The CO2 injection project involves the design, construction, and operation of wells and facilities to inject and store CO2 extracted from the natural gas feed into the LNG plant. Storage will be in a deep reservoir—the Dupuy formation—a massive sand body that lies 2,300 m below the surface of the island.
A purpose-built rig spudded the first well in September. The unit was designed to meet the project’s quarantine requirements and it incorporates automated hands-free equipment to replace many of the normal manual handling tasks on a rig. This is to create a safe working environment.
The CO2 project includes nine wells that will be directionally drilled from three drill centers. This will minimize the area of land needed on Barrow for well sites, surface pumping equipment, pipelines, and roads.
Chevron, as project operator, expects to inject 3.4-4 million tonnes of CO2 into the Dupuy each year and says there is likely to be a total of 100 million tonnes injected during the 40-year life of the project.
This is calculated to reduce greenhouse gas emissions from the Gorgon-Jansz project by about 40%.
The Australian government has committed $60 million (Aus.) to the injection project as part of its Low Emissions Technology Demonstration Fund.
The depth of the Dupuy formation will ensure the injected CO2 remains in a supercritical phase—that is, it retains the density of a liquid as well as the properties of a gas which allows it to fill the maximum available pore space.
The structure of the Dupuy provides predictable migration pathways. The formation contains a number of less permeable interleaved siltstone layers that will impede migration of the CO2 plume. In addition the Dupuy sand is overlain by a major seal and there are numerous other impervious seals between that and the surface.
Chevron is confident that there is no likelihood of jeopardizing current or future oil production from the Barrow Island oil field. If there is any down-dip migration of the CO2 it will move no more than 2 km laterally and will not affect other oil operations to the east and north of the island.
There will be close monitoring of the subsurface pressure regimes and the movement of the CO2 plume throughout and well after the life of the Gorgon-Jansz project.
Gorgon gas contains about 12% CO2 content.