This research was undertaken by Dr. Xavier Garcia during his PhD studies while at Imperial College under the supervision of Dr. J-P Latham and with the assistance of Dr. Julian Mindel, Dr. Lateef Akanji, and AMCG’s Dr. Gerard Gorman and Mr. Dimitrios Pavlidis
Reservoir engineering, whether for oil, gas, Carbon sequestration or for water resources and filtration, has aimed to model flow through packed beds of grains.
To create a mathematical description of the grain skeleton defining the solid phase, researchers have increasingly turned to micro-CT scanning of real rock specimens, or else they have used process models using numerical simulations such as DEM, that position grains numerically into a grain pack by mimicking the stages in sedimentation, compaction and diagenesis. Computational meshes can be obtained of the surfaces of the solid grains. These provide the boundaries for sophisticated meshing tools that can handle the complex topologies of the interstices of void chambers. Two flow simulation approaches were used, one for low Reynolds number and one for high Reynolds number.
Low Reynolds number flow was directly simulated in the void space of the resulting models using a Finite Element method fluid flow in the limit of negligible Reynolds numbers, to investigate the effect of the particle shape and grain size polydispersity on the hydraulic permeability of the packs. The flow simulations were performed in collaboration with the PERM group in the Earth Science and Engineering Department of Imperial College. The figure below shows the pressure drop from front (red) to back (blue) of a representative elemental volume of porous media created used DEM deposition of realistic sand grain packs. The meshing, flow simulation details and results obtained are reported in Garcia et al. (2009)where results are also compared with experimental permeability-porosity correlations reported previously in the literature including the Kozeny-Carman relation.
To investigate larger and significant Reynolds number flows in the range 1 to 100, Garcia adopted a different flow simulation model, employing ‘Fluidity’ and the two-phase method for coupled flow problems, see Garcia et al. (2010). The meshing is achieved, very simply, by exploiting the adaptive mesh optimisation features of Fluidity’ as described under fluid-solid interaction technology. The type of detail achievable is shown in the figure below.
Garcia, X, Lateef, A, Blunt, M, Matthai, S, Latham J.-P, 2009. Numerical study of the effects of particle shape and polydispersity on permeability, Physics Review E, Vol 80, doi/10.1103/PhysRevE.80.021304
Garcia, X., Pavlidis, D., Gorman, G.J., Gomes, J.L.M.D.A., Piggott, M.D., Mindel, J.E., Aristodemou, E., Pain, C., Latham, J.-P. ApSimon, H.M. 2010. A two-phase adaptive finite element method for solid-fluid coupling in complex geometries, International Journal for Numerical Methods in Fluids. (In Press)