Acid fracturing is a critical stimulation technology for enhancing production in ultra-deep marine carbonate reservoirs. A significant challenge in this process is maintaining the conductivity of acid-etched fractures under ultra-high temperature and high closure stress conditions. To address this

conductivity experiments were conducted using various acid solutions and their combinations. The morphology of the acid-etched fractures was captured using a three-dimensional laser scanner. The degree of fracture closure was analyzed using the Airy stress function and the complex variable method

integrated with the local cubic law and an acid fracturing model to create a numerical calculation method for evaluating the conductivity of acid-etched fractures. The results show that under high closure stress（90 MPa）

the conductivity of acids and their combinations decreases by an order of magnitude compared to low closure stress（5 MPa）. As closure stress increases

different acids and combinations exhibit distinct patterns of conductivity reduction

with potential for two rapid decline phases. Furthermore

specific acid combinations have been identified that enhance the conductivity of fractures under extreme conditions of temperature and pressure. The average error between the conductivity values calculated by the model and those obtained from experimental results is relatively low

about 10.6%

indicating that the model can effectively characterize the distribution and magnitude of conductivity across different points within the fracture. In Sichuan Basin

under identical engineering parameters

the conductivity of acid-etched fractures in the 4th member of Dengying Formation is higher than that in the 2nd member. This research provides valuable theoretical guidance for optimizing the design of acid fracturing stimulation schemes in ultra-deep marine carbonate rocks in Sichuan Basin.