Quantitative Characterization of Coal Cleat Pores Based on NMR and Its Application

The pore system of coal beds is dominated by matrix pores and cleat pores, and has typical dual-pore structure characteristics. Cleat pores are the main seepage channels and one of the core parameters of coalbed methane drainage recovery. The corresponding NMR T2 spectrum characteristics of cleat pores have been ascertained by conducting NMR experiments on coal cores. The quantitative characterization method for cleat porosity and cleat width has been established by quantitatively analyzing the NMR T2 spectrum. The cleat permeability has been calculated based on the cleat pores. The result shows that the error between the calculated permeability and the core measurement permeability is controlled at an order of magnitude. The research method and characterization technology have been applied in the quantitative evaluation of coal bed cleat pores by NMR logging, providing key parameters for the evaluation of CBM reservoirs.