Logging-while-drilling azimuthal electromagnetic measurements for high-resistivity coal seams

Authors

ZHAO Weina, School of Science, Qingdao University of Technology, Qingdao 266520, ChinaFollow
ZHENG Dongfang, School of Science, Qingdao University of Technology, Qingdao 266520, China
AI Weiping, CNPC Engineering Technology R&D Company Limited, Beijing 100206, China
XIE Xia, CNPC Engineering Technology R&D Company Limited, Beijing 100206, China

Abstract

Objective and Method To determine the boundary detection capability of logging-while-drilling (LWD) electromagnetic azimuthal measurements for high-resistivity coal mines, this study simulated geosignal responses under varying operating frequencies, transmitter-receiver coil spacing conditions, and formation resistivity values. Then, key parameters for boundary detection for high-resistivity coal seams were optimized. Accordingly, this study proposed design schemes for LWD instruments with short (< 80 inches) and long (approximately 240 inches) transmitter-receiver coil spacing for short-distance (2.032 m) and long-distance (6.096 m) detection, respectively. Results and Conclusions LWD electromagnetic azimuthal measurements exhibit a significantly decreased depth of detection (DOD) in high-resistivity coal seams compared to that in low-resistivity hydrocarbon reservoirs. Consequently, the existing methods for selecting the operating frequency and transmitter-receiver coil spacing are no longer applicable. In high-resistivity coal seams, increasing the operating frequency and transmitter-receiver coil spacing appropriately can enhance the strength and DOD of geosignals. Under transmitter-receiver coil spacing of 50‒85 inches (1.270‒2.159 m) and an operating frequency of (2‒5) MHz, the DOD can reach 3 m, meeting the need for roof and floor detection. When the transmitter-receiver coil spacing increases to 5 m and the operating frequency decreases to 200‒400 kHz, the DOD of electromagnetic signals in high-resistivity coal seams can extend to 10 m, offering a foundation for long-distance detection of low-resistivity anomalies.

Keywords

logging while drilling (LWD) of electromagnetic measurement, boundary detection, high-resistivity coal seam, geosteering, parameter optimization

DOI

10.12363/issn.1001-1986.25.05.0380

Recommended Citation

ZHAO Weina, ZHENG Dongfang, AI Weiping, et al. (2025) "Logging-while-drilling azimuthal electromagnetic measurements for high-resistivity coal seams," Coal Geology & Exploration: Vol. 53: Iss. 11, Article 6.
DOI: 10.12363/issn.1001-1986.25.05.0380
Available at: https://cge.researchcommons.org/journal/vol53/iss11/6

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