Numerical Simulation Study on Wormhole Propagation Morphology in Fractured Carbonate Rocks during Acidizing

State Key Laboratory of Oil & Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu, Sichuan, 610500, China

^* Corresponding author Email address: 2622681634@qq.com (Weiren Mo); swpifrac@163.com (Yongming Li)

Abstract

Carbonate reservoirs are key targets for global oil and gas exploration, accounting for more than 50% of both reserves and production. However, due to the widespread existence of fractures, vugs, and strong heterogeneity in these reservoirs, they are prone to damage during drilling and production operations, which can lead to a decline in well productivity. Matrix acidizing has become a core technique for restoring and enhancing the productivity of carbonate reservoirs. This paper presents a non-isothermal, three-dimensional acidizing model for fractured carbonate rocks. By integrating a three-dimensional embedded discrete fracture model (EDFM) with the two-scale continuum model, the model accurately captures the three-dimensional topological structure of natural fracture networks. A fully coupled thermo-hydro-chemical model is employed to investigate the effects of acid-rock reaction heat, injection temperature, and formation thermal conduction on the reaction rate. The results indicate that injection rate, acid concentration, and temperature have significant impacts on the morphology of wormhole propagation. Furthermore, the study reveals the critical role of fracture architecture in controlling acid fluid diversion and the competitive growth of wormholes.