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THEROLEOF OIL-I N-WATER14JLSI E ONS INTHERMALILRECOVERY O PROCESSES
by E. H. Garthoffner, Tenneco Oil Co.

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ight 1979,AmerbanInstkuteof Mining,Metallurgbal,andPetroleumEnginaara,no. l %fWrwav*ntdattK 1979C@ifomlaRq~@ MWtingofmeWaWof PetioleumEngln@raofAlMEmldinVemura,Californla,AWlll8-2O, 979.Thematerlalia8ut@ot 1 CI orraotbnby thaauthor,Permiaslon oqv ia raatrbtedto an abatractof not morethan 200words.Write:62W N. OantrelEXPWY., o to Dallaa,Texaa75206

ABSTRACT It has long been known that some California oil fields produce oil, a fraction of which is in the form of an emulsion. This is particularly true, “of those fields producing heavy oils. This paper proposes a recovery mechanism which is thought to occur as a result ofthermal operations in some Califoirna oil fields. The mechanism is the formation of oil-in-water (0/W) emulsions in the reservoir. Evidence is presented that under the right conditions such emulsions have more favorable flow characteristics than heavy oil. The mechanism is discussed in relation to cyclic steam, steamflood and in-situ combustion operations. The mechanism is thought to be more effectivein the cyclic steam process than in the other two. It is also suggested that the formation of O/W emulsions increases both the producing rate and the ultimate recovery in thermal projects. A better understanding of the mechanism should make it possible to increase its effectiveness or to induce the mechanism where the conditions are not suitable in the natural state. INTRODUCTION Since theintroduction of thermal oil recovery methods, the list of recovery mechanisms thought to be effective in increasing oil recovery by these methods has g~own. An early investigation by Willman et al focussed on suet’ mechanisms as thermal expansion, viscosity reduction and steam distillation of oil. As more research followed, the complexity of the various processes became apparent. An extensive list ofphenomena attributed to thermal recovery processes has recently been published by Prats . In general, the mechanisms which have been postulated are the result of the elevation of reservoir temperatures,displacement of reservoir fluids by injected fluids, and chemical changes caused by the injection of foreign fluids and heat. References and il lustrations at end. of pape;; It is the purpose of thispaper to propose another mechanism. which is also thought to be beneficial in increasing oil recovered by thermal methods. The proposed mechanism is thought to be the result of mechanical energy contained in or produced by fluids injected into the reservoir. The mechanism is thought to be effective in certain California heavy oil reservoirs but may be effective in other oil provinces where similarconditions exist. The characteristics which make one type of crude oil more susceptible to the mechanism than another type of crude oil will be discussed. It will be shown that conditions favorable to the formation of O/W emulsions do exist and that the formation of such emulsions should be beneficial in increasing oil recovery. THEORY It is proposed that the injection of steam or air (when itsupports in-situ combustion) into certain hydrocarbonreservoirscauses the formation It is of O/W emulsions in these reservoirs. suggested that such emulsions have more favorable flow characteristics, within certain temperature ranges, than the oil from which they are formed and this leads to higher oil producing rates and higher The mechanism will be ultimate oil recovery. more effective at lowtemperatures than at high temperatures. NATURE OF O/W EMULSIONS — Becker 3 states, llAn emulsion is a heterogeneous system, consisting of at least one immiscible liquid intimately dispersed in another in the form of droplets whose diameters, in genSuch systems possess eral, exceed 0.1 micron. a minimal stability, which may be accentuated by such additives as surface-active agents, finelydivided...