SOCIETY OF PETROLEUM ENGINEERS OF AIME 6200North Central Expressway =~~ SPE 2481 Dallas, Texas i’5206

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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. The tube was packed witln very little additional “creaming”occurred ad coarse-grainedmaterial, except that a layer about 1/2 cm thick of fine-grainedmaterial was WE2481 JOHN C. CARTMILL i d PARKE A. DICKEY

placed between manometer holes B and C. Plugs that of the continuous component. In many of glass wool were placed inside the stoppers respects it behaves like a solid, and this at either end to hold the porous media in material plugging the pores caused the great place. loss in permeability.

Various porous media were used to pack the Run 2: Quartz Sand tube, including fine-grainedparticles of quartz, glass, chert [novaculite],and styro- The tube was filled with quartz sand foam. ranging between 250 and 350 microns in diameter, A layer 0.5-cm thick of the same sand, crushed Experiments and screened to between 37 and 8$ microns, was included between the B and C manometers. About Run 1: Glass Beads 5,000 cc of emulsion were passed through the system, and results were the same as with the The cylinder was packed mainly with glass glass beads. Mediately after the flow was 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 beads having a diameter of 200 microns. Be- started, a collectionof oil appeared at the tween nanometer holes B and C a layer 1/2 cm interfacebetween the coarse and the fine media thick of crushed glass beads screened to 37 to [Fig. ~]. There was also a slight collection 8$ microns were placed over a 1.5-cm layer of of oil at the top of the sand where the emul- crushed beads sized 88 to 200 microns [Fig. 3]. sion first entered it. The width of the oil- Distilled water was passed through for several saturatedband increased as the flow continued. hours, and the average permeability of the Growth occurred in both directions from the coarse layer was determinedto be 53 darcys, interface,but mostly into the fine medium. while the interval between B and C containing The permeability decreased steadily. The A to the crushed beads was 9.5 darcys. After XO B section retained 90 percent of its original . . mmutes the emu~slon ‘wasturned m. ~.~ flow permeability,and the C to D section retained rate began to decrease steadily [Fig. 4]. Oil 93 percent. The B to C interface, containing began to collect in the pores of the coarse the oil collection,retained onlY 44 Percent of material at the top of the pack and in the fine its original permeability. The effluent con- layer. Obviously, the oil was not being tained 8 ppm oil, so 75 percent was retained in screened out by capillary forces, for the oil the tube. droplets were less than 2 microns in diameter while the grains in the pack were 200 microns Run 3: Emulsion with Surfactant iQ the coarse and 37 to 88 microns in the fine. Presumably the pore openings were of the same ~@her Tlm was made using glass beads as order of magnitude. The oil collected at the in Run 1. An emulsion was prepared using interfacesbetween the glass wool and the surfactant. Its concentrationwas not measured coarse beads, and between the coarse beads and but it contained several times as much oil as the fine beads. The maximum oil saturationwas the regularly used emulsion. Its surface ten- just below the interface in the fine medium. sion was 34 dynes per cm. After passing 1,750 cc, the fine layer showed no oil collection and The collection of oil caused a marked lost only .50percent of its permeability, decrease in permeability,as shown by the although much more oil passed through it than increasingpressure drop between the top and in the case of Run 1. The photometer showed no Manometer A and between Manometers B and.C. rer,ovalof oil by the porous media. After 4,6oo cc of emulsion had passed through, the interval between manometer holes A md B Run 4: Oil-Wet Glass Beads had retained 74 percent of the original permea- bility, while the interval between B and C had The plastic cylinder was charged with retained only 20 percent of its original glass beads as in Run 1. The tube was filled permeability. with petroleum ether containing Arquad, a wet- ting agent. The system was then evacuated, The porous media were removed from the which removed the petroleum ether and air. The tube and examined under the microscope. The voids were then filled with distilled water, removal dispersed the grains, but many of them and distilled water was run through the system had clusters of oil droplets sticking to them for 100 minutes. About 2,500 cc of regular [Fig. 5]. Other clusters and long chains of emulsion with 61 dynes surface tension were w oil droplets floated about in the water [Fig. through. A little oil collected at the coarse- 61. Some droplets had coalesced to form larger fine interfaces,but much less than when the ones, but most of them were their original size beads were water-wet. Some oil collected Apparently the collection of oil occurred by throughout the porous medimn. The permeabilit~ agglomerationand flocculation of droplets into of all three intervals declined; the A to B a mass. Such a mass of small drops of one interval retained 40 percent of its original fluid in another is an emulsion wherein the permeability, the B to C interval I-1percent, volume of the discontinuous component exceeds and the C to D interval 10 percent. . FLOW OF A DISPERSE EMULSION OF CR1 )EOIL IN WATER IN POROUS MEDIA SPE 2481 .

Virtually all the oil was retained in the of the electrical charge at the point of con- porous media, and the effluent was quite clear. tact, leaving a deficiency on the opPosite side Its surface tension remained at 61 dynes, so ~f the droplet. This deficiencymight attract the water did not pick up any wetting agent another droplet, which would cause it to attach from the beads. itself there, and to it a third, and so on. I’huslong strings and eventuallymasses of Mamy other runs were made using the same iropletswould form. As these packed into the and different materials, and the restits were pores, they would form a concentratedemulsion. generally consistent. The preceding four are Perhaps during the course of time the droplets consideredthe most significant. They are would coalesce. summarized in Table 1. The results of these experiments can uucLy...w...-T..+...... V.+D+;~* hardly be applied to geological situations without many additional experimentsto verify In these experiments, oil was removed the phenomenon and to develop explanationsfor 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 from the flowing stream at izte~f~c?swhere the it. They tend to confirm the possibility that grain size abruptly decreased,but the mechan- oil can migrate through sands in tklefmrm of a ism of removal was not capillary screening. fine disperse oil-in-wateremulsion and be Three possibly significantphenomena were screened out at interfaceswith finer material. observed: However, the screening does not take place according to the rules of capillarityas these 1. The disperse oil droplets of l-micron have been developedby students of fluid diameter suspended in water were able to travel behavior in porous media. Instead, quite a appreciable distances in water-wet porous different set of laws seems to govern the media. behavior of fine disperse emulsions.

2. They tended to collect by attachment ——REFERENCES to the solid surfaces and to each other when- ever the pore diameter of the porous medium was 1. Baker, E. G.: “Distributionof Hydrocar- abruptly reduced. bons in petroleum”,Bull., AAFG [1962]~, 76-84. 3. They collectedby means of floccula- 2. Botset, H. G.: “Flow of Gas Liquid Mix- tion and joined to form a very concentrated tures through ConsolidatedSands”, Trans., em’ulsio~,with little tendency to coalesce. Am [1940] 136, 91-105. 3. Bii&ley, S. E.‘ud LeverettJ M. C.: The reason for this behavior is not “Mechanismof Fluid Displacement in Ssmds”, immediately clear. It may be that oil droplets Trans., AIME.[1941] 146, 107-116. small enough to form a stable emulsion have an 4. =, P. A.: “The=fect of Underground electrical double layer at the oil-water Waters in Localizing Oil Accumulations”, in%erface. These electrical charges are able Economics of the Petroleum Industry, Gulf to repel other droplets and solid surfaces. Publishing co., H~~~~~fi[19651 5@l. When the droplets are forced against a solid 5. Hobson, G. D.: Some Fundamentalsof surface by a current of water, however> they Petroleum Geology, Oxford U. Press, London stick to it. Possibly the sharp corners and [1954J @-99 . broken surfaces of the crushed grains had sites 6. Illing, V. C.: “Some Factors in Oil of opposite charges. When a droplet stuck to a Accumulation”,Inst. Pet. Tech. J. [1939] solid surface, it might cause a concentration —25, 201-225. [;toL c to 1) F to F Percent Perm. Pern:. ,-. .-. .1.+<.,- Perm. Oe+c. nti cm Lulll” , n L, v= .’G!..-!!..- ,, Oi i in Water petenti on petenti on Throuqh-put I:edi um Percent Run Emulsion !lnrrfmt (Iedi um Percent_ — ~ubi ~ cm ~jedi ~~ ! .Lre-,.- Vumber —— G1 ass 80 79 —— ?lass 20 e- A cln Glass 73 }]ea~~ iiO surTac- -* U,” tie ads Beads kWT tant added and One 201M?11 Frushed oi 1 class tieads

75 Quartz w W&tz 44 NO surf ac- 5 ,l)i)o Sand Wn tant added and

F.JIJ 30/mg/l Crushed 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 oi 1 (!uartz

51 G1ass fllass Glass Sliqht $urfactant 1 ,75U Scads lieads Reads Run used in and Tb re.s emulsion Crushed preparation ‘lass

11 (;lass 10 Glass 41 Glass NO surf ac- 2,550 bea~~ !,eads tant added heads (nil Run (oil wet) and Four Crushed vet ) Glass I;eads (uil Vwt)

Oil in water suspension Fig. 1 - ~~~ on menacfiometer Slide. squares are 50 microns (0.05 mm) on a slide. ! I I 1PPPPPPPPPP? I*GLASS WOOL -OIL STAIN PERMEABILITY .33 DARCY

GLASS BEADS 193 MICRON PERMEABILITY 53 DARCY BEFORE FLOW ~;~;;;~j~~$?;~ 38,5 OARCV AFTER FLOW 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 *OIL STAIN CRUSHEO BEADS 37-88 MICRON ;:: ~,...... :,.::<...;. .. ..~,.;.. :.::: ;: .....:.:...,.,...::...... 5.3 DARCV BEFORE OIL COLLECTED :::::.’.’::::..:...,..%::...>. ::::...... 1 0.13 OARCY AFTER OIL COLLECTED

-’h DIAGRAMMATIC SKETCH OF PLASTIC CYLINDER WITH DIAGRAM OF PACK USING GLASS BEADS AND CRUSHED GLASS BEADS, FOUR MANOMETERS A, B, C, AND D.

Fi&. 2 - IIiagrav of phstic cylintier showing manometers. Fig. 3 - Diagram of pack using glass bea3.s and crushed The tribewas packed xith glass beads and quartz Santiof glass beads (Run 1). Oil collected in the pores of the about 2’:0micrm size. A bed of tbe sar,ematerials beads at the top of the column and at the interface crushe6 to ,bout 50 microns was F1. c.3 between between the course and fine beads. non..xeters B ens C. Oil coilected in this bed, although the pore openings were very much larger than the size of the drcplets.

100 INTERVAL C TO D

90 ‘4

z 0 80 zW A 2 t *\ 70 z INTERVAL A TO B [ w 1- 60 = u -INTERVAL TOP TO A t z 50 I u t B TO C INTERVAL- / 1- 40L -1 - ‘ 50 z ,-*-.*-##------% + ~. / ------K L ‘* : -%--- u ‘*- 1 20 FLOWhRAT E-*s--- .25 ;. ; 1 ------10 --’ ---- g r 1 ~: 100 TIME, MINUTES

FLOW RATE AND PERMEABILITY CHANGE, RUN ONE

Fig. h - F1OW rate a“d permeability change (Run 1) . After starting ev,ulsion through flow rate declined. IJ3ssof permeability occurred wheTe a%: collected at top of pack and between mo”ometers B and C. 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

Fig. 5 - Unbroken glass bead with oil droplets sticking to it.

Fig. 7 - Oil collectingat interface between course and crushed sand.

Fig. 6 - Fragments of crushed glass with oil droplets sticking to them.