Application of Exploration Geochemical Methodology Application of Exploration Geochemical Methodology to CO₂ Monitoring

Victor T. Jones¹ and Robert J. Pirkle^2
1Exploration Technologies, Inc., Houston, TX
²Microseeps, Inc., Pittsburgh, PA

The determination of sequestered CO₂ leakage from a subsurface reservoir requires measurements to be made within natural seepage pathways controlled by geological conduits. Measurements conducted over reservoirs studied for carbon sequestration potential have had limited success to date because flux chambers and monitoring stations have not been placed within active seepage pathways controlled by the geologic system. Seepage pathways are very discrete and localized, seepage magnitudes are driven principally by pressure gradients, with secondary influences related to lithology, soil moisture and barometric pumping. Successfully measuring active seepage flux requires not only geologic knowledge, but must be guided by geochemical measurements that can determine natural seepage patterns. Exploration soil gas methodology provides the most accurate and cost-effective approach for identifying flux chimneys in near surface sediments.

Petroleum reservoir leakage characterization studies, coupled with observations from environmental monitoring, can provide the required monitoring. Extensive databases of near surface exploration and environmental studies generated over the past 32 years can adequately address the following questions: how reservoirs leak, how the leaks can be detected at the surface, what are the conduits, how long do migrating gases take to reach the surface, how are seeps distributed in the near surface soils, are tracers necessary, and what is the range of concentrations and distribution of CO₂ typically present in near surface soils prior to sequestration?

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas