The up-to-date requirements suggests that the design of a carbonate rock matrix treatment should be calculated based on the models of key physical and chemical processes by means of a specialized software. In wells with a heterogeneous vertical permeability, the problem of acid distribution across the reservoir zone cannot be addressed correctly without using a numerical simulation. Moreover, numerical simulators help find solutions for the feasibility assessment of acidizing operations by simulating scenarios with different injection volumes and rates, agent staging, and initial economic conditions.
The paper describes the design optimization problem in carbonate reservoir acidizing using viscous diverter fluids. The mathematical model of acidizing process was created in the well scale. This model accounts for the flow of insoluble clay and silica particles in a porous medium and their deposition at the pore throats. Core laboratory tests showed that the treatment pressure is affected by a suffosion process. Numerical simulation allowed calculating acid concentration in the reservoir at different injection stages, as well as pressure; porosity and permeability dynamics; the treating agent distribution and flow in the layered heterogeneous reservoir; the skin factors in target zones; and the effect of the diverter fluids. These calculations help to determine the optimal parameters, which drive the acidizing efficiency. The incremental oil production rate and variance of post-treatment productivity for the heterogeneous reservoir are used as the target parameters for treatment optimization. The developed simulator of the heterogeneous laminated reservoir acidizing was applied for evaluating the real field operations, and the results were found consistent with actual historical data.