CA1102728A - Demulsifying petroleum emulsions with polyalkylene oxide resins and alkali metal halides - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A process for recovering oil from stabilized oil-in-water petroleum emulsions by subjecting them to the action of an optimum amount of non-ionic, water-soluble, ultra-high molecular weight polyalkylene oxide resins at a pH of 7 to 10, and then adding a saturated aqueous alkali metal halide solution. The process is carried out at between 60°F and 210°F and the mixture is allowed to stand in the quiescent state for a period of 3 to 12 hours to allow the halide solution to increase the specific gravity of the resulting aqueous phase by at least 0.019 thereby causing the bitumen to float thereabove to facilitate recovery thereof.

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Description

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BACKGROUND OF THE INVENTION
Field of the Invention This invention is concerned with the resolution of stabilized water-bituminous emulsions by treatment with polyethylene oxide resins of optimum molecular weight and a saturated alkali metal halide solution. The invention is also concerned with the separation of water from bitumen which has been brought to the surface in the form of oil-in-water emulsions by an in-situ recovery process.

STATEMENT OF THE PRIOR ART
Numerous hot water extraction methods exist for separating crude oil from bituminous sands (tar sands, oil sands and the like) which involve mixing such sands with hot or cold water and separating the sand from the resulting emulsions.
The technical difficulty encountered wi~h emulsions ' produced by in-situ operations is that the liquid mixture is a highly stabilized emulsion which is difficult to break with standard treating chemicals.
The attempts made in the prior art to break emulsions resulting from hot water extraction processes are represented, inter alia, by the techniques described in U.~.
Patents 3,808,120, 3,607,721 and 3,487,003.
U.S. Patent 3,808,120 describes a method for 1, ;, ~ separating at least water and solids from the froth produced in a hot water process for separating bitumen from tar sands by treating the froth in at least one cyclone zone, after ~ which it is treated in at least two centrifuging zones.
.'f~ ~ In U.S. Patent 3,606,721, a process for the removal o solids and emulsified water from a bituminous emulsion is disclosed which comprises diluting the emulsion with a hydrocarbon diluent; maintaining the resulting mixture in , f , ' ` ~
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a settling zone; removing the emulsion when substantially free of solids and emulsified water from the top of the settling zone; withdrawing settled sludge from the bottom of the settling zone and centrifuging the withdrawn sludge to separate bitumen and diluent from the settled solids and the emulsified water.
U.S. Patent 3,487,003 describes a method for reducing the solids content of an effluent discharge from a hot water process for separating oil from bituminous sands by adding a flocculatig agent which may be organic, inorganic or even a polyalkylene oxide of undisclosed molecular weight to this effluent; adjusting the pH of the effluent to less than 7.5 or more than 9 to effect floccula-tion of at least a portion of the solids therein; centrifugins the effluent now containing flocculated solids and recover-ing the effluent discharge substantially reduced in solids content. This method treats not an oil-in-water emulsion but rather an effluent comprised of the effluent from the sand tailings layer and the middlings layer. Further, there is no appreciation of the necessity fox maintaining the temperature within a given range during treatment with the flocculating agent.
U.S. Patent 2,964,478 describes a process for breaking an oil-in-water emulsion by subjecting the emulsion to the sole action of a polyalkylene oxide having a r~olecular weight of 100,000 to 3 million. In the practice of that process the mixture of the resin is allowed to stand ~ -quiescent for about 13 hours at a settling temperature to 160F, after which some of the oil rises to the surface of the pond or sump and is removed.
In coassigned, copending application Serial ~lo.

713,456, filed August 11, 1976, now U.S. Patent ~,~5~, ~3 there is disclosed a process for recovering oil from oil-.

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in-water and water-in-oil emulsions by demulsifying the emulsions by adding thereto an effective amount of non-ionic, water-soluble, polyethylene oxide polymers having a molecular weight in the range of 100,000 to 7,000,000 and calcium chloride and separating the oil from said water. Preferably, ~-in that process, the emulsions are diluted following addi-tion of the polymer with from 30 to 50 volume percent of a hydrocarbon diluent and, after maintaining the temperature of the resulting mixture at between 150 and 210F, the oil therein is centrifuged from the solids and the water. Un-expectedly, the process of this invention gives 'aster separation at a lower cost since a diluent is not needed.
Also generally known is the use of salt as a diluent in the separation of bitumen and water. Previously, rig tanks were filled with production fluid and salt added to the fluid. The results were relatively clean water but the bitumen could not be reduced below a water cut of about 20 percent. None of the above techniques discloses or suggests the present invention.
SUMMARY OF THE INVENTION
The main object of this invention is to achieve functional demulsification of emulsions at a minimal cost and in a minimal amount of time.
This object is attained by the present invention which resides in the concept of demulsifying emulsions stabilized by clays, surfactants, both naturally occur-rying and those formed in-situ and by asphaltenes, by adding thereto from 25 to 100 parts per million of non-ionic, water-soluble polyalkylene oxide resins having a 30 molecular weight in the range of 100,000 to 7,000,000 B ~3~

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Then the specific gravity of the resulting aqueous phase is increased by at least 0.019 by adding an alkali metal halide solution in an amount ranging from 5 to 20~ bv volume of said emulsion, sufficient to effect said increase. This causes the oil to rise above the aqueous phase.
The resulting system is allowed to remain in the quiescent state for 3 to 12 hours at a temperature in the range of 60 to 210F., then the oil is removed from the system.
With a saturated alkali metal halide solution it will normally be satisfactory to add about 1 part per 10 parts by volume to the emulsion, The ~olyalkylene oxide polymers remove substantially all the stabilizing materials from the oil and deposit them in the 1: .
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water phase, whilst the increased specific gravity of the mixture caused by the addition of alkali metal halide causes the oil to rise. The ionic effect of the salt in solution is also thought to assist the demulsification process.
Other aspects of this invention will be apparent to those skilled in the art from a reading of this disclosure and of the appended claims, in particular when taken with -the accompanying drawing wherein:
Figure 1 is a graph, the curve of which shows the effect of resin concentration and of time on the concentra-tions tested;
Figure 2 is a graph, the curve of which allows the effect of resin concentration on total solids;
Figure 3 is a graph, the curve of which shows the effect of resin concentration with time as the parameter;
Figure 4 is a graph, the curves of which show the effect of brine concentration on the water cut; and Figure 5 is a graph, the curves of which compare various demulsifier systems.
DETAILED DESCRIPTION OF THE INVENTION
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The process of the invention can be used to treat oil-bearing fluids derived by various methods from bitu~inous sands and conventional crude petroleum emulsion. In one such method, steam is injected in the sands fGrmation through a center well in a multi-well pattern and the fluids are produced in the adjoining wells. The produced fluids are stable dilute oil-in-water emulsions containing an average of 15 percent oil with variations in oil phase concentrations i from 0 to 40 percent.
The produced fluids can be treated in a conventional hori~ontal treater operated at about 210F and about 20 psig :
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pressure to separate the oil from the water phase. In the present process, to the resulting oil~in-water emulsion at a pH in the range of about 7 to about lO is added from about 25 to about 100 parts per million of an ultra-high molecular weight alkylene oxide polymer having a molecular weight in the range of 100,000 to 7,000,000. These polymers are poly-oxiranes such as polyethylene oxide, polypropylene oxide, polybutylene oxide and copolymers thereof having a molecular weight of at least 100,000. The preferred demulsifiers are polyethylene oxide polymers marketed by Union Carbide Corpora-tion under the trademarked name of "Polyox WSR 301". These resins are high polymers with the structure (O-CH2CH2)n with the degree of polymerization "n" ranging from 200 to about lO0,000 giving a molecular weight range of 100,000 to about 7,000,000. After adding the above polymer, a saturated solution of an alkali metal such as KCl or NaCl is added in an amount ranging from 5 to 20% by volume of the emulsion. .
For obvious reasons of cost, a salt brine solution is preferred.
In the practice of the process of the invention, it has unexpectedly been discovered that if the polymeric molecule is added to the emulsion first the rate of sPpara-tion of the oil phase is faster than if the brine is added first or, for that matter, where they are added simultaneously.
It is postulated that the reason for this behavior is that where the polymeric material is first added there is less chance that the solids and the water will be entrained in the oil phase.
Mixing can be effected at a temperature of 60 to 70F and the temperature of the system is brought up to between 190 and 170F,or the latter temperature range can ~e used for the entire operation. Mixing is carried out in steel treating vessels with the reagents added by means of a proportioning pump. After the oil rises to the surface .

of the fluid, it is removed by means of an overflow weir.
The separated water containing very little of the previously emulsified oil can be discarded.
With a view to more fully describing the present process, the following examples are given in a non-limiting sense.
EXAMPLES
A 'IPolyox'' WSR 301 and brine solution were added in various amounts to 750 mls of production fluid consisting of natural crude petroleum oil-in-water emulsions.
The results of the 16 examples run on the salt and "Polyox"-salt system are tabulated in Table 1. The samples used in testing were a mix~ure of all the production fluid on site. At no time during the testlng was diluent incorporated. All the tests with the exception of Example II were run at 150-170F.
~ The data in Table 1 shows the mls of saturated salt brine added per lO0 mls of production fluid and the concentration of "Polyox" in the final solution. The Table also gives comments and cuts, where applicable. From this data, it is obvious that salt on its own gives some separa-tion and the combinatlon of 'IPolyoxll-salt does an exc.ellent job. It was also noted that very little mixing was required to obtain excellent results. This is probably due to both ~ the produced fluid and treating chemical having water in ; common. It was also noted that separation with the "Polyoxl'-salt system was somewhat faster than the existing hydrocarbon-diluent treating scheme; probably once again due to the mixing and mechanism. In the present treating system, the additive must act before the diluent will even mix with the bitumen to give the driving force for separation. In the "Polyox"-salt system the "Polyox" virtually knocks the solids out of the bitumen and coalesces it while, at the .
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same time, the salt brlne provides the driving force for separation. Both components are believed to work in parallel, and not in series. The salt brine also helps disperse the "Polyox".
The data from Table 1 have been statistically analyzed and plotted in Figures 1-4. Figure 1 shows the effect of time on the various combinations tested. From this plot, it is quite obvious the "Polyox"-salt system is superior to straight salt. It also shows to some degree ; 10 the effect of temperature, as seen with the 50 ppm samples at 60F versus 150-170F. The effect of various concent~a-tions of salt and 1'Polyox" are also evident. Thus, it can be seen that 10 mls of salt brine per 100 mls production fluid is about the optimum concentration, while 25 ppm "Polyox" appears quite adequate. Additional "Polyox" gives some improvement, but not significantly.
; It should also be noted that when the oil samples were analyzed for water cut, some solids were also obtained.
When the solids cut of the oil's B.S.&W. (Basic Sediment and Water) was correlated to the "Polyox" concentration, the graph in Figure 2 resulted. Using just brine for separation gave about 50% of the total B.S.&W as solids. As "Polyox"
was added the solids cut decreased until, if the graph was extended, there would be no solids left in the oil at all with a "Polyox" concentration of about 175 ppm. From these tests, it would appear that it is not necessary to remove all the solids, just enough to allow fairly rapid coalescense of the bitumen. A concentration of 25-50 ppm "Polyox", removing about 50% of the initial solids, thus appears to 30 be adequate. At a low temperature, the "Polyox" was not as -effective, removing only about 38% of the solids at 60F as compared to 50% at 150-170~.

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The data in Figure l and Table l have been re-organized in Figures 3 and 4 to illustrate the effect of brine and "Polyox" concentration. Figure 3 shows the effect of "Pol~ox" concentration, with time as the parameter. This figure shows quite conclusively that 25 ppm "Polyox" is about the lowest concentration that could be use for practical treating. The similarity between the curves in this figure and that in Figure 2, the solids correlation, is particular-ly noteworthy.
Figure 4 gives the effect of brine concentration on water cut, also with the parameter of time. The tendency for the water cut to increase with brine concentration could be the result of experimental error in measuring the cuts. No runs where "Polyox" and salt were used in conjuct-tion showed this tendency. The two items of importance in this figure are the minimum water cut of 6~ obtained only after 4 days residence time and the sharp cutoff between adequate treating (l~ mls/lO0) and totally inadequate treat-ing (5-7.5 mls/lO0). The minimum water cut and long residence time show that salt will not treat the production fluid by itself. The sharp break between adequate and in-adequate treating shows that the minimum specific gravity difference required between the oil and water for separation is about 0.019, or the equivalent of 15~ diesel dilution.
These calculations were done on the basis that all the solids in the bitumen had been removed, thus making the bitumen as light as possible.

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RESULTS OF NaCl TESTS
Example NaCl Polyox No.(ml/100 ml) (ppm) Rem_rks 1 2.; - Essentially no effect.
2 5.0 - Partial breaking of emulsion.
3 7.5 - Toucy interface. Clean water;
20% water cut (8 HR).

4 10.0 - Clean water; 18.5% water cut (2 HR); 7.5% water (48 HR).
Solids made up about 50% of the above cuts.) 20.0 - Similar to the above. Clean water; 8% water cut (48 HR).
6 30.00 - Similar to the above. Clean water; 10% water cut (48 HR).
7 5.0 25 Partially broken. 75% water cut (3 HR).
8 10.0 12.5 Clean water; 18.5% water cut (5 HR). (Solids made up about 35% of cut.) 9 10.0 25 Clean water; 3% water cut ; (5 HR). (Solids made up about 30% of cut.) I0 10.0 50 Clean water; 2.5% water cut (3 HR); 0.75% water cut (24 HR). (Solids made up about 25% of cut.) 11 10.0 50 Run at 60F gave 21% water cut HR). (Solids made up about 31% of cut.) 12 15.0 18.75 Clean water; 8~ water cut (5 HR). (Solids made up 38~ of cut.) 13 15.0 37.5 Clean water; 0.9% water cut (24 HR). (Solids made up about 28% of cut.) 14 15.0 75 Clean water; 0.25% water cut (24 HR~. (Solids made up about 20~ of cut.) 20.0 25 Clean water; 3% water cut (3 HR). (Solids made up about 30%
of cut.) 16 20.0 100 Clean water; 2.5% water cut (3 HR). (Solids made up about 1S% cut.) ,' -: :
' Note: All examples, except No. 11, run at between 150 and 170F. At 6-70F when mixed.
Another series of tests was run to demonstrate the superiority of the present process. Superiority has been based on cost and the speed of reducing the oil phase's water content.
In all the above examples the ingredients were mixed at room temperature and the solution heated to and held at 150-170F. To make the present tests more represent-ative, all data included were obtained using production fluid heated at 170F prior to any treating attempt. The chemicals, diluent, etc. used in the tests were then mixed with the hot fluid. The temperature was kept at 160-170F for the dura-tion of each test. Also, mixing was kept to a minimum.
The results obtained in these examples are present-ed in Figure 5. In this figure, water cut is plotted as a function of time for:
1. The Polyox-diesel system.
2. Straight salt brine.
3. Polyox-salt, adding the salt brine first.
4. Polyox-salt, adding the Polyox first.
The procedure followed in the above tests is outlined in Table 2 below.

TESTI~G PROCEDURE
SALT SYSTEM
` - heat 500 mls of production fluid to 170F. -- add 50 mls of saturated salt brine.
- mix for 15 seconds while adding brine.
- sample oil phase with syringe when required.
- maintain temperature at 160-170~F.
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POLYOX-SALT SYSTEM (SALT FIRST) - heat 500 mls of production fluid to 170F.
- add 50 mls of saturated salt brine.
- mix 15 seconds.
- add 11 mls of 0.25 wt. ~ Polyox solution.
- mix 15 seconds.
- sample oil phase when required.
- maintain temperature at 160-170F.
POLYOX-SAL~ SYSTEM (POLYOX FIRST) ~.
- IDENTICAL TO THE ABOVE EXCEPT THE ORDER OF
ADDING POLYOX AND SALT BRINE IS REVERSED.
POLYOX-DIESEL SYST M
- heat 500 mls of production fluid to 170F.
- add 65 mls of diesel fuel.
- add ll mls of 0.25 wt. % Polyox solution.
- mix for one minute.
- sample oil phase when required.
~ - maintain temperature at 160-170F.
; NOTES: All mixing done with stirring rod. Chemicals and diluent added to top of fluid.
It is obvious from the data in Figure l which treating schemes give the fastest cleanup of the oil. Both "Polyox"-salt systems proceed at much higher rates than do the other two schemes, g~tting the water cut down to accept-able levels (23%) in one and six hours, respectively, while it takes the "Polyox"-diesel system in excess of four days.
~- The steeper slope of the "Polyox"-salt curves can be explain-ed by considering the process's mechanism. With the "Polyoxll-salt system the brine and "Polyox" work in parallel. The ` "Polyox" is coalescing the oil at the same time the brine is ; supplying the driving force for separation. With the other ~ 30 systems the chemical has to aO its job before the bitumen :.

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and diesel will mix. This results in a bottleneck giving slower separation and cleanup.
It was found during the testing that the order of addition of the chemicals and diluent, and the rate and timing at which mixing took place, could greatly affect the outcome of the tests, in particular those were diesel was used. In the "Polyox"-diesel system this was particularly evident. With the procedure in Table 2, one minute of mixing was used and found to be quite inadequate. Subsequent to the mixing, free diesel would accumulate on the surface of the sample indicating one of two things:
l. The diesel had not contacted the bitumen.
2. The "Polyox" had not broken the emulsion to the point where diesel would dilute the bitumen.
Probably both of these resulted in the poor dilution, but the - latter was the controlling factor~ Additional testing showed that if the same initial procedure was followed by additional mixing at the 30-60 minute mark of the test much faster cleanup of the oil and water would result. ~pparently, the added time allows the "Polyox" to do its job, making the bitumen easier to dilute. Accordingly, the process of this invention contemplates a field treating facility with the following features:
1. An in-line static mixer immediately down-stream of the "Polyox" addition point requiring a low energy input.
2. A surge vessel to give a ~ - 1 hour residence time for the "Polyox" to function.
3. A high efficiency mechanical mixer associated with the diluent addition point. (High energy input).

4. Separation facilities similar to a 5,000-barrel tank.

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With the "Polyox"-salt system of this invention very few problems are encountered with mixing since the process is more one of dispersion than 'brute force' contacting of bitumen and diluent. Both the "Polyox" and salt brine are water phase materials and readily mix with the water phase of the production fluid.
Of more importance in the "Polyox"-salt system of treating is the order in which the materials are added. The results in Figure 5 definitely show this. If the "Polyox"
is added first the rate of cleanup of the oil phase is more rapid than the case where the salt brine is added firstj or for that matter where they are both added at once. It appears that where the "Polyox" gets to act first there is less chance of solids and water being entrained in the oil phase with resultant faster cleanup of the oil phase.
It is to be understood that the foregoing specific examples are presented by way of illustration and explana-tion only and that the invention is not limited by the details of such examples.
The foregoing is believed to so disclose the present invention that those skilled in the art to which it appertains can, by applying thereto current knowledge, readily modify it for various applications. Therefore, such modifications are intended to fall within the range of equivalence of the appended claims.

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Claims (4)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process for recovering oil from oil-in-water emulsions stabilized by clay comprising first subjecting said emulsions to the action of non-ionic, water-soluble, polyalkylene oxide polymers having a molecular weight in the range of 100,000 to 7,000,000 at a pH of 7 to 10 with from 25 to 100 parts per million of polymer being added on the basis of the volume of said emulsion; increasing the spec-ific gravity of the resulting aqueous phase by at least 0.019 by adding an alkali metal halide solution in an amount ranging from 5 to 20 percent by volume of said emulsion sufficient to effect said increase whereby said oil rises above said phase; allowing the resulting system to remain in the quiescent state for 3 to 12 hours at a temperature in the range of 60° to 210°F. and removing said oil from said system.

2. The process of Claim 1, wherein said emulsions are production fluids produced by an in-situ recovery oper-ation.

3. The process according to Claim 1, wherein said polyalkylene oxide is polyethylene oxide, polypropylene oxide, polybutylene oxide and copolymers thereof.

4. The process according to Claim 1, wherein said alkali metal halide is sodium chloride.