硫酸钡结垢动力学瞬态模型研究

Study on Transient Dynamic Model of Barium Sulfate Scale Formation

注水是维持地层压力及提高原油采收率的最主要开发方式。当注入水与地层水混合后,由于注入水中的SO_4^(2-)与地层水中的Ba^(2+)的化学不相容性,将产生BaSO_4垢,堵塞储层的孔隙与喉道,造成严重的储层损害。为了定量预测硫酸钡结垢量,首先,在Bedrikovetsky经典动力学模型的基础上,详细推导了含扩散项的硫酸钡结垢动力学瞬态模型,对模型有限差分并利用第四和第五阶Runge-Kutta方程求出数值解,避免了国内外已有的模求解过程中做出岩芯入口端Ba^(2+)浓度与SO_4^(2-)浓度比远小于1的假设,提高了模型的适用性。然后,通过岩芯瞬态驱替实验测定岩芯出口端Ba^(2+)的浓度,利用浓度数据反演出模型中的两个重要系数——扩散系数和反应速率常数。最后,研究了低SO_4^(2-)浓度的注入水驱替不同PV时岩芯中硫酸钡结垢量的分布。结果表明:随着驱替体积增加,岩芯内的硫酸钡结垢量增大;沿岩芯长度方向上的结垢量呈先增大后减小趋势;岩芯内最大结垢量的位置向岩芯中部偏移。

When injected water is mixed with formation water,the chemical incompatibility between SO2?4in the injected water and Ba2+in the formation water produces BaSO4scale,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 SO24at the core entrance is much less than1in 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 SO2?4concentration 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.