Identifying the lithologies and thicknesses of coal seam roofs and floors based on multiparameter logging of boreholes

Authors

LI Zhe, State Key Laboratory Cultivation Base for Gas Geology and Gas Control, Henan Polytechnic University, Jiaozuo 454003, China; College of Safety Science and Engineering, Henan Polytechnic University, Jiaozuo 454003, ChinaFollow
GAO Baobin, State Key Laboratory Cultivation Base for Gas Geology and Gas Control, Henan Polytechnic University, Jiaozuo 454003, China; College of Safety Science and Engineering, Henan Polytechnic University, Jiaozuo 454003, ChinaFollow
LEI Wenjie, College of Safety Science and Engineering, Henan Polytechnic University, Jiaozuo 454003, China; School of Public Safety and Emergency Management, Anhui University of Science & Technology, Hefei 230000, China
LI Donghui, State Key Laboratory Cultivation Base for Gas Geology and Gas Control, Henan Polytechnic University, Jiaozuo 454003, China; College of Safety Science and Engineering, Henan Polytechnic University, Jiaozuo 454003, China
LI Zixin, State Key Laboratory Cultivation Base for Gas Geology and Gas Control, Henan Polytechnic University, Jiaozuo 454003, China; College of Safety Science and Engineering, Henan Polytechnic University, Jiaozuo 454003, China

Abstract

Background In the process of coal mining, effective exploration methods for stratigraphic characteristics are crucial to underground operations. The reason is that the accurate stratigraphic characteristics of coal seams, along with the surrounding rocks of coal seam roofs and floors, facilitate the treatment of gas in coal seams, thereby ensuring safe and efficient coal mining. Methods Based on the multiparameter logging of boreholes crossing strata in a bottom drainage roadway, this study highlighted the lowstand, upgoing borehole trajectories, as well as the variations in parameters including natural gamma rays, spontaneous potential, and resistivity. By comprehensive comparison of the trajectories, video-derived images, and logging results of multiple boreholes, this study detailed the distributions of the coal seams and surrounding rocks of the mining face and determined the accurate types and true thicknesses of various rocks. Besides, using the logging curves of boreholes and corresponding video-derived images, this study identified zones with anomalous coal structures and the water-bearing zones within coal seams. Results and conclusions The results indicate that the coal seam roofs and floors in the study area consist primarily of sandy mudstones, mudstones, fine-grained sandstones, and coals, which exhibit significantly different logging responses. The combination of the lithologic classification results and corresponding borehole trajectories allows for the effective definition of coal seams, as well as the horizons of the surrounding rocks of coal seam roofs and floors. Repeated logging of a single borehole can improve the accuracy of identified lithologies and thicknesses of rocks. With errors of thickness measurements within boreholes controlled at below 0.2 m, the logging results proved valid. The cross plot of spontaneous potential and resistivity curves reveals a zone with anomalous coal structures measuring 8.4 m in length and 1.1 m in thickness between the third and fourth groups of boreholes in the bottom drainage roadway. Additionally, the cross plot of natural gamma ray and resistivity curves and borehole videos suggest the presence of a water-bearing zone with a length of 3.4 m and a thickness of 0.9 m between the boreholes of the sixth group. These results align with the results obtained using the transient electromagnetic method (TEM), suggesting regionally weak water-yield properties. Overall, multiparameter logging serves as an efficient method for rapidly determining target horizons in underground drilling, demonstrating promising prospects for advancing the geological transparency of coal mines.

Keywords

multiparameter logging, drilling trajectory, rock type, lithologic classification, logging curve

DOI

10.12363/issn.1001-1986.24.03.0177

Recommended Citation

LI Zhe, GAO Baobin, LEI Wenjie, et al. (2024) "Identifying the lithologies and thicknesses of coal seam roofs and floors based on multiparameter logging of boreholes," Coal Geology & Exploration: Vol. 52: Iss. 12, Article 18.
DOI: 10.12363/issn.1001-1986.24.03.0177
Available at: https://cge.researchcommons.org/journal/vol52/iss12/18

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