Towards Experimental Measurement of Methane Adsorption Isotherm in Shale Reservoirs

Abstract

Unconventional petroleum resources, especially shales, constitute an increasing frontier of reserves additions as conventional production declines. This research is a study to investigate the interactions between shale rocks with gaseous hydrocarbons and mainly uses NMR logging which is a powerful tool to obtain in-situ rock and fluid properties of hydrocarbon reservoirs. In this study, a novel procedure is developed to quantitatively estimate the excess adsorption of gaseous hydrocarbon on shale gas reserves using direct measurements of an in-house built NMR setup. NMR experiments are conducted to measure NMR-porosity, relaxation distribution, and pore size distribution. These measurements are compared at different pressures in porous media with different adsorption capacity. As a result, adsorbed hydrocarbon gas content is estimated, and finally, adsorption isotherm is presented. Additional experiments such as gas expansion porosity and gravimetric adsorption are conducted to validate the new NMR method. In this research, for the first-time LowField NMR relaxometry with frequency close to logging tools is used for quantitative determination of adsorption isotherms of methane in shale reservoirs. These measurements help estimate the gas content and differentiate between adsorbed and free gas in porous media, paving the way for studies such as natural gas storage in shale rock, CO2 sequestration, and tight enhanced recoveries such as gas flooding and cyclic solvent injection.