Application of Mercury Intrusion Porosimetry in Coal Pore Structure Characterization: Conformance Effect and Compression Effect Correction

Mercury intrusion porosimetry (MIP) is commonly used to characterize coal pore structures, but conformance effect and compression effect can overestimate pore volume. This study uses MIP data from coal with varying metamorphic degrees in China to compare existing correction methods and propose a new approach based on apparent and true density for pore volume correction under no confining pressure. The study also analyzes the impact of conformance and compression effects on MIP data. Correctly identifying the “actual initial intrusion pressure” and “closure pressure” is essential for accurate data correction. The fractal dimension method offers a more robust theoretical foundation, while the conformance and intrusion pressure identification method is simpler. The stage correction method is reliable but requires repeated MIP tests, adding to the workload. The new method, which corrects both coal matrix and mercury volume compression, provides a simpler and reliable solution. Results show that conformance volume accounts for 9.91–83.26% of the apparent mercury intrusion volume and increases with coal metamorphism. Coal matrix volume compression represents 99.86–99.90% of the corrected total volume, with mercury volume compression being negligible. The corrected pore volume decreases as coal metamorphism increases, indicating the effectiveness and simplicity of the proposed method.