US supermajor Chevron has continued to face teething problems at its flagship carbon capture and storage (CCS) project in Western Australia.
A freedom of information disclosure released this week by the Australian government revealed the CCS scheme at Chevron’s Gorgon liquefied natural gas development on Barrow Island had only been operating at partial capacity for the 2021 financial year, which ended 30 June last year.
In an annual report dated 30 September 2021, Chevron revealed the Gorgon CCS scheme had only injected a total of about 2.26 million tonnes of carbon dioxide over the 12 months to 30 June 2021, well below its targeted 4 million tonne per annum capacity.
Chevron claims injection rates matched the CO2 volume extracted from the feed gas during the first half of the reporting period.
However, the project was operating under an injection limit imposed by Western Australia’s Department of Mines, Industry, Regulation & Safety (DMIRS) in late 2020, limiting the injection rates over the second half of the financial year.
DMIRS placed an injection limit on the scheme of 70 million cubic feet per day due to issues with the start-up of the project’s pressure management sites.
Chevron revealed in the previous year’s annual report that the commissioning of the pressure management system had been delayed due to the loss of injectivity at the project’s two water injection wells, with the loss believed to be related to plugging of the injection wells with “higher than expected solids production” from the four water production wells.
The produced water management is part of the pressure management system that creates more space for higher volumes of CO2 injection storage over time. It involves pumping water out of the Dupuy formation beneath Barrow Island to make room for the CO2, and pumping it back into the overlaying Barrow Group.
Chevron confirmed in the 2021 report it had initiated a “de-sanding project” to remediate the issues with the pressure management system.
This involved an upgrade of the surface facilities to remove sand from the process stream, with Chevron revealing the upgraded facilities were successfully started up at both drill centres by the end of the 2021 financial year.
At the time of the report, the imposed injection limit was to run until 30 November 2021, with Chevron stating in the report that it was on track to meet the requirements of the conditional consent to operate by the deadline.
CO2 system remediation works
The annual report also revealed that Chevron had kicked off two projects in the 2021 financial year to help support the CCS scheme’s "long term system reliability and availability".
This included increasing compressor capacity at the project to allow for increased discharge pressure from the CO2 compressors, which is aimed at enabling sustained injection rates as pressure in the reservoir increases.
Chevron stated, at the time the report was published on 30 September, that all hardware had been installed and was expected to be operational in early 2022.
The company also initiated a project to upgrade the surface facilities at the two pressure management sites.
This included installing sand management equipment at drill centres D and E to alleviate the high sand production from the producing wells.
Chevron stated that the equipment had been installed by the end of the 2021 financial year and full production was expected to occur in the second half of the 2021 calendar year.
Upstream has contacted Chevron for an update on the current status of the project’s pressure management system and CO2 system remediation works outlined in the report.
Trouble start for flagship CCS project
Chevron has had a troubled start with its flagship CCS project at Gorgon, with it being revealed last year the project had failed to meet its promised injection rates.
Under the terms of Gorgon’s project approval, Chevron is required to sequester at least 80% of the CO2 emissions released from the reservoirs that feed the Gorgon LNG plant over a five-year period.
While it has been designed with a 4 million tpa injection capacity, Chevron admitted in July last year the project had injected 5 million tonnes of CO2 since the August 2019 start-up.
Despite the significant shortfall, at the time, Chevron claimed it represented the largest volume of injection achieved over the same time period by any CCS system with comparable specifications.
However, the failure to meet the terms of the project approval resulted in Chevron revealing late last year it would be investing A$40 million (US$28.8 million) in Western Australian lower carbon projects, as well as acquiring and surrendering 5.23 million greenhouse gas offsets to address the CO2 injection shortfall.
The Gorgon CCS project sees CO2 separated from the gas stream before processing and liquefaction on Barrow Island. Instead of being flared, it is injected into the Jurassic Dupuy Formation at a depth of about 2500 metres.
The project includes nine CO2 injection wells at three drill centres, two pressure management drill centres, two reservoir surveillance wells, a seven-kilometre underground pipeline from the LNG plant site to the drill centres and three CO2 compressor modules.
Chevron has previously claimed the CO2 injection system will reduce greenhouse gas emissions from the Gorgon project by about 40%, or more than 100 million tonnes over the life of the project.
Chevron operates the Gorgon project with a 47.3% interest and is partnered by ExxonMobil and Shell, each on 25%, Osaka Gas on 1.25%, Tokyo Gas on 1% and Jera on 0.417%.