Abstract
This study was conducted in the framework of the PILOT CO2-DISSOLVED project, which provides an additional approach for CO2 sequestration, with the aims of capturing, injecting, and locally storing the CO2 after being dissolved in brine. The brine acidity is expected to induce chemical reactions with the mineral phase of the host reservoir. A set of continuous radial CO2 flow experiments was performed on cylindrical carbonate rock samples under geological storage conditions. The objective was to interpret the dissolution network morphology and orientation involved. To explore the three-dimensional architecture of dissolution arrays and their connection integrity within core samples, we used computed tomography. A structural investigation at different scales revealed the impact of the rock heterogeneity on the dissolution pathways. The initial strike of the observed mesoscopic wormholes appears to be parallel to dilatational fractures, with a subsequent change in major trends of dissolution along master shears or, more specifically, a combination of synthetic shears and secondary synthetic shears. Antithetic shears organize themselves as slickolitic surfaces, which may be fluid-flow barriers due to different mineralogy, thus affecting the permeability distribution-wormhole growth geometry induced by CO2-rich solutions.
Highlights
Capture, transport, and subsequent injection of anthropogenic CO2 into deep geological horizons of highly-permeable sedimentary rocks effectively reduces atmospheric emissions of CO2 derived from the combustion of fossil fuels
This study highlights the phenomenon of the structural control of the propagation of the dissolution network, as shown by the correlation between the direction of the different wormholes and the main regional stress field
The interplay of intra-stratification, fracture systems, and their kinematical environment largely controls the dissolution pattern induced by CO2 -rich fluids
Summary
Transport, and subsequent injection of anthropogenic CO2 into deep geological horizons of highly-permeable sedimentary rocks effectively reduces atmospheric emissions of CO2 derived from the combustion of fossil fuels. The injection of CO2 into deep geological formations uses technologies that have been traditionally applied and verified by the oil and gas industry. Validating potential storage reservoirs from the standpoint of environmental risks, which may arise from uncertainties in geometrical characteristics of leakage pathways from injection wells into adjoining stratigraphic intervals, is crucial. 1500 m in the central part of the Paris Basin (France) for supercritical CO2 storage installation. These include 70–80-m-thick oolitic carbonate horizon from the Dogger and uppermost carbonate Leakage of CO2 could have various impacts, including contamination of groundwater, which affects local health and safety.
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