Study on the uniform acidification mechanism of the self-diverting acid in the rock with multi-flow units based on the correct-hydro-temperature-chemical multiphysics coupling model

The strong heterogeneity of carbonate reservoirs gives rise to multi-flow units with significant permeability contrast, substantially impacting the effectiveness of uniform acidization. In this study, we developed a mathematical formula for the oil–water acidizing process of the self-diverting acid (SDVA) combined with correct-hydrologic–thermal–chemical (CHTC-SDVA). Additionally, a new semi-implicit weakly coupled solution strategy (SIWC) and a dynamic pressure boundary control method [proportional–integral–derivative (PID)] were proposed to solve the CHTC model. Results indicate that under individual flow unit conditions, the SDVA exhibits diversion development during single-phase acidizing and competitive development during two-phase acidizing. In the case of multi-flow units, the SDVA can still effectively acidize low-permeability regions, with an overall uniform acidization effect significantly superior to that of HCl. Moreover, the larger the interlayer permeability contrast, the more prominent the advantage of the over HCl. The model and calculation strategy established in this work can accurately reflect the automatic flow rate distribution process of multiple flow units in real physical problems, providing theoretical and simulation support for optimizing matrix acidization technology in heterogeneous carbonate reservoirs.