This presentation includes quantitative discussions on the extent the surface heterogeneities influence the storage of supercritical methane in model kerogen pores.  Various investigations have previously been done to understand physical and chemical properties of the organic matter associated with source rocks. Kerogen is an amorphous organic material, which has a variable chemical composition and a complex pore network that is dependent on the catagenesis. Physical analysis based on electron diffraction suggests that kerogen is composed of stack of aromatic sheets, similar to a stack of graphene making up graphite. Consequently, investigators analyzing kerogen-hydrocarbon interactions have often developed slit-shape model pores consisting of parallel sheets of graphite. However, so far, no one has investigated how inner most surface heterogeneities of the pore walls, such as defects, vacancies, and nitrogen doping,  could affect the storage of hydrocarbons in kerogen. In addition, although the pore size distribution of kerogen could vary significantly, the average size is typically less than 10 nm. It is also unclear how the nano-scale confinement of the small organic pores affects the storage. The presentation is based on quantum mechanics calculations using MP2/6-311g, and Grand Canonical Monte Carlo simulations of fluid-solid interactions in model organic pores. Results show that there is no variation in the adsorbed amount as the size of the pore is reduced from 5 to 2nm; hence, the nanopore confinement influences mainly the free gas storage. Excess amount stored due to confinement effect on free gas is most pronounced at pore pressure in the range of 1,000-5,000 psi. In addition, among the investigated heterogeneities, it is found that nitrogen-doping influences both the adsorbed and the excess amount 63% and 37%, respectively, depending on the nitrogen concentration on the surface. Our research conclusively shows that the surface heterogeneities and nanopore confinement have potential impact on fluid storage in kerogen.

Gas storage in model kerogen pores with surface heterogeneities

251st National Meeting (2016)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.