Well stimulation involves injecting fluids into a well to open existing pathways between the particles in the rock formations to facilitate gas flow and collection. Stimulation varies in size and duration depending on the type; every effort is made to recover as much of the fluids as possible and all recovered fluids are removed from the project area for proper disposal. Arizona laws prohibit unpermitted discharge of recovered fluids. Related to helium gas recovery, there are two types of low-pressure well stimulation currently permitted in Arizona:
- Acidic solution — Following well installation, a solution of water and acid is injected at low pressure into a well to clean out the wellbore and facilitate gas flow in an area not to exceed 300 feet surrounding the well. The solution is also used to eliminate clay particles that accumulate and reduce flow within a few feet of the well, similar to using an acidic wash to clean residential air conditioning unit coils as dirt builds up and reduces efficiency. Most of the acidic solution is neutralized when it comes in contact with the formation. Stimulation activities vary in duration from 30 minutes to several hours and use approximately 16,800 gallons of solution per well, which is similar to the volume of a residential swimming pool.
Proppant — Following well installation, a mixture of mostly sand and water is pumped at a well-specific, calculated rate and low pressure to facilitate increased gas flow by propping open spaces created from clay particle removal. Stimulation activities are generally 45 to 60 minutes in duration and use approximately 21,500 gallons of mixture per well.
As part of any helium gas extraction activity, each permitted gas extraction well requires authorization from both ADEQ and AOGCC before any well stimulation activities can take place.