Abstract: When injected water is mixed with formation water, the chemical incompatibility between SO₄^2- in the injected water and Ba²⁺ in the formation water produces BaSO₄ scale, which clogs the pores and throat of the reservoir to cause serious damage to the reservoir. To quantitatively predict the amount of barium sulfate scale, we first used Bedrikovetsky classical dynamics model to deduce a detailed transient kinetic model of barium sulfate scale formation with diffusion term. Finite difference analysis was performed on the model, and the fourth and fifth order Runge-Kutta equations were used to obtain the numerical solution. This approach improves the applicability of the model by avoiding the assumption that the concentration ratio between Ba²⁺ and SO₄^2- at the core entrance is much less than 1 in solving the model, which has been used in models reported by domestic and international researchers. Then, the concentration of Ba²⁺ at the outlet end of the core was determined by the transient displacement experiment with the core, and two important coefficients in the model-diffusion coefficient and reaction rate constant-were deduced by inversion of the concentration data. Finally, the distribution of barium sulfate scale in the core with different PVs and injection water with low SO₄^2- concentration was studied. The results show that with increasing displacement volume, the amount of barium sulfate scale in the core increases, and the amount of scaling along the direction of the core length first increases and then decreases. The location with the maximum amount of scaling in the core moves towards the center of the core.

Key words: barium sulfate scaling, formation damage, kinetic model, finite difference