Quantitative Evaluation of “Four Qualities” in Deep CBM Using Logging Data

Abstract The four qualities of deep CBM (CBM resources buried depth greater than 2000 m), including coal rock quality, reservoir quality, well completion quality, and coal seam roof and floor quality, are important factors that determine the degree of coal rock gas enrichment, preservation conditions, and effective mining. Taking the deep CBM in the Ordos Basin as the research object, based on coal core experiments, sensitive logging information research on the “four qualities” key parameters of coal rock reservoirs is carried out, and a quantitative logging evaluation method for key reservoir parameters is established to provide support for the comprehensive evaluation of deep CBM. Coal rock quality parameters include macroscopic coal rock type, coal industrial components, coal macerals, coal structure, etc. The key parameters of reservoir quality include coal rock porosity, permeability, and gas content. The key parameters of well completion quality include rock mechanics parameters, stress and fracture pressure. The parameters of coal seam roof and floor quality include comprehensive evaluation of the lithology, stability, and sealing ability. By delving into the “four qualities” of deep CBM in logging data, combined with drilling, mud logging, coal core analysis and laboratory data, and using corresponding quantitative evaluation methods for logging, we aim to provide logging technical support for the optimization of favorable target areas for deep CBM exploration, single well fracturing layer selection, and reserve calculation.