Klinkenberg (or slip) effect
The Klinkenberg effect is a gas flow phenomenon and occurs if the mean free path is of the same magnitude as the pore diameter. Gas then no longer “sticks” to the walls of the pore channels but slips along them. The mean free path of Brownian motion depends on pressure, temperature and the type of gas. It decreases with increasing pressure. According to Klinkenberg (1941) the apparent permeability (falsified by the slip effect) ka is a function of the true permeability k0, the mean, absolute gas pressure within the specimen p and a the Klinkenberg factor bk:
ka = k0*(1 + bk/p)
Plotting ka vs. 1/p gives bk as the gradient of the regression line of the individual data points and k0 as the intersection point of this regression line with the ordinate at 1/p = 0 bar-1. The Klinkenberg effect increases with decreasing permeability, decreasing gas pressure and decreasing gas viscosity. For practical considerations it can be assumed that the Klinkenberg effect plays an important role for k < 0.1µm2. In case of sandstone and dolomite the Klinkenberg factor bk can be assumed to follow the empirical relation:
bk = 4.84*10-3ka-0.35 (Häfner et al. 2009).
In September 2019 the Swiss National Cooperative for the Disposal of Radioactive Waste (NAGRA) commisioned Gesteinslabor with UCS, Brazilian and triaxial tests on neighbouring rocks of the Opalinus Clay - the rock which will host Switzerland's future facilities for nuclear waste disposal.
Gesteinslabor receives funding grant for the development of a novel test rig to determine capillary threshold pressure with hydrogen
Gesteinslabor receives funding from BMWi for the development of a new test rig. With this funding, our company will open up a new business field in renewable energies by implementing an innovative technology to determine the capillary threshold pressure with hydrogen on cap rock of underground gas storage facilities.