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Fabrication of a 3-D Mini-Model System With Controllable Micro- and Nano-Scale Porosities for Carbonate Reservoirs


A significant proportion of the world's oil reserves are found in carbonate reservoirs. For example, it is estimated that around 70% of oil and 90% of gas reserves are held in carbonate reservoirs in the Middle East. Reservoir micromodels, such as microfluidic channels, have been widely used to mimic the underground oil-reservoir environment for multi-phase flow studies, enhanced oil recovery, and reservoir network mapping. However, these micromodels only have 2D structures which cannot replicate the 3D morphology of real rocks, and most of the micromodels are built by glass or polymer materials which limits their representative to geochemical surface of the carbonate reservoir rocks.

We have developed a simple method to create 3D calcite (CaCO3) micromodels for carbonate reservoirs. Highly monodispersed silica spheres in controlled sizes both in micron and nanometer ranges are first synthesized via colloidal synthesis method, and then their surfaces are converted to calcite by in situ coating a thin layer of CaCO3 nanocrystals. The CaCO3 coated spheres are packed to form a nearly 3D close-packed structure in mini-columns with desired porosity at micrometer or nanoscale scale. With similar procedure, quartz sand grains can also be coated with a thin layer of CaCO3, and the sand grains with a random-packed structure in a mini-column can create porosity at large micron scale in ~36% pore volume. By filling the voids of CaCO3 coated sand column with the CaCO3 coated silica spheres, a 3D minimodel system with combined porosities in micro- and nano-scale in a controlled manner are fabricated for carbonate reservoirs. We have demonstrated that the new 3D minimodel system can be used as a preliminary method to study oil-water phase behavior by advanced spectroscopic imaging techniques for rapid screening EOR process with small volume of samples at low cost.