Evaluating reservoir properties and seal capacities of volcaniclastic rocks for hydrocarbon containment and their application to CO2 storage

Simon R. Passey, Charlotte E. McLean

Research output: Contribution to journalArticlepeer-review

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.
Original languageEnglish
Article numberSP547-2023-156
JournalGeological Society Special Publications
Volume547
Issue number1
Early online date22 Mar 2024
DOIs
Publication statusE-pub ahead of print - 22 Mar 2024

Keywords

  • Geology
  • Ocean Engineering
  • Water Science and Technology

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