Model for simulating hydromechanical responses in aquifers to induced hydraulic stresses: Laboratory investigation and model validation

• Hydraulic pressure and permeability will change in upper aquifer during flow injection in shale gas production.
• Different induced hydraulic stresses create variable hydraulic pressures and permeabilities, which are quantified.
• An Experimental device is developed to investigate the hydromechanical effect of the induced hydraulic stresses.
• The coupled hydromechanical model produces better numerical results compared to the single hydraulic model.
• A higher injection pressure is found to increase the permeability of the upper layer.

The environmental consequences of the hydraulic fracturing of shale beds have raised widespread concern, especially with regard to groundwater. For example, the hydraulic pressure and permeability in an upper aquifer may be affected by a flow injection process owing to the interaction between the fluids and the deformation of porous media. To experimentally investigate the hydromechanical (HM) effect of the induced hydraulic stresses, a column device was developed. The acquired experimental data was used to develop a coupled HM numerical model, which was used to further investigate the upper aquifer properties. A multiphysics simulator was used to implement the relationship between the permeability and the volumetric strain, and the permeability of the numerical model was calibrated by an error analysis. The results of the HM model were compared with those of a single flow model, and the variations of the hydraulic pressure and permeability with the injection pressure were also analyzed. It was found that the coupled HM model was more sensitive to changes in the permeability compared to the single flow model, and that the former produced better numerical results. The hydraulic pressure in the upper aquifer was determined to decrease with increasing height and the largest change was 1.13 times the initial value. Furthermore, the largest permeability change was observed to correspond to an injection pressure of 40 kPa and was 3.33E-4 times the initial value. This maybe neglected. A higher injection pressure was further found to increase the permeability, which also generally increased with increasing height.