Canadian Patents Database / Patent 1223791 Summary

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(12) Patent: (11) CA 1223791
(21) Application Number: 435231
(54) English Title: METHOD OF BREAKING A WATER-IN-OIL EMULSION
(54) French Title: METHODE DE RUPTURE D'UNE EMULSION D'EAU ET D'HUILE
(52) Canadian Patent Classification (CPC):
  • 134/54
  • 204/99.07
(51) International Patent Classification (IPC):
  • C10G 33/00 (2006.01)
  • C10G 33/04 (2006.01)
  • C10G 33/06 (2006.01)
(72) Inventors :
  • PARKER, RICHARD J. (Canada)
  • LAKSHMANAN, VAIKUNTAM I. (Canada)
  • RANGANATHAN, RAMASWAMI (Canada)
  • LAST, ANTHONY J. (Canada)
(73) Owners :
  • SASKATCHEWAN OIL AND GAS CORPORATION (Not Available)
(71) Applicants :
(74) Agent: KIRBY EADES GALE BAKER
(74) Associate agent: KIRBY EADES GALE BAKER
(45) Issued: 1987-07-07
(22) Filed Date: 1983-08-24
(30) Availability of licence: N/A
(30) Language of filing: English

English Abstract



-1-
Abstract:
A method is described for breaking a water-in-crude
oil emulsion. A crude oil feedstock is tangentially
injected into the upper portion of a vortex chamber
operating on the vortex principle with the emulsion
rotating within the chamber and the velocity of the
emulsion increasing toward the center of the vortex
whereby concentric layers of emulsion having different
tangential velocities apply shear stresses to the dis-
persed water in the crude oil causing the interfacial
film between the water and the oil to rupture. This
enables chemical demulsifiers, added prior to the vortex
operation, to act more quickly and efficiently. There-
after, the dewatering of the crude oil is easily
accomplished by usual methods.


Note: Claims are shown in the official language in which they were submitted.




Claims:

1. A method for breaking a water-in-crude oil emulsion
which comprises adding a demulsifier thereto and injecting
the emulsion with demulsifier into at least one tangential
inlet of a radially symmetrical vortex chamber operating
on the vortex principle with the emulsion rotating within
the chamber along a spiral path toward the central axis and
the velocity of the emulsion increasing toward the center
of the vortex whereby concentric layers of emulsion having
different tangential velocities apply shear stresses to the
dispersed water in the crude oil sufficient to disrupt the
interfacial film between the water and the oil but not
enough to materially affect the water particle size in the
oil and discharging the product obtained through at least
one discharge nozzle at the central axis of the vortex
chamber.
2. The method according to claim 1 wherein the emulsion
enters the vortex chamber at a pressure of less than 5
p.s.i.
3. The method according to claim 1 wherein a hydrocarbon
solvent is added to the crude oil feedstock to reduce the
viscosity and density of the oil phase.
4. The method according to claim 1 wherein water is add-
ed either as a solvent for the demulsifier or to provide
coalescing sites for the smaller droplets inherently pre-
sent in the emulsion or to remove dissolved or suspended
inorganic salts from the emulsion.
5. The method according to claim 1, 2 or 3, wherein the
product from the vortex chamber is dewatered in the pre
sence of an electrostatic precipitator.


-9-

Note: Descriptions are shown in the official language in which they were submitted.

379-~

-- 1 --




Method of breakinq a water-in-oil emulsion

This invention relates to a method of breaking a
water in-crude oil emulsion.
During the production of crude oil, water is ~requent]y
found entrained in the oil as a water-in-oll emulsion.
This water is dispersed as ~ine droplets which do not
readily separate from the oil. The crude oll must, there~
fore, be subjected to one or more of several treating
processes to remove the water.- These processes may
include the addition of chemical demulsifiers, diluents,
heat, centrifugation and electrostatic precipitation 7
rhe water droplets in a crude oil emulsion, being
heavier than the oil, should sink through the oil to form
a separate coherent phase. The rate of separation of the
water from the oil is dependent on the size of the drop-
lets, the viscosity of the oil phase, the density differ-
ence between the oil and water phases and the strength of
any applied force, e.g. gravitational, centrifugal or
electrical. The viscosity of the oil and the density
difference are both fixed at a constant temperature. The
only parameter which can be adjusted to increase the rate
of separation is the size of the water droplets. Typical
water droplets in a water-in-oil emulsion are in the range
of 1-5 ~m in diameter. Collisions between individual
droplets of water should promote coalescence into larger
droplets which subsequently separate more rapidly. This
coalescence is often prevented by the presence of a
~, , .

~2~3~9~
--2--

stabilizing film at the interface between the water droplets
and the crude oil. This film may be naturally occuring sur-
face active agents from the oil or fine solids produced from
the underground formation along with the oil and water.
It is common practice to add chemical demulsifiers to the
emulsion to displace or disrupt the interfacial film. Once
the film has been displaced, coalescence of water droplets
~an more readily take place and larger, faster separating
drops are formed. Electrical fields may also be used to dis-
rupt the interfacial film. The water droplets become ellip-
tical in shape when subjected to high electrical charge. In
this manner, the interfacial film is stretched and weakened
and the energy barrier to coalescence is reduced.
Mechanical rupturing of the film is also known. The use
of a hydrocyclone for this purpose is described in Snavely,
U.S. Patent 3,489,680. In this system, the emulsion is sub-
jected to shear forces which rupture the film prior to con-
tacting the water droplets with a coalescing membrane.
Another technique of disrupting the interfacial film is
the use of a hydroshear as described in Peczeli et al, U.S.
Patent 4,142,806. The high shear forces of this technique
lead to disruption of the water droplets and so a finer
emulsion. This becomes more difficult to separate.
It will, of course, be appreciated that crude oil is a
very difficult material to dewater and it is the object of
the present invention to provide a low shear technique to
disrupt the interfacial film in crude oil emulsions.
Thus, the present invention in its broadest sense re-
lates to a method of breaking a water-in-crude oil emulsion
which comprises tangentially injecting a crude oil feedstock
containing water together with a demulsifier into at least
one tangential inlet of a radially symmetrical (cylindrical)
vortex chamber operating on the vortex principle with the
emulsion rotating within the chamber along a spiral path
toward the central axis and ~he velocity of the emulsion

37~

--3--

increasing toward the center of the vortex whereby concen-
tric layers of emulsion having different tangential velo-
cities apply low shear stresses to the dispersed water in
the crude oil, causing the interfacial film between the
wa~er and oil to rupture. In this method, the shear
stresses are just sufficient to disrupt the interfacial
film but not enough to materially affect the water parti-
cle sizes in the oil. The product obtained is discharged
through at least one discharge nozzle at the central axis
of the vortex chamber. Therafter the dewatering of the
crude oil is easily carried out by known methods.
The vortex operates at low pressure, e.g. less than 5
p.s.i., and allows the demulsifiec to be distributed where
the interfacial film is being disrupted and thereby act
more quickly and efficiently so that either electrical or
centrifugal methods can be used to separate the oil. The
demulsifier used can be any of a variety of known chemical
demulsifiers.
It is advantageous to add a hydrocarbon solvent to the
crude oil feedstock to reduce the viscosity and density of
the oil phase prior to the vortex stage. In some instances
heat alone can be used to lower the viscosity with the same
result.
It may also be desirable to add water either as a sol-
vent for the demulsifier or to provide coalescing sites forthe smaller droplets inherently present in the emulsion.
Certain preferred embodiments of the present invention
are illustrated by the attached drawings in which:
Figure 1 is an isometric view of a vortex chamber in
partial section;
Figure 2 is a plan view in section showing the flow
paths;
Figure 3 is an elevational view in section showing
the flow pattern; and
Figure 4 is a plan viewing in section of a double
discharge vortex chamber.

7~
-- 4 --

The vortex chamber is generally shown in Figures 1 to
3 and contains a main body portion 10, an axial discharge
no~zle 11 and a tangential inlet tube 13. The oil emulsion
enters tangentially through tube 13 under a pressure of
less than 5 p.s.i. and rotates within the chamber 10. It
is gradually forced toward ~he center as shown in Figures
2 and 3 and the velocity of the liquid increases as it
moves toward the center of the vortex. This forms what are
essentially concentric layers of liquid 14 having different
tangential velocities and these differing velocities apply
shear stresses to the dispersed water in the crude oil
emulsion. During this action, the interfacial film between
the water and the oil is ruptured and the water droplets
can coalesce or fragment depending on the shear stresses
and the interfacial tension between the oil and the water.
The product is removed in this condition through dis-
charge nozzle 11 and complete separation of the wa~er from
the oil is carried out by usual techniques which are not
illustrated.
According to another feature as shown in Figure 4, the
chamber 10 may be provided with two discharge nozzles 11
and lla to increase the capacity.
Certain preferred embodiments of this invention are
illustrated by the following examples.

EXAMPLE 1
A water-in-crude oil emulsion was precondition~d by
the addition of 35% toluene as a diluent and Natco~L-620
as a chemical demulsifier.
This feedstock was then split into three samples, the
first sample being retained for ordinary dewatering, the
second sample being passed through a vortex of the type
described above and the third sample being subjected to
mechanical mixing prior to dewatering. During the vortex
stage, some four percent of water was added.

-- 5 --

The ease of separation of water from the three
emulsions was evaluated using a bench scale electrostatic
precipitator. The time necessary for the current passing
through the oil to drop to zero was measured, i.e. the
peak breakdown time. It had previously been established
that if this time was less than two minutes on the bench
scale tests, the process would be applicable to full scale
field operations. This would provide separated crude oil
having pipeline quality (less than 0.5% BSW).
The test conditions and results are set out in Table I
below:

Table 1

Sample Volume 200 ml
Demulsifier Natc ~ L-620
Diluent Toluene 35%
Temperature 40C
Vortex time 4 minutes
Added water 4~
Peak Breakdown Time No mixing 1.50 minutes
vortex 0.63 minutes
electric mixer 0.88 minutes

From the above table, it will be seen that the vortex
provided the lowest measured time.

EXAMPLE 2
Example 1 above was repeated precisely except that
only 20% toluene was utilized as diluent. The processing
conditions and results are set out in Table 2 below:

~2~3~
-- 6

Table 2

Sample Volume 200 ml
Demulsifier Natc ~ L-620
Diluent Toluene 20%
Temperature 40C
Vortex time 4 minutes
Added water 4%
Peak Breakdown Time No mixing 5.13 minutes
Vortex 1.69 minutes
Electric mixer No result

It will be seen from the above table that the vortex
provided by Ear the shortest peak breakdown time and this
also showed that when the toluene diluent is dropped to
20%, water could not be removed within two minutes unless
the crude oil emulsion had been subjected to the vortex
treatment.

EXAMPLE 3

Using the same feedstock as in Examples 1 and 2
above, a further dewatering was carried out, utilizing as
demulsifier 1600 ppm of Witc ~ DRC-164. Three different
tests were carried out using different amounts of toluene
as diluent, namely 5%, 10% and 20~. The process conditions
and the results obtained are shown in Table 3 below:

~37~3~


Table 3

Sample Volume 200 ml
Demulsifier Witc ~ DRC-164
Concentration 1600 ppm
Tempera~ure 70C
Vortex time 4 minutes
% Diluent Peak Breakdown Residual Water
(Toluene) Time (minutes) (~)
0.25 0.05
1.63 0.31
2.88 1.50

It will be seen that the addition of toluene reduced
the peak breakdown time and cut down the residual water
left in the oil phase. Both the 20% and 10~ toluene
concentrations gave pipeline quality of oil (<0.5~ water)
within the two minute time limit.

EXAMPLE 4

The procedure of Example 3 was repeated using 10~
toluene as diluent and varying amounts of Witc ~ DRC-164
demulsifier. The amount of demulsifier ranged from 300 to
1,000 ppm. The process conditions and results obtained
are set out in Table 4 below:

37~
-- 8 --

Table 4

Sample Volume 200 ml
Demulsifier Witc ~ DRC-164
Temperature 70C
Vortex time 4 minutes
Diluent Toluene 10~

Demulsifier Peak Breakdown Residual Water
Concentration (ppm) Time (minutes) (%)
1000 2.44 0.36
900 1.69 n . 32
700 1.~3 0.15
500 1.63 0.15
400 3.0 0~55
300 2.75 Q.55

From the above results it will be seen that the
concentration of the demulsifier altered both the peak
breakdown time and the residual water. Under the
conditions of this example, the optimum demulsifier
concentration was 700 ppm which gave the minimum time
of 1.43 minutes and least residual water.

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Admin Status

Title Date
Forecasted Issue Date 1987-07-07
(22) Filed 1983-08-24
(45) Issued 1987-07-07
Expired 2004-07-07

Abandonment History

There is no abandonment history.

Payment History

Fee Type Anniversary Year Due Date Amount Paid Paid Date
Filing $0.00 1983-08-24
Current owners on record shown in alphabetical order.
Current Owners on Record
SASKATCHEWAN OIL AND GAS CORPORATION
Past owners on record shown in alphabetical order.
Past Owners on Record
None
Past Owners that do not appear in the "Owners on Record" listing will appear in other documentation within the application.

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Drawings 1993-08-04 1 30
Claims 1993-08-04 1 37
Abstract 1993-08-04 1 20
Cover Page 1993-08-04 1 17
Description 1993-08-04 8 263