Study: Well complexity leading factor in offshore accidents

The complexities of deep wells and extended-reach drilling are bigger factors in offshore accidents than water depth or whether the operator is a major or independent producer, an academic analyst told members of the International Association of Drilling Contractors at a Houston conference.


Sam Fletcher
OGJ Online

HOUSTON, Feb. 7�The complexities of deep wells and extended-reach drilling are bigger factors in offshore accidents than water depth or whether the operator is a major or independent producer, an academic analyst said at an International Association of Drilling Contractors conference here.

�Well complexity, specifically well depth and reach, increases the likelihood of (safety) incidents, while other well characteristics such as water depth do not. Equally important is the evidence rejecting the hypothesis that company profiles and (cyclical) operating environment variables have an effect on health, safety and environment outcomes,� said Christopher J. Jablonowski, with the energy department of Pennsylvania State University.

Those conclusions are based on his analysis of industry accidents reported to the US Minerals Management Service in 1990-1998. Of the 8,193 wells drilled during that period �with complete and usable records� for his study, fewer than 1% experienced a reportable incident, said Jablonowski in an abstract of his study presented Tuesday. He was among the speakers at the IADC�s 2-day annual health, safety and environmental meeting, which concluded Wednesday.

Safety improves
In the period encompassed by his study, Jablonowski said, �There are not a significant amount of accidents during drilling and workover operations.� Moreover, he said, �In 1999, the global drilling industry posted its most dramatic decline in its lost time incidence rate in recent years.�

Safety has been a priority for the offshore oil and gas industry, especially since the deadly explosion on the Piper Alpha platform in the North Sea in 1988.

If offshore safety were simply a dollars-and-cents issue, said Jablonowski, the industry might invest in accident prevention only to the point where marginal costs equal marginal benefits. But the push by opponents to ban offshore drilling in many areas has made safety a key factor in the industry�s �license to operate.�

As a result, Jablonowski said, �The incentive is to get ahead of the problem and to be preventative, not reactive.�

Offshore drilling is inherently dangerous, with its combination of heavy equipment, immense physical forces, geologic uncertainty, and the large number of workers, he said. Weather, water, and geologic forces will always be present, and the basic nature of drilling operations isn�t likely to change soon. So aside from chance equipment failures, most offshore operators and drilling contractors have focused on improving worker behavior as the key to offshore safety.

There�s a general perception that the major integrated companies are more concerned about safety and better equipped to sustain safety programs. Certainly the operator of a lease and wells can influence safety with high standards and additional training. And an integrated company with retail customers might be expected to work vigorously to protect itself from the bad publicity of accidents and disasters, Jablonowski said.

His study �did not support this perception,� however. Drilling and workover contractors actually have the most influence on safety programs, said Jablonowski. While data on contractors were available for those wells that reported incidents to the MMS, he said, that information was not available in a tractable format for all wells and was not included in his study.

Therefore, he didn�t address the issue of crew experience, although other studies do support the industry-wide perception that inexperienced workers are most prone to accidents and incidents.

Complex wells
Deeper wells, including both total measured depth and true vertical depth �means longer bit runs and wiper trips, increased pipe handling, and longer casing strings, and casing job duration,� Jablonowski said. Higher bottom hole pressures in deep wells also increase the risk of well control incidents.

Extended reach drilling, increasing the horizontal distance between the surface location and the bottom hole, also increases the complexity of the well design and raises the risks of stuck pipe and other problems.

The complexities of deep and extended wells require more workers from more contractors providing special tools and services. The increased number of individual tasks performed on such wells tends to dilute the focus on incident prevention among all participants, said Jablonowski.

Industry sources report that 28% of the drilling injuries in 1999 occurred during tripping or pipe handling operations, while 18% happened during rigging up, rigging down, or actual drilling. Material handling was involved in 11% of the accidents, and rig repair accounted for 14%. The remaining 29% was attributed to �other� causes.

Although drilling complexities increase safety risks, duration�measured in the number of days it takes to drill a well�proved to be �not a significant variable� in the study, Jablonowski reported.

A complex well certainly may take longer to drill, thereby increasing exposure time to potential dangers. But other factors may influence the outcome.

Operators and contractors try to put their most experienced crews on potentially complex and difficult wells, which may offset some of the danger. And while a long-term drilling job may increase project fatigue as workers become complacent, Jablonowski noted, longer projects also provide more continuity to establish and enforce safety expectations.

Issues remain
Jablonowski said his study has raised other issues that should be examined, including the role played by drilling contractors in offshore safety.

He also wants to look at the effect of turnkey drilling operations, which have evidenced consistent growth in the last 2 decades.

�Many E&P companies avoid turnkey drilling, citing (safety) concerns,� said Jablonowski. �Is this concern based in fact, or is it merely a self-preservation tactic for internal drilling departments?�

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