5:15 PM - 6:30 PM
[HSC05-P02] Experimental Study on the Effect of Salt Concentration on the Flow Characteristics of Supercritical Carbon Dioxide for the Application to Carbon Dioxide Capture and Storage
Keywords:Carbon dioxide capture and storage, Supercritical carbon dioxide, Salt concentration
Recently, carbon dioxide capture and storage has been attracting attention as a countermeasure against global warming. Among the strata deeper than 800 m where supercritical conditions can be maintained after carbon dioxide injection, deep aquifers made of porous rocks that contain highly concentrated salt water, which is of little agricultural and industrial value, are considered as suitable reservoirs.It has been pointed out in previous studies that the salinity of the groundwater in the aquifer can affect the flow characteristics of carbon dioxide (Sokama-Neuyam, 2019). The previous study have reported the flow properties of carbon dioxide in saline water at higher concentrations than seawater in order to consider the effect of salt precipitation. On the other hand, since most of the deep aquifers in Japan have a salinity below seawater, there is a need to measure the flow characteristics of carbon dioxide for salinities below seawater. Therefore, the purpose of this study is to experimentally investigate the effect of salinity on the flow characteristics of carbon dioxide.
We designed an experimental apparatus to determine the amount of carbon dioxide released from rocks and the amount and concentration of salt water when supercritical carbon dioxide was injected into rocks saturated with salt water, and used the apparatus to measure and compare the flow characteristics of multiple rocks. The effect of salt concentration on the flow characteristics was also investigated by observing the cross-section of rocks after injection of carbon dioxide.
Figure A shows a schematic diagram of the experimental setup created to observe the flow characteristics. The solid line in Fig. A is the line where carbon dioxide flows, and the dotted line is the line where water flows apply pressure.The rock used in the experiment was a sintered glass bead that imitates sandstone (hereafter referred to as simulated sandstone, Berge, 1995). The other experimental conditions were as follows: salt concentration in the saturated water was 0-0.4 mol/L, salt type was sodium chloride, pore pressure of the rock was 10 MPa, confining pressure of the rock was 20 MPa, and temperature was 40°C. Supercritical carbon dioxide was distributed into the simulated sandstone at a flow rate of 2 ml/min, and fluid flow rate and differential pressure were measured.
Figure B shows the relative permeability curves calculated using Darcy's equation from the experiments at saturated water-salt concentrations of 0, 0.2, and 0.4 mol/L. The relative permeability increased with decreasing water saturation. Also, the relative permeability tended to increase with increasing the salt concentration, indicating that carbon dioxide could pass through more easily as the salt concentration increased.
Two factors that may affect the flow properties of carbon dioxide with increasing salt concentration are salt precipitation (Sokama-Neuyam, 2019) and contact angle change (Arif, 2016). As the salt concentration increases, the contact angle between supercritical carbon dioxide, salt water, and rock increases, and the relative permeability increases as the capillary pressure decreases. In contrast, salt precipitation is expected to reduce the relative permeability by blocking the flow path of carbon dioxide. In this study, the relative permeability tended to increase as the salt concentration increased, suggesting that the effect of contact angle change was greater than that of salt precipitation.
The cross-section of Sandstone analogs after carbon dioxide distribution was observed by electron microscopy, and it was found that most of the sodium chloride precipitated in elongated form under the condition of high salt concentration, and very few of them precipitated in cubic form and blocked the carbon dioxide flow path. This result suggests that the precipitation of salt does not affect the flow characteristics of carbon dioxide under the conditions of the present study.
We designed an experimental apparatus to determine the amount of carbon dioxide released from rocks and the amount and concentration of salt water when supercritical carbon dioxide was injected into rocks saturated with salt water, and used the apparatus to measure and compare the flow characteristics of multiple rocks. The effect of salt concentration on the flow characteristics was also investigated by observing the cross-section of rocks after injection of carbon dioxide.
Figure A shows a schematic diagram of the experimental setup created to observe the flow characteristics. The solid line in Fig. A is the line where carbon dioxide flows, and the dotted line is the line where water flows apply pressure.The rock used in the experiment was a sintered glass bead that imitates sandstone (hereafter referred to as simulated sandstone, Berge, 1995). The other experimental conditions were as follows: salt concentration in the saturated water was 0-0.4 mol/L, salt type was sodium chloride, pore pressure of the rock was 10 MPa, confining pressure of the rock was 20 MPa, and temperature was 40°C. Supercritical carbon dioxide was distributed into the simulated sandstone at a flow rate of 2 ml/min, and fluid flow rate and differential pressure were measured.
Figure B shows the relative permeability curves calculated using Darcy's equation from the experiments at saturated water-salt concentrations of 0, 0.2, and 0.4 mol/L. The relative permeability increased with decreasing water saturation. Also, the relative permeability tended to increase with increasing the salt concentration, indicating that carbon dioxide could pass through more easily as the salt concentration increased.
Two factors that may affect the flow properties of carbon dioxide with increasing salt concentration are salt precipitation (Sokama-Neuyam, 2019) and contact angle change (Arif, 2016). As the salt concentration increases, the contact angle between supercritical carbon dioxide, salt water, and rock increases, and the relative permeability increases as the capillary pressure decreases. In contrast, salt precipitation is expected to reduce the relative permeability by blocking the flow path of carbon dioxide. In this study, the relative permeability tended to increase as the salt concentration increased, suggesting that the effect of contact angle change was greater than that of salt precipitation.
The cross-section of Sandstone analogs after carbon dioxide distribution was observed by electron microscopy, and it was found that most of the sodium chloride precipitated in elongated form under the condition of high salt concentration, and very few of them precipitated in cubic form and blocked the carbon dioxide flow path. This result suggests that the precipitation of salt does not affect the flow characteristics of carbon dioxide under the conditions of the present study.