BIOGEOCHEMICAL REACTIONS IN RESPONSE TO CO2 LEAKAGE IN A TEST WELL IN THE NEWARK BASIN

Potential leakage of CO₂ from deep intervals used for geological sequestration to shallow aquifers can have important negative impacts on drinking water resources, thus it is very important to understand the biogeochemical response to elevated CO₂ plumes and develop diagnostic monitoring systems.

An experimental injection, composed of one atmosphere partial pressure CO₂, was conducted in fracture zones in a sand and clay aquifer in the Newark Basin and incubated for three weeks. The geophysical logging of the borehole and tracer tests using bromide and SF₆ indicated a weak background ambient flow in the aquifer. Monitoring of groundwater parameters showed a decrease of pH from 8.2 to 6.1, in addition to silicate and carbonate dissolution, and the release of 16 trace metals, including iron, manganese, cobalt, zinc, nickel, and uranium. Changes in bacterial abundance and community diversity were also tracked in parallel with geochemical transitions.

A bench incubation experiment in the laboratory has been designed to compare the mineral dissolution and trace metal release rates, as well as the microbial community’ response to 1 and 5 bars of pCO₂ under anaerobic and aerobic conditions.

This research will provide criteria for site selection for geological CO₂ sequestration, investigate the vulnerability of shallow aquifers to CO₂ leakage, and develop the diagnostic testing techniques to assess risk.