All petroleum and geothermal wells drilled in State jurisdictional areas are subject to State legislation and regulation administered by the department. The three primary areas of regulation are:
- resource management (which includes well integrity).
Primary to the department’s resource assessments of the subsurface activity are the protection of aquifers and resources. A properly designed well ensures that these protections and well integrity are retained over the life of the well. The conceptual ‘life of a well’ clearly extends beyond the initial drilling phase.
When a field eventually ceases production, the final phase is decommissioning. This broadly involves the plugging of all wells with cement, cleaning of manifolds and pipelines, and the removal of all facilities.
The Western Australian petroleum legislation has defined procedures and responsibilities for the plugging and abandonment (decommissioning) of petroleum wells. Well decommissioning procedures isolate the subsurface formation for long term environmental protection. The intent of all decommissioning operations is to achieve the following:
- isolate and protect all fresh water zones from ingress and egress from surface and subsurface
- isolate all hydrocarbon bearing zones
- prevent in perpetuity leaks from or into the well
- remove surface structures so that the landform can be rehabilitated back to its former use.