Abnormal pressures encountered in sedimentary basins are defined as pore pressures that are above or below hydrostatic pressure (Hubbert & Rubey, 1959; Figure 1a). Sedimentary basins generally contain vertical sequences of near-horizontal aquifers separated by less-permeable aquitards (confining units). Aquitards may serve as effective barriers for preventing fluid flow between successive aquifers. In this role, aquitards are often referred to as the caprock with respect to a given aquifer, with no connotation imposed on relative thickness of aquifer and caprock. In the context of geological carbon sequestration (GCS), caprocks are relied upon as confining units to contain injected buoyant free-phase CO 2 and may limit inter-aquifer groundwater/brine flow that would otherwise occur due to local overpressure arising from CO 2 injection.In many sedimentary basins, abnormal pressures generated by geologic forcings persist due to the presence of aquitards even without CO 2 or other fluid injection/withdrawal. Geologic forcings that cause natural overpressurization of deep aquifers and aquitards include topographically and/or osmotically-driven flows, sedimentary deposition, tectonic compression (e.g., Gulf Coast, North Dakota, California) or hydrocarbon generation (e.g., Uinta Basin, Utah) (McPherson & Bredehoeft, 2001;Neuzil, 1995;Osborne & Swarbrick, 1997). Underpressurization may also occur because of both natural processes (e.g., uplifting, melting of ice sheets, erosion, cooling, and topographically-driven flow) and manmade processes such as fluid extraction (Hunt, 1990;Neuzil, 1995). Despite the common occurrence of abnormal pressures in sedimentary basins in North America, regulations for GCS in the U.S. related to estimation of the Area of Review (AoR) (the region surrounding the GCS project where USDWs may be endangered by the injection activity) were developed assuming normal (hydrostatic) pressures. This causes ongoing challenges for project permitting of GCS, particularly in reservoirs with pre-injection