5:15 PM - 6:30 PM
[HSC05-P04] Artificial barrier formation in hot spring water containing CO2
Keywords:Geological CO2 storage, Sealing performance, Artificial barrier, Caprock, Carbonate, Water glass
In geological CO2 storage, the well is most likely to be the leakage path. In order to reduce the risk of such leakage, it is effective to inject a CO2 solidification promoting substance at the end of CO2 injection to form a solid film around the well. For the purpose of developing technology to form an artificial barrier around the well, experiments to produce carbonates or other solids by CO2 were conducted in hot spring water using various natural harmony type chemical substances.
Berea sandstone, as a rock sample imitating a reservoir rock, was formed into a cylindrical shape with a diameter of 14 mm and a height of 10 mm. These samples were placed in the reaction pipe so that the cylindrical direction was parallel to the water flow. The study adopted three types of chemicals, sodium hydroxide (NaOH), strontium hydroxide (Sr(OH)2), and sodium silicate (water glass: Na2O・nSiO2). Each chemical was added to the original hot spring water at various concentrations, and the sealing effect accompanied by CO2 injection was investigated. In the experiment, the solution was circulated in the reaction tube in advance at about 0.4 MPa, and then CO2 was mixed at a constant pressure from the middle of the pipe to maintain the total pressure at 0.44 to 0.56 MPa. The change in the flow rate was measured by collecting the running water within a predetermined time with a measuring cylinder and calculating the average value during that period. Some experiments inserted pipes directly inside the Berea sandstone to ensure solid formation inside the rock.
When CO2 was injected into hot spring water mixed with NaOH and Sr(OH)2, no significant decrease in the flow rate was observed. Therefore, it is expected that a sufficient amount of carbonate was not produced to block the inside of the rock under the experimental conditions. In fact, CO2 blockage occurred in some experiments, which is thought to be because the carbonate produced accidentally blocked the flow path inside the rock. On the other hand, when water glass was used, solid matter was immediately generated in the pipe, and the flow was stopped due to the complete sealing effect. This means that the substance proposed by Ito et al. (2014) is useful also in natural hot spring water. Regarding water glass, there was a problem that it solidified in the pipe before reaching the rock sample because of its strong effect, but this study clarified the appropriate concentration range.
Berea sandstone, as a rock sample imitating a reservoir rock, was formed into a cylindrical shape with a diameter of 14 mm and a height of 10 mm. These samples were placed in the reaction pipe so that the cylindrical direction was parallel to the water flow. The study adopted three types of chemicals, sodium hydroxide (NaOH), strontium hydroxide (Sr(OH)2), and sodium silicate (water glass: Na2O・nSiO2). Each chemical was added to the original hot spring water at various concentrations, and the sealing effect accompanied by CO2 injection was investigated. In the experiment, the solution was circulated in the reaction tube in advance at about 0.4 MPa, and then CO2 was mixed at a constant pressure from the middle of the pipe to maintain the total pressure at 0.44 to 0.56 MPa. The change in the flow rate was measured by collecting the running water within a predetermined time with a measuring cylinder and calculating the average value during that period. Some experiments inserted pipes directly inside the Berea sandstone to ensure solid formation inside the rock.
When CO2 was injected into hot spring water mixed with NaOH and Sr(OH)2, no significant decrease in the flow rate was observed. Therefore, it is expected that a sufficient amount of carbonate was not produced to block the inside of the rock under the experimental conditions. In fact, CO2 blockage occurred in some experiments, which is thought to be because the carbonate produced accidentally blocked the flow path inside the rock. On the other hand, when water glass was used, solid matter was immediately generated in the pipe, and the flow was stopped due to the complete sealing effect. This means that the substance proposed by Ito et al. (2014) is useful also in natural hot spring water. Regarding water glass, there was a problem that it solidified in the pipe before reaching the rock sample because of its strong effect, but this study clarified the appropriate concentration range.