3D FEM simulation of responses of LWD multi-mode resistivity imaging sonde

A new multi-mode resistivity imaging sonde, with toroidal coils as source, can conduct three resistivity measurements: azimuthal resistivity, lateral resistivity, and bit resistivity measurements. Thus, the logging time and cost are greatly saved. The toroidal coils are simplified as an extended vol...

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Bibliographic Details
Published in:Applied geophysics 2018-09, Vol.15 (3-4), p.401-412
Main Authors: Kang, Zheng-Ming, Ke, Shi-Zhen, Li, Xin, Mi, Jin-Tai, Ni, Wei-Ning, Li, Ming-Yu
Format: Article
Language:English
Subjects:
Azimuth
Boreholes
Computer simulation
Detection
Earth and Environmental Science
Earth Sciences
Electrical resistivity
Geophysics/Geodesy
Geotechnical Engineering & Applied Earth Sciences
Imaging techniques
Logging
Measurement
Mud
Simulation
Sondes
Toroids
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Summary:A new multi-mode resistivity imaging sonde, with toroidal coils as source, can conduct three resistivity measurements: azimuthal resistivity, lateral resistivity, and bit resistivity measurements. Thus, the logging time and cost are greatly saved. The toroidal coils are simplified as an extended voltage dipole and the response equations are derived for a homogenous formation. Based on 3D FEM, the depth of investigation (DOI), vertical resolution, circumferential azimuthal capacity, borehole diameter, mud resistivity, thickness of target formation, and the resistivity of the surrounding formation and mud invasion are simulated. The results suggest that the three measurement modes of the new sonde are different in vertical resolutions and DOIs. The circumferential detection ability of the azimuth button depends on the contrast between the anomaly and formation resistivity and the open angle of the anomaly. Whether the borehole is truncated at the bit or not has a great influence on the simulation results. The borehole and mud invasion affect the apparent resistivity in all modes, but the effects of resistivity of surrounding formation and thickness of the target formation are only corrected for lateral resistivity measurement.
ISSN:1672-7975
1993-0658
DOI:10.1007/s11770-018-0692-7