Coal-Free Zone Genesis and Logging Response Characterization Using a Multi-Curve Signal Analysis Framework.

Area of Science:

• Geology
• Mining Engineering
• Geophysics

Background:

• Coal-free zones decrease recoverable reserves and elevate water inrush risks in mining.
• Traditional methods for identifying these zones face limitations due to coring, lithology, and geological complexity.

Purpose of the Study:

• To establish a multi-curve framework for analyzing the genesis and logging responses of coal-free zones.
• To develop a quantitative indicator for mine water inrush risk.

Main Methods:

• Integration of Singular Spectrum Analysis (SSA), Maximum Entropy Spectral Analysis (MESA), and Integrated Prediction Error Filter Analysis (INPEFA).
• Application of a two-stage SSA workflow for noise reduction and construction of a Trend-Fluctuation Composite (TFC) curve.
• Utilizing the minimum singular value order (N) from SSA-decomposed INPEFA curves as a risk indicator.

Main Results:

• Coal-free zones originate from inhibited peat-swamp development and subsequent fluvial scouring.
• These zones exhibit dense inflection points and cyclic fluctuations in TFC curves, with absent low anomalies in natural gamma-ray logs.
• The framework effectively delineated genetic mechanisms and boundaries using multi-curve logs, core data, and 3D resistivity surveys.

Conclusions:

• The proposed framework improves logging-based stratigraphic interpretation.
• It provides practical support for mine layout and water hazard prevention strategies.