Description:
As part of WESTCARB Phase III, the AZGS is evaluating the
potential for CO2 sequestration in geologic formations that
are below a level of 800 meters (m) depth below land surface
(bls). This evaluation is directed at porous and permeable
geologic formations with impermeable sealing strata in
Cenozoic sedimentary basins in the Basin and Range Province,
and Paleozoic sedimentary formations in the Colorado
Plateau. An initial screening of Cenozoic sedimentary basins
with significant depth and volume below the 800 m bls level
resulted in ten candidate basins from a total of 88 basins
(Spencer, 2011). This report represents ongoing WESTCARB
assessment of CO2 storage potential in the Mohawk basin,
one of ten Cenozoic basins in Arizona identified during
the preliminary evaluation, and is part of Tasks 2 and 3 of
Arizona WESTCARB Phase III. Task 2 consists primarily of
characterizing basin structure, stratigraphy, lithology, and
the nature of seals or a cap rock. This task also includes
determining the storage capacity of permeable sediments
below 800 depth (Spencer, 2011). Task 3 is to determine if,
and at what depth, saline groundwater approaches 10,000
milligrams per liter (mg/L) of total dissolved solids (TDS), characterized in a separate study (Gootee and others, 2012).
This concentration represents the threshold above which water is considered non-potable and unsuitable as drinking
water (United States Environmental Protection Agency). Individual-basin studies such as this study are intended to
provide estimates of the volume of permeable strata that are capped by impermeable strata (with an interface at
depths greater than 800 m), and that are saturated with saline groundwater (>10,000 mg/L TDS).