A review of matrix acidizing for carbonate reservoirs

Carbonate reservoirs are rich in geothermal and petroleum resources, and matrix acidizing is one of the main methods for such reservoir's stimulation. This study systematically reviewed the research progress of matrix acidizing technology for carbonate reservoirs. It introduced the development history of acidizing technology, judgment method of whether to use matrix acidizing, acid-rock reaction mechanism and steps, acid system and its optimization methods, the influencing factors and simulation methods of wormhole, acid distribution processes, optimization methods of construction parameters, real-time diagnosis and effectiveness evaluation methods of acid treatment. Then, the future development trend of matrix acidizing for carbonate reservoirs was prospected. Some interesting insights were as follows. Firstly, due to the influence of factors such as closure stress and rock mechanical properties, there were significant differences in the critical permeability values suitable for matrix acidizing in different reservoirs. Secondly, compared to strong acids, the reaction between weak acids and rocks involved an additional step. Starting from the idea of controlling the steps of acid-rock reaction, a new approach was provided for the development of slow reactive acid fluids for high temperature reservoirs. Thirdly, the dual scale wormhole model had good prospects at the engineering scale, and in the future, it should focus on breaking through the three-dimensional radial flow wormhole extension simulation considering pores, cracks, and caves. Fourthly, uniform acid distribution methods included two categories, i.e., mechanical and chemical methods, with four and six subcategories respectively. Its action areas were in the wellbore and the formation respectively, and the mechanical methods were generally more expensive. Fifthly, the acidizing efficiency was highest when forming the dominant wormhole, and the displacement should be appropriately increased with the increase of injection time during acid treatment. Lastly, it was necessary to focus on establishing evaluation criteria for diversion methods and evaluation method for acidizing effects considering complex reservoir and diversion acidizing.