关键词: 回灌堵塞, 定流量回灌, 非完整井, 井流力学, 半解析解

Abstract:

To investigate the effect of clogging of aquifers around well on the flow dynamics in the well vicinity during the constant-rate recharge using a partially penetrating injection well, an analytical model for well hydraulics was proposed with special consideration of the clogging-related permeability reduction, which was assumed to reduce exponentially with time. By means of the variable substitution and the Laplace and finite Fourier cosine transforms, the solutions for the hydraulic head increment in the Laplace domain were derived and then the solutions in the real-time domain were obtained using the Stehfest numerical inversion method. A parametric study indicates that: a smaller asymptotic hydraulic conductivity K_r,∞ can not only increase the hydraulic head increment and the injection pressure during the recharge process but also accelerate the flow dynamics of the recharged aquifer at the quasi-steady state, whereas a larger permeability reduction exponent λ only result in larger hydraulic head increment and the injection pressure during the recharge process but doesn’t affect the flow dynamics at the quasi-steady state. The hydraulic head difference distribution due to various K_r,∞ and λ values reaches its maximum value in the wellbore and then decreases gradually with the radial distance. The findings of this study can offer theoretical reference for the estimation and prediction of the clogging in the aquifer around well during the constant-rate injection test.

Key words: clogging of aquifers around well, constant-rate injection, partially penetrating well, well hydraulics, semi-analytical solutions