Tidal measurements are of great significance since they may provide us with essential data to apply towards protection of coastal communities and sea traffic. Currently, tide gauge stations and laser altimetry are commonly used for these measurements. On the other hand, muography sensors can be located underneath the seafloor inside an undersea tunnel where electric and telecommunication infrastructures are more readily available. In this work, the world’s first under-seafloor particle detector array called the Tokyo-bay Seafloor Hyper-Kilometric Submarine Deep Detector (TS-HKMSDD) was deployed underneath the Tokyo-Bay seafloor for conducting submarine muography. The resultant 80-day consecutive time-sequential muographic data were converted to the tidal levels based on the parameters determined from the first-day astronomical tide height (ATH) data. The standard deviation between ATH and muographic results for the rest of a 79-day measurement period was 12.85 cm. We anticipate that if the length of the TS-HKMSDD is extended from 100 m to a full-scale as large as 9.6 km to provide continuous tidal information along the tunnel, this muography application will become an established standard, demonstrating its effectiveness as practical tide monitor for this heavy traffic waterway in Tokyo and in other important sea traffic areas worldwide.
It is significant to understand the values and trends of the contact angle of CO2/brine/mineral systems to evaluate and model the sealing performance of CO2 Geo-Sequestration (CGS). It has been reported that the contact angles of the CO2/brine/muscovite systems increase as pressure increases from ambient conditions to reservoir conditions. This trend suggests a decrease in seal integrity. In this paper, we studied its mechanisms and the contributing factors by calculating the Frumkin-Derjaguin equation, which is based on the thermodynamics of the interfacial system. Results show that a decrease of pH is a critical factor for the wettability alteration at a lower pressure range (0.1 MPa to 3.0 MPa). In contrast, the increase of CO2 density and the decrease in the interfacial tension of CO2/brine are significant for the wettability change at a higher pressure range (3.0 MPa to 10.0 MPa). Also, sensitivity analysis shows that the contact angle is sensitive to the interfacial tension of CO2/brine and the coefficients of hydration forces.
We performed molecular dynamics (MD) simulations to study structure, stability, and dynamics of the water adsorption layer on muscovite mica at several temperatures (from 298 K to 673 K) and pressures (0.1 MPa, 10 MPa, and 50 MPa). We studied the structure of the adsorption layers with three characteristic peaks of density and orientation of H2O molecules in one-dimensional and two-dimensional profiles. The results show that the water adsorption layers become less structured and more mobile as the temperature increases. We also found the first and the second layers are less diffusive than the third one, and the difference of diffusivity gets unclear as the temperature increases. Finally, we discuss implications to hydration forces and wettability, which are significant interfacial properties of the multiphase fluids system such as water/gas/mineral systems, from the viewpoint of water adsorption film with nanometer thickness.
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