CO2 Storage and Flow Capacity Measurements on Idealized Shales from Dynamic Breakthrough Experiments

摘要

Dynamic column breakthrough (DCB) measurements were carried out on idealized shale samples for the first time, based,on a custom-designed system. To better understand the contribution of different shale minerals on flow and storativity, measurements were carried out on composition-controlled shales having known weight percentages of total organic carbon (TOC) and illite. CO2 was assessed for its potential for sequestration, as well as its applicability as a fracturing fluid for enhanced gas recovery in shale formations. Experimental results reveal an increase in permeability and CO2 adsorption with either increasing TOC or illite content. This is attributed to the complex porous structure of kerogen, as well as the interlayering characteristics of clay minerals, resulting in large surface area and pore volume ratios. Permeant permeability reduction was noted with CO2 due to adsorption-induced swelling that is proportional to the amount of gas adsorbed. Helium permeability post CO2 adsorption decreased by 63% and 31.5% for the 46.3% and 25.4% illite series, respectively. In fact, DCB experiments reveal the potential for CO2 storage in shale formations With adsorption capacities exceeding that of CH4 by 4-12 times, depending, on the content of TOC and illite. Through a series of low-pressure gas adsorption experiments, it was found that each weight percent increase in TOC has a larger influence on the pore volume and surface area, compared to each weight percent increase in illite content. An similar to 3.5 wt % increase in. TOC leads to an similar to 0.005 cm(3)/g increase in pore volume, whereas it takes a similar to 20 wt % increase in illite to achieve a 0.003 cm(3)/g increase. The TOC series pore volume increases by similar to 1.4 x 10(-3) cm(3)/g for each weight percent increase in TOC, whereas the illite series pore volume only increases by similar to 0.4 x 10(-3) cm(3)/g for each weight percent increase in illite content. The coupled results clearly establish the comparative role of the organic versus inorganic adsorbing components of gas shales while overcoming the material heterogeneity through the investigation of "idealized" compositions.