Journal of MMIJ

Special Edition for Geological CO2 Storage (II)

Published: July 01, 2015 Updated: July 01, 2015

Displaying 1-3 of 3 articles

Volume 130 (2014) Issue 7 Pages 391-395 Published: July 01, 2015
Legislative Issues Concerning CCS
Koji NAKUI

This paper overviews policy and regulatory developments of the countries that introduce comprehensive framework for enabling commercially viable CCS projects. In the analysis, CCS related laws are categorized by their roles into, those oblige or urge operators to take emission reduction measures, those permit operators to implement CCS activities and those support demonstration projects with a goal of CCS commercialization. Governments with a progressive vision are found to have developed legal systems consisting of all three categories of laws.
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Volume 130 (2014) Issue 7 Pages 396-403 Published: July 01, 2015
Dissolution Experiments of Serpentinite and Kinetic Modeling of CO₂ Behavior for Underground Sequestration of CO₂ in Deep Serpentinite Aquifers
Naotatsu SHIKAZONO, Yumiko OKUYAMA, Tomoaki UMEMURA, Hirohiko KASHIWAGI

Dissolution experiments were performed on serpentinite samples containing serpentine, brucite, olivine and pyroxene from Mt. Iwanai, Hokkaido, northern Japan. From the results, we obtained dissolution rate constants for serpentine (Mg, Fe)(Si₂O₅)(OH)₄), brucite (Mg(OH)₂) and olivine (Mg, Fe)₂SiO₄) as functions of pH. These constants and obtained mineral surface area (A) / mass of water (M) ratio were used in a kinetic model (PATHARC) ^{1, 2)}to calculate the temporal variation of the amounts of minerals in serpentinite and the chemical composition of groundwater in which CO₂ is injected (P_CO2=100 bar and total CO₂ in groundwater=1 mol/kgH₂O, pH=3) at a depth of 1,000 m and a temperature of 40℃. The results indicate that the amounts of primary minerals (brucite, olivine, and pyroxene) decrease over time due to dissolution. Artinite forms as a product of this dissolution in the early stages and then its amount decreases as magnesite forms. 100% of the injected CO₂ will be fixed as magnesite in 22 years for sample A, a harzburgite serpentinite, and in 3 years for sample B, a dunite serpentinite. These periods are very short compared with other types of rocks like basalt, granite, and sedimentary rocks from Japan studied in our laboratory ^3-5). This indicates that the serpentinite rocks are potentially useful aquifer host rocks for underground sequestration of CO₂.
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Volume 130 (2014) Issue 7 Pages 404-410 Published: July 01, 2015
Numerical Simulation of Capillary Trapping of CO₂ in Porous Media
Tetsuya SUEKANE, Kensuke TAKEHANA

Capillary trapping is one of the major mechanisms to hold CO₂ in reservoirs against buoyancy force. In present paper, the effect of porous structures on the residual gas saturation was investigated numerically by means of lattice Boltzmann method (LBM). Numerical simulations were carried out for twelve artificially-generated porous media. Water was injected into the porous media filled with supercritical CO₂ at constant pressure difference until the residual gas trapping condition. The residual gas saturation increases with a decrease in the porosity and the average pore throat radius. At the relatively high capillary number of 10^-4, lower pore throat radii with higher capillary pressure tend to hold CO₂ bubbles against the pressure gradient. Under the hydrophilic conditions, the residual gas saturation decreases monotonically with an increase in the contact angle. However, the positions and sizes of trapped gas bubbles change absolutely with the contact angle.
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