Evaluation and Characterization of Gas Shale Pore Space Using Low-Pressure Gas Adsorption for CO2 Sequestration Applications

The need for practical solutions to both carbon capture and carbon sequestration becomes imperative as the climatic impact of anthropogenic CO2 emissions become increasingly clear. With current global CO2 emissions increasing beyond 30 gigatons per year , all potential CO2 reservoirs should be evaluated for sequestration applications. The current focus on non-conventional natural gas resources has the potential to free intriguing reservoirs for sequestration. Many questions , including CO­2 capacity and permeability , exist regarding the viability of shale reservoirs for CO2 storage and studying the pore space due to the heterogeneity of shale. In addition , a better understanding of organic-rich shale can increase the understanding of non-hydrocarbon producing shale , which are considered to be important cap rocks for traditional reservoirs. Low-pressure gas adsorption has been used to evaluate shale samples from active gas plays , including the Haynesville and Eagle Ford formations. Adsorption and desorption isotherms were created for the entire sample using N2 at 77 K , Ar at 87 K and CO2 at 273 K and evaluated for both total pore volume and pore size distribution using density functional theory models. The samples were then partitioned into 4 size bins of 100 μm each , and additional isotherms were performed. In this manner , changes in pore volume and pore size distribution can be deduced. Further analysis was performed to support the gas adsorption observations , including Fourier transform infrared spectroscopy (FTIR) , scanning electron microscopy (SEM) , elemental analysis and total and inorganic carbon contents.