The paper presents results of comprehensive studies aimed at development of a unified approach to engineering of acidizing designs. The studies involved laboratory analysis of acid compositions and synthetic formation water, physical modeling of bottomhole treatment process, generalization of dependencies. Series of core flooding experiments included flushing of core samples with different acid compositions at different velocities, and made it possible to determine parameters of carbonate dissolution kinetics and formation of wormholes. These parameters were further used to populate acidizing simulator with data. To get better insight into the process of wormhole formation, seventy-two core flooding tests using carbonate samples from five development targets of the Volga-Ural petroleum play were used. Three acid systems used for flooding of core samples differed in concentration and reaction velocity control agents. In the process of interpretation of experiments results, necessary data for matching of mathematic models were obtained including initial data on acid injection rate and characteristics of wormholes formation, i.e., amount of injected acid pore volumes vs. onset of wormhole. For each development target, minimum values of acid pore volumes were obtained, which characterize the rate of wormhole formation. Laboratory analysis of physicochemical properties allowed to prioritize acid compositions considering specific reservoir conditions. The obtained quantitative and qualitative data will be interpreted for further use in physical and mathematical models of the processes of bottomhole treatments and acid fracturing of carbonate reservoirs.
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