For facilities that are onshore or in coastal waters, each State or Territory is regulated by their respective Government Department.
When a natural gas well is no longer actively producing, it must be decommissioned and the site fully rehabilitated. The project infrastructure will be progressively decommissioned and the land rehabilitated throughout the project life.
Final decommissioning and rehabilitation will be undertaken at individual infrastructure sites once production is complete in that area – or an exploration site was proven to be uncommercial in nature and didn’t reach production.
Rehabilitation standards are set well before any activities commence on site – so the operator, the landholder and the regulator have a clear understanding of an operator’s intentions and commitments.
For onshore decommissioning programs, the operator must set rehabilitation completion criteria. The completion criteria should be outlined in the environment plan (EP) and be specific with measurable targets. For example, completion criteria may relate to the stability of landforms, percentage cover of vegetation, and diversity of species compared to the surrounding area.
In all jurisdictions in Australia, companies are required to:
- Isolate groundwater aquifers within the well from each other and hydrocarbon zones;
- Isolate hydrocarbon zones from groundwater aquifers and zones with different pressure;
- Isolate surface casing or production casing from the open hole;
- Place a surface cement plug in the top of the casing; and
- Remove the wellhead.