Abstract

The distribution of nanometer-size pores in ten selected Eagle Ford Group, Haynesville, Marcellus, and Barnett shale samples was similar when comparing relative numerical abundances of maximum pore diameters but not when comparing relative abundances of pore areas (pore sizes). Differences also existed between units in the association of pores with organic material. Pores were measured on argon-ion-milled (AIM) samples and examined with a field emission environmental scanning electron microscope (SEM). One Haynesville sample was also evaluated using a focused ion beam (FIB) SEM to compare to the AIM results. With the AIM samples, pore types were subdivided into three categories—organic pores, mixed matrix/organic pores, and matrix pores—based on the amount and type of material (organic or inorganic) surrounding the pores. Organic pores are pores generally associated with kerogen macerals, whereas mixed matrix/organic pores are pores that are probably associated with bitumen or pyrobitumen. Matrix pores are not associated with any organic matter. Within the sample set studied, only the Barnett samples contained pores almost exclusively within organic particles. The majority of the maximum pore diameters were less than 100 nm within all the samples examined. Only the Barnett samples, however, had a majority of their pore areas (or porosity) comprised of pores less than 10,000 nm² (which is the area of an equi-dimensional pore with the maximum pore diameter of 100 nm).