Implications for Geologic Sequestration of CO_2 Based on Geochemistry of a Deep Sedimentary Basin in the Midwestern USA

摘要

Brine samples were collected during the testing program for a 2,800 m-deep characterization borehole at the American Electric Power (AEP) Mountaineer Plant in New Haven, West Virginia, USA. The hydrochemical results indicate that the formation brine waters are consistent with the limited available Appalachian Basin regional data for these formations, and can be classified as a Na-Cl or Na-Ca-Cl hydrochemical type. Results of the initial analysis clearly indicated that brine samples collected from the Rose Run formation and basal sandstone were contaminated with drilling mud. After approximately seven months, while conditions inside the well stabilized, the fluid chemistry of the permeable zones changed appreciably from the time that the initial measurements were taken. Using ion concentration ratios it was shown that K/Na ratios trended toward lower values over time, which brought the potassium concentrations into closer agreement with Rose Run data for wells in Ohio. Results from stable isotope analysis and other hydrochemical measurements indicate that the candidate storage reservoir formations at the AEP borehole location are similar geochemically to other deep formations in the region and are isolated from overlying surface and shallow potable groundwater sources. Simulations to predict the effects of injecting CO_2 into a formation with fluids comparable to the test well do not indicate precipitation of solids that would inhibit flow of the injectate.