Characterization of pore structure in sandstone from the Phitsanulok basin

Abstract

Tight sandstone has increasingly received interest as an unconventional reservoir in the petroleum industry due to its large oil and gas reserves. Microstructures of tight sandstone are difficult to be characterized because of their small grain sizes, low porosity, pore geometry, and pore throat. Complex microstructures and properties can be derived from advanced analytical tools as synchrotron X-ray tomography. Synchrotron X-ray experiments provide high spatial resolution of 3D information and nondestructive the samples. The average of grain size in PH1, PH2, and PH3 is 61.15, 30.01, 41.11 µm which are classified into very fine sand, medium, silt, and coarse silt respectively. Three type of pore are observed in the samples which are pore between grains, pore at the edge of rigids grains and fracture pores. The 3D aspect ratio of pore in PH1 and PH2 are comparable, 0.48 and 0.47 and suggesting oval shape of pore. In contrast the 3D aspect ratio in PH3 is 0.35 and show tabular and flat shape of pore. The diameter of pore throat in all samples are mostly spheroid and rod-like, ranging from 0.36 to 2.67 µm which is consistent with tight sandstone from other reservoirs such as Texas the greatest number of Basin. In addition, porosity range 9.41 to 24.34% while permeability ranges from 0.12 to 0.49 mD. The highest permeability is PH3 which contains of the greatest number of fracture pores, tabular and flat pore shape from 3D aspect ratio, the number of high-volume pores, rod and spheroid pore throat, and the biggest size of average pore throat diameter. In contrast, the lowest permeability PH2 contains low connectivity of pore shape, low pore volume, plate like pore throat, and small pore throat diameter.