The Bureau of Land Management's (BLM) recent approval for fluid mineral leasing on public lands the Salt Basin, New Mexico, introduces extensive development and underground injection disposals with no special provisions for the protection of ground-water resources. Included in these lands is Otero Mesa, a Chihuahuan desert grassland home to a variety of flora and fauna. The Salt Basin is underlain with a high-density fractured limestone aquifer and a prominent structural feature referred to as the Otero Break. This zone of intensely-fractured limestone may act as a conduit for potential contamination from the injection of saline waters, produced as a byproduct from the extraction of oil and gas, to migrate through the subsurface and jeopardize the fresh water aquifer. At this time, no direct field evidence exists that identifies a regional impermeable layer in the Salt Basin to warrant deep well injection. This evaluation uses an existing regional ground-water flow model of the Salt Basin to simulate the deep well injection of produced waters over two 20-year projected build-out scenarios. The first scenario represents the BLM's projection of84 production wells, resulting in a total of three injection wells. The second scenario represents exploratory success in the Salt Basin generating 1,196 production wells, reSUlting in a total of 42 injection wells. Anticipated injection rates ranged from 1.1 to 10 gallons per minute per well, with total dissolved solid concentrations of 7,400 milligrams per liter. Model-predicted results indicate that the injected waters will migrate from the zone of deep injection to the shallow aquifer and horizontally away from the zone of injection at a rate of 0.05 miles per year. A limiting factor to this simulation is that the model does not account for flow in a fractured system. As such, it is possible that injected brines in the Salt Basin could move at a much higher rate, placing the anticipated uses of the fresh water aquifer at risk.
Otero Mesa, Salt Basin, Otero Break, Chihuahua Desert, Deep well injection, Fluid mineral leasing, Natural gas
Luna, Melanie L.. "Potential for Ground-Water Contamination from Deep Well Injection of Produced Waters in the Salt Basin, New Mexico." (2009). http://digitalrepository.unm.edu/wr_sp/21