Pulse Decay Properties
Pulse decay experiments are routinely used to measure petrophysical properties of tight cores by flowing helium under pressure gradient. The setup primarily consists of upstream reservoir, core holder and downstream reservoir.
The simulation model is simple, consisting of a line of continuum elements to represent the flow through the sample and specialised boundary condition at each end that represents a gas reservoir. The initial conditions correspond to prescribed initial fluid pressure in the sample and both reservoirs. For this experiment, the constitutive model for flow includes the Klinkenberg effect, in which the slip flow of gas at pore walls enhances gas flow when pore sizes are very small. This causes the measured permeability of gas to be higher than the absolute permeability of the sample.
ParaGeoInv is used to identify the two material parameters: absolute permeability and Klinkenberg B factor.
The objective is to find the permeability and Klinkenberg B factor of the coal sample subject to the pore pressure evolution at both inlet and outlet
The algorithm approaches optimal values of permeability and Klinkenberg B factor
Misfit and solution error. The optimal solution has a misfit value lower than 1% error. The corresponding pore pressure evolution at both inlet and outlet are almost identical, as indicated in the solution error plot.
Misfit and solution error. The optimal solution has a misfit value lower than 1% error. The corresponding pore pressure evolution at both inlet and outlet are almost identical, as indicated in the solution error plot.
Misfit and solution error. The optimal solution has a misfit value lower than 1% error. The corresponding pore pressure evolution at both inlet and outlet are almost identical, as indicated in the solution error plot.