorporated into HEAT’s efforts. These collaborative efforts are evident in other bulletins and recommendations that have been developed, including:

• Recommended Practice 95J,Gulf of Mexico Jackup Operations for Hurricane Season - Interim Recommendations, First Edition, June 2006
• API Recommended Practice 95F,Interim Guidance for Gulf of Mexico MODU Mooring Practice 2006 Hurricane Season, First Edition, May 2006
• API Bulletin 2TD,Guidelines for Tie-downs on Offshore Production Facilities for Hurricane Season, First Edition, June 2006
• API Recommended Practice 95F,Interim Guidance for Gulf of Mexico MODU Mooring Practice - 2007 Hurricane Season, Second Edition, April 2007

But, even broader industry collaboration is needed. The offshore industry stakeholders are numerous and include oil companies, drilling rig owners, contractors/consultants, equipment and logistic suppliers, onshore facility operators, and regulatory bodies, principally the MMS and the US Coast Guard. All parties have focused recent efforts on damage assessment and are striving to adjust standards to minimize consequences and disruption of production in future storms.

The widespread and diverse impacts of hurricanes Ivan, Katrina, and Rita across the breadth of oil and gas industry facilities indicate that a broad approach is necessary to evolve design standards and industry practices that safeguard US energy production, industry assets, and most importantly, the safety of people.

A key area for future collaboration is the measurement and handling of offshore metocean and structural performance data. Pipelines are an important area where more collaboration is needed as well.

Segments of the industry that have previously operated in separate “silos” must now come together in a collaborative discussion and address these issues in a holistic, thoughtful manner.

API has begun the process for this collaboration through the work of the API HEAT group. Not only is API issuing a significant number of interim guidance documents, but the accompanying dialogue to gather and process the data and explain the good work already taking place is equally important.

Acknowledgements

The authors gratefully acknowledge the contributions by many dedicated industry members that support these and other organizations, and whose work has and continues to contribute to the efforts to improve industry standards and practices.