The Perdido spar began its 13,200 km journey to Texas in May 2008, arriving in the Gulf of Mexico in August 2008. The 170 m cylindrical spar was secured to the sea floor and Shell completed the installation of the drilling and production platform on top of it. Around 270 staff live on the platform and an adjacent floating hotel - or flotel.
Credit: Shell
CRANFIELD: Decommissioned offshore rigs may be reused to create artificial deep-sea reefs for biological conservation, Australian scientists have announced.
This research could save the oil and gas industry billions of dollars and enhance fishery resources by protecting cold-water corals from fishing trawlers, particularly as decommissioning targets rise.
"Rigs-to-reefs programs offer the opportunity to conserve deep-sea marine communities on unprecedentedly large scales, however considerable research is required before it can be done responsibly," said marine scientist Ashley Fowler from the University of Technology, Sydney, and author of the study in the journal Frontiers in Ecology and the Environment.
How rigs are reused
The first rigs-to-reefs conversion dates back to 1979 when the steel structure of an abandoned rig was used to create shelter for marine life off the coast of Florida. However, rigs-to-reefs programs have only been considered for shallow marine water sites until now.
Fowler and his colleagues report this week that relocating old rigs from shallow to deep waters (>500 m) could increase hard substrate available for reef-dwelling organisms and be beneficial to deep sea ecosystems.
The authors used shallow water examples to highlight the costs and benefits of adding artificial structures to the marine environment. They then applied these findings to the deep sea, by discussing aspects unique to deep-sea ecosystems.
Removing rig structure may not be best option
Rigs have numerous crossbeams and large interstitial spaces that can support high reef-fish diversity and abundance (Figure 1).
"The oil and gas industry worldwide is looking at the decommissioning of 6500 offshore rigs by 2025," said professor of marine ecology David Booth from the University of Technology, Sydney. Removal and disposal activities will costs the industry billions and "would leave a major carbon footprint."
"It may be that, in certain circumstances, total removal of the rig structure from the ocean does not provide the best environmental outcome," Booth said.
However, professor of marine biology Mark Hixon at Oregon State University, U.S., who was not involved in the study, cautioned that "Rigs-to-reefs is a highly controversial idea from which the oil companies would definitely gain much financially, yet the oceans may or may not benefit."
