Research on the Acid Rock Reaction Law and Technology for Stimulation of Strongly Heterogeneous Reservoir

Carbonate reservoirs are characterized by heterogeneous natural fractures and complex lithology, Acid rock reaction kinetics parameters are key parameters in the analysis of reaction characteristics, evaluation of acid fluid system effect and reservoir reconstruction design. This article conducted acid rock reaction kinetics experiments on the cores of dolomite and limestone reservoirs at 140 ℃ through indoor experiments. The acid rock reaction kinetics equations for two common carbonate rocks, dolomite and limestone, were established under the same experimental conditions. The experimental results showed that the reaction rate, reaction rate constant K, reaction order m, and mass transfer coefficient De of both increased with the increase of acid concentration and rotational speed, The reaction rate constant of limestone is 1.2 times faster than that of dolomite, but the reaction order is 0.77 times slower, indicating that the reaction rate of limestone is less affected by acid concentration than that of dolomite. At the same time, with the increase of limestone composition, the reaction rate of acid rock increases significantly, the activation energy is 1.2 times lower than that of dolomite, and the H+ transfer coefficient is twice as high as that of dolomite. In summary, for the high temperature reservoir with both dolomite and limestone, the pre-treatment of cooling and filtration should be given priority in reservoir reconstruction process, and then acid fracturing construction should be carried out according to different engineering objectives. If the engineering goal is to dredge the near wellbore fractures and cavities, measures can be taken to increase the acid strength of the main acid solution after cooling and filtering pretreatment, fully communicating with the reservoir fractures and cavities; If the engineering goal is to communicate with the distant well fracture cavity, the acid fracturing process of alternating injection of cooling and filtering pre fluid and main acid fluid can be adopted. At the same time, the targeted use of temporary plugging technology in the fracture can increase the drainage area by creating long fractures, attempting to communicate with the distant well fracture cavity, and fully improving the efficiency of communication with the fracture cavity body.