This
paper adopts the measurement of mercury intrusion porosimetry
and nuclear magnetic resonance (NMR) to analyze the pore system and
the pore structure of coal samples, and the measurement of maceral
group composition, scanning electron microscopy, and energy dispersive
X-ray spectroscopy to obtain the organic/inorganic composition of
coal samples. Gravimetric and NMR methods are both used to calculate
irreducible water saturation of the samples, and qualitative and quantitative
research studies are therefore conducted. The following knowledge
is obtained. Coal samples can be classified as micro-trans-pore-dominated
samples, meso-macro-pore-dominated samples, cleat-dominated samples,
and even development samples. The main composition of the samples
is organic, and a little kaolinite and pyrite can be observed. Irreducible
water saturation obtained by the gravimetric method is almost close
to that gained by the NMR method. The influencing parameters can be
divided into two categories. The first category contains the maximum
vitrinite reflectance, volumetric factor, fixed carbon yield, volatile
yield, vitrinite percentage, and inertinite percentage, which have
a strong correlation with irreducible water saturation. The second
category includes the buried depth and median radius, and they have
a weak correlation with irreducible water saturation. Multivariate
regression shows that there is a linear quaternion equation between
irreducible water saturation and independent variables such as maximum
vitrinite reflectance, volumetric factor, volatile yield, and vitrinite
percentage.