Displacement of a Micellar Slug Foam in Unconsolidated Porous Media

Abstract

This paper was prepared for the 48th Annual Fall Meeting of the Society of Petroleum Engineers of AIME, to be held in Las Vegas, Nev., Sept. 30-Oct. 3, 1973. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal provided agreement to give proper credit is made. Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines. Abstract An experimental study was performed to see if foam will displace micellar slugs that had, in turn, displaced crude oil in sand packs. Experiments simulating both secondary and tertiary recovery processes were conducted. Two micellar solution slug sizes of 0.05 and 0.10 of the pore volume were used in each case. The same experiments were carried out again using thickened water instead of foam to displace the micellar slug. It was found that micellar-solution slugs can be displaced by foam to obtain both secondary and tertiary oil recovery. The experiments indicate that, in the systems described here, secondary recovery of oil by either waterflooding or a micellar slug followed by foam are about the same. Tertiary recovery (after waterflooding) by a micellar slug followed by foam does lead to additional oil recovery. Introduction Micellar solutions may be used to recover either secondary or tertiary oil. These solutions are surfactant-stabilized dispersion of water in hydrocarbon. When a micellar solution slug is injected in the formation, it recovers the oil by miscible-type water-flooding. Some of the newer recovery processes require following a micellar slug by a mobility buffer such as an aqueous polymer solution. The slug and the mobility buffer are driven through the reservoir by water. The micellar solution slug completely removes the oil from the portion of the formation it contacts. It forms an oil-and-water bank in which the oil saturation and the flowing water-oil ratio reach definite, fixed values that depend on the composition of the slug and the oil and water mobilities. The saturations of oil and water in the bank are independent of the original oil and water saturations. Therefore, the displacement mechanism should be the same for secondary and tertiary recovery operations for a particular reservoir type. Oil is produced first in case of secondary recovery, whereas water is produced first in case of tertiary recovery. When the bank reaches the production end the oil cut increases suddenly from zero to the value of the fractional flow of oil. The slug displaces the brine immiscibly. Therefore, part of the brine may become immobile and then will be left behind the slug, resulting in a higher fractional flow of oil than brine ahead of the slug.