Two-scale continuum model for simulation of acid fracturing in carbonate reservoirs with two main mineral components

To investigate the morphological changes of acid-etched fractures during acid fracturing in carbonate reservoirs with different mineral compositions, this article develops acid fracturing mathematical models and numerical simulation methods for pore type carbonate reservoirs based on the classic two-scale continuum model. Practically, these morphological changes of fractures are quantified by characterizing the porosity variation, and different acid-rock reaction models are built for dolomite and calcite. Compared with physical simulation, the models proposed in the study are accurate in simulating the acid-etched fracture morphological evolution during acid fracturing. Moreover, efforts are made to evaluate numerical simulation results of acid fracturing in reservoirs with different mineral contents under conditions of different acid pump rates and concentrations. It is recommended to apply higher pump rates and lower acid-rock reaction rates in reservoirs with higher calcite contents, while lower pump rates and higher acid-rock reaction rates are recommended for reservoirs with higher dolomite contents.