A new method for gas effective diffusion coefficient measurement in water-saturated porous rocks under high pressures

A new method for determining the gas effective diffusion coefficient in brine-saturated porous rocks was developed on the basis of the radial diffusion model. The experiment was conducted in a high-pressure diffusion cell containing a brine-saturated porous column in the middle and gas in the annulus between the porous column and the cell. The two end faces of the porous column were sealed and the gas diffused into the column only through the radial direction. A small-pressure decay technique was employed to measure the amount of gas diffused into the column as a function of time. A mathematical model was derived to determine the effective diffusion coefficient from the measured pressure decay. To test the presented method, eight measurements were made for CO2 diffusing into brine-saturated Berea and Benthiemer rock plugs at a pressure range of 2.4 to 7.3 MPa. The results are compared with the limited data in the literature.