Abstracts - KTH Mechanics

Mechanisms of gas migration through porous media
Michael Stöhr ∗ and Arzhang Khalili ∗
The mechanism of buoyancy-driven gas flow in a porous medium has important
implications such as gas scape from a seabed. The aim of this study is to characterize
experimentally gas escape mechanism through a porous medium using the light
transmission technique. The experimental setup is composed of a rectangular standing
box filled with a saturted porous medium (natural sand or broken glasses) and an
air flow through a nozzle placed at the container bottom. A series of experiments for
different combinations of natural and artificial sediments were performed. Figure 1
shows the results for a combined study of gas injection into natural sand and granular
broken glass with a gas flow rate of 2.5 ml/min. The temporal evolutions of pressure
at the inlet show a number of similarities. The connection between the behavior of
the gas in the sediment and the corresponding features of the pressure curve is then
established by the analysis of the respective images of the transparent sediment.
Corresponding studies of gas injection into sediments with other mechanical properties
reveal fundamentally different mechanisms. The results show that the amount
of gas which has to build until it penetrates into the water column, i.e. the capacity
of the sediment to retain the gas, varies strongly with the sediment type.
The detailed phenomenon is explained in a manuscript sbmitted 1 .
∗ Max Planck Institute for marine microbiology, Celsiusstr. 1, 28359 Bremen, Germany.
1 Stöhr and Khalili, Submitted to Phys. Rev. Lett. (2005).
Figure 1: Comparison of gas migration in a natural and a transparent, artificialsediment.
Left images: temporal evolution of inlet pressure. Right image: features of gas
migration at the surface and inside the sediment, repectively.
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