ASSESSMENT OF THE POTENTIAL OF DIABASE SILLS IN THE MID-ATLANTIC REGION FOR LONG-TERM CARBON DIOXIDE SEQUESTRATION

With anthropogenic CO₂ concentrations rising, geologic carbon sequestration is an essential process in mitigating climate change. Conventional geologic carbon sequestration involves the capture of anthropogenic CO₂ and injection into depleted oil/gas reservoirs or saline formations with an impermeable cap rock to prevent the buoyant migration of CO₂. The risk of eventual CO₂ migration through these low permeability cap rocks adds expensive monitoring costs to this traditional sequestration strategy. Another method for CO₂ sequestration utilizes the reaction of CO₂ with mafic and ultramafic rocks. CarbFix, a sequestration project in Iceland, has accelerated this process to produce carbonates in less than 2 years. Storage as carbonates in mafic rocks is stable over geologic time scales. Injection into or below smaller, mafic intrusions proximal to CO₂ sources in the Mid-Atlantic Region could be an economic and technically feasible way to offset CO₂ emissions.

Diabase cores from sills near Harrisburg, PA, were obtained from the Pennsylvania Geologic Survey. Core are characterized at the National Energy Technology Laboratory in Morgantown, WV. Medical CT images have been collected and will be utilized to characterize the cores at different depths, from which the permeability can be qualitatively estimated. The mineralogy of the diabase has been assessed using the a Geotek Multi-Sensor Core Logger that includes a portable XRF, and with XRD and petrography. Discrete samples will be exposed to CO₂ to assess the ability of the core to react and produce carbonate minerals like dolomite. Precipitates will be identified by scanning electron microscope and electron dispersal spectrometry. CO₂ storage capacity within the diabase will be limited by the connected porosity and permeability. If the diabases have geochemical and petrophysical potential to be useful for CO₂ storage, further studies will be required to assess the reservoir characteristics and geo-engineering challenges. If the diabases are unsuitable for storage, we will have assessed their potential as cap rocks for CO₂ injection into the intercalated Triassic redbeds.