The Impacts of Igneous Systems on Sedimentary Basins and their Energy Resources
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Igneous processes within sedimentary basins impact energy resource plays across a range of scales from regional tectonics to reservoir porosity. Understanding these interactions has a direct influence on hydrocarbon, carbon capture, geothermal, hydrogen and helium projects. This volume demonstrates state of the art thinking around these often complex systems.
Evaluating reservoir properties and seal capacities of volcaniclastic rocks for hydrocarbon containment and their application to CO2 storage
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Published:August 14, 2024
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CiteCitation
Simon R. Passey, Charlotte E. McLean, 2024. "Evaluating reservoir properties and seal capacities of volcaniclastic rocks for hydrocarbon containment and their application to CO2 storage", The Impacts of Igneous Systems on Sedimentary Basins and their Energy Resources, B. Kilhams, S. Holford, D. Gardiner, S. Gozzard, L. Layfield, C. McLean, S. Thackrey, D. Watson
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Abstract
Volcaniclastic rocks are commonly overlooked as reservoirs or seals in hydrocarbon plays because their compositions are variably unstable and reactive during burial diagenesis. This study investigated the petrography and petrophysical characteristics of 60 volcaniclastic and four siliciclastic samples from three Paleogene volcanic provinces – East Greenland, Faroe Islands and Ethiopia. The volcaniclastic samples have highly variable helium porosities (average 25.2%), but negligible total optical porosities (average 1.9%), implying reduced reservoir potential. The samples have, however, highly variable air permeabilities (average 11 mD), suggesting that they could make tight reservoirs. The permeabilities are related to either early calcite cements or the devitrification of volcanic glass. Mercury injection capillary pressure data were collected for a subset of 33 samples that at leakage/breakthrough saturations could, under near-surface conditions, hold oil column heights of between 4 and 1181 m (average 240 m). The best seals consistently have zeolite contents of >20 vol% owing to their small pore throat radii. Conversely, the worst seals are dominated by smectite and a conspicuous absence of zeolite minerals. The zeolite-rich volcaniclastic rocks could, therefore, make good shallow seals. These features also apply to CO2 storage, but questions remain about the reactivity of the volcanic material and secondary minerals with injected CO2, but also the adsorbent properties of zeolites, particularly clinoptilolite, in the presence of CO2.