Permeability Evolution During Reactive Flow Experiments on Cores Under CO2 Sequestration Conditions and Development of Fully Coupled Reactive Flow Simulations at the Reservoir Scale

Abstract:

Physical, chemical, thermal, and mechanical processes can modify permeability and affect CO₂ injectivity and reactive fluid flow during geologic CO₂ sequestration. Here we report permeability evolutions observed in core-flood experiments using CO₂-charged fluids under various formation conditions. Temperature-series experiments on consolidated dolomite cores show a permeability increase due to dissolution, followed by a two-step permeability decrease due to CO₂ exsolution and secondary dolomite precipitation, as temperature is increased from 21 to 50°C and then to 100°C, respectively. CO₂ mass balance calculations suggest that, under dynamic steady-state conditions, CO₂ saturation and its relative permeability can only reach up to ~0.5 and ~0.0065, respectively. Permeability reductions of ~1/3 and mass losses of ~2% are observed both in a 52-day recycling and in two 3-day single-pass experiments with K-feldspar-rich sandstone (150°C, 200 bar). Water chemistry, SEM, and XRCT data suggest feldspar dissolution and precipitation of either boehmite (recycling) or kaolinite (single-pass) during the experiments. These observations indicate that permeability can decrease with increasing porosity due to mineral precipitation in critical pore throats. Single-pass experiments on nine dolomite cores (150°C and 150 bar with NaCl) reveal permeability enhancements and dissolution patterns at different flow rates. Permeability-porosity data indicate an increase in permeability enhancement rate per increase in porosity with reaction progress as dissolution channels lengthen along the core. These experimental observations provide the requisite data for informing up-scaled, fully-coupled reactive transport simulations of CO₂ sequestration in interbedded siliclastic-carbonate sedimentary reservoirs, which we present.

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