WATCHING THE WORLD ONCE A YEAR IS AMPLE, SAYS SHELL

With David Knott from London Webster's dictionary defines "unmanned" as either not manned or without people aboard and operating by either automatic or remote control. Oil and gas companies use the word to describe platforms that are without resident crew. In practice, such platforms can be manned as many as 3 days/week while maintenance and operational tasks are carried out.

Oct. 11, 1993

3 min read

Webster's dictionary defines "unmanned" as either not manned or without people aboard and operating by either automatic or remote control.

Oil and gas companies use the word to describe platforms that are without resident crew. In practice, such platforms can be manned as many as 3 days/week while maintenance and operational tasks are carried out.

Shell U.K. Exploration & Production, which operates in the U.K. on behalf of itself and Esso U.K. plc, has identified costs associated with temporary manning during maintenance as a major factor in wellhead platform developments.

Shell engineers have created the limited access wellhead (LAW) platform concept as a means of economically developing small oil and gas reservoirs as satellites to existing fields that have spare production capacity. A LAW platform would require only one maintenance visit/year.

FEASIBILITY STUDY

To refine the concept, Shell has let contract for a feasibility study to Kvaerner H&G Offshore Ltd., Croydon, U.K. Kvaerner will work on an outline design for a field in 360 ft of water 10 km from a host platform.

This is no hypothetical reservoir, although Shell did not identify it. A spokesman said the study will be based on a northern North Sea prospect. The first LAW platform could be in place by 1997.

The platform will have 16-20 slots in a 570 metric ton topsides deck carrying wellheads and man ifolds. This will stand on a four legged piled jacket weighing about 4,000 metric tons.

Shell said a conventional unmanned platform of similar capacity would have a topsides weight of about 1,200 metric tons. Control and monitoring, including start-up, shut down, and well testing, will be handled from the host platform.

NO TRIMMINGS

A spokesman said Shell is prepared to pay a premium for reliability in a bid to cut costs on maintenance visits. Each item on the LAW platform will have to be shown to be essential for operations or safety.

Against higher equipment costs, a LAW platform would have no need for a helipad, accommodation, temporary refuge, lifeboats, fixed firefighting facilities, a crane, or power generation.

During the annual maintenance trip, a jack up rig or support vessel would be stationed alongside the platform. The 12-20 man maintenance crew would return to the rig or vessel for creature comforts and emergency procedures.

"We describe LAW as zero-based engineering, because anybody who wants to add an item of equipment is going to have to justify its benefit," said Robert Weener, Shell development director.

"The concept means stripping out everything that cannot justify its inclusion. Anything put on a platform adds to maintenance costs. We will not provide facilities that can be supplied more economically from elsewhere."