Over the past several decades, tens of thousands of monitor, injection and extraction wells have been constructed at various locations throughout the United States. Wells have been completed on very small parcels, such as retail petroleum/dry cleaners, on multiple-acre sites for manufacturing/refining facilities, and on multiple-square-mile sites, such as Department of Energy/Defense locations.
As sites reach the remediated/closed stage, the wells may not be required, and can be a hindrance to future development. We now are seeing a significant increase in well abandonment activities across a wide variety of sites. Specific well abandonment procedures differ widely, depending on many variables, including, but not limited to:
- state and local regulations,
- well depth and diameter,
- screen and casing composition,
- physical well location, and
- final surface restoration requirements.
- Visit site as necessary.
- Secure permits.
- Confirm access agreements.
- Determine whether there are pumps/other equipment in the
- Deal with all other standard pre-construction issues.
Air-knife (vacuum extraction) Rig and Crew Mobilize to Site
- Verify all power disconnects have been made and system
- Remove well box/vault.
- Air knife around the well seal (grout) to between 8 feet and 10 feet
below ground surface, or as specified by the client.
- Backfill the excavation and air-knife holes with native material
(well cap still in place).
- Asphalt patch the surface, and demobilize.
Drill Rig Mobilizes to the Site
- Excavate the patch over the well.
- Run tremie pipe to the bottom of the well using the drill
- Mix and pump backfill material, as specified by regulations, (cement/bentonite
grout, cement or high-solids bentonite grout) from the bottom of the well to
the surface, as the tremie is being pulled with the rig.
- Once the water is displaced from the well, and the backfill material
no longer is dropping in the casing, a pressure head is placed on the well, and
an air compressor is used to place between 25 psi and 35 psi on the well for
between 15 and 45 minutes.
- Bleed pressure from system and remove pressure head.
- Visually inspect grout in well and top off with backfill material,
using tremie pipe if necessary.
- Use hollow-stem augers to drill out the top 5 feet to 10 feet of the
- Backfill top 5 feet to 10 feet, per local regulations.
- Restore surface.
- Complete and submit all required forms.
Because of the current hyper-competitive nature of the drilling and consulting business, owners, consultants and drilling contractors always are trying to identify less expensive methods for well abandonment. Recently, we have seen bid requests for well abandonment projects utilizing air-knife equipment only. While this may be a less expensive method, we have identified several significant safety/technical issues, including:
- Lowering tremie pipe into the well and retrieving by hand
increases the risk of back strains and hand injuries.
- Not running tremie pipe to the bottom of the well, which is outside
of industry standards for pressure grouting operations – manually lifting and
holding grout hoses at the well head is a potential back-strain
- Attempting to remove the top 5 feet of well casing by hand – the unscrewing method rarely is successful, and may lead to back strains and hand injuries. When the unscrewing method fails, the contractor then must attempt to cut the casing below grade by hand. This is a highly dangerous activity.
We understand the need to reduce costs in today’s challenging business climate. However, proposing to use an inexpensive/faster method without a thorough safety and technical review can lead to accidents and non-compliance with regulations. The safety of our employees, consultant partners and the public must be the driving force in how we conduct our work every single day. Taking the time to think “what is the worst thing that can happen?” needs to be second nature for every activity performed in the field. It is imperative all procedures be reviewed prior to field activities to assess potential hazards and mitigation methods. The Job Safety Analysis (JSA) protocol was created for a reason, and should be reviewed and followed. If a JSA does not exist for an activity/method, then that specific operation should not occur until a JSA has been developed, reviewed and approved. While the industry may limit costs by performing abandonment activities with the use of an air knife only, we must not underestimate the potential safety issues for our workers. Ask yourself, “Are we using an alternative method because the right way takes too long and is expensive, or is the task we are proposing equally safe and technically feasible?” Cost reduction must never be the driving force behind a field operation if it exposes our employees, consultant/client partners and the public to additional safety and technical risk.