Impact of Formation Permeability and Pumping Well Properties on Hydraulic Drawdown in Poroelastic Confined Aquifers

Traditional methods to analyze and interpret pumping induced hydraulic drawdown do not generally account for wellbore storage and skin effects, or the hydromechanical coupling in the porous formations. We present analytical solutions for transient flow to a finite-radius well in a poroelastic confined aquifer that is subjected to a constant-rate pumping. The interactions between effects of wellbore storage, skin zone types/thickness, and formation permeability on the spatiotemporal evolution of the pressure-front is explored. Numerical examples show that traditional methods substantially underestimate the drawdown at pumping wells in low-permeability formations compared to the drawdown predicted using fully coupled poroelastic models. Hydraulic drawdowns in far-field observation wells are also sensitive to poroelastic effects. The differences are more pronounced when a finite-thickness positive skin is present. Further, wellbore storage significantly delays the evolution of drawdown at the pumping well and tends to mask the poroelastic effect in its vicinity. This study provides useful guidance for analysis of pumping test data and design of observation well network, especially for applications in which low permeability aquifers are encountered or is desired - such as enhanced geothermal systems, nuclear waste repositories, and carbon sequestration.