Characterization of Pore Size Distribution in Tight Sandstones from the Northern Songliao Basin

Pore size distribution is a crucial parameter in reserve estimation and better understanding the transport and storage mechanisms of tight sandstone gas. Nitrogen gas adsorption (N2GA), mercury intrusion porosimetry (MIP) and nuclear magnetic resonance (NMR) were carried out tight sandstone samples from the Lower Cretaceous Shahezi Formation in the northern Songliao Basin to gain insight into pore structure and to detect the applicability of these techniques in characterizing full pore size distribution (PSD). For the tight sandstone with high clay content, the NMR-derived PSD is consistent with the right peak of PSD from N2GA technique and there are evident deviations between the result of N2GA and NMR for the very small pores (diameter < 15nm). However, for the tight sandstone with low clay content, the NMR-derived PSD is consistent with the left peak of MIP-derived PSD but is evidently different from the PSD from N2GA. The combination of N2GA and NMR is applied as complementary techniques to characterize full PSD and reveals that the studied samples have a broad pore size distribution ranging from 2 nm to 20 mm. Nano-scaled pores become the crucial storage space in tight sandstone samples.