In 2016, AGL announced that exploration and development of upstream gas assets will no longer be a core business for the company due to the volatility of commodity prices and long development lead times.
Since early 2016, we've completed the extensive decommissioning and rehabilitation program for our wells and infrastructure in the Gloucester region. We're also progressively decommissioning wells and rehabilitating sites at the Camden Gas Project prior to ceasing production in 2023.
The decommissioning of coal seam gas wells is done in line with the NSW Government's Code of Practice for Coal Seam Gas to ensure that it is completed safely without risks to health or the environment.
The code of practice requires that coal seam gas well decommissioning ensures “the environmentally sound and safe isolation of the well, protection of groundwater resources, isolation of the productive formations from other formations, and the proper removal of surface equipment." The code of practice requires that:
- the well-head equipment is removed,
- the subsurface water is kept isolated from the coal seams,
- the coal seams are isolated from other aquifers,
- risk to future mining of the coal seams is minimised.
In rehabilitating its well sites, AGL will ensure:
- The equipment at the top of the well is safely removed.
- Purpose-specific cement, which complies with the standards set by the NSW Government's Code of Practice for Coal Seam Gas Well Integrity, is placed inside the well from bottom to top in stages.
- This cement seals the wellbore and adds to the integrity of the well.
- The well casing is cut off, at least 1.5 metres below the surface, so that it does not interfere with agricultural and other future land uses. A steel cap, containing data such as the name of the well, the operator, the well depth and when it was decommissioned, is welded to the top of the casing.
- The decommissioning works are overseen by the Department of Planning & Environment (DP&E) and the Environment Protection Authority (EPA) Gas Regulation branch, and conducted within stringent health, safety and environment guidelines. A full report is provided to the regulator once all decommissioning works have been completed.
The rig is usually set up on site for approximately 2-3 weeks.
The first 200m-long cement plug is injected and allowed to set for at least six hours. It is then pressure-tested before adding the next cement plug. Cement then placed in additional stages to full depth and allowed to set.
Well casing cut to at least 1.5m below ground level. An information plate is welded to well casing, sealing it. This data is sent to relevant government agencies. The locations of decommissioned wells are kept on a live map at Common Ground website maintained by NSW Division of Resources and Geoscience available at www.commonground.nsw.gov.au
Initial rehabilitation returns the surface of the site to the original contour of the land, usually seed is sown, or as agreed with the landowner.
Rehabilitation then continues over 12-18 months until both the regulator and landowner are satisfied.
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