SEQUESTRATION SYSTEM ANALYSIS OF THE SILURIAN TUSCARORA-CLINCH SANDSTONE, CENTRAL APPALACHIAN BASIN, USA

Sequestration systems analysis defines the geologic components of carbon dioxide injection and storage that are critical to the overall framework and design of an effective subsurface carbon dioxide management program. Geologic information on candidate subsurface CO₂ storage and sealing units are ranked based on properties such as structural setting, porosity, permeability, mineralogy, thickness, depth and distribution.

This study investigates the regional structure and stratigraphic trends of a candidate saline aquifer, the Silurian Tuscarora-Clinch Sandstone and overlying seal, the Rose Hill Formation, in the subsurface of West Virginia, southwestern Virginia and eastern Kentucky. The Tuscarora-Clinch Sandstone is regionally widespread and occurs at depths of 5000 to 8000 ft which is below the TD of many thousands of abandoned wells in the Appalachian Basin. Data from 60 geophysical well logs, published core descriptions and collected well cuttings were integrated to develop new cross sections, structural & lithofacies maps, and petrographic descriptions of the Silurian interval.

The Tuscarora-Clinch Sandstone is identified in subsurface core and outcrop as a quartzarenite, commonly subdivided into a porous upper member and a shaly lower member. Sandstone averages 82 ft in thickness, generally thinning from southeast to northwest and has been interpreted as fluvial to shallow marine in origin (Castle, 1998). The Rosehill Formation primarily consists of red gray shale, ranges from 164 – 490 ft in thickness and contains thin hematite-cemented sandstone horizons. Shales of the Rose Hill have been interpreted as low energy inner ramp lagoonal-muds (Goodman, 1994). Scanning electron and petrographic microscopy suggest that the fine grained hematite cemented Rosehill lithologies should provide good confining characteristics.

The Tuscarora-Clinch Sandstone is proposed as a primary target for saline aquifer CO₂ sequestration. Initial analyses show generally low porosities (~ 4%), with fairways of higher primary and secondary porosity. Conservative screening estimates of storage capacity range from 40 - 160 million tons of supercritical CO₂.