Estimate of Soil Permeability and Porosity Using An Analytical Solution Considering Gas Compressibility
Xun-Hong Chen
DOI: 10.2190/3NYD-DVGB-FNGH-EWBL
Abstract
An analytical solution considering gas compressibility is developed for radial gas flow in the vadose zone. Simulation results indicate that a solution not considering the gas compressibility provides a close approximation only when the change in pressure is less than 0.2 atmosphere. Error increases with the increase of pressure variation, and the error can reach about 20 percent when the pressure variation is 0.5 atmosphere. This article also presents two methods for the estimate of the soil parameter values from pneumatic test data using the developed analytical solution. the first method is a computer automatic fitting procedure using time-pressure data from a single observation well, and the second method requires gas pressure data from two observation wells and steady-state gas flow. Numerical experimental examples show that the inversely estimated permeability and porosity values considering the gas compressibility are different from these estimated not considering the gas compressibility.
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