A carbonate microfluidic model with controllable nanoscale porosity and methods are described. The method for fabricating a carbonate nanofluidic micromodel with controllable nanoscale porosity for studying fluid behaviors in an underground oil-reservoir environment includes: disposing a plurality of polymer spheres into a transparent flow cell; initiating crystallization of the plurality of polymer spheres to form a template with an opal structure; filling the transparent flow cell with a calcium-based solution and a carbonate-based solution to form nanocrystals in voids of the opal structure; and removing the template formed by crystallization of the plurality of polymer spheres from the transparent flow cell leaving an inverse opal structure with a plurality of nanoscale pores and a carbonate surface. The model includes: a transparent flow cell including a first end defining an inlet and a second end defining an outlet; and an inverse opal structure of carbonate inside the transparent flow cell.