Analysis: Work Group To Update Jackup Site Assessment Standard

The Work Group of technical service provider GL Noble Denton met in Hamburg, Germany last week to discuss implementing a new international standard for site specific assessment of mobile offshore jackup drilling units.

Work Group members, including class societies, designers, shipyards, oil companies, drilling contractors and authorities from different countries, intend to submit their results as the final draft of the new standard for site assessment for jackup platforms to the International Organization of Standardization (ISO), ISO 19905-1.

All mobile offshore units, particularly self-elevating drilling units such as jackups, are subject to an unusual design and assessment process in that they not only must be designed to a set of criteria such as owner's specifications, classification society rules, and flat state requirements, but also must be assessed for each new location at which they are to operate, GL Noble Denton said.

Site assessments are needed for jackups because they move from location to location on a regular basis, each location offering a new set of unique conditions. Not only will the water depth be different, but there will be differences in the foundations, the environmental conditions, rig orientation, air gap requirements for workover, and required variable load.

There also could be a different set of requirements for each location as a result of local regulations and specific user requirements, with the two most critical areas being the predicted metocean extremes of the site, and the foundation, GL Noble Denton said.

According to DL Denton, factors that need to be considered for a jackup at each location include the ability of jackup legs' length to cope with the water depth and other conditions; overturning stability; strength of the legs and leg holding system; and ability of soils at a location to resist additional penetration and spudcan sliding.

"The site specific assessment of jackups has evolved over the years from a relatively simple, pragmatic assessment based on a series of trade-offs to a much more rigorous detailed assessment that may involved nonlinear time domain dynamic analysis incorporating detailed soils models," GL Noble Denton said in a statement.

"The standards used to address the feasibility of jackup operations have also had to follow this progression, carefully controlling what is determined to be acceptable, but without stifling technological advances. The new and updated standard ISO 19950-1, at present under development, will be a sound basis for the site specific assessment of jackups."

The group's work started in the late 1980s when a Joint Venture Project managed by DL Noble Denton was funded to develop a jackup assessment methodology. In 1994, the Society of Naval Architects and Marine Engineers (SNAME) published the results: "T&RB 5-5A Site Specific Asssessment of Mobile Jack-Up Units." Since then, the document has been continuously modified and updated.

In 1997, ISO TC67/SC7 resolved to develop an ISO Standard for the Site Specific Assessment of Mobile Offshore Units, using T&RB 5-5A as the basis document. This includes incorporation of ongoing research and harmonizing as far as possible with the standards for other offshore structures.

Mike Hoyle, chairman of the GL Noble Denton Technical Policy Board, heads up the Work Group ISO TC67/SC7/WG7. The seven technical panels developing ISO 19905-1 and the SNAME OC7 panel and two of its subcommittees also met last week.

Growing Demand for Premium Jackups

The new ISO standard for jackup site assessment comes at a time when premium jackups with capabilities to drill in deep, more challenging environments are being sought. Both Seadrill and Atwood Oceanics have recently signed deals for the construction of new jackup rigs or acquired existing jackup rigs to meet this growing demand.

Seadrill, the largest operator of jackups built after the year 2000, last month reported it has a sound market outlook for premium jackups with a US $1.9 billion backlog for jackup contracts. This month, Seadrill inked a contract with Sembcorp Marine for the construction of two jackups and options to build four additional jackups. The company also acquired seven benign environment jackups through its acquisition of Scorpion Offshore and acquired a harsh environment jackup rig earlier this year.

With "easy" oil gone, operators require jackups with greater capabilities than rigs built in the 1980s, Seadrill CEO Alf C. Thorkildsen said at the Barclays Capital CEO Energy- Power conference last month. Seadrill sees growing demand for new jackups, which feature increased deckload, greater engine horsepower and longer independent leg configurations, as operators pursue oil and gas exploration programs featuring deeper wells, deeper water, more challenging reservoirs and more remote locations. The redevelopment of older fields worldwide also is bolstering demand for premium jackups.

Atwood Oceanics earlier this month awarded a contract to PPL Shipyard for the construction of two newbuild jackup units. Scheduled for delivery in 2012, the rigs will become the twelfth and thirteenth rigs owned by the company group. At last month's Barclays Capital CEO Energy-Power Conference, company officials reported they are seeing customers opting for newer rigs, which have the capacity and efficiency needed to drill higher pressure, higher temperature wells in more remote locations.


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