Aging Offshore Fields Demand New Thinking
Authors: Rassenfoss Stephen 
Published: February 2015

Decommissioning

Aging Offshore fields Demand New Thinking

When he started his firm focused on removing obsolete offshore structures, Brian Twomey chose the name: Reverse Engineering Services. The thinking was that taking out a structure is like building it, but in reverse.

Based on a career spent planning, managing, analyzing, and teaching classes on decommissioning, the managing director of Reverse Engineering has concluded: “It is the wrong name.”

“I started out thinking decommissioning is the reverse of installation; it is not,” Twomey said. “The first thing to know about decommissioning is there is a lot of uncertainty and unknowns that have developed over time due to wear and tear, changes, the environment, and loading all this other stuff” on the structure.

Those complications can lead to costly jobs and budget overruns when plugging wells and removing platforms. That adds to the pain of an obligation with no return on the investment.

 

Winds of Change Reduce Cost of Removing Gulf of Mexico Platforms

A strong reason for removing old platforms from the Gulf of Mexico, rather than trying to squeeze more years of marginal production out of them, is hurricanes.

Based on the damage left after a run of four hurricanes from 2005 to 2008, the cost of pulling a mangled structure from the seafloor “is six to 10 times what it would cost if the structure had not been toppled over,” said Don Stelling, president of Chevron Environmental Management Co., whose operations include decommissioning fields.

Hurricanes Katrina, Rita, Gustav, and Ike left Chevron with 30 platforms and 18 caissons to be removed in short order, along with 325 associated wells that needed to be permanently plugged. Over the next 6 years, Chevron upped the pace of removals. First, it needed to clean up after the storms. Then, in 2010, federal regulators put in new rules requiring faster removal of “idle iron” in fields that no longer were producing.

What was the cradle of new offshore drilling methods has now become a proving ground for how to remove platforms, caissons, and pipelines left from the beginning of offshore exploration and development.

 

Searching For New Ways To Make The Cut

In the realm of platform removal, the cutting edge of technology can be taken literally.

Much of the new technology development occurring now is aimed at finding better ways to sever the thick, tough steel structures and wellheads so that they can be removed. There are abrasive cutters that can burrow into the mud, a 2-in. thick abrasive cable like the blade in a giant hacksaw, and even work on sending powerful blasts of laser light through cables that can sever the strongest wellheads.

“With cutting, the promising stuff started up with the understanding that cutting with an oxyacetylene torch by a diver is not very safe,” said Alan Stokes, global decommission manager for WorleyParsons. Manual cutting was followed by cutting using high-pressure streams of grit, abrasive-diamond wire looping the pipe, and powerful hydraulic shears.

“The next stage is laser cutting because the trouble with diamond wire and shearing is…the cutting is quick but it takes time to set up,” he said.

One of the biggest supporters of new alternatives has been Chevron, which is looking for ways to reduce the time and risk of cutting, which traditionally has depended on divers and involved cutting torches or explosives. “If there is an alternative to diving we are doing it,” said Don Stelling, president of Chevron Environmental Management. It has adopted a number of cutting methods and is seeking others.