Effect of Fracture and Vug Network on the Dolomite Carbonate Acid Stimulation Process

Summary Acid stimulation in carbonate rocks represents a classic example of reactive flow in subsurface porous media and is also an extremely effective improved oil recovery technique with broad applications. The acid solution is injected into the formation under the formation fracture pressure to increase formation permeability while bypassing damaged domains around the wellbore. This work extends an integrated two-scale continuum model that contemplates mass, momentum, and energy changes to study the acid stimulation process in complex carbonate acid stimulation systems with the development of fracture and vug networks. Numerical examples are designed to examine the impact of isolated fracture and vug parameters on the results of acid stimulation. Results show that the improved two-scale continuum model offers a novel method for describing the momentum transport of fluids within complex media. It eliminates the necessity of introducing and determining additional physical parameters through numerical simulations and experimental research. The presence of isolated fractures and vugs has a limited contribution to the hydraulic parameters of permeability. Isolated fractures and vugs reduce the consumption of acid fluid required to break through the target core sample but do not change the optimum injection rate for wormhole formation. The development of fractures and vugs can guide the development pathways of wormholes within the matrix core but does not alter the dissolution patterns corresponding to the specific acid injection rate.