(535g) Adsorption Isotherm Measurements of Gas Shales for Subsurface Temperature and Pressure Conditions

Carbon dioxide emissions from fossil fuels combustion have been significantly increasing compared to that in the pre-industrial era, which has caused significant increase in global average temperatures. To stabilize atmospheric CO2 emissions, one possible approach may be to inject and store CO₂ into gas shale, where significant amounts of methane are present and can be exploited and recovered. Experimental studies indicate that CO₂ has enhanced adsorption over CH₄, thus the injected CO2 may displace the adsorbed methane inside the gas shale, thereby potentially enhancing methane recovery efficiency. However, the adsorption properties of CO₂ and CH₄ on gas shale are not fully understood, and need to be investigated both experimentally and theoretically.

In our recent work, excess adsorption isotherms of CO₂ on gas shale samples have been measured under subsurface temperature and pressure conditions, using a Rubotherm magnetic suspension balance. The sample used in the study is from the Eagle Ford reservoir located in Texas, United States. Both core chip and powdered forms of sample have been investigated. According to our preliminary results,  the shale sample in the powder form always gives higher gas capacity than the same sample in chip form. The ruduced macropore mass-transfer resistance in the powdered sample is a possible explanation for its higher gas capacity.

Since kerogen and clay are the major components contributing to the adsorption behavior in gas shale, adsorption isotherm measurements for carbon-based and clay-based model materials have been performed to determine the relative roles that each of these natural systems play on the overall shale adsorption mechanism and capacity estimates.

In addition, Grand Canonical Monte Carlo (GCMC) simulations have been used to predict the adsorption behavior of carbon-based material with different pore size distributions and chemical heterogeneity. Results from simulation and experiment are compared to further investigate the mechanisms of adsorption in gas shale.