Once a well has reached the end of its useful life, it must be remediated (the industry term is ‘plugged and abandoned’) to prevent the leaking of fluids and gases and protect future generations.
Effective remediation isolates oil and gas producing zones from aquifers, and remediates the surface for alternative uses, such as agriculture, to meet the relevant regulatory standards.
Steps taken to remediate a well are usually well defined by the relevant state or federal regulator.
Well remediation typically requires using a drilling rig to remove any equipment in the wells, such as subsurface pumps and pipe tubing.
The rig then pumps cement into the well and sets mechanical plugs as a back-up, to create long-term barriers to fluid flow and isolate rock zones.
Once this is done, the well-head is removed. In onshore wells, the well-head is cut off below ground level so that agriculture or other practices can resume over the well site.