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Decommissioning and Rehabilitation

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Review of gas assets and exit of gas exploration and production

AGL announced on 4 February 2016 that following a review, it has taken a strategic decision 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.

AGL has implemented an extensive decommissioning and rehabilitation program for its well sites and other infrastructure in the Gloucester region. AGL are also progressively decommissioning wells and rehabilitating sites at the Camden Gas Project prior to ceasing production in 2023.

ASX Release: 4 February 2016

Gas Well Rehabilitation

When a coal seam gas well is no longer required, it must be decommissioned and the site fully rehabilitated.

Well decommissioning is undertaken to standards set in the NSW Government’s Code of Practice for Coal Seam Gas (Well Integrity) which has been established “to ensure that well operations are carried out safely, without risk to health and without detriment to 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 ‘beneficial aquifers’ – the subsurface water that is used by farmers – are 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 Code of Practice, is placed inside the well from bottom to top in stages. The impermeable cement seals the wellbore and adds to the integrity of the well casing which already has several layers of steel and cement.
  • 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 exact location, the well depth and when it was decommissioned, is attached to the top of the casing. This information also is recorded by the NSW Government so that accurate records can be maintained.
  • The site is rehabilitated to the satisfaction of the land owner and our licence requirements.

Step 1 - Non-Perforated Case Well

A purpose-designed cement slurry is placed to full depth in stages and allowed to set, filling length of entire well.

Step1_nonPerforatedCasedWell

Step 1 - Perforated Case Well

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.

Step1_a_PerforatedCasedWell

Step 2

Well casing cut to at least 1.5m below ground level.

Step2_DecomRehab

Step 3

Information plate welded to well casing, sealing it. This data, including coordinates, is sent to relevant government agencies.

Step3_DecomRehab

Step 4

Site rehabilitated to the satisfaction of the landholder and in accordance with licence conditions.

Step4_DecomRehab

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