14:00 〜 14:15
[SCG54-14] Characteristics of silicate minerals dissolution in chelating agent-assisted CO2 storage environments
キーワード：キレート剤、鉱物溶解、CO2貯留
To address climate change, greenhouse gas emissions must decline 43% by 2030, necessitating the removal and storage of approximately 10 Gt CO2 annually by 2050. Among the various CO2 storage options, geological storage and mineralization of CO2 in mafic and ultramafic rocks, such as basalt, have attracted significant global attention. However, this process faces several challenges, including limited effective porosity, permeability, and rock reactivity, difficulties in using seawater for CO2 capture, and uncontrolled carbonation.
To overcome these challenges, our research group has recently developed a novel approach for CO2 geological storage and mineralization with the utilization of biobased biodegradable chelating agents such as N,N-Bis(carboxymethyl)-L-glutamic acid (GLDA). An acidic chelating agent solution is employed to increase the effective porosity and permeability through enhanced mineral dissolution. Subsequently, alkaline chelating agent–containing seawater improves CO2 capture and geological storage efficiency by inhibiting mineralization, thus maintaining injectivity while providing ions for mineralization and further expanding storage space. Last, controlled mineralization is achieved by adjusting chelating agent biodegradation. The feasibility of this approach has been confirmed through laboratory experiments; however, to assess the long-term effectiveness of this approach, it is essential to understand the characteristics of mineral dissolution in chelating agent solutions.
In this study, powders of various silicate minerals, including olivine ((Mg,Fe)2SiO4), augite ((Ca,Mg,Fe)2Si2O6), anorthite (CaAl2Si2O8), and orthoclase (KAlSi3O8), were dissolved in GLDA solutions with a pH range of 1 to 6 at 35 °C for up to one month. Fluid chemistry monitoring indicated that the presence of divalent metal ions in the minerals plays a crucial role in triggering the chelating agent’s ability in enhancing mineral dissolution. All silicate minerals dissolved with the formation of silica-rich secondary minerals (e.g., amorphous SiO2), which covered the mineral surfaces but did not significantly inhibit further dissolution. Furthermore, the coexistence of Al ions with divalent metals in the minerals further reinforces the chelating agent's ability in enhancing mineral dissolution. This study is important for the development of simulators that evaluate spatial and temporal changes in reservoir properties at the kilometer scale in the presence of chelating agents.
To overcome these challenges, our research group has recently developed a novel approach for CO2 geological storage and mineralization with the utilization of biobased biodegradable chelating agents such as N,N-Bis(carboxymethyl)-L-glutamic acid (GLDA). An acidic chelating agent solution is employed to increase the effective porosity and permeability through enhanced mineral dissolution. Subsequently, alkaline chelating agent–containing seawater improves CO2 capture and geological storage efficiency by inhibiting mineralization, thus maintaining injectivity while providing ions for mineralization and further expanding storage space. Last, controlled mineralization is achieved by adjusting chelating agent biodegradation. The feasibility of this approach has been confirmed through laboratory experiments; however, to assess the long-term effectiveness of this approach, it is essential to understand the characteristics of mineral dissolution in chelating agent solutions.
In this study, powders of various silicate minerals, including olivine ((Mg,Fe)2SiO4), augite ((Ca,Mg,Fe)2Si2O6), anorthite (CaAl2Si2O8), and orthoclase (KAlSi3O8), were dissolved in GLDA solutions with a pH range of 1 to 6 at 35 °C for up to one month. Fluid chemistry monitoring indicated that the presence of divalent metal ions in the minerals plays a crucial role in triggering the chelating agent’s ability in enhancing mineral dissolution. All silicate minerals dissolved with the formation of silica-rich secondary minerals (e.g., amorphous SiO2), which covered the mineral surfaces but did not significantly inhibit further dissolution. Furthermore, the coexistence of Al ions with divalent metals in the minerals further reinforces the chelating agent's ability in enhancing mineral dissolution. This study is important for the development of simulators that evaluate spatial and temporal changes in reservoir properties at the kilometer scale in the presence of chelating agents.