Dynamic three-dimensional pore-scale imaging of reaction in a carbonate at reservoir conditions.
Quantifying CO2 transport and average effective reaction rates in the subsurface is essential to assess the risks associated with underground carbon capture and storage. We use X-ray microtomography to investigate dynamic pore structure evolution in situ at temperatures and pressures representative of underground reservoirs and aquifers. A 4 mm diameter Ketton carbonate core is injected with CO2-saturated brine at 50 °C and 10 MPa while tomographic images are taken at 15 min intervals with a 3.8 μm spatial resolution over a period of 2(1/2) h. An approximate doubling of porosity with only a 3.6% increase in surface area to volume ratio is measured from the images. Pore-scale direct simulation and network modeling on the images quantify an order of magnitude increase in permeability and an appreciable alteration of the velocity field. We study the uniform reaction regime, with dissolution throughout the core. However, at the pore scale, we see variations in the degree of dissolution with an overall reaction rate which is approximately 14 times lower than estimated from batch measurements. This work implies that in heterogeneous rocks, pore-scale transport of reactants limits dissolution and can reduce the average effective reaction rate by an order of magnitude.
Qatar Carbonates and Carbon Storage Research Centre, Department of Earth Science and Engineering, Imperial College London, London SW7 2AZ, U.K.
Hannah P
HP
Menke
Qatar Carbonates and Carbon Storage Research Centre, Department of Earth Science and Engineering, Imperial College London, London SW7 2AZ, U.K.
Branko
B
Bijeljic
Qatar Carbonates and Carbon Storage Research Centre, Department of Earth Science and Engineering, Imperial College London, London SW7 2AZ, U.K.
Matthew G
MG
Andrew
Qatar Carbonates and Carbon Storage Research Centre, Department of Earth Science and Engineering, Imperial College London, London SW7 2AZ, U.K.
Martin J
MJ
Blunt
D002119:Calcium Carbonate / Q000737:chemistry*; D002245:Carbon Dioxide / Q000737:chemistry*; D057965:Carbon Sequestration; D002254:Carbonates; D060587:Groundwater / Q000737:chemistry*; D010539:Permeability; D016062:Porosity; D011189:Potassium Chloride / Q000737:chemistry; D012492:Salts / Q000737:chemistry*; D012965:Sodium Chloride / Q000737:chemistry; D055114:X-Ray Microtomography
D002254:Carbonates; D012492:Salts; C017082:brine; D002245:Carbon Dioxide; D012965:Sodium Chloride; D011189:Potassium Chloride; D002119:Calcium Carbonate