US2257997A - Breaking petroleum emulsions - Google Patents

Description

Patented a. 7, 1941 BREAKING PETROLEUM EMULSIONS Robert Bowling Barnes, Stamford, Conn., as-

signor to American Cyanamid Company, New York, N. 1., a corporation of Maine Application November 27, 1940, Serial No. 367,421

This invention relates to a method and apparatus for the breaking or resolution of oil field emulsions. Emulsions of this class are of the water-in-oil type. and are frequently encountered in crude oil. production. They consist of very fine droplets of water dispersed in the petroleum hydrocarbons which constitute crude oil, and they are frequently very difficult to break or resolve since sodium, potassium, calcium or magnesium salts may be dissolved in the water and asphaltic, bituminous or other tarry and film-forming ingredients may be occluded at the water-oil interface.

Emulsions oi the above described type are objectionable in petroleum technology, both because they give rise to diificuities in distillation and refining processes and because the water constitutes a diluent for the oil. Although complete resolution is not always necessary, it is customary to set a maximum water content among the specifications for crudes admissible for pipe line transportation, and some demulsification of the oil to the extent necessary to meet these specifications must be employed.

I have now discovered that oil field emulsions of the above and similar types can be resolved or broken either completely or to the extent necessary to bring the water content within the specifications set for pipe line transmission by subjecting the emulsion to the action of ultrasonic vibrations of the type generated by a quartz piezo crystal when it is placed between the electrodes of a high frequency alternating current.

' Vibrations of this type are known as ultrasonic vibrations, since they have a frequency above the audible range; i. e., above about 16,000-20,000 per second. Although vibrations of any frequency within the ultrasonic range may be used, I find that the most efilcient results are obtained at a frequency between about 50,000 per second and about 900,000 per second.

The vibrations generated by a quartz crystal or by magnetostriction of a metal rod having a similar vibration period are a series of purely mechanical impulses, and should not be confused with electrical vibrations of the type represented by high frequency alternating electric currents. when the mechanical vibrations used in my present invention are generated in a liquid medium, as in an oil bath surrounding the quartz crystal or other vibrator, they create a series of standing waves having a frequency and amplitude dependent upon the power input and the dimensions of the vibrator. Areas of physical pressure are created at the nodes of these standing waves, 55 the oil emulsion.

and I have discovered that these pressure areas are operative to bring about a coalescence of the minute water droplets of oil field emulsions that results in demulsification of the oil.

In practicing my invention the emulsion may be subjected to the action of the ultrasonic vibratory waves in any suitable manner, as by suspending a suitably insulated vibrating quartz crystal in a body of the emulsion in any suitable container. One of the most important features of the invention, however, resides in the fact that the demulsifying action of high frequency pressure vibrations on the average oil field emulsion is extremely rapid. By reason of the rapid enlargement of the water droplets by coalescence it is unnecessary to subject the emulsion to the pressure vibration for any very extensive period of time, and this fact permits the use of wide variations in the method of application.

One of the most important methods of application, and one which constitutes a specific feature of my invention, is a method which employs the step of passing a moving stream of the emulsion in juxtaposition to an active source of ultrasonic vibrations, after which the separated water may be removed by settling. This method is illustrated in the accompanying drawing, in which:

Fig. 1 is a graph showing the rate of dehydration of the oil, and

Fig. 2 is a diagrammatic illustration'of an apparatus which I have used in obtaining the results illustrated in Fig. 1.

Referring to Fig. 2, the source of ultrasonic vibrations is a quartz crystal 5 having electrodes 6 and I on opposite sides thereof. These electrodes are attached by wires 8 and 9 to a suitable source of high frequency alternating current: in the example shown a Hartley, oscillator'circuit was used that was capable of tuning to any desired frequency between about 15,000 and 900,000 cycles per second with 600 watts input. At vibrations of 200,000 to 840,000 cycles per second, within which range the optimum results appear to be obtainable, the acoustic output of the quartz was about 25% or 240 watts.

The quartz crystal 5 is supported on the bottom [0 of a suitable vessel II which is preferably provided with cooling coils If, as considerable heat is generated by the vibration. A pressure transmitting liquid that is also an eflicient insulator, such as light mineral oil, is placed in the vessel to insulate the electrodes 8 and I and to transmit the vibrations of the quartz plate to A conduit ll passes through the vessel II in juatapositiontothsquartsplatel. Thisconduit mayconsistof a singlecylindrical pipaorofa serlesofpipesconnected toheader'sateitherend ofthsvessel ll,oritmaybeasingleclosed conduit of relatively small height but considerable cross sectional area. In larger installations a number of quartz plates similar to the crystal I, and having electrodes attached thereto, may be spread out along the bottom of the vessel H to provide a greater energy input. In any case, however, a moving stream of the emulsion is pamed through a conduit adjacent to one or more vi- -brators of the type illustrated by a quartz plate or crystal, after which the separated water is removed as by settling. In the modification shown the outlet pipe It leads to a settling tank.

which may be provided with steam coils for heat- 1 ing, where the water separates from the oil by gravity.

The rapidity of the demulsiflcation obtainable by my invention is remarkable, even when small laboratory equipment is used. A flask containing an emulsion prepared from Signal Hill (California) crude oil and sea water was immersed in the oil bath described above and subjected to the action of ultrasonic vibrations at 287,000 cycles per second, and the course of the demulsi flcation was followed by photomicrographs. In the original emulsion the average particle size was on the order of one micron, with maximum particles of 2 microns. After 30 seconds vibration a second photomicrograph showed that the average particle size was about 5 microns, and an 90% resolution was obtained in one minute. The

resolution was complete after 2 minutes, the

course of the demulsification being shown in the graph constituting Fig. 1 of the drawing.

Since an initial enlargement of the water droplets is obtained by even a very short exposure of the petroleum emulsion to the action of ultrasonic vibrations, another important feature of my invention'resides in the treatment of a petroleum emulsion both by this means and by chemicals. It is well known that a number of classes of chemical compounds, such as sulfonated vegetable oils of the type of sulfonated castor oil, sulfonated fatty acids, sulfonated fatty acid esters and sulfonated esters of higher alcohols with monocarboxylic and polycarboxylic aliphatic and aromatic acids, are demulsiflers for many types of petroleum emulsions when used in suitable concentrations. Even more effective results are frequently obtainable with compounds having .slrrface-active properties, such as alkyl naphthalene sulfonic acids and their salts, higher alkyl esters of aliphatic sulfodicarboxyiic acids such as sodium dioctyl sulfosuccinate, and sulfonated terpenyl alkyl phenol condensation products. I have discovered that the action of these and similar classes of compounds in resolving petroleum emulsions is frequently enhanced when the emulsion is subjected to the action of high frequency mechanical vibrations of the type described above for even short periods of time, as the vibration conditions the emulsion by enlarging the droplets thereof. Satisfactory results can be obtained either by adding the chemical before vibrating or by first conditioning the emulsion by a preliminary vibration and-then adding the chemical.

The invention will be described in greater detail by the following specific examples. It should be understood, however, that althoughthese examples may describe in detail some of the more thereto.

[sample 1 Samples of a mineral oil emulsion prepared from'l5partsofcrudsflignalllilloilfrom California and 25 parts of sea water were placed in 15 cc. graduated centrifuge tubes/and immersed in an oil bath containing water-cooled coils and a quarts crystal connected to a Hartley oscillator circuit. Samples were subjected to vibrations at the rate of 287,000 per second for vllrylnl times up to 30 minutes and were then centrifuged at 1950 R. P. M. for 5 minutes to clarify the water separated. It was found that of the water was separated in 1-2 minutes.

Oneof the 15 cc. samples was vibrated for only 30 seconds. 1.5 cc. of an 0.01% solution of sodium dicotyl sulfosuccinate was then added and the tube was permitted to stand for 10 minutes. It was then centrifuged for 5 minutes at 1950 R. P. IL, whereupon a complete separation of the water was obtained.

Example 2 A water-in-oll emulsion obtained from a produclng well in Corpus Christi, Texas, was found, upon toluene distillation, to have a water content of 295%. A sample of this emulsion was agitated for 30 seconds with 500 parts per million of Tretolite M-3", which is a standard emulsion breaking composition now in wide commercial use. After shaking with the chemical the sample of emulsion was heated in a water bath at F. for 1 hour and allowed to stand overnight. The water separated by the action of the chemical was drawn off and a sample of the supernatant oil was again analyzed for water by means of a toluene distillation. 0.5% of water was found in the oil.

Another sample of this emulsion was shaken for 30 seconds with 500 parts per million of Tretolite M and was then subjected to ultrasonic vibration in the manner described in Example 1 for 2 minutes. The sample was then heated at 140 F. for 1 hour, allowed to stand overnight, and the water separated out. The supernatant oil was clear and a toluene distillation proved that it contained no water. Comparison of the results obtained with this emulsion shows that the application of ultrasonic vibrations to emulsions pretreated with chemical demulsifying agents improves the demulsifying action of the latter.

What I claim is:'

l. A method of breaking petroleum oil field emulsions of the water-in-oil type which comprises the step of subjecting the emulsion to the action'of ultrasonic vibrations of the type generated by a quartz crystal when placed between the electtrodes of a high frequency alternating curren 2. A method of breaking petroleum oil field emulsions of the water-in-oil type which comprises the step of subjecting the emulsion to the action of ultrasonic mechanical vibrations of a frequency between about 50,000 per second and 900,000 per second.

3. A method of breaking petroleum oil field emulsions of the water-in-oil type which comprisesthestepsofpassingamovingstreamof the emulsion in juxtaposition to an active source of ultrasonic vibrations and then removing the separated water by settling.

4-Amethod0fbreakingpetroleumoflfle1d speciiieaspectsofthsinventiontheyaregiven emulsions of the water-in-oil type which comprises the steps of passing a moving stream of the emulsion in juxtaposition to a quartz crystal operative to generate standing waves mounted between the electrodes of a high frequency alternatlng current corresponding to the frequency of ultrasonic vibrations and then removing the separated water by settling.

5. A method of breaking petroleum oil field emulsions of the water-in-oil type which comprises the steps of passing a moving stream of the emulsion through a conduit surrounded by a pressure transmitting liquid and creating standing waves within said conduit by vibrating a quartz crystal at an ultrasonic frequency in said liquid.

6. A method of breaking petroleum oil field emulsions of the water-in-oil type which comprises the steps of passing a moving stream of the emulsion through a conduit surrounded by a pressure transmitting liquid and creating stand- 50,000-900,000 per second.

'I. A method of breaking petroleum oil fleld emulsions of the water-in-oil type which comprises the step of immersing a suitably insulated, quartz crystal therein and vibrating said crystal at an ultrasonic frequency.

8. A method according to claim 1 in which a chemical demulsifying agent is added to the emulsion.

9. A method accordingto claim 2 in which a chemical demulsifying agent is added to the emulsion.

10. A method according to claim 3 in which a chemical demulsifying agent is added to the emulsion.

emulsion.

ROBERT BOWLING BARNES.

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