X-Ray CT scanning imaging for the Nubia sandstone as a tool for characterizing its capillary properties

The Nubia sandstone is among the most important aquifers/reservoirs system in and around the Gulf of Suez province in Egypt. It is composed of very fine to coarse siliceous highly porous sandstone. It can be differentiated into four formations, named Araba, Naqus, Abu Durba and Malha. The capillary imbibition properties of the Nubia sandstone have been studied using two different techniques: 1) Increasing mass against time and 2) X-Ray CT scanning imaging. Both methods are valuable in characterizing the different capillary properties of the studied rocks, i.e., the coefficient of capillary 'C' (measured in g/(cm(2).s(1/2)) using the first method and the capillary parameter 'A' (measured in cm/s(1/2)) using the second one. In addition, porosity (17.7 to 23.5%) was measured using two techniques: 1) Water saturation under vacuum, and 2) mercury injection 'MCP' under high pressure. The mercury injection test indicated homogeneity in the pore throat distribution of the studied samples. Liquid permeability (41.6 to 374.2 md) was measured using water flow; it is very good to excellent and mostly controlled by the rock porosity and average pore throat diameter. Both capillary parameters 'A' and 'C' show a positive correlation with permeability. On a limited set of samples the anisotropy linked to pore fabric could be estimated.