11:30 AM - 11:45 AM
[HSC05-10] Numerical simulation of electromagnetic exploration for CO2 monitoring in horizontal multi-layered earth
Keywords:electromagnetic exploration, CCS, FDEM, horizontal multi-layered earth
In this study, we focused on the issue of CO2 injection monitoring, and developed a calculation program and conducted numerical simulations for the monitoring by electromagnetic survey method for a three-dimensional transmitter-receiver configuration in a horizontal multilayer structure. The accuracy of the program for the horizontal multi-layered structure was confirmed by verifying the analytical and numerical solutions of the magnetic field response at the surface of the homogeneous earth, and the simulation was carried out for the horizontal multi-layered structure model with a shielding layer above the CO2 reservoir.
In the monitoring, the seismic reflection survey (seismic survey) is the main method. In addition to the method, gravity survey and electromagnetic survey are also being considered. Electromagnetic survey has the advantage of being less costly than seismic reflection surveys. Moreover, this survey can monitor resistivity, as opposed to the seismic velocity (density) structure in seismic reflection surveys.
For these reasons, we investigate the possibility of monitoring the CO2 injection model in CCS under different conditions by varying the transmitter arrangement and transmission frequency in the application of frequency-domain electromagnetic (FDEM) method. The magnetic field and its rate of change due to CO2 injection were calculated under a total of nine conditions by combining the transmitter locations and frequencies.
The FDEM method is simpler in principle and analysis than the time-domain electromagnetic method, but the primary field, which does not include the influence of the subsurface structure, and the secondary field, which is the response of the subsurface structure, cannot be acquired separately. The amplitude of the total field is the magnitude of the response itself, which can be expressed by adding up the transmitted field as the primary field and the field due to the resistivity structure of the subsurface as the secondary field. The primary field is often known, so when estimating the resistivity structure, the secondary field is the value obtained by removing the effect of the primary field from the total field. The electromagnetic field is measured by amplitude and phase, and can be regarded as a complex number, but its imaginary component contains only the response of the earth. In this study, the amplitude of the imaginary component of the total field response was used to calculate the magnetic field response and its rate of change due to the subsurface resistivity structure. Based on these data, we evaluated the effects of CO2 injection layer and shielding layer with high and low resistivity and discussed CO2 injection monitoring by electromagnetic exploration method.
In the monitoring, the seismic reflection survey (seismic survey) is the main method. In addition to the method, gravity survey and electromagnetic survey are also being considered. Electromagnetic survey has the advantage of being less costly than seismic reflection surveys. Moreover, this survey can monitor resistivity, as opposed to the seismic velocity (density) structure in seismic reflection surveys.
For these reasons, we investigate the possibility of monitoring the CO2 injection model in CCS under different conditions by varying the transmitter arrangement and transmission frequency in the application of frequency-domain electromagnetic (FDEM) method. The magnetic field and its rate of change due to CO2 injection were calculated under a total of nine conditions by combining the transmitter locations and frequencies.
The FDEM method is simpler in principle and analysis than the time-domain electromagnetic method, but the primary field, which does not include the influence of the subsurface structure, and the secondary field, which is the response of the subsurface structure, cannot be acquired separately. The amplitude of the total field is the magnitude of the response itself, which can be expressed by adding up the transmitted field as the primary field and the field due to the resistivity structure of the subsurface as the secondary field. The primary field is often known, so when estimating the resistivity structure, the secondary field is the value obtained by removing the effect of the primary field from the total field. The electromagnetic field is measured by amplitude and phase, and can be regarded as a complex number, but its imaginary component contains only the response of the earth. In this study, the amplitude of the imaginary component of the total field response was used to calculate the magnetic field response and its rate of change due to the subsurface resistivity structure. Based on these data, we evaluated the effects of CO2 injection layer and shielding layer with high and low resistivity and discussed CO2 injection monitoring by electromagnetic exploration method.