Open AccessModeling Oil Recovery for Mixed Macro- and Micro-Pore Carbonate Grainstones
Author(s) -
Yun Xu,
Qiuzi Li,
H. E. King
Publication year - 2017
Publication title -
scientific reports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.24
H-Index - 213
ISSN - 2045-2322
DOI - 10.1038/s41598-017-09507-4
Subject(s) - porosity , percolation theory , saturation (graph theory) , percolation (cognitive psychology) , porosimetry , percolation threshold , materials science , porous medium , permeability (electromagnetism) , carbonate , chemistry , composite material , mathematics , physics , metallurgy , biochemistry , conductivity , combinatorics , quantum mechanics , neuroscience , membrane , biology , electrical resistivity and conductivity
In general, modeling oil-recovery is a challenging problem involving detailed fluid flow calculations with required structural details that challenge current experimental resolution. Recent laboratory experiments on mixed micro- and macro-pore suggest that there is a systematic relationship between remaining oil saturation (ROS) and the fraction of micro-pores. Working with experimental measurements of the pores obtained from X-ray tomography and mercury intrusion capillary pressure porosimetry, we define a digital rock model exemplifying the key structural elements of these carbonate grainstones. We then test two fluid-flow models: invasion percolation model and effective medium model. Although invasion percolation identifies the important impact of macro-pore percolation on permeability, it does not describe the dependence of ROS on micro-pore percentage. We thus modified the effective medium model by introducing a single-parameter descriptor, r eff . Oil from pores r ≥ r eff is fully removed, while for the remaining pores with r < r eff , their contribution is scaled by (r/r eff ) 2 . Applying this straightforward physics to pore size distributions for the mixed-pore grainstones reproduces the experimental ROS dependence.