Paper Title
Determination of Sandstone Porosity and Permeability Using X-Ray Microtomography

Abstract
Sandstone samples representing regional aquifer in Northeastern Thailand were investigated for hydraulic properties. In this study, the results of 3D synchrotron x-ray microtomography are compared with results obtained by traditional methods. The core samples were prepared, and experimental procedures following ASTM standard practices were conducted to obtain porosity and intrinsic permeability values. The average porosity determined by water contents of the studied sandstones ranged from 4.68% to 7.83%. The intrinsic permeability values calculated from gas-permeability tests ranged from 2x10-17m2 to 9x10-17m2 for the normal-to-bedding direction and from 4x10-16m2 to 1x10-15m2 for the parallel-to-bedding direction. Representatives of the sandstones were experimented by 3D X-ray tomography at BL1.2 XTM, Synchrontron Light Research Institute (Thailand). This technique enabled the investigation in x, y, z directions and created 3-D images of the samples. The porosity and permeability values were calculated by the software Octopus, the average porosity values of the sandstones ranged from 15.51% to 24.05%, and the average permeability values ranged from 2.77x10-16m2 to 4.47x10-16m2 for the normal-to-bedding direction and from 4.82x10-16m2 to 6.38x10-16m2 for the parallel-to-bedding direction. The results show that the porosity values obtained from microtomography are equal or varied to 3-4 times higher than the lab experiments whereas the permeability values are equal in fine-grained sandstone samples and slightly different in medium-grained sandstone samples. The strengths of the x-ray tomography are obviously recognized. The technique is non-destructive and enabled for qualitative and quantitative assessment. The 3-D images reveal shape and orientation of micro pores and detrital grains which cannot be viewed by polarized-light microscopy. The software can helps in rapid calculation and estimation of hydraulic properties of studied geomaterial with high degree of resolution and reliability. Index Terms - Computed Tomography, porous aquifer, Khorat Group, 3D image