Quantitative Analysis of the Effects of Inclination and Flow Feature Length Ratio on Wormhole Development and Acidizing Efficiency

Carbonate reservoirs are typically characterized by well-developed natural fractures, and complex fracture-network geometries can significantly affect the effectiveness and efficiency of acidizing. In this study, a numerical simulation program for acidizing reactive transport in fractured carbonate reservoirs was developed based on a dual-continuum theory coupled with an Embedded Discrete Fracture Model. By decoupling complex fracture characteristics, we systematically investigated the controlling mechanisms of fracture dip angle and feature length ratio (FLR) on wormhole evolution and acidizing efficiency. The results show that fractures with small dip angles favor the development of the main wormhole trunk, whereas fractures with large dip angles redirect wormhole growth and promote the formation of complex branches. Under low FLR conditions, wormhole propagation is primarily governed by matrix heterogeneity, while a higher FLR markedly enhances the influence of fracture dip angle on overall wormhole development. The response of acid breakthrough volume (PVBT) to dip angle is strongly regulated by FLR. When FLR < 0.2, PVBT first increases and then decreases with dip angle, reaching a maximum at 45°, whereas for FLR > 0.2, PVBT increases approximately linearly with dip angle, indicating a substantial reduction in breakthrough efficiency. This study provides a theoretical basis for optimizing acidizing treatments in heterogeneous fractured carbonate reservoirs.