Study On Reaction Rule Of Carbonate Rocks In Jinshan Formation In Tazhong Area

Acid fracturing is an important technique of reservoir stimulation in Tazhong area. Gelled acid and temperature controlled acid are commonly used in Tazhong area to improve the etching distance and communicate the storage space. However the research on acid-rock reaction law of gelled acid and temperature controlled acid are relatively shallow. Effective datas can not be offered in acid fracturing design which influences construction effect. So it is necessary to research the acid-rock reaction mechanism and perform simulated experiments.Based on the survey and research of the acid-rock reaction mechanism and experiments, on the condition of mass transfer limited reaction, by introducing the velocity model, mass transport model is developed. The mass transport model includes the influence of non-Newtonian shear thinning. The calculation method of some parameters are obtained, like the shear rate on the reaction surface, effective diffusion coefficient of H+, acid-rock reaction kinetics parameters, reaction activation energy.By rheological properties test, gelled acid and temperature controlled acid both show as non-Newtonian fluid. Temperature and acid concentration have a little effect on the apparent viscosity of gelled acid. As the polymer concentration increased, the apparent viscosity of gelled acid increased. The apparent viscosity of temperature controlled acid is controlled by the degree of crosslinking. The lower the temperatue and the acid concentration, the smaller the degree of crosslinking, and the acid may not crosslinked. The higher the temperature and the acid concentration, the greater the degree of crosslinking and the acid may occur over crosslinking or gelout.Through the rotating disk experiment, it is found that the relationship between acid-rock reaction rate and shear rate can be represented by binomial. The surface reaction rate can be predicted. The main reason that temperature and acid concentration affect the mass transfer rate of temperature controlled acid is that the temperature and the acid concentration affect the apparent viscosity. However the main reason that temperature and acid concentration affect the mass transfer rate of gelled acid is that the temperature and the acid concentration directly affect the activity of H+. Finally the effective diffusion coefficient of H+, the acid-rock reaction kinetics parameters, and the reaction activation energy have been calculated. The reaction activation of gelled acid with limestone is18.0357kJ/mol. The reaction activation of temperature controlled acid with limestone is22.1656kJ/mol.The study shows with taking the change of the viscosity of the acid into consideration, acid-rock reaction law can be obtain in depth. In construction of acid fracturing, acid-rock reaction law should be taken into consideration so that reasonable liquids and pump injection program can be designed. Acid fracturing can be successful.