Nanofluidic chips as micromodels for carbonate reservoirs
Methods and systems for generating a nanofluidic chip as a reservoir model are provided. In an example described herein, a nanofluidic chip for reservoir modeling includes a microfluidic chip that includes microchannels etched in a substrate. Silica spheres are assembled in the microchannels to form nanochannels. A carbonate coating is disposed over the surfaces of the nano channels and the silica spheres.
1. A method for modeling a reservoir with a nanofluidic chip, comprising fabricating the nanofluidic chip by:
synthesizing silicon dioxide spheres;
functionalizing a surface of the silicon dioxide spheres to form functionalized spheres;
functionalizing a surface of microchannels in a microfluidic chip to form a functionalized microfluidic chip;
assembling the functionalized spheres in microchannels of the functionalized microfluidic chip to form a precursor nanofluidic chip; and
forming calcium carbonate nanocrystals on functionalized surfaces of the precursor nanofluidic chip to form the nanofluidic chip.
2. The method of claim 1 , further comprising synthesizing silicon dioxide spheres of about 50 to about 2500 nm in diameter.
3. The method of claim 1 , further comprising synthesizing substantially monodisperse silicon dioxide spheres.
4. The method of claim 3 , further comprising synthesizing the silicon dioxide spheres by hydrolyzing a tetraalkylorthosilicate compound in a water-alcohol mixture with ammonia as a catalyst.
5. The method of claim 1 , further comprising functionalizing the surface of the silicon dioxide spheres by:
hydrolyzing the surface of the silicon dioxide spheres to form hydroxyl groups; and
injecting a silane coupling agent comprising carboxylate groups, wherein the silane reacts with the hydrolyzed surface and the carboxylate groups are exposed.
6. The method of claim 1 , further comprising functionalizing the surface of the microchannels in the microfluidic chip by:
injecting a reagent to hydrolyze the surface of the microchannels to form hydroxyl groups; and
injecting a silane coupling agent comprising carboxylate groups, wherein the silane reacts with the hydrolyzed surface and the carboxylate groups are exposed.
7. The method of claim 1 , further comprising assembling the functionalized spheres in the microchannels of the functionalized microfluidic chip by:
suspending the functionalized spheres in ethanol to form a colloidal suspension; and
injecting the colloidal suspension into the microfluidic chip, wherein the functionalized spheres are trapped in the microchannels of the microfluidic chip to assemble into random close-packed structures.
8. The method of claim 1 , further comprising forming the calcium carbonate nanocrystals by:
flowing a calcium chloride solution through the precursor nanofluidic chip; and
iterating between:
flowing a sodium carbonate solution through the precursor nanofluidic chip; and
flowing the calcium chloride solution through the precursor nanofluidic chip.
9. The method of claim 8 , comprising:
iterating for between five and 20 cycles; and
forming a layer of calcium carbonate nanocrystals having a thickness of about 5 nm to about 100 nm.
10. The method of claim 8 , further comprising flowing a magnesium chloride solution, or a mixed calcium chloride and magnesium chloride solution, through the precursor nanofluidic chip during an iteration.
11. The method of claim 1 , further comprising controlling a size of channels in the nanofluidic chip by selecting a size of the silicon dioxide spheres, wherein the size of channels in a network of voids is between about 10 nm to about 1000 nm.
12. The method of claim 1 , further comprising:
assembling the precursor nanofluidic chip from functionalized spheres of two different sizes; and
generating mixed nanoscale porosity.
13. The method of claim 1 , further comprising using the nanofluidic chip to study oil-water phase behavior in nanoscale pores of the reservoir.
14. The method of claim 1 , further comprising using the nanofluidic chip to study rock-fluid interactions in nanoscale pores of the reservoir.
15. The method of claim 1 , further comprising using an optically transparent nanofluidic chip in microscopic studies of interactions between fluids and surfaces.
16. The method of claim 1 , further comprising using the nanofluidic chip in spectroscopic studies of interactions between fluids and surfaces.