Objective Acid fracturing serves as a core technology for controlling reserves and enhancing production in ultra-deep carbonate reservoirs. The acidizing fluid system functions as "lifeblood" of acid fracturing engineering, which is crucial for the innovation of acid fracturing technology and the improvement of reservoir stimulation effects. Therefore, it is essential to review the current state of acid fracturing technology for ultra-deep carbonate reservoirs and outline potential directions for future research.

Method Based on the literature pertaining and engineering practicing, the performance differences between hydrochloric acid-based and non-hydrochloric acid-based retarded system were comparativly analysed.

Result Hydrochloric acid-based retarded acid systems primarily consist of viscosificatio retarding gelled acid, cross-linked acid, diversion acid, and H⁺-shield adsorption ratarded single acid; the non-hydrochloric retarded acid mainly included the composited organic acid controlling the production rate of H⁺ and self-generating hydrachloric acid, etc. The differences of different acid system grooving and etching mechanism were apparent.

Conclusion The current acidizing fluid systems are capable of meeting the requirements for reservoir stimulation at temperatures below 180 ℃. However, for high-temperature applications exceeding 180℃, further research is required in key areas such as the development of functional additives, formulation of acidizing fluid systems, mechanistic analysis, and integration of application technologies in order to achieve technical breakthroughs.