Well Abandonment and Decommissioning
Well Abandonment and Decommissioning
This domain tests how to permanently close a well so it cannot act as a pathway for contamination or intermix aquifers. Abandonment is not “fill the hole with dirt.” New York expects proper sealing with approved materials, removal or cutting of casing, and documentation. The method depends on whether the well is flowing, whether casing can be removed, and whether the borehole is stable.
Core rules
- Seal the full interval: place neat cement or bentonite slurry from the bottom to the top of the borehole or casing; do not bridge or leave voids.
- Casing: remove or perforate/cut casing where required so the seal contacts the formation; if casing remains, seal the annulus and cap.
- Flowing wells: control the flow before sealing; use weighted grout or a packer system as designed.
- Documentation: record well location, depth, diameter, materials, seal volume, and method.
Worked example
A 12-in borehole is 120 ft deep. Volume = π/4 × (1 ft)² × 120 = 94.2 ft³. At about 1.15 ft³ per sack of neat cement, 94.2 ÷ 1.15 ≈ 82 sacks; add 10% for loss, giving about 90 sacks. Reason it through: use actual borehole diameter, account for casing that remains in place, and confirm the approved seal material and any required casing removal before mixing.
Traps
- Filling with sand, gravel, or drill cuttings instead of an approved seal.
- Leaving casing in place without sealing the annulus, creating a vertical pathway.
- Sealing a flowing well without controlling flow, so grout is diluted or displaced.
- Failing to document the abandonment; future owners and regulators need the record.