SOCIETY OF PETROLEUM ENGINEERS OF AIME 6200North Central Expressway =~~ SPE 2481 Dallas, Texas i’5206 THIS IS A PREPRINT --- SUBJECT TO CORRECTION Flow of a Disperse Emulsion of Crude Oil in Water in Porous Media By Downloaded from http://onepetro.org/speatce/proceedings-pdf/69fm/all-69fm/spe-2481-ms/2069416/spe-2481-ms.pdf by guest on 25 September 2021 John c. (!artmill,U.S. Geological Survey, and Parke A. Dickeyj u. of ~lsa~ Members Am @ Copyright 1969 . m ... IM?-!-- M..a-ll.. -Anm American msmute of Iumwg, 1.1CLC9.SUX~lua.,I -w.“A .P&A.~m.. .. .. l@@?ers9 h!. This paper was prepared for the khth Annual Fall Meeting of the Society of Petroleum Engineers of AIME, to be held in Denver, Colo., Sept. 28-Ott. 1, 1969. Permission to copy is restrictedto an abstract of not more than 300 words. Illustrationsmay not be copied. The abstract should contain conspicuousacknowledgmentof where and by whom the paper is presented. Publicationelsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JCXJRNALis usually granted upon request to the Editor of the appropriate journalprovided 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 discussionmay be presented at the above meeting and, with the paper, may be consideredfor publication in one of the two S?E magazines. ABSTRACT disperse, oil-in-wateremulsions. Our current ideas on multiphase flow in porous media may It has been suggested that oil migrates not apply to disperse emulsions. through reservoir sands in the form of a fine, disperse emulsion of oil in water, and that oil INTRODUCTION accumulationsoccur where the stream enters finer-grainedrock such as silt or shale. In The physical mechanisms of the migration order to investigatethe possible mechanisms, of oil, including the expulsion of oil from the stable emulsions of oil in water were prepared source rock, its migration, and its accumula- without the use of wetting agents. They con- tion in the reservoir rock, are very poorlY sisted of droplets 1/2 to 1-1/2 microns in understood. Most authoritiesbelieve that the diameter, in a concentrationof 20 to 40 Parts expulsion of water from compacting shale causes of oil per million of water. These emulsions regional flows of water within the pores of the passed freely through filter paper and ordinary enclosing sediments, and the water somehow sand. A plastic tube containingglass beads carries the oil with it. Hydrocarbonsheavier of 200-microns diameter included a bed l/?-cm than decane have such a low volubility in water thick of crushed beads 37 to 88 microns in that it is inconceivablethat large quantities diameter. When the emulsion was passed through could have migrated as true solutions. Most this tube, up to 80 percent of the oil was subsurfacewaters have near normal oil-water screened out at the coarse-fine interface. The interracialtension, so that migration in amount removed depended on the contrast in “solubilized”form as suggestedby Bakerl is grain size, the nature and the preferential improbable. Conventionalreservoir mechanics nettability of the media. Similar results require that oil occupy more than 15 percent of occurred when quartz sand was used as the the pore volume in order to exist as a continu- coarse, and crushed sand as the fine medi~. OUS, mobile component.2 NO doubt migration in ‘I!hisscreening did not occur as a result of the continuousphase has occurred frequently, capillary effects, because the pores were manY especially secondarilywhen previously formed times the diameter of the droplets. The oil oil accumulationshave been shifted by tilting collected as a result of flocculationof the of the reservoir rocks. However, such move- droplets into strings and clusters, and the oil ments should leave residual oil saturationsand saturation in the pores consisted of masses of staining in the flow paths. Isolated globules droplets with very little coalescence. Possi- of oil larger than the pore openings will not bly electrostaticforces are more important move, because of a lack of unbalanced forces than capillary in the behavior of fine, which would be required to distort the globules References and illustrationsat end of paper. P -—FT,(7J-----OF —-A I)——..——.ISPE?,SE.-— _EMKLSIONOF CRUDE CIL IN WATER IN POROUS MEDIA SFE 248~ ‘“ in opposition to the interracialtension which the underlying emulsion was quite stable. tries to maintain their sphericity. The stable emulsion was almost clear, but Oil is often fountisaturating lenses of exhibited a strong ‘lyndalleffect, showing the coarse sand, while adjacent beds of finer .%md path of a beam of light. It was examined under have no detectable oil content. This situation the microscope on a glass hemacfiometer slide ~QQfo~~ with the capillary behavi~rcof used to count blood-corpuscles. This slide is -...1-,4 immiscible fluids in porous media.~)” Oil will L-UJ.GU into ~quares 200 microns [0.20 mm] on a enter only the larger pores, and then only when side, and the cover glass is 100 microns [0.10 t~.e~AW~~l&Tein the oil phase is higher th~ mm] above the slide [Fig. 11. Each square thus that in the water phase.- However, it is hard has a v~lum of 4,QQQJO00 cu microns [.004 cu to imagine how the oil got into the lenses of mm] . The size of the droplets ranged from 0.5 coarser sand if they are completely surrounded to 1.5 microns, and their average abundance was by fine sand containingno oil. Oil pools about 100 per square. Assigning the maximum often appear to be surroundedby clean saad dimension of 1.5 microns to all the oil drop- Downloaded from http://onepetro.org/speatce/proceedings-pdf/69fm/all-69fm/spe-2481-ms/2069416/spe-2481-ms.pdf by guest on 25 September 2021 with no oil staining. lets, an oil concentrationof 44 ppm was computed volumetrically. This approximate con- It has been suggestedby everal authors, centrationwas too high since the average oil especially Hobson5 md Dickey,t that the oil droplet size was less than 1.5 microns. When might move in the form of extremely small the concentrationsof the several emulsions was dispersed droplets, fine enough to pass freely determinedby solvent extraction and weighing through the pores of sands. When the migrating of the recovered oil, they fell between 23 and water re-enters a finer medium, such as a silt 35 PPIIIby volume. Emulsions of known concen- or shale, the oil would be screened out of the tration were diluted by known amounts of water flowing stream by a capillary filtering and the light transmittedwas measured with a mechanism. The oil droplets can not re-enter photometer. The concentrationsof the the fine pores without distortion, so they tend effluents from the several systems was deter- to pile up against the interface and coalesce mined by measuring their light transmission. to form an accumulation. Oil accumulations ~hz~~fit+.lJsbe faud at capillary barriers When observed under the microscope, the formed by updip pinchouts, and in the crests fine oil dzmplets s..uh.wh..,-d RrO~iEUI-- movement, but of anticline through which large amounts of no tendency to coalesce, and very little ten- water had to pass shortly after the deposition dency to attach themselves to the glass. When of the sediments. a water current carried a free droplet towards a fixed droplet on a collision course, the free This mechanism is logical and seems to fit droplet made a last-minute detour to avoid the observed facts of both geologic structure hitting the fixed one. Clearly the droplets and what is known about the flow of mixed were fine enough that electrostaticforces fluids through porous media. However, no caused them to be repelled by each other and by experiments had been performed to show that most solid surfaces. very fine droplets of oil are free to travel indefinitelythrough porous media, and that The droplets passed easily through filter they are screened out at capillary interfaces. paper with no retention of oil. They also The experiments to be described suggest that passed through “nuclepore”filters with holes this concept may have limited application. less than l-micron diameter when suction was Droplets much smaller than the pore diameters was applied. The emulsions passed through do appear to be able to flow freely through funnels filled with sand. When mud was mixed sand, but they are affected by electrostatic with the sand, water went through but most of rather than capillary forces. the oil was screened out. The Emulsion The Apparatus The crude oil used in the experimentswas In order to observe the behavior of the from the PennsylvanianBurgess sand in the emulsion in porous media, a tube of transparent Bird Creek field, Tulsa County, Okla., and had plastic was constructedas shown in Fig. 2. It an API gravity of 35°. It was emulsifiedwith was 2.48 cm in diameter and 41 cm long, with an tap water by heating the water to 200F and effective volume of 185 cc. The emulsion was mixing with a vibrating perforated disc. No brought in at the top and moved downward by emulsifying agent was added, and the emulsion gravity. Four holes were bored through the had a surface tension of about 60 dynes. Sea tube at various elevations near the bottom, aad water and connate water would not suspend as to these manometer tubes were attached. By much oil as fresh water. Tknelarger ~r~plets this means the pressure drops along the tube rose to the surface, but after several days could be determined.