SPECIAL REPORT: Well-specific guidelines adopted for dynamic positioning

Nov. 27, 2006
In the last decade, offshore operators have developed and refined an emergency response system with standardized format and nomenclature for dynamically positioned drilling operations.

In the last decade, offshore operators have developed and refined an emergency response system with standardized format and nomenclature for dynamically positioned drilling operations.

For each well or location, a dynamically positioned rig is given well-specific operational guidelines (WSOG), which determine when alerts should be given and what action is appropriate.

This article discusses the issue of operational limit setting used in DP operations. It traces the history of WSOG since 1998 and also examines the reasons behind its widespread use in DP drilling and other operations.

Modern WSOG has its origins with the Ocean Alliance campaign in the late 1990s on the Nyk High, Vema Dome, and Helland Hansen prospects in the Norwegian Sea.

The WSOG principle was further developed during the 1998-2000 commissioning of the drillship West Navion. WSOG became a cornerstone of the Statoil DP work requirements document that became the company’s principal corporate DP requirement document, TR1029, in 2000.

Since then, other major operators have introduced corporate dynamic positioning requirements, all of which contain WSOG as the chosen regime for limit setting offshore.

The examples cite the European approach to deepwater drilling risk management in terms of limit settings. It also discusses two incidents: one in which WSOG worked as intended and one in which WSOG failed in its objectives.

The article concludes with a summary of the reasons WSOG has had such widespread use and challenges the industry to ensure its continued effective use.

What is WSOG?

The well-specific operating guidelines document is used to define actions to be taken by a dynamic-positioning operator (DPO) in the event of certain changes to the DP unit’s station-keeping capability (ability to maintain position and heading). WSOG also serves as a DP emergency response primer and ready-reckoning checklist for DP operators and facilitates collaboration and understanding between all parties (Fig. 1).

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WSOG is used widely across the DP drilling industry today, in a number of different forms. The majority of the world’s DP drilling contractors are making use of WSOG in the format discussed in this article. All DP drilling activities on the Norwegian Shelf are conducted with WSOG procedures, and it is the primary method of conducting the station-keeping hazard and operability analysis (HAZOP) and limit setting exercise.

The central tenet of WSOG is that it clearly defines, prior to operations, the four different DP operating-status conditions against known possible failure modes. WSOG brings together the rigs design basis, changes during design, personnel, clients, and so forth.

WSOG is effectively a purpose-built HAZOP for DP drilling that, because of its design simplicity, has been widely adopted around the world. As well as being a simple and effective tool, it provides the following advantages:

  • Defines an emergency response matrix for DP.
  • Assists training of key personnel without the need to retrain across contractors.
  • Brings together driller and DPO (drilling and marine).
  • Brings together contractor and client.
  • Shows that the contractor has a credible system.
  • Demonstrates a case of operational risk management.
  • Allows for and is designed to handle change, e.g., new personnel or equipment, change of site, geographic location, or client.

One of the major benefits of WSOG to the DP drilling industry is that drilling supervisors should be able to build a body of experience from operating on different DP units across different contractors. This was seen by Statoil as a great advantage early on.

WSOG is, effectively, a link between known failure events and operating conditions of different type of actions. Each action-green, advisory, yellow, and red-have defined, agreed responses. The WSOG form can be amended or expanded to capture additional conditions. WSOG is also valid for use in HAZOPs for operations such as drillstem testing and dual activities where additional safeguards may be needed.

WSOG history

The UK Department of Energy produced one of the first semi-formal guidance documents for DP drilling in March 1982. It came out at a time when the first Pelican-class DP ships were drilling in the UK sector of the North Sea. Basic by today’s standards, the document nonetheless highlighted the need for effective operational limits to be defined. The concept of well specific limits was included in the document.

Ocean Alliance conducted a drilling campaign in the Norwegian sector of the North Sea in 1997 and 1998. A great deal of risk analysis was carried out prior to the rig operating. The first version of the Ocean Alliance WSOG was four pages long and clearly defined the use of the “advisory” condition to allow for reporting events that could lead to higher alert status levels.

The three wells drilled by Ocean Alliance during the campaign were:1

1997: Ormen Lange (886 m, operator: Norsk Hydro/BP); original Ormen Lange gas field discovery; wellbore entry July 27, 1997; exit Oct. 7, 1997.

1997: Vema Dome (1,238 m, Statoil); wellbore entry Oct. 12, 1997; exit Mar. 22, 1998.

1998: Helland Hansen prospect (684 m, Norske Shell); wellbore entry Mar. 28, 1998; exit July 4, 1998.

Statoil development-1998

The challenges in 1998 were the acceptance and compliance issues surrounding the entry into service of the Class 3 drillship, West Navion.

Within Statoil, a review process began during 1998 following the Ocean Alliance DP campaign. The DP-related verification work included the Ocean Alliance joint venture (Norway), using Doc. 1.0 (Sept. 22, 1997) as the start point.

In late 1999, the station keeping case for West Navion was accepted by the regulator and WSOG was used from the beginning of operations on the vessel.

Statoil DP requirements

  • Rev 1-Statoil’s B&B-TB-10-20E dynamic positioning requirements were issued on Jan. 20, 2000, and approved on Feb. 21, 2000. The first revision of the Statoil DP requirements document mandated an early version of the WSOG (Fig. 2).
  • Rev 2-Following further involvement within worldwide asset teams, Statoil published the second edition of the corporate requirements document, entitled WR0581, Version 4 on Aug. 29, 2001.
  • Rev 3-Statoil republished the DP requirements as “TR1029” technical requirements in early 2002.
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Other operators, such as Norsk Hydro and BP PLC (2005), have since issued corporate requirements for dynamically positioned drilling and well-intervention operations.

It should be noted that all corporate DP requirements issued by oil majors use the same WSOG process as the principle means of establishing alerts (common definitions of green, advisory, yellow, and red).

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BP issued a set of corporate DP requirements for drilling, testing, and well intervention in late 2004. Following extensive internal review, this became Version 8 and was issued in February 2005 (Fig. 3). The BP standard uses the same WSOG process as the earlier Statoil document. Version 9 is due to be released in late 2006.

2001 presentation

The WSOG process and wider verification model was presented at the International Association of Drilling Contractors Northern Deepwater conference in Stavanger, May 2001. The technical paper presented at IADC used case studies to show how different oil companies and drilling contractors are adopting the processes begun in Norway for the benefit of proving an effective operational risk management case for their DP operations.

The WSOG model form has had a significant influence worldwide. In 2004, det Norske Veritas prepared a report for the US Minerals Management Service titled, “Guidance on safety of well testing.”2 The report includes reference to WSOG in the form presently used.

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Many operators-Shell/Enterprise, BP, ExxonMobil, ConocoPhillips, Marathon, Amerada Hess, Elf Exploration Angola, Woodside, BHP Billiton, and Apache Corp.-have made use of the WSOG form during their drilling campaigns. A number of drilling contractors have also adopted this process, in one form or another, in their DP operations manuals (Fig. 4).

Additional uses of WSOG

The WSOG alert and reporting protocol is being used on well-intervention units Regalia, Seawell, and Island Frontier, working for Statoil in the North Sea.

The DP floatel industry in the Norwegian sector of the North Sea has developed FOGS (floatel operating guidelines) along the same principles as WSOG.

In addition, Statoil is currently working on updated requirements for moored units, due to the large number of incidents with dropped chains and dragged anchors. The group is proposing WSOG principles to be implemented on moored units as an efficient early warning and HAZOP tool.

The non-DP moored unit sector in the US may find advantages in this approach, given the complexity of seabed pipelines and installations throughout the hurricane-prone Gulf of Mexico.

Observations

WSOG has proven that it has an important role to play in the establishment of safe working practices for offshore drilling units. There are a great number of lessons to be captured from its use, fostering continual improvement.

Having drilling personnel trained in one process has great appeal to oil majors. It means that experience can build between rigs or ships of different contractors.

Contractors must accept that operators have a vested interest in operational risk issues (procedures, reporting). This will always increase because station-keeping incidents will continue.

Effective operating limits must be agreed between the contractor and operator before spudding a well in order to avoid confusion caused by offshore contractual arrangements.

WSOG eliminates negative reporting if followed correctly (see incident No. 2). But incorrect figures written into the WSOG can make the DP drilling operations less safe. There have been incidents caused by incorrect figures.

WSOG is an ideal tool for HAZOP and has been successfully used in other nondrilling DP scenarios.

Limit-setting HAZOP should take place before each well (even if everything is the same). The limit setting exercise should involve, as far as possible, personnel who have working knowledge of the rigs operating criteria. The supply of experienced and competent crew is central here and further reenforces worries in the industry.

There must be consensus following the WSOG limit setting exercise and sign-off.

In the US Gulf of Mexico, some operators view advisories as crucial, therefore fundamentally supporting the use of WSOG.

WSOG clearly works equally well with drillships and semisubmersible drilling units and has also been introduced in nondrilling DP sectors such as the floatel market. Norway is even advancing the WSOG concept for use in moored operations as an early warning HAZOP process.

History has shown that having a mature WSOG system aboard will satisfy oil operator’s and regulator’s verification processes. There has been wide use of this simple form since 1999, suggesting that the process works.

References

  1. Petroleum Safety Authority Norway, www.ptil.no/English.
  2. Det Norske Veritas, “Guidance on safety of well testing,” DNV 4273776, Nov. 15, 2004.

The author

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Alan Adamson (adamson@ menas.com.bh) is operations manager and Navarea IX subarea coordinator at Middle East Navigation Aids Service (MENAS), Manama, Bahrain. He has also served as offshore assurance manager with BP Shipping, senior marine assurance auditor at Global Maritime, Stavanger, following 12 years offshore in DP operations. Adamson holds a UK Master Mariners license and diploma in nautical science. He is a member of the Society of Petroleum Engineers, Nautical Institute, and an active participant in the work of the Marine Technology Society.