ROCK CHARACTERIZATIONS THROUGH NITROGEN ADSORPTION

This poster illustrates rock characterization of various types of rocks from different formations through nitrogen adsorption. Nitrogen adsorption has been proven to be a reasonable method to measure the porosity up to nanoscale. The process of nitrogen adsorption includes degassing the sample under a vacuum condition and a suitable temperature that does not modify the rock texture. Then, the sample is safely isolated with nitrogen liquid while allowing the system to reach equilibrium point before determining the volume adsorbed at each pre-set relative pressure. Two different surface area and pore volume analyzing machines from different companies are used in nitrogen adsorption with slightly different adaptations. The poster compares porosity of sedimentary rocks (sandstone and shale) and metamorphic rocks (Hawaii Lava rocks). These sample rocks also come from different lithology, namely Bakken, Hawaii, Niobrara and even Najmah formation from Kuwait. According to the experimental results, several hypotheses can be derived regarding the lithology. Although Hawaii Lava rocks are from similar formations, their pore volume and surface area vary depending on the depth of the formation. The isotherms of Hawaii Lava rocks obtained from the two analyzing machines show similar pattern, with a little difference in the volume of nitrogen adsorbed. The larger the amount of sample mass used in the experiment, the more accurate the results will be. Hawaii Lava rocks, being a metamorphic rock without any organic content, tend to have a higher pore volume than the kerogen filled Najmah rocks. Clay samples, such as smectite, illite and montmorillonite, act as the constant in these experiments due to their ability to reproduce similar isotherms despite their origin or lithology.