Streaming potential of a sand column in partial saturations conditions

The understanding of the streaming potential in partial water saturation conditions in porous media is of great interest for the interpretation of spontaneous polarization observations. We built a device which allows us to quantify the streaming potential at various saturation conditions using a sand column of 1-m height and 8-cm diameter. This is the first time that such a quantification has been performed. Different gases such as argon, nitrogen, and carbon dioxide are injected into the sand to decrease its water saturation, and to make the fluid flow within the sand. The measured electrokinetic coupling coefficient in partial saturation is either constant or decreases by a factor 3 with decreasing water saturation from 100 to 40%, whereas the sand electrical resistivity is enhanced by a factor of 5.