1-4 Possible Use of Class II Wells for Disposal of Desalination Waste Fluids

Session: Energy Geology

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Abstract:

Desalination of brackish or saline groundwater is used and being promoted to provide drinking water in areas of water scarcity with Florida, California, and Texas having the most desalination plants.  However, the disposal of the residual waste fluids is a major concern in inland areas because of the risks of seismic activity and/or aquifer contamination (these waste fluids have high salinity and, in some, cases, concentrated organics or NORMs). Class II injection wells are designated by the US EPA for fluids associated with the production of oil and gas for enhanced oil recovery (EOR) and/or fluid disposal. These wells only accept liquid oil and gas exploration and production wastes, but if repurposed could dispose other fluids. Class II wells are most common in California, Oklahoma, Kansas and in Texas (where there are over 34,000 active Class II Injection wells with over 8,000 disposal wells). The disposal wells are generally shallower than the oil & gas reservoirs and well above the crystalline basement, so seismic risks are minimal. Three analytical and one numerical model are used predict the area of review or “zone of endangering influence” and applied to sites in Texas. The Bear and Jacobs analytical model was found suitable and comparison with numerical modeling incorporating fluid density effects and well partial penetration indicated that it can predict safe buffer distances for disposal. Abandoned EOR wells in depressurized petroleum reservoirs also offer a promising option for safe disposal of highly toxic liquid wastes because of their generally greater depth, stratigraphic barriers, and hydraulic constraints. Selected reclassification of Class II wells to accept residual waste fluids from desalination should be conducted.

Geological Society of America Abstracts with Programs. Vol. 58, No. 1, 2026

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