Permeability Prediction and Distribution in the Confined South Georgia Rift Red Beds With Implications for CO2 Storage

Abstract

The lack of a permeability log necessary to assess reservoir injectivity as well as aid the correlation and interpretation of existing porosity and resistivity logs for reservoir quality characterization for CO2 storage in the South Georgia Rift red beds provides the motivation for this study. CO2 sequestration seems to be the most viable near-term solution to global warming. Besides, the significant cost ($10 M - $100M) associated with drilling and logging for in situ permeability coupled with the limited resolution of existing core data further makes this work compelling. Knowledge of permeability will also aid dynamic reservoir modeling of the distribution of fluid flow to better characterize the CO2 injection distribution and efficiency for the purpose of storage optimization and management. We applied a methodology 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 non-uniform distribution with depths possibly due to reservoir response and sensitivity to geologic changes in the confined and heterogeneous red beds. It also manifests 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. The regional significance of this is that the South Georgia Rift red beds and possibly the ones encountered in other buried Triassic-Jurassic basins in the Southeastern United States are most likely to be low permeable rocks in view of the similarities in age, geologic history and composition. We conclude that while the low permeability aided by the low resistivity depicted in the red beds suggests increased confining stress and reduced injectivity, any pore pressure increase with CO2 injection over time may counteract these thereby opening pores for improved injectivity.

AAPG Datapages/Search and Discovery Article #90291 ©2017 AAPG Annual Convention and Exhibition, Houston, Texas, April 2-5, 2017