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Toward Reservoir-on-a-Chip: Fabricating Reservoir Micromodels by insitu Growing Calcium Carbonate Nanocrystals in Microfluidic Channels Wei Wang, Sehoon Chang, and Ayrat Gizzatov ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.7b10746 • Publication Date (Web): 09 Aug 2017 Downloaded from http://pubs.acs.org on August 11, 2017
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ACS Applied Materials & Interfaces
Toward Reservoir-on-a-Chip: Fabricating Reservoir Micromodels by in-situ Growing Calcium Carbonate Nanocrystals in Microfluidic Channels Wei Wang*, Sehoon Chang, Ayrat Gizzatov Aramco Research Center–Boston, Aramco Services Company, 400 Technology Square, Cambridge, Massachusetts 02139, USA ABSTRACT: We introduce a novel and simple method to fabricate calcium carbonate (CaCO3) micromodels by in situ growing a thin layer of CaCO3 nanocrystals with thickness of 1-2 µm in microfluidic channels. This approach enables us to fabricate synthetic CaCO3 reservoir micromodels having surfaces fully covered with calcite, while the dimension and geometries of the micromodels are controllable based on the original microfluidic channels. We have tuned the wettability of the CaCO3 coated microchannels at simulated oil reservoir conditions without introducing any chemical additives to the system; and thus the resulting oil-wet surface makes the micromodel more faithfully resemble a natural carbonate reservoir rock. With the advantage of its excellent optical transparency, the microfluidic channels allow us to directly visualize the complex multiphase flows and geochemical fluid-calcite interactions by spectroscopic and microscopic imaging techniques. The CaCO3 coated microfluidic channels provide new capabilities as a micromodel system to mimic real carbonate reservoir properties, which would allow us to perform a water-oil displacement experiment in small volume samples for rapid screening of candidate fluids for enhanced oil recovery (EOR). The immiscible fluid displacement process within carbonate micromodels has been demonstrated showing the wateroil-carbonate interactions at pore-scale in real time by fluorescence microscopic imaging. KEYWORDS: Calcite micromodel, Calcium carbonate nanocrystal, Microfluidic channel, Reservoir-on-a-chip, Optical imaging
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INTRODUCTION In oil reservoirs, when extracting oil by natural pressure differences is no longer possible, waterflooding, i.e. injection of waters without or with surfactants, is usually applied to recover the residual oil phase in the reservoir rock. Traditional lab-scale flooding experiments have used a cylindrical core from a sample reservoir-rock collected during drilling to estimate the oil recovery data, through what is known as a core-flooding experiment. However, the fluid transport processes in a reservoir rock occur at a pore-scale on the order of nano- to millimeters,1-4 and the conventional core flooding tests are not able to provide structural information at such a scale. In order to develop efficient methods for oil recovery, we need to understand the underlying physical processes which occur at pore scale. For example, in the Ghawar Arab-D reservoir in Saudi Arabia, the largest collection of carbonate reservoirs in the world, the microporosity (pore throats and channels
