Quantitative Analysis of Heterogeneity Effects and Heat Transfer on Self-Diverting Acid Performance in Multi-Layered Carbonate Reservoirs

The severe heterogeneity of carbonate reservoirs poses a significant challenge to matrix acidizing, making the achievement of uniform stimulation across multiple strata a persistent engineering difficulty. To address this, a numerical simulation program for self-diverting acid (SDVA) in multi-layered rocks was developed based on the two-scale continuum model and the open-source framework FMOT. This study primarily investigates the regulatory effects of heterogeneity intensity and initial temperature on uniform acidizing performance. The results indicate that, compared to conventional HCl, SDVA significantly enhances the uniform acidizing efficacy in low-permeability layers. Furthermore, SDVA induces a unique “competitive propagation” pattern among multi-layered rocks, which is fundamentally distinct from the fluid diversion behavior of HCl. As the formation heterogeneity intensity increases, the resulting wormhole morphology becomes increasingly complex, accompanied by more pronounced inter-layer flow competition. Moreover, unlike HCl, whose flow distribution pattern and wormhole morphology are insensitive to thermal changes, the acidizing performance of SDVA exhibits marked temperature dependence. At lower temperatures, the competitive propagation pattern diminishes significantly; however, as the temperature rises, the inter-layer fluid competition becomes progressively intensified, and this competitive state persists until the ultimate breakthrough of the rock matrix.