Sinking CO2 in Supercritical Reservoirs.

Francesco Parisio,Victor Vilarrasa

doi:10.1029/2020gl090456

Abstract

Geologic carbon storage is required for achieving negative CO2 emissions to deal with the climate crisis. The classical concept of CO2 storage consists in injecting CO2 in geological formations at depths greater than 800 m, where CO2 becomes a dense fluid, minimizing storage volume. Yet CO2 has a density lower than the resident brine and tends to float, challenging the widespread deployment of geologic carbon storage. Here, we propose for the first time to store CO2 in supercritical reservoirs to reduce the buoyancy‐driven leakage risk. Supercritical reservoirs are found at drilling‐reachable depth in volcanic areas, where high pressure (p > 21.8 MPa) and temperature (T > 374°C) imply CO2 is denser than water. We estimate that a CO2 storage capacity in the range of 50–500 Mt yr−1 could be achieved for every 100 injection wells. Carbon storage in supercritical reservoirs is an appealing alternative to the traditional approach.

Highlights

Carbon Capture and Storage (CCS) is envisioned as a key technology to accomplish net negative carbon dioxide (CO2) emissions during the second half of the century and meet the COP21 Paris Agreement targets on climate change (Bui et al, 2018; Intergovernmental Panel on Climate Change [IPCC], 2018)
Geologic carbon storage is required for achieving negative CO2 emissions to deal with the climate crisis
Supercritical reservoirs are found at drilling‐reachable depth in volcanic areas, where high pressure (p > 21.8 MPa) and temperature (T > 374°C) imply CO2 is denser than water

Summary

Introduction

Carbon Capture and Storage (CCS) is envisioned as a key technology to accomplish net negative carbon dioxide (CO2) emissions during the second half of the century and meet the COP21 Paris Agreement targets on climate change (Bui et al, 2018; Intergovernmental Panel on Climate Change [IPCC], 2018). CCS should overcome two main hurdles, namely, the risks of induced seismicity (Vilarrasa & Carrera, 2015; Zoback & Gorelick, 2012) and CO2 leakage (Lewicki et al, 2007; Nordbotten et al, 2008; Romanak et al, 2012), before its widespread deployment takes place. Proper site characterization, monitoring, and pressure management should allow minimizing the risk of perceivable induced seismicity in Gt‐scale CO2 injection (Celia, 2017; Rutqvist et al, 2016; Vilarrasa et al, 2019). A few concepts have been proposed to date to reduce the risk of CO2 leakage These concepts consist either in promoting fast mineralization or storing CO2 already dissolved in the resident brine. Regarding rapid CO2 mineralization, injecting CO2 in shallow basaltic rock allows a quick mineralization thanks to the PARISIO AND VILARRASA

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