Site-Selective In Situ Grown Calcium Carbonate Micromodels with Tunable Geometry, Porosity, and Wettability

© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 1 wileyonlinelibrary.com to modify wettability within micromodels to mimic the reservoir’s wettability.[16–19] Previous micromodels have mostly been made of glass,[7,8] silicon,[9,19] and polymeric materials[10–18] instead of real rock.[20,21] As a result, they have limitations in studying geochemical fluid–rock interactions, such as acid fracturing to increase the oil production from carbonate reservoirs[22,23] or changes in wettability due to aging or adsorption of molecules added during simulated enhanced oil recovery (EOR). Features have been wet etched[20] and laser machined[21] directly into rock samples and then sealed to make micromodels. These top-down approaches result in large (≈ μ 100 m ) and relatively simple features. By comparison, microporosity (pore throats and channels < μ 10 m ) comprises up to 50% of the total porosity in the Ghawar Arab-D carbonate reservoir (the largest collection of carbonate reservoirs in the world) and critically affects the oil recovery.[24,25] A simple and controllable method that enables creation of patterned, large-area real rocks with smaller pore-length scales in the microfluidic channels is thus a desirable goal. Bottom-up strategies inspired by biomineralization have received special attention as a key technology to understand formation mechanism of inorganic materials in nature and to prepare precipitations in synthetic systems.[26–29] There have been reports on the fabrication of complex carbonate structures via organic templates and a wide range of synthetic methods such as vapor[30–38] or double diffusions,[39] and Kitano methods.[40] Simple reaction-diffusion processes can also generate hierarchical nanoand microstructures.[41,42] These studies indicate that control over the microenvironments, epitaxy, and inorganic or organic precursors plays an important role in the formation of minerals.[30–44] Most bottom-up fabrication methods involve both homogeneous and heterogeneous nucleation, and growth processes in solutions and on templates, which result in inevitable problems of undesirable mineralization on channel walls and blocking of the channel.[45–47] For these reasons, the previous methods cannot be applied to fabricate carbonate micromodels with complex features. In addition, preparing the template fully covered with carbonate requires an additional nucleation process and long process time because negatively charged organic molecules (e.g., acidic polymers) of the template can act as inhibitors of mineral deposition.[48–50] Therefore, Site-Selective In Situ Grown Calcium Carbonate Micromodels with Tunable Geometry, Porosity, and Wettability