Improved Pseudo-section Representation for CSAMT Data in Geothermal Exploration

Southeast Asian Conference on Geophysics

Grandis, Hendra^1 ; Sumintadireja, Prihadi^2

Applied and Exploration Geophysics Research Group, Faculty of Mining and Petroleum Engineering, Institut Teknologi Bandung, Jalan Ganesha 10, Bandung

40132, Indonesia^1

Applied Geology Group, Faculty of Earth Science and Technology, Institut Teknologi Bandung, Jalan Ganesha 10, Bandung

40132, Indonesia^2

关键词: Apparent resistivity;    Artificial sources;    Audio frequencies;    Data representations;    Geothermal exploration;    Quantitative interpretation;    Resistivity distributions;    Sounding techniques;   

Others  :  https://iopscience.iop.org/article/10.1088/1755-1315/62/1/012035/pdf
DOI  :  10.1088/1755-1315/62/1/012035

来源: IOP

【 摘 要 】

Controlled-Source Audio-frequency Magnetotellurics (CSAMT) is a frequency domain sounding technique employing typically a grounded electric dipole as the primary electromagnetic (EM) source to infer the subsurface resistivity distribution. The use of an artificial source provides coherent signals with higher signal-to-noise ratio and overcomes the problems with randomness and fluctuation of the natural EM fields used in MT. However, being an extension of MT, the CSAMT data still uses apparent resistivity and phase for data representation. The finite transmitter-receiver distance in CSAMT leads to a somewhat "distorted" response of the subsurface compared to MT data. We propose a simple technique to present CSAMT data as an apparent resistivity pseudo-section with more meaningful information for qualitative interpretation. Tests with synthetic and field CSAMT data showed that the simple technique is valid only for sounding curves exhibiting a transition from high - low - high resistivity (i.e. H-type) prevailing in data from a geothermal prospect. For quantitative interpretation, we recommend the use of the full-solution of CSAMT modelling since our technique is not valid for more general cases.