Note: Descriptions are shown in the official language in which they were submitted.
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1215
PROCESS FOR BREAKING PETROLEUI!I EMULSIONS
Background of the Invention
1~ Field of the Invention
The invention relates to processes for the
enhanced reCQvery of oil in which the oil is obtained from a
producing well in an oil-in-water emulsion or dispersion.
2. Description of the Prior Art
Processes for enhanced oil recovery can involve
the injection of heat, chemicals, or gases into an oil
reservoir in order to lower the ViSCQsity of the oil, strip
it from the rock surface, and push it towards producing
wells. Enhanced oil recovery processes are often called
tertiary oil recovery processes because they often follow
primary (pressurized) and secondary (water flooding)
recovery methods at a well field It has been estimated
that an average of 67% of the original-oil-in-place remains
in the reservoir rocks subsequent to primary and secondary
methods of oil recovery.
Where the oil is recovered by tertiary methods in
combination with a large amount o water, as is the case
generally with methods such as micellar-polymer flooding
techniques, the separation of the produced oil and water
mixture into two phases is generally accomplished by the
addition of demulsifying agents~ These vary in effective-
ness with various crude mineral oils and with the type of
surfactant utilized to reduce oil-water interfacial tension
in recovering the oil by tertiary methods. As demulsifying
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agents, alkyl sulfates and alkyl aryl sulfonates as well as
petroleum sulfonates in the form of amine salts already have
been proposed. Also, the addition products of ethylene
oxide with active hydrogen compounds such as alkyl phenols,
fatty acids, fatty alcohols, and alkyl phenol aldehyde
resins have also been proposed. Despite the large number of
demulsifiers available on the market, it has not been
possible to obtain efficient recovery of the petroleum oil
contained in emulsion form in aqueous media from tertiary
oil recovery processes. The alkyl phenol aldehyde resin
alkoxylates as a class are more particularly described in
U.S. 2,49g,370 for use in a process for breaking petroleum
emulsions~
Summarv of the Invention
. _ ~ .
It has been found that petroleum emulsions of the
oil-in-water type obtained by tertiary petroleum oil
recovery methods, particularly micellar-polymer flooding
enhanced oil recovery techniques, can be effectively
separated into oil and water phases by subjecting the oil-
in-water emulsion obtained from a producing well to the
action of at least one first nonionic demulsifier selected
from the group consisting of the reaction product of
ethylene oxidP and at least one other lower alkylene oxide
with an alkyl phenol aldehyde resin and thereafter
separating and recovering a water phase and an oil phase.
Thereafter, the water phase is subjected to at least one
second nonionic demulsifier selected from the group
consisting o the reaction product of ethylene oxide with an
alkyl phenol aldehyde resin and thereafter the oil phase is
recovered therefrom.
Detailed Description of the Invention
The demulsifiers o the invention are suitable for
demulsifying oil-in-water emulsions generally, but are
particularly suitable for demulsifying those petroleum ~
sul~onate-derived oil-water-emulsions obtained by tertiary
recovery methods, particularly micellar-polymer flooding
methods of tertiary oil recovery. In the micellar-polymer
flooding process, it is common to proceed in three stages,
namely, preflush, micellar-flood (displacing fluid), and
mobility control ~polymer) flood and brine or water as
driving fluid.
The preflush is used to adjust the salini~y oE the
reservoir brine and cause precipitation and removal of
divalent ions from the brine which would otherwise cause
increased adsorption of surfactant onto the rock.
Sacrificial agents such as sodium tripolyphosphate, sodium
carbonate, nitrilotriacetic acid and pyridines are also
sometimes introduced into the well to Eurther reduce
surfactant adsorption and improve wetting of the reservoir
rock surfaces.
The micellar-flood is the primary active chemical
component utilized in micellar-polymer flooding processes~
Generally a petroleum sulfonate surfactant is utilized at a
concentration of about 2 to about 17 percent active
--3--
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ingredient in water in order to reduce oil~water interfacial
tension from roughly 35 to less than 0.01 dynes per centi-
meter. As interfacial tension is reduced in the well,
micelles (micro-emulsions) of oil and water are Eormed.
This allows the oil to be carried along in the surfactant-
water flood as a stable, single-phase, low-viscosity
medium. In addition to aqueous mixtures of petroleum
sulfonater the petroleum sulfonate can be utilized in the
well in combination with soluble oil rather than water as a
carrier.
The amount of petroleum sulfonate utilized in the
well is determined by the rate of dilution by the oil in the
brine of the well and adsorption on the well rock
surfaces. The petroleum sulfonates are anionic and there-
fore the negative:Ly charged hydrophilic end of the molecule
will be attracted to the positively charged sites on the
reservoir surfaceO The duration of flood and the quantity
of surfactant employed is a function of the pore volume
which is equal to the volume of all pores and fractures in a
reservoir which can be contacted by fluids. Usually the
petroleum sulfonate constitutes 0.1 to about 12% of the pore
volume at a 5 to about 11% by weight active petroleum
sulfonate concentration in water.
Flooding of the well is typically designed to be
at an injection rate of one foot per day through the
reservoir but the actual rate can be much less should
injection problems occur. In the well, the formation of
micelles ~micro-emulsions) by the contact of the petroleum
sulfonate with the oil can in itself increase the viscosity
of the mixture of petroleum sulfonate and water or oil
carrier enough to positively influence sweep efficiency.
However, it is occasionally necessary to enhance the
viscosity of the petroleum sulfonate and carrier mixture in
order to avoid by-passing of residual oil.
The petroleum sulfonates generally used in the
formation of microemulsions within the well in tertiary oil
recovery processes are selected from compounds having the
following general formulaD
R -o-(cnH2no)m~R2-so3x
R3
wherein Rl is a henzene, toluene or xylene monovalent
radical having a linear or branched alkyl substituent
containing from about 6 to about 24 carbon atoms; R2 is an
alkyl, cycloalkyl~ alkene or aryl radical containing up to
about 8 carbon atoms; R3 is a hydrogen atom, a hydroxyl
radical, or an aliphatic radical containing from 1 to about
8 carbon atoms; n has a value of 2 or 3; m generally has a
value of from 1 to about 20; and X is a cation selected from
ammonium and alkali metal ions.
Petroleum sulfonates have classically been
produced as by-products of white oil manufacture. They are
characterized as the oil-soluble, monosulfated "mahogany"
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sulfonates and, as the water-soluble, disulfonated "green
acid sulfonates". Typical mahogany sulfonates have a broad
equivalent-weight distribution. The equivalent weight for
sulfonates is the molecular weight divided by the number of
sulfonate groups present in the molecule. The water-
soluble, low equivalent weight compounds in these products
tend to solubilize the higher molecular weight, oil-soluble
compounds. The available range of average equivalent
weights (about 350 to 550) provides sufficient variety for
blending to obtain the optimum surfactant system. Recently,
replacements of the traditional mahogany sulfonates have
become available. Thus, petroleum sulfonates can be
produced as by-products of linear alkyl benzene manufacture
by reacting a suitable olefin with benzene and then
sulfonating. They can also be manufactured by treating a
petroleum product with SO3.
Generally, the petroleum sulfonates are utilized
in combination with co~surfactants and co-solvents. Co-
surfactants can be oxyalkylated linear or branched chain
alcohols, sulfated ethoxylated alcohols, ethoxylated alkyl
phenols, naphthylene sulfonates, ligno-sulfonates~ or tall
oil sulfonates. Useful co-solvents are alcohols having 3 to
about 8 carbon atoms such as isopropyl, isobutyl, amyl, and
hexyl alcohols. The co-solvents reduce the surface tension
of small drops of oil so they become more mobile through the
pores of the rock strata.
Sodium tripolyphosphate and other agents are oEten
advantageously used in conjunction with the petroleum
sulfonates as so-called "sacrificial agents" to tie up
multivalent ions 50 as to lower the adsorption of petroleum
sulfonate onto the rock and increase the tolerance of the
petroleum sulfonate to oil reservoir brines. An additional
advantage is the increase in reservoir pH which occurs upon
adding these agents to the reservoir. This effect is
important because generally alkaline conditions increase the
tertiary oil recovery efficiency of surfactant solutions.
Alternatively, sodium carbonate has also been utilized to
precipitate divalent ions within the well. In addition,
ligno-sulfonates are alternatively useful sacrificial
agents. These materials can be used to impart a negative
charge to rock surfaces, les~ening the loss of the anionic
petroleum sulfonates. Ligno-sulfonates also lower inter-
facial tension as well as reduce surfactant adsorption thus
increasing oil recovery.
Tertiary oil recovery methods often utilize a
mobility control (polymer) flood. Instead of the usual
brine or surface water, polymer thickened water can be used
as the driving fluid to move the petroleum sulfonate water
mixture toward the production well from the injection well
in which it is added. Usually, the drive Eluid is injected
following the injection of the micellar flood containing the
petroleum sulfonate surfactant. In polymer flooding, the
molecular weight of the polymer is generally tailored to the
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conditions of the reservoir. A high molecular weight
polymer will yield hiyh viscosities at low concentrations
but may cause excessive plugging in low permeabili~y
formations or may not be injectable readily enough for
economic development. Typically, in a medium specific
gravity crude reservior, about 1.5 times the pore volume of
polymer solution is injected. Polymers that are effective
water thickeners are acrylamide/acrylic a~id copolymers,
acrylamide/acrylic acid~vinyl terpolymers, polysaccharides,
polyethylene oxide, polycarboxymethyl cellulose, and
hydroxyethyl cellulose.
In addition to the effect of all the above
additives on the emulsion stability of the mixture of oil
and water recovered from the producing well in tertiary oil
recovery methods, the stability of the emulsion is also
affected by the formation of surfactants by the various
alkaline materials added in the injection well upon reaction
with the acids normally present in the petroleum oil
reservolr .
The alkoxylated alkyl phenol aldehyde demulsifiers
and the ethoxylated alkyl phenol aldehyde demulsifiers
employed in accordance with the process of the present
invention are liquid substances which can be dispersed or
dissolved in water and certain organic solvents. They can
be added to the oil-in-water petroleum emulsion obtained
from the producing well either directly or in the form of
concentrated solutions or dispersions. Good results are
also obtained when the demulsifiers useful in the process of
the invention are dissolved in small amounts of organic
solvents such as, for example, toluene or methanol or high
aromatic naphtha and subsequently added directly to the
petroleum emulsion or further diluted with wa~er prior to
addition to the petroleum emulsion. Generally, the
surfactant demulsifiers are added to the oil-in-water
produced mixtures as about 10 to about 50 percent, prefer-
ably abou~ 20 to about 40 percent, most preferably about 25
to abou~ 30 percen~, all by weight~ active aqueous
solutions.
The alkoxylated phenol aldehyde resin demulsifiers
useful in the process of the present invention are reaction
products of ethylene oxide and at least one other lower
three to four carbon atom alkylene oxide such as propylene
oxide, butylene oxide and tetrahydrofuran with an alkyl
phenol aldehyde resin. The useful alkyl phenol aldehyde
resins are soluble in organic solvents and contain free
hydroxyl groups. These are in turn reacted with ethylene
oxide, or ethylene oxide and at least one other lower
alkylene oxide as recited above to prepare the demulsifiers
useful in the process of the invention.
Generally, alkyl phenols are required to prepare
the alkyl phenol aldehyde resins. These are preferably
monoalkyl phenols with straight chain or branched alkyl
groups having about 4 to about 18, preferably about 6 to
about 14, carbon atoms in the ortho or para position. These
g_
monoalkyl phenols are converted into resins preferably by
reaction with formaldehyde or substances which yield
formaldehyde under the conditions of the acid or alkaline
condensation reaction utilized. For instance, acetaldehyde
and higher aldehydes such as propionaldehyde or butyr-
aldehyde can also be used alone or in combination with other
of said aldehydes or with formaldehyde in the preparation of
these resins. The quantity of aldehyde utilized during
condensation generally amounts to approximately 0.5 to about
2~0 moles, preferably about 0.9 to about 1.1 moles, per mole
of phenol. The reaction takes place in a known manner in
the presence of an acid or an alkaline catalyst with or
without the addition oE inert solvents.
The alkyl phenol-formaldehyde resins are oxy-
ethylated or oxyalkylated using oxyalkylation or oxyethyla-
tion agents, the amount of which is employed depends partly
upon the length of the alkyl groups contained in the
starting alkyl phenol aldehyde resin. Generally, about 2 to
about 20 moles, preferably about 4 to about 12 moles, and
most preferably about 4 to about 10 moles, of ethylene oxide
or a combination of ethylene oxide and one other lower
alkylene oxide per single hydroxyl equivalent of the alkyl
phenol aldehyde resin are used so as to obtain a demulsifier
having a molecular weight of about 500 to about 25,000,
preferably about 1000 to about 15,000, and most preferably
about 1000 to about 5000. These contain about 10 percent to
about 90 percent, preferably about 20 to about 80 percent,
--10--
by weight of ethylene oxide residue or mixed alkylene oxide
residues based upon the total weight of the demulsifier.
A preferred de~ulsifier is a block copolymer
prepared by first oxypropylating the reaction product of an
alkyl phenol aldehyde such as the reaction product of nonyl
phenol and formaldehyde to add about 4 to about 12 moles of
the residue of propylene oxide per hydroxyl equivalent of
said reaction product and second oxyethylating said oxy-
propylated reaction product to add about 4 to about 12 moles
of ethylene oxide residue per hydroxyl equivalent.
Both block and heteric polymerizates of ethylene
oxide and one other lower alkylene oxide as well as
ethoxylates of said alkyl phenol aldehyde resin are useful
demulsifiers. Methods for the preparation of these demulsi-
fiers are generally described in U.S. 2,499,370 .
The following examples illustrate the various
aspects of the process of the invention. Where not other-
wise specified throughout this specification and claims,
temperatures are given in degrees centigrade and parts,
percentages, and proportions are by weight.
Example 1
Utilizing a crude petroleum-water ~oil-in-water)
mixture obtained by tertiary oil recovery means at the Gary
Energy Micellar Flood Project in the Belle Creek field,
Belle Creek, Montana, the process of the invention was
evaluated by bottle testing.
Normal production data is as follows for the well.
Volume of produced fluid 2000 barrels per day
Volume of produced oil 240 barrels per day
Volume of produced water 1760 barrels per day
The bottle testing procedure was as follows:
utilizing a sample size of 800 cc and a demulsifier solution
active concentration of 10 percent by weight, 2.4 cc of a
first demulsifier under test was injected into the 800 cc
sample of produced oil-in-water emulsion fluid. The sample
was shaken 100 times and the oil was allowed to separate
from an aqueous layer. The oil phase was pippetted off and
the remaining produced water was treated by injecting 0.8 cc
of a second 10 percent by weight demulsifier solution under
test and shaken 100 times. The oil phase produced was
removed and the amount of oil remaining in the water
determined.
The demulsifiers utilized are described as
follows:
Demulsifer A is a block copolymer of a nonylphenol
formaldehyde reaction product (resin) containing 4O3 moles
of propylene oxide per phenol (hydroxyl) equivalent of said
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nonylphenol formaldehyde reaction product and 5.7 moles of
ethylene oxide per phenol equivalent of the nonylphenol
formaldehyde resin. The block copolymer is first oxy-
propylated and then oxyethylated in the preparation
thereof.
Demulsifier B is an ethoxylated nonylphenol
formaldehyde resin containing 7.8 moles of ethylene oxide
residue per phenol equivalent of the nonylphenol
formaldehyde resin. Both the nonylphenol formaldehyde resin
and the alkoxylated or ethoxylated derivatives thereof are
produced by known processes using an acid or a basic
catalyst.
The use of a 10 percent by weight aqueous
solutions of these demulsifiers in accordance with the test
procedure described above resulted in 2000 parts per million
of oil remaining in the aqueous phase subsequent to the
addition and shaking of the sample with Demulsifier A
included therein and 40 parts per million of oil remaining
in the aqueous phase subsequent to the addition of
Demulsifier B and the shaking of the sample prior to
evaluation.
Example 2
(Comparative axample forming no part of this invention)
Example 1 was repeated utilizing the same
demulsifiers ~ut reversing the order in which they are used,
namaly, Demulsifier B was utilized first in the amount oE
2.4 cc and Demulsifier A was utilizad second in the amount
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of 0.8 cc of the 10 percent by weight aqueous solutions
thereof. The amount of oil remaining in the aqueous phase
was considerably higher in each stage oE the testing
indicating inferior results by reversing the order of use of
the demulsifier compositions.
Example 3
(Control sample forming no part of this invention~
The procedure of Example 1 was modified so that a
mixture of Demulsifier A and B were utilized in the amount
of 2.4 cc of Demulsifier A and 0.8 cc of Demulsifier B. The
mixture was added to 800 cc of the oil-in-water emuls.ion
produced fluid utilized in Examples 1 and 20 After shaking
the sample includinq the combination of demulsifiers for 100
times, an oil phase and a water phase were allowed to form
and the oil phase was pippetted off. The remaining produced
water phase was found to have substantially greater oil
content than that obtained after the process of Example 1.
While this invention has been described with
reference to certain specific embodiments, it will be
recognized by those skilled in this art that many variations
are possible without departing from the scope and spirit of
the invention and it will be understood that it is intended
to cover all changes and modifications oE the invention
disclosed herein or the purposes of illustration which do
not constitute departures from the spirit and scope o the
invention.
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