Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to an apparatus and method
for treating an oil field emulsion, and in particular for
separating water from oil containad in an oil and water ~ `
emulsion which may contain sand and gas.
The treating of oil field emulsions is presently
performed in vertical or horizontal treaters. The treaters in
question are intended to process field production fluids
containing up to 30% water in the form of free water and
~` ~emulsified water. A common conventional apparatus for
treating such emulsions include vertical treaters which
utilize heat combined with chemical additives for separating
water from oil and water. Vertical treaters are primarily~ ~ `
intended for use in low volume situations, and perform at
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pressures from atmospheric to 50 psi in standard systems and
up to 100 psi or higher in special systems. When using
vertical emulsion treaters, the emulsions are broken using
heat and baffle trays containing a filter medium in which
large water droplets are formed. The water, being heavier
than oil settles to the bottom of the treater and the oil
rises to the top.
A second type of treater, which is the type proposed
in this application is a so-called horizontal style treater,~-
i.e. a treater which is elongated horizontally. Produced
fluids enter the treater above a firetube, and flow downwardly
for distribution beneath the firetube. Liberated gases pass
through a gas equalizer into a heating compartment. Oil and
emulsion flow upwardly around the firetube, while free water
falls to the bottom of the vessel for discharge.
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Examples of horizontal treating apparatuses are
described in Canadian Patents Nos. 1,146,901, issued to H.R.
Bull on May 24, 1983; 1,296,263, issued to G.G. Aymong on
February 25, 1992 and 1,314,490, issued to M. McCants on March
16, 1993, and U.S. Patents Nos. 4,233,154, issued to C.L. ~
Presley on November 11, 1980; 4,722,800, issued to G.G. Aymong ~ `
on February 2, 1988; 4,824,579, issued to A.L. George on April
25, 1989 and 4,995,495, issued to S.~. Krynski on February 26, ~:
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1991.
Many conventional horizontal treaters are somewhat
complicated and expensive to fabricate. Moreover,
conventional treaters often require large water handling
vessels and equipment such as free water knockouts, filtration
systems and atmospheric settling tanks. Perhaps of even
greater significance is the fact that conventional treaters
are designed to operate at low pressures.
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An object of the present invention is to overcome
the disadvantages of existing apparatuses by providing a
treater which can operate in the pressure range of above 40,
preferably 75 to 200 psi, and which does not rely on large
water handling ves6els or auxiliary equipment such as free
water knockouts.
Another object of the invention is to provide a
treater~ which being adapted to operate at high pressures,
allows a relatively large volume of fluid to be processed in a
small vessel.
According to one aspect, the present invention
relates to an apparatus for separating oil from water
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comprising elongated horizontal casing means; partition means
dividing said casing means longitudinally into a heating
chamber and a coalescing chamber; heater means extending into
said heating chamber for heating an oil and water emulsion in ;.
said heating chamber to facilitate separation of the oil and
water; inlet mean6 at an inlet end of said casing means for .
introducing an oil and water emulsion into said heating .:
chamberj whereby a water stream is established in the bottom.~.
of said casing meansl with a gas stream at the top of said i-
casing means, and an oil stream between said water and gas
streams in said heating chamber; weir means attached to said
partition means for receiving oil separating from water in
said heating chamber; distributor means extending from said
partition means into said coalescing chamber for receiving oil
overflowing said weir means and distributing the oil in the
coalescing chamber near the bottom thereof; elongated
horizontal coalescing bed means completely spanning the
coalescing chamber, whereby the entire oil stream passes
through said bed, said bed means including a plurality of
spherss for promoting separation of residual water from the
oil stream in said coalescing chamber; water outlet means at
an outlet end of said casing means opposite said inlet end;
oil outlet means in said outlet end; and gas outlet means in
the top end of the casing means proximate said outlet end.
According to a second aspect, the invention relates
to a method of separating water from an emulsion containing
oil, water and gas comprising the steps of introducing the
emulsion into a trough in the top of a heater chamber in a
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closed tank under a pressure of 75 to 200 psi, whereby gas is
separated from the emulsion to form a gas stream in the top of
the tank; passing the emulsion downwardly through a downcomer ~-
tube to the bottom of the tank heater chamber; heating the
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emulsion in the heater chamber to promote the separation of
water from the oil creating a water stream in the bottom of
the heater chamber and an oil stream above the water stream;
passing the gas stream over a vertical partition in the tank
to a gas outlet for discharge from the tank; passing the water
stream beneath the partition to a water outlet for discharge
from the tank; passing the oil stream over a weir in the
heater chamber of the tank beneath the top of said partition
and through said partition proximate the bottom thereof into a
coalescing chamber; distributing the oil stream over the water
stream in said coalescing chamber; passing said oil layer
upwardly throuyh a coalescing bed of plastic spheres extending
the length and width of said coalescing chamber; and
overflowing the oil stream above said coalescing bed into a
discharge box for discharging the oil stream from the tank.
The invention will be described in greater detail
with reference to the accompanying drawings, which illustrate
a preferred embodiment of the invention, and wherein:
Figure 1 is a schematic flow diagram of the system
used in carrying out the process of the present invention;
Figure 2 is a schematic, longitudinal sectional view
of a treater used in the system of Fig. 1;
Figure 3 is a cross section taken generally along
line III-III of Fig. 2;
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. - .......................................................................... . Figure 4 is a side view of an inlet for introducing
an oil and water emulsion into the treater of Fig. 2;
Figure 5 is a side view of an inlet trough for use
in the treater of Fig. 2;
Figure 6 is an end view of the inlet trough as seen
from the right of Fig. 5;
Figure 7 is an end view of the treater as seen from
the left of Fig 2;
Figure 8 is a cross section of the lefthand end of
the treater taken generally along line VIII-VIII of Fig. 7;
Figure 9 is a plan view of desand or flush headers
used to clear solids from fîretubes and the bottom of the
treater of Fig. 2;
Figure 10 is a schematic side view of one of the
flush headers of Fig. 9;
Figure 11 is a cross section taken along line XI-XI
of Fig. 10;
Figure 12 is a side view of another of the headers
o~
Fig. 9;
Figure 13 is a cross section taken along line
XIII-XIII of Fig. 12;
Figure 14 is a plan view of a desand baffle used in
the treater of Fig. 2;
Figure 15 is a side view of the baffle of Fig. 14;
Figure 16 is a cross section taken generally along
line XVI-XVI of Fig. 15;
Figure 17 is a bottom view of a portion of the
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baffle of Figs. 14 and 15;
Figure 18 is a perspective view of a weir and
partition used in the treater of Fig. 2;
Figure 19 is a plan view of oil distributors used in
the treater of Fig. 2;
Figure 20 is a side view of one of the oil
distributors of Fig. 19;
Figure 21 is a cross section taken generally along
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line XXI-XXI of Fig. 20;
; 10 Figure 22 is a perspective view of a length of the
distributor of Fig. 20;
Figure 23 is a partly sectioned, plan view of grates ~-
used in the treater of Fig. 2;
Figure 24 is a schematic side view of the grates of
Figs. 23;
Figure 25 is a cross section taken generally along
line XXV-XXV of Fig. 2;
Figure 26 is a cross section taken generally along
line XXVI-XXVI of Fig. 24; ; ~;
Figure 27 is a longitudinal sectional view of a gas :
outlet used in the treater of Fig. 1; ;~
Figure 28 is a cross section of a mounting frame
taken generally along line XXVIII-XXVIII of Fig. 27; and
Figure 29 is a cros~ section of a second mounting ;
frame used in the gas outlet taken generally along line
XXIX-XXIX of Fig. 27
With reference to Fig. 1, the system employed to
cerry out the procesR o the present invention includes a
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treater generally indicated at 1 for receiving an emulsion of
oil and water which could also contain gas and solids. The
emulsion is introduced into the treater 1 via an inlet 2. ~he
treater is used to separate the constituents of the emulsion
5 which are discharged separately from the treater. The gas is
discharged from the top of the treater 1 via a line 3
containing a valve 4. Oil is discharged through an line 5
from one end of the treater 1 and a valve 6. Solids are
discharged from the treater 1 via lines 7 and 8, respectively,
valves 9 and 10 in such lines, and a drain line 11. The water
separated from the emulsion in the treater 1 contains residual
oil. In order to remove water the residual oil, the latter is
fed via line 12 and valves 13 and 14 to a hydrocyclone 15.
The water can bypass the hydrocyclone and be discharged from
the system via valve 16 and line 17. The residual oil
separated from the water in the hydrocyclone 15 is discharged
via line 18. The water is discharged via line 19 to the line
17, and out of the system through valve 20.
With reference to Figs. 2 and 3, the treater 1 is an
elongated cylindrical tank 23, which is divided longitudinally
into a preliminary treatment or heating section 24 and a
coalesclng section 25 by a vertical partition 26. An emulsion
of oil and water containing gas and solids is introduced into
the tank 23 via an inlet 28. As best shown in Fig. 4, the
inlet 28 is in the form of a pipe 29 with a flange 30 on top ;
thereof. A semi-cylindrical extension 31 is provided on the
bottom end of the pipe 29, and a disc-shaped deflector 33 is
provided on the bottom end of the exten:ion 31. The deflector
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33 is perpendicular to the direction of flow of the emulsion
through the pipe 29. In effect, the deflector sprays the
emulsion entering~the tank 23 into an inlet trough 34.
As best shown in Figs. 5 and 6, the inlet trough 34
is generally triangular in cross section, including downwardly
converging side walls 35 with flanges 36 extending outwardly
from the top edges thereof. Ga~i separates from the mixture
entering the trough 34, and forms a gas stream 39 (Fig. 2) at
the top of the tank 23. The emulsion flows downwardly from
the end of the trough 34 opposite the inlet 28 through a
downcomer pipe in the form of an inclined, square cross
section tube 40, which is connected to the body of the trough
by flanges 41 and 42. The tube 40 extends downwardly between
a pair of generally U-shaped tubular firetubes or heaters 44
for discharging the emulsion through the open bottom end 45
towards the bottom of the tank. Due to gravity emulsion
discharged from the tube 40 forms a continuous water layer 47
and an oil layer 48. Of course, the water layer 47 contains
residual oil, and the oil layer contains some water.
Each of the heaters 44 (Fig. 8) includes an
elongated tubular body 50 extending into the tank 23 through a
convex head assembly 51. The head assembly 51 includes a
convex shoulder 53 tapering inwardly through a concave radius
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to a narrow neck 54. An annular flange 55 i6 mounted on the
neck 54, and a thick plate 56 is connected to the flange 55 by
bolts or studs 58. The plate 56 is used to support the
firetubes 44, which are cantilevered inwardly from the plate.
Flanges 59 are provided on the outer ends of the arms of the
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firetube 44. The bottom flanges 59 are used to connect the
firetubes 44 to burners (nok shown), and the top flanges 59
connect the firetubes to flues (not shown) for discharging the
products of combustion. '
Any solids contained in the emulsion discharged from
the downcomer 40 begin to settle to the bottom of the tank 23,
or remain suspended between the oil and water layers. As
mentioned above, the solids are discharged through lines 7 and
8. The lines 7 are connected to desand outlets 61 in the
bottom of the tank 23. Desanding of the bottom portion of the
tank 23 iB expedited by flushing headers 63 and 64 containing
a plurality of nozzles 66 (Figs. 9 to 11). Suitable nozzles
66 are available under the trade-mark "Veejet". The headers
63 and 64 are similar, including inlet tube 67 in the bottom
of the tank 23, and U-shaped pipes 68. The pipes 63 and 64
are suspended above the bottom of the tank 23 from cross bars ',
70 using U-brackets 71. The flushing headexs 65 which are ~;
located outside o~ the firetubes 44 are attached to a pair of `,'';'
inlet pipes 72 connected by vertical extensions 73 and T- ~, "
joints 74. The headers 76 and 77 also contain a plurality of '
nozzles 66. The headers 65 are supported by posts 78 and U- ''~
brackets 79. By spraying water through nozzles 66 in the in
the headers 63, 64 and 65, solids deposited on the tank bottom
and on,the heater surfaces are moved downwardly. ' ;~
The solids pass beneath baffles 81, which are spaced
from the bottom of the tank 23 by feet in the form of small ~ ''
crossbars 82. The baffle 81 inclucles a generally triangular '~ ,,
casing 83, which is maintained in position by posts 85 (Fig.
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16) welded to the bottom of the tank. The top ends of the
posts 85 are threaded for receiving nuts 86.
The mainly oil portion of the emulsion rises in the
heater section 24 of the tank 23 and passes over a weir 88
(Fig. 18~ which is mounted on the partition 26. The partition
26 is in the form of a circular plate 89, with segments
- removed from the top and bottom thereof, so that the gas
stream 39 can pass over the top of the partition, and the
water stream 47 can pass beneath the partition. The weir 88,
which is generally L-shaped in cross section, including a
vertical arm 90, which is similar in shape to the partition
plate 89, but shorter tha~ such plate, and a rectangular
horizontal arm or baseplate g2 extending between the plates 89 ~ ; -
and 90 and the sides of the tank 23.
A pair of truncated, triangular openings 93 (Figs.
18 and 21) are provided near the bottom of the partition 26 -~
above the baseplate 92 for discharging oil from the heater ~;
section 24 to the coalescing section 25 of the tank. Oil
flowing through the openings 93 flows across the top of the ~;
water layer 47, and is distributed in the coalescing section
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25 by generally triangular distributors 95. As best shown in
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Fig. 22, each distributor 95 includes a generally triangular
body defined by inclined side walls 96, a horizontal top wall
97 and short vertical bottom ends 99 on the side walls 96. An
end wall (not shown) is provided on the outer free end of each
distributor 95. The distributors 95 are mounted on crossbars
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101 defined by angle irons extending across the tank 23. L- ; -
shaped brackets 102 connect the distributors 95 to the
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crossbars 101. A plurality of spaced apart holes 104 are
provided in each of the side walls 96 near the top end thereof
for discharging oil into the coalescing section.
Oil rising in the coalescing section 25 must pass
through a coalescer bed defined by a plurality of beads 106.
The bead6 106 are for example plastic spheres which serve to
separate residual water from the oil. The beads 106 are
mounted between a pair of grates 107 and 108. The beads 106
entirely fill the space between the grates 107 and 108, except
at the discharge end, the centre of which is occupied by an
oil discharge box 110. The grates 107 and 108 are defined by ;
a plurality of longitudinally and transversely extending bars
111 and 112, respectively supported by a plurality of
transversely extending crossbars 114. The oil box 110 at the
outlet end of the coalescing section includes a bottom wall
116, side walls 117, and an inner end wall 119. A level
control 120 (Fig. 2) is used to control the level of the oil `~
in the box 110. Oil is discharged from the box 110 via an
outlet 121 to line 5 (Fig. 1). Water is discharged from the
water layer 47 through an outlet 122 to the line 12. Inlet
ducts 123 are provided in the discharge end of the tank 23 for ~`
receiving level controls (not shown).
With reference to Figs. 2 and 27 to 29, any gas
separating from the emulsion in the heating section 24 or from
25 the oil in the coalescer section 25 of the tank 23 is ~ ~ ~
discharged via a large diameter outlet 125 containing a ~ ~ `
demister pad 126. A suitable demister pad is available ~rom
Otto H. York Company, Inc. The outlet 125 includes a tubular
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casing 127 connected to a large diameter cover 128 containing
a small diameter flanged outlet pipe 130. The pad 126 is
suspended in the tube 127 by means of top and bottom frames
132 and 133, respectively. The top frame 132 is generally H-
shaped, including crossbars 134 extending between oppositesides of the tube 127, and a centre bar 135. The bottom frame
133 includes an outer ring 137 and a pair of crossbars 138 at
90 to each other. A rod 140 extends downwardly from the
centre of the top frame 132 through a sleeve 141 in the centre
of the bottom frame 133. Complimentary threads are provided
at the bottom end of the rod 140 and in the sleeve 141.
During operation, fluid enters the inlet 2 of the
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tank 1 and is distributed into the inlet trough 34. In the
trough 34 solution gas is liberated from the liquid phases,
and the liquid phases are directed through the downcomer tube
40 to a level below the heating elements defined by the
firetubes 44 and an established liquid interface level, i.e.
the interface between the water stream 47 and the oil stream
48. At this point, the fluid phases are coalesced and
20 separated by gravitational forces, fluid turbulence from ;~
additional solution gas breakout and the co-mingling between
liquid phases. An interface level between the water and the
oil streams is established by the bottom end of the weir 88.
The interface is established with the lighter fluid (oil)
assuming the upper layer and the heavier layer (mainly water)
being below the interface. The gas phase rises to form a gas
stream 39 at the top of the tank 1. The gas phase is
discharged through the outlat 125. The gas outlet flow is
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controlled by the gas back pressure valve 4 ( Fig . 1 ), which
maintains a back pressure on the process. The liquid phase or
stream passes beneath the partition 26 and i5 ultimately
discharged via outlet 123.
The oil stream rises in the heating or inlet chamber
24, passes over the weir 88 and through the openings in the
partition 26 into the coalescing chamber 25. Because the
coalescing bed extends the length and width of the chamber 25,
the oil stream is forced to pass through the plastic spheres ~ ;
106, which assist in promoting the separation of residual
water from the oil. When the oil level in the chamber 25 is
sufficiently high, the oil stream overflows the into discharge
box 110, and the oil is discharged from the tank through the
outlet 121.
The water discharged through the outlet 123 is fed
via line 12 and valves 13 and 14 to the hydrocyclone 15 where
additional oil is separated from the water stream. A suitable
hycrocyclone is the Krebs deoiler Model L2-M8 available from
Krebs Eng.ineers, Menlo Park, California. ;
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