Decommissioned gas wells from a Santos project off the coast of Western Australia have been leaking from the seabed for a decade, according to documents published by the national petroleum regulator.
The leaks, first reported by WA Today, are located at the Legendre gas field north of the Pilbara port of Dampier, and were detected by an underwater vehicle in 2013.
In a report to the petroleum regulator, Nopsema, Santos wrote it was “not feasible” to stop the leaks, which are described on the regulator’s website as “ongoing gas seepage in the form of small bubbles”.
The company has proposed monitoring the wells for five years under an environment plan.
A Santos spokesperson said the company had engaged the national science agency, the CSIRO, to “undertake an in-depth monitoring program”.
“Findings to date show that the gas is nontoxic and unlikely to present an environmental hazard,” they said.
“Santos is currently implementing a management plan that includes a regular monitoring program.”
A Nopsema spokesperson said the regulator had asked Santos to “undertake activity to show the cause of the reported seepage and required that Santos submit an environment plan to demonstrate the appropriate management of any works undertaken”.
The spokesperson said the regulator could not comment on the specifics of the environment plan while it was under assessment.
Jeff Waters, an offshore fossil gas campaigner at the environment group Friends of the Earth, disagreed with Santos’s assessment the leaks were nontoxic.
“Certainly it’s toxic to the environment in the sense that it’s adding to the greenhouse gas emissions of Australia,” he said.
“My question to [climate and energy minister] Chris Bowen is ‘how many greenhouse gas initiatives are being cancelled out by rogue emissions from leaking wells and what’s the government going to do about it?’”
A spokesperson for Bowen said estimates of greenhouse gas emissions from abandoned gas wells were reported in Australia’s national greenhouse gas inventory and were taken into account against Australia’s emissions reduction targets.
Nopsema has regulatory oversight of 873 wells. Of these, 457 are operational wells, while 326 are shut-in, suspended or temporarily abandoned wells. The remaining 90 have been plugged and abandoned and are awaiting final signoff from Nopsema that it is satisfied those works are complete.
The Legendre project ceased production in 2011 and wells were decommissioned by the then-operator, Apache.
Santos took over management of Legendre in 2018 and continued with this program and subsequent surveys, including the most recent surveys in 2022.
