Using Drill Stem Test Data to Construct Regional Scale Potentiometric Surface in Deep Aquifers

Ordovician and older age formations are being targeted for storage of carbon dioxide as a climate change mitigation strategy. These deep aquifers are selected as they not only are separated from shallower potable aquifers by shaley confining zones, but because at depths exceeding 2500 feet, the temperature and pressure conditions are such that CO₂ exists in the (dense) supercritical state which maximizes storage.

The volumetric quantities involved in commercial CO₂ capture and storage are quite large. The average emission from a power plant in the U.S. is approximately a million tons per year. Injecting such large quantities of CO₂ from multiple sources for periods of decades can result in elevated subsurface pore pressures at distances exceeding several hundred miles. In order to simulate the induced pressures and predict the eventual fate of CO₂, knowledge of the ambient groundwater flow field is essential for calibrating simulation models and specifying boundary conditions. However, due to the high cost of constructing deep observation wells, the potentiometric surface of deep aquifers is generally not known with certainty. As part of the (U.S. DOE sponsored) initiative to characterize the CO₂ storage capacity in Kansas, drill stem test data was used to construct a potentiometric surface map of the Cambrian-Ordovician Arbuckle aquifer in Kansas, which is being evaluated for widespread commercial-scale CO₂ storage. The results are highly encouraging, and have been verified with known hydraulic data, which validates the (incremental DST-pressure based) technical approach developed to construct region-wide potentiometric surfaces at multi-state scale. The findings are being used for constructing multiphase models to simulate the effect of commercial scale injection in Kansas.