Vol. 226 No. 12

New Rig Designs

Sixth-generation drilling rig is under construction

Aker ASA initiated a project this past spring to build the Aker H-6e the next (sixth) generation of semisubmersible drilling rigs. Designed for harsh environment and ultra-deep water, the company’s two new rigs will cost NOK 3.8 billion ($600 million) per rig. Aker Kvaerner will build the rigs under a turnkey construction contract; the order was received in October.

The Aker H-6e design is an enhancement of the Aker H-4.2 column floater with a transverse truss arrangement between the eight columns.

Presently, the world’s deepwater (>4,000 ft water depth) and harsh-weather rig fleet is near 100% utilization. Newbuilds under construction or in the planning stages will be able to expand the potential supply from 90 to 111 rigs by 2010. However, Aker anticipates strong demand will require more than 150 rigs, leaving the market supply-constrained. The company is responding to this expected demand by building two new rigs immediately and has secured options to build two more rigs in following years, as needed.

The increasing demand situation is driven by offshore exploration. Deepwater acreage represents the main area where new exploration efforts are occurring. Deep water also is the main area for offshore production growth. In fact, deepwater oil and gas output is projected to triple by 2010. This will push the deepwater share of offshore oil and gas production from 9% to 21% by 2010, requiring new rigs to drill and service the new field discoveries.

Production from harsh environment regions represents about 7% of global supply (about 6 million bopd). Large natural gas reserves in harsh environment areas are being considered as an LNG reserve base that will need to be developed. More frontier acreage will be offered for the industry to consider, and much of the new acreage will be in the harsh environment areas of the Arctic, Norwegian Continental Shelf, Canada, Atlantic Margin and Greenland. In addition, new areas of the deepwater Gulf of Mexico and Australia are considered harsh environments.

Off Norway in the Barents Sea, more than 300 exploration and development wells could be drilled in the coming 15 to 30 years. So far, 41% of wells drilled have proven oil and gas reserves. Similarly off northern Russia – especially Shtokman field and in the Kara Sea – more than 2,700 exploration and development wells could be drilled in the next 15 to 30 years. Should this occur, exploration and development drilling will require 15 rigs for 30 years.

Enhanced Design

The Aker H-6e design is an enhancement of the Aker H-4.2 column floater. It has a transverse truss arrangement between the eight columns and is configured for dynamic positioning. The company is pressing the technology envelope by producing a vessel design that combines a 10,000-ft water depth capability with harsh environment readiness and full winterization.

The design has the deepwater fleet’s largest deck area: 90 m by 70 m (6,300 sq m) and a variable deck load of 7,700 tonnes. Each vessel will displace 56,900 tonnes and be zero-discharge capable for environmental benignity. The design will have 750-m riser stacks for vertical racking and a low center of gravity. It will have a hookload of 1,000 tonnes. A rig of this size must be efficient, so the design calls for a Dual RamRig that should provide a 20% to 40% efficiency gain.

The deck will ride high above the water, with an air gap of 18.5 m to weather waves up to 36 m. Flexible accommodation spaces will house and service crews of 140 to 160 workers.

The new rigs are scheduled to be ready for drilling operations by February 2008 and October 2008, respectively.