Manson Construction Co. has partnered with some of North America’s largest oil and gas corporations to decommission abandoned oil platforms for removal or repurpose in the Gulf of Mexico (GoM). Manson is part of a small pool of marine contractors who have the experience, capability and expertise to work on these challenging structures.
Purpose of Platform Abandonment
This highly specialized work involves the removal of aging platforms that support the extraction of natural gas and petroleum located in oil wells beneath the seabed. These aging platforms become less productive over time, until they are no longer economically viable. “These platforms are often abandoned and must be decommissioned as regulated by agencies like the Bureau of Safety and Environmental Enforcement (BSEE),” says Offshore Construction Estimator Hogan Bourgeois. The BSEE has an ‘idle iron’ policy that states that any platforms that are no longer operational must be dismantled within one year. According to Hogan, an “idle” platform is an unmanned structure that has failed to produce resources over a five-year period.
Why Platform Abandonments are Necessary
According to the Outer Continental Shelf Lands Act (OCSLA) and the U.S. Department of the Interior, non-producing platforms must be removed as they may pose safety, environmental, and/or navigational risks. During severe weather conditions, oil platforms can topple, causing significant damage to the surrounding environment. Various components from these structures, such as electronic equipment, wiring, and tanks, can sink to the bottom of the ocean, affecting marine life. In addition, loose material and supplies pose a financial risk. Damaged structures can cause oil wells to leak into the ocean, posing serious risks to the ecosystem, marine life, and to personal and commercial vessels.
Manson In the Gulf of Mexico
In 2022, Manson was contracted by oil and gas corporations to complete more than thirty lump sum platform removals. The derrick barge E.P. PAUP—one of Manson’s mainstay vessels in the GoM—will continue to work into late 2022.
Decommissioning projects like these can take anywhere from a few days to a couple of weeks, with the E.P. PAUP staying busy during the GoM standard weather window from May to October. After that, the derrick barge will return home to Houma, LA, to wait out the Winter season and prepare for the next working season.
Preparation for Decommissioning Platforms
Forecasting, scheduling, regional weather considerations, and length of project are among the many things that must be monitored prior to mobilization. Weather conditions play a large role in these jobs and are usually at the top of the list when planning decommissioning.
In addition, maintaining equipment during the offseason, and training of company personnel contributes to the success of each decommission.
Lastly, completing regulatory compliance, work plans and load charts, and ensuring material barge turnaround well in advance allow timelines to be met as early as possible.
How Removals Are Performed
Over the past decade, the offshore energy industry has averaged 200 platform removals per year. Platforms generally consist of two parts for decommissioning purposes: the topside (the structure visible above the waterline) and the substructure (the parts between the surface and the seabed, or mudline). In most cases the topsides that contain the operational components are taken to shore for recycling or re-use. The substructure is severed around 15 ft. below the mudline, then removed and brought to shore to sell as scrap for recycling or refurbished for installation at another location.
Converting Platforms to Artificial Reefs
As of 2021, more than 600 platforms have been converted into permanent artificial reefs in the GoM. After several years in the water, each structure becomes covered by epifaunal organisms such as oysters, mussels, barnacles, tunicates, sponges and corals. These create an increasingly complex surface that provides thousands of nooks and crannies for organisms such as crabs, worms, sea urchins and blennies to enjoy. This small ecosystem of creatures provide food for larger fish species, allowing the structure to benefit ocean life.
Since 2009, Manson has converted 38 platforms into artificial reefs in the GoM. The process can be completed by using three different methods (1) Reef in place; (2) Topple in place; and (3) Tow-and-place.
The first method—Reef-in-Place—involves topping the jacket structure by mechanically severing it a minimum of 85’ below waterline. The base remains uncut, the upper is either disposed on shore or set next to the base.
The second method is to Topple-in-Place. This method topples the jacket structure that is detached from the seabed on its side in-place. Piles and jacket legs are severed at least 15 ft. below the mudline. Finally, the Tow Method involves severing the structure from the sea floor either using explosives or mechanical cutting techniques, towing the structure to the selected reef site, and toppling the structure using the Anchor Handling Tug.
