Permeability Prediction in the South Georgia Rift Basin – Applications to CO2 Storage and Regional Tectonics

Abstract

The lack of the permeability log data necessary to assess reservoir injectivity as well as aid in the correlation and interpretation of existing porosity and resistivity logs for reservoir quality characterization for potential CO2 storage in the heterogenous and complex South Georgia Rift (SGR) basin provides the motivation for this study. The focus was on the Triassic-Jurassic red beds buried, entrenched beneath the Cretaceous-Cenozoic Coastal Plain sediments. Moreover, the significant cost typically between $10 M to $100M associated with drilling and logging for in situ permeability coupled with the limited resolution of existing core data further makes this work necessary. The purpose is to relate, use the interpretation of the predicted permeability distribution to assess feasibility for safe and long-term CO2 sequestration. This study also intends to establish the impacts of active and passive tectonism that has shaped and/or re-shaped the evolution of the basin on the present-day permeability. A methodology was applied that utilizes the pore space and geohydraulic properties of the reservoir from existing laboratory and well data to produce a newly derived permeability log. It shows a non-uniform distribution with depths possibly due to geologic changes in the confined and heterogeneous red beds. The derived log displays characteristics consistent with observations from the porosity and resistivity logs. The interpretation of these logs provides evidence for the presence of low permeable, tightly cemented and compacted red beds. We conclude that the low permeability aided by the low resistivity depicted in the red beds suggests increased confining stress and reduced injectivity, and that the uncharacteristically low permeability reflects a deformed basin shaped with episodes of uplift and erosion.

Simulation of carbon dioxide mineralization and its effect on fault leakage rates in the South Georgia rift basin, southeastern U.S.

“…Predicting leakage areas, estimating the time at which leakage occurs, and fault hydraulic properties are not yet fully understood. Simulation modeling studies are required to support the importance of identifying key permeability values that allow for the seal to be effective in containing CO 2 in the reservoir ( Akintunde et al., 2017 ).…”