Pore scale analysis of oil shale pyrolysis by X-ray CT and LB simulation

There are important questions concerning the quality and volume of pore space that is created when oil shale is pyrolyzed for the purpose of producing shale oil. In this paper, we pyrolyzed 1.9 cm diameter cores at different temperatures and heating rates. Detailed 3D imaging of the core before and after pyrolysis was done to establish pore structure of the core after reaction using multiscale x-ray CT for imaging. The pore structure of the unreacted material was not clear. Selected images of a core pyrolyzed at 400oC were obtained at a voxel resolution from 39 microns to 60 nm. Some of the pore space created during pyrolysis was clearly visible at this resolution and it was possible to distinguish between the reaction products and the host shale rock. The pore structure deduced from the images was used in Lattice Boltzmann simulations to calculate the permeability in the pore space. The permeabilities of the pyrolyzed samples of the silicate-rich zone were on the order of milli-Darcies, while the permeabilities of the kerogen-rich zone after pyrolysis were very anisotropic and about four orders of magnitude higher.