A mathematical model for seepage of deeply buried groundwater under higher pressure and temperature

Deeply buried groundwater, such as brine, is an important industrial raw material with high economic value. Because brine frequently exists under higher temperature and pressure, the quantitative prediction of its seepage field is very difficult. Here we study the migration of deeply buried groundwater by using a numerical simulation based on laboratory test results. In particular, we express the pressure and temperature variation of seepage parameters such as hydraulic conductivity K and specific storage coefficient S in terms of the corresponding variation of the solid skeleton's permeability k, porosity n, compressibility coefficient β_s, and seepage fluid's viscosity μ and compressibility coefficient β_w. Then through mathematical transformation and linearization methods, the mathematical model with pressure and temperature dependent coefficients is reduced to the same form as the standard one for seepage flow. The results are successfully applied to the Moxi structure in Sichuan basin. The results show that the effect of higher pressure and temperature should be taken into account for quantitative study of deeply buried groundwater, and that the effects are easily included by the transformation of the mathematical model to standard form.