Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

Petroleum Geoscience

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Web of Science (3) Citing Articles via Google Scholar Google Scholar Articles by Teige, G. M. G. Articles by Nordgård Bolås, H. M. Search for Related Content GeoRef GeoRef Citation

Capillary resistance and trapping of hydrocarbons: a laboratory experiment

¹ Statoil ASA, Arkitekt Ebbellsvei 10, Rotvoll, N-7005 Trondheim, Norway (e-mail: gmgt@statoil.com)
² Statoil ASA, N-4035 Stavanger, Norway
³ Reslab, N-4033 Forus, Norway

Low permeability cap rocks retain oil by capillary forces when the pore throats of the seals are sufficiently small to prevent a flux of oil into the cap rock. In order to investigate the influence of aquifer overpressures on oil retention, water pressure was applied to a water-wet, highly permeable (1988 mD) core sample, which was oil-saturated to irreducible water saturation S_wi and mounted with a low-permeability and water-wet membrane at the outlet. A water pressure difference of 0.5 MPa was applied across the core. This pressure was high enough to ensure fluid flow through the sample. The experiment was designed to see whether the water pressure would force oil through the membrane or if capillary forces at the sandstone–membrane interface would retain the oil, in which case water flow might take place in the (residual) water in the core and through the membrane.

The experiment showed that oil was kept in place by capillary forces while water flowed through the core and the membrane. Accordingly, residual water can move through sandstones that are saturated to S_wi. The experiments also demonstrated that the permeability associated with this residual water is high enough to prevent overpressures in the aquifer below the oil–water contact from pushing oil through a membrane seal. Thus, even for this highly permeable sandstone, the overpressure in the aquifer will not cause capillary seal failure.

KEYWORDS: membrane sealing, water permeability, ‘irreducible’ water flow, capillary seal failure, overpressure, capillary pressure