FIELD OF THE INVENTION
[0001] The present invention relates to a method for downhole cyclone separation and, in
particular, a method that can be used for oil/water separation in producing oil wells.
BACKGROUND OF THE INVENTION
[0002] United States Patent number 5,296,153 teaches a method of reducing the amount of
formation water in oil recovered from an oil well through the insertion of a cyclone
separator downhole in an oil well producing a stream of mixed oil and water. In accordance
with the described method, a first outlet of the cyclone separator is connected to
a recovery conduit extending to surface. The recovery conduit conveys a recovery stream
of oil with a reduced water content to surface. A second outlet of the cyclone separator
is connected to a disposal conduit. The disposal conduit conveys a disposal stream
of mainly water to a disposal site, which is usually a downhole formation chosen to
be a disposal zone. The reference goes on to describe various pumping configurations
which, when used in combination with the cyclone separator, can further enhance recovery.
[0003] United States Patent 4,822,551 which issued to Pendergast in 1989 and United States
Patent 5,154,826 which issued to Pendergast et al in 1992 an apparatus for cyclone
separation that utilizes multiple cyclone separators. PCT Application WO 94/13930
filed by Read Process Engineering and published June 23, 1994 describes the use of
cyclone separators downhole in producing oil and gas wells.
[0004] When the production stream from the oil well has a high gas content, great care must
be taken in the selection of the pumping configuration. During downhole processing
through the cyclone separator and the pump, "gas breakout" inevitably occurs. Gas
breakout involves the release of entrained gases from the liquid being pumped. This
gas breakout can adversely affect the efficiency of the pumping configuration and
may also impact the operation and efficiency of the cyclone separator.
SUMMARY OF THE INVENTION
[0005] What is required is an improved method for downhole cyclone separation that is less
prone to problems associated with gas breakout.
[0006] According to the present invention there is provided a method of downhole cyclone
separation. This method include the following steps. Firstly, placing a cyclone separator
downhole in an oil well producing a mixed stream of oil, water and gas. The cyclone
separator includes a separation chamber wherein liquids of differing densities are
separated, at least one mixed liquids inlet through which liquids pass into the separation
chamber, a first outlet for liquids of a first density range to pass from the separation
chamber, and a second outlet for liquids of a second density range to pass from the
separation chamber. Secondly, connecting the first outlet to a recovery conduit extending
to surface. Thirdly, connecting the second outlet to a disposal conduit extending
to a selected disposal site. The method being characterized by the further step of,
fourthly, connecting the at least one mixed liquids inlet to pumping means and pumping
a mixed stream of oil, water and gas into the separation chamber of the cyclone separator.
The mixed stream is separated into a recovery stream of oil with a reduced water content
which flows out of the first outlet and along the recovery conduit to the surface
and a disposal stream of mainly water which flows out of the second outlet and along
the disposal conduit to the selected disposal site.
[0007] Gas breakout adversely affecting pumping operation occurs due to pressure drop and
agitation as the mixed stream passes through the separation chamber of the cyclone
separator. Placing pumping means upstream of the cyclone separator, as described above,
is a more effective pumping configuration. The pump, being upstream, is isolated from
whatever gas breakout may occur as the mixed stream passes through the separation
chamber and is separated into the recovery stream and the disposal stream. Pumping
fluids through the separator reduces gas breakout, as it increases the pressure of
fluids within the separator and forces the gas to remain in solution.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] These and other features of the invention will become more apparent from the following
description in which reference is made to the appended drawings, wherein:
[0009] FIGURE 1 is a schematic diagram of a first form of pumping configuration in accordance with
the described method.
[0010] FIGURE 2 is a schematic diagram of an enhanced form of pumping configuration in accordance
with the described method.
[0011] FIGURE 3 is a side elevation view in longitudinal section of an apparatus developed for use
with the described method.
[0012] FIGURE 4 is a schematic diagram of a pumping configuration involving the apparatus illustrated
in
FIGURE 3.
[0013] FIGURE 5 is a side elevation view in longitudinal section of a plurality of the apparatus
illustrated in
FIGURE 3 connected in series.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0014] A method of downhole cyclone oil/water separation will now be described with reference
to
FIGURES 1 through
5.
[0015] Referring to
FIGURE 1, the preferred method includes the following steps. Firstly, place a cyclone separator
12 downhole in an oil well 14 producing a mixed stream of oil, water and gas. Cyclone
separator 12 includes a separation chamber 16 wherein liquids of differing densities
are separated, a mixed liquids inlet 18 through which liquids pass into separation
chamber 16, a first outlet 20 for liquids of a first density range to pass from separation
chamber 16 and a second outlet 22 for liquids of a second density range to pass from
separation chamber 16. Secondly, connect first outlet 20 to a recovery conduit 24
extending to surface (not shown). Thirdly, connect second outlet 22 to a disposal
conduit 26 extending to a selected disposal site (not shown). Fourthly, connect mixed
liquids inlet 18 to a pump 28 and pump a mixed stream of oil, water and gas into separation
chamber 16 of cyclone separator 12. The mixed stream is separated in separation chamber
16 into a recovery stream of oil with a reduced water content which flows out of first
outlet 20 and along recovery conduit 24 to the surface and a disposal stream of mainly
water which flows out of second outlet 22 and along disposal conduit 26 to the selected
disposal site.
[0016] Referring to
FIGURE 2, an enhanced pumping configuration is disclosed in which a backpressure valve 30
is positioned on disposal conduit 26. The use of backpressure valve 30 ensures that
there is sufficient pressure maintained to get the disposal stream into an underground
disposal formation selected as a disposal site, while at the same time ensuring that
the pump and cyclone separator are both operating within their most efficient operating
ranges. It also enables a more accurate assessment to be made as to the amount of
fluid being pumped into the disposal site. There are other backpressure control means
that can be used such as a flow restriction orifice. Backpressure valve 30 is preferred
as it prevents a reversal of flow when pump 28 is turned off. In field installations
which include pumps adversely affected by a reverse flow when stopped, the flow reversing
the pump motor turns backward preventing the pump from being restarted. Referring
to
FIGURE 2, there is also provided a secondary pump 32 is positioned on the recovery conduit
24. Secondary pump 32 is intended to assist in conveying the recovery stream to the
surface. The problem of gas breakout, previously described, does not adversely affect
the operation of secondary pump 32 due to the fact that pump 28 provides sufficient
pressure to maintain the majority of the gas in solution.
[0017] An apparatus for downhole cyclone separation, generally identified by reference numeral
40, been especially developed for use with the described method. When apparatus 40
is used with the described method separation capacity and production flow rates can
be greatly increased. This apparatus will now be described with reference to
FIGURE 3. Apparatus 40 includes a multiple cyclone separator housing 42 having an interior
cavity 44, an mixed liquids inlet 46, a disposal stream outlet 48 and a recovery stream
outlet 50. Although single inlets and outlets are illustrated, it will be appreciated
that multiple inlets or outlets into housing 42 could be utilized depending upon the
installation environment. A plurality of cyclone separators 12 are disposed in interior
cavity 44 of multiple cyclone separator housing 42. As previously described, each
of cyclone separators 12 has a separation chamber 16 wherein liquids of differing
densities are separated, a mixed liquids inlet 18 through which liquids pass into
separation chamber 16, a first outlet 20 for liquids of a first density range to pass
from separation chamber 16, and a second outlet 22 for liquids of a second density
range to pass from separation chamber 16. Some means must be used for channelling
the various flow streams flowing into mixed liquids inlet 18 and out of first outlet
20 and second outlet 22. The channelling means illustrated in
FIGURE 3 is by way of conduits 52 and 54. It should be noted that only two conduit are required
as in the illustrated embodiment interior cavity 44 of multiple cyclone separator
housing 42 can serve as one of the channelling means. Conduit 52 has been connected
as an inlet conduit allowing liquids to pass from mixed liquids inlet 46 in multiple
cyclone separator housing 42 to mixed liquids inlets 18 of each of cyclone separators
12. Conduit 54 has been connected as an outlet conduit allowing liquids to pass from
first outlet 20 of each of cyclone separators 12 to recovery stream outlet 50 of multiple
cyclone separator housing 42. Second outlet 22 of each of cyclone separators 12 discharges
directly into interior cavity 44, so that interior cavity 44 serves to connect second
outlet 22 of each of cyclone separators 12 with disposal stream outlet 48.
[0018] When apparatus 40 is used with the described method the following steps are taken,
as illustrated in
FIGURE 4. Firstly, multiple cyclone separator housing 42 is placed downhole in an oil well
producing a mixed stream of oil, water and gas. Secondly, recovery stream outlet 50
of multiple cyclone separator housing 42 is connected to recovery conduit 24 extending
to surface. Thirdly, disposal stream outlet 48 of multiple cyclone separator housing
42 is connected to disposal conduit 26 extending to a selected disposal site. Fourthly,
a mixed stream of oil, water and gas is pumped by means of pump 28 into mixed liquids
inlet 46 of multiple cyclone separator housing 42. The mixed stream of oil, water
and gas is channelled by inlet conduit 50 to mixed liquid inlets 18 of each of cyclone
separators 12, whereupon the oil and water is separated in separation chamber 16 of
cyclone separators 12. A recovery stream of oil with a reduced water content passes
through first outlet 20 of each of cyclone separators 12 for channelling by outlet
conduit 54 to recovery stream outlet 50 in multiple cyclone separator housing 42 for
conveyance through recovery conduit 24 to the surface. A disposal stream of water
is discharged from second outlet 22 of each of cyclone separators 12 into interior
cavity 44 for channelling to disposal stream outlet 48 of multiple cyclone separator
housing 42 for disposal through disposal conduit 26 to the selected disposal site.
[0019] The use of apparatus 40 provides numerous advantages. The flow rate is increased.
The pressure drop across each of separators 12 is reduced, which reduces the power
requirements and reduces the chance of gas breakout downstream. Multiple cyclone separators
12 provide a redundancy, if any one cyclone separator ceases to function, the remaining
cyclone separators can continue to function.
[0020] A cyclone separator has a separation ratio that the percentage of the fluids flowing
through first outlet 20 bears to the entire volume of fluids flowing through separation
chamber 16. There is no minimum percentage. This means that in wells with an extremely
high water content, the majority of the fluids (ie. the water) can be left downhole.
There is however a maximum percentage of approximately 25 percent of the total volume
leaving via first outlet 20. At this maximum percentage approximately 75 percent of
the fluids are leaving via second outlet 22. This creates a problem with oil wells
having a low water content. There is a danger that a portion of the oil can be pumped
into the disposal zone along with the water. Referring to
FIGURE 5, in oil wells with a low water content, a plurality of apparatus 40 containing multiple
cyclone separators can be connected in series. In this way a sequential reduction
in the oil content can occur prior to pumping the disposal stream to the selected
disposal site.
[0021] It will be apparent to one skilled in the art that modifications may be made to the
illustrated embodiment without departing from the spirit and scope of the invention
as defined by the Claims.
1. A method for reducing the amount of water in an oil-and-water stream to be produced
from an oil well wherein the stream includes dissolved gas, comprising the steps of:
(a) providing a cyclone separator device sized to fit within the well bore for separating
the oil-and-water stream into a higher density stream and a lower density stream,
the separator device having an inlet, a first outlet for the lower density stream
and a second outlet for the higher density stream;
(b) providing a first pump for pumping fluids into the inlet of the separator device;
(c) connecting the first outlet of the separator device outlet to a lower density
fluid conduit for producing the lower density stream;
(d) connecting the second separator device outlet to a higher density fluid conduit
for conducting the higher density stream to an underground formation;
(e) placing the separator device, the first pump and the lower density fluid conduit
and the higher density fluid conduit in the well; and
(f) activating the pump so as to move the fluids through the separator device and
into the lower density and higher density fluid conduits without allowing gas breakout
to occur.
2. The method of claim 1, wherein the first pump is selected to provide sufficient pressure
in the oil-and-water stream passing through the pump to retain the majority of dissolved
gas in solution while the stream passes through the pump and the housing.
3. The method of claim 1 additionally comprising the step of providing a backpressure
control in the higher density fluid conduit.
4. The method of claim 3, wherein the backpressure control is a valve.
5. The method of claim 3, wherein the backpressure control is a orifice.
6. The method of claim 1 additionally comprising the step of providing reverse flow control
in the higher density conduit.
7. The method of claim 1 additionally comprising the step of providing a second pump
between the first outlet of the separator device and the lower density conduit for
assisting in movement of the lower density stream for production of the stream and
selecting and operating the first pump to retain the majority of dissolved gas in
solution thus without allowing gas breakout to occur while the stream passes through
the first pump, the separator device, and into the second pump.
1. Verfahren zum Verringern der Wassermenge in einem aus einer Erdölbohrung zu fördernden
Strom aus Öl und Wasser, wobei der Strom aufgelöstes Gas enthält, mit den Schritten:
(a) Bereitstellen einer in das Bohrloch passenden Zyklonabscheidevorrichtung zum Aufspalten
des Stroms aus Öl und Wasser in einen Strom höherer Dichte und einen Strom geringerer
Dichte, wobei die Abscheidevorrichtung einen Einlaß, einen ersten Auslaß für den Strom
geringerer Dichte und einen zweiten Auslaß für den Strom höherer Dichte hat;
(b) Bereitstellen einer ersten Pumpe zum Pumpen von Flüssigkeiten in den Einlaß der
Abscheidevorrichtung;
(c) Verbinden des ersten Auslasses der Abscheidevorrichtung mit einer Leitung für
eine Flüssigkeit geringerer Dichte, um den Strom geringerer Dichte zu erzeugen;
(d) Verbinden des zweiten Auslasses der Abscheidevorrichtung mit einer Leitung für
eine Flüssigkeit höherer Dichte, um den Strom höherer Dichte zu einer Untertageformation
zu leiten;
(e) Plazieren der Abscheidevorrichtung, der ersten Pumpe und der Leitung für die Flüssigkeit
geringerer Dichte und der Leitung für die Flüssigkeit höherer Dichte in das Bohrloch;
und
(f) Einschalten der Pumpe, um die Flüssigkeiten durch die Abscheidevorrichtung und
in die Leitungen für die Flüssigkeiten geringerer Dichte und höherer Dichte zu bewegen,
ohne das Auftreten eines Gasausbruches zu gestatten.
2. Verfahren nach Anspruch 1, bei dem die erste Pumpe so ausgewählt ist, daß sie genügend
Druck in dem durch die Pumpe gehenden Strom aus Öl und Wasser erzeugt, um den größten
Teil des gelösten Gases in Lösung zu halten, während der Strom durch die Pumpe und
das Gehäuse geht.
3. Verfahren nach Anspruch 1, zusätzlich mit dem Schritt, daß eine Gegendrucksteuerung
in der Leitung für die Flüssigkeit höherer Dichte bereitgestellt wird.
4. Verfahren nach Anspruch 3, bei dem die Gegegendrucksteuerung ein Ventil ist.
5. Verfahren nach Anspruch 3, bei dem die Gegendrucksteuerung eine Öffnung ist.
6. Verfahren nach Anspruch 1, zusätzlich mit dem Schritt, daß eine Gegenstromsteuerung
in der Leitung für die Flüssigkeit höherer Dichte bereitgestellt wird.
7. Verfahren nach Anspruch 1, zusätzlich mit dem Schritt, daß eine zweite Pumpe zwischen
dein ersten Auslaß der Abscheidevorrichtung und der Leitung für die Flüssigkeit geringerer
Dichte bereitgestellt wird, um den Strom geringerer Dichte bei der Bewegung zwecks
Erzeugung des Stromes zu unterstützen, und daß die erste Pumpe so ausgewählt und betrieben
wird, daß der größte Teil des gelösten Gases in Lösung gehalten wird, um somit das
Auftreten eines Gasausbruches nicht zu gestatten, während der Strom durch die erste
Pumpe, die Abscheidevorrichtung und in die zweite Pumpe geht.
1. Procédé de réduction de la quantité d'eau dans un flux de pétrole et d'eau devant
être produit à partir d'un puits de pétrole dans lequel le flux comprend du gaz dissous,
comprenant les étapes consistant à :
(a) prévoir un dispositif séparateur à cyclones dimensionné pour s'adapter à l'intérieur
du trou du puits afin de séparer le flux de pétrole et d'eau en un flux à densité
plus élevée et un flux à densité plus faible, le dispositif séparateur comportant
un orifice d'entrée, un premier orifice de sortie destiné au flux à densité plus faible,
et un second orifice de sortie destiné au flux à densité plus élevée,
(b) prévoir une première pompe destinée à pomper les fluides jusque dans l'orifice
d'entrée du dispositif séparateur,
(c) raccorder le premier orifice de sortie de la sortie du dispositif séparateur à
une conduite pour fluides à densité inférieure destinée à produire le flux à densité
inférieure,
(d) raccorder le second orifice de sortie du dispositif séparateur à une conduite
pour fluides à densité plus élevée destinée à conduire le flux à densité plus élevée
jusqu'à une formation souterraine,
(e) placer le dispositif séparateur, la première pompe, ainsi que la conduite pour
fluides à densité inférieure et la conduite pour fluides à densité plus élevée dans
le puits, et
(f) activer la pompe de manière à déplacer les fluides à travers le dispositif séparateur
et juste dans les conduites pour fluides à densité inférieure et à densité plus élevée
sans permettre à un dégagement de gaz de se produire.
2. Procédé selon la revendication 1, dans lequel la première pompe est sélectionnée de
façon à procurer dans le flux de pétrole et d'huile passant à travers la pompe une
pression suffisante pour retenir la majorité du gaz dissous en solution pendant que
le flux passe à travers la pompe et le carter.
3. Procédé selon la revendication 1, comprenant en outre l'étape consistant à prévoir
une commande de contre-pression dans la conduite pour fluides à densité plus élevée.
4. Procédé selon la revendication 3, dans lequel la commande de contre-pression est une
soupape.
5. Procédé selon la revendication 3, dans lequel la commande de contre-pression est un
orifice.
6. Procédé selon la revendication 1, comprenant en outre l'étape consistant à prévoir
une commande de contre-courant dans la conduite pour fluides à densité plus élevée.
7. Procédé selon la revendication 1, comprenant en outre l'étape consistant à prévoir
une seconde pompe entre le premier orifice de sortie du dispositif séparateur et la
conduite pour fluides à densité inférieure afin de faciliter le déplacement du flux
à densité inférieure en vue de la production du flux, et à sélectionner et mettre
en oeuvre la première pompe de façon à retenir la majorité du gaz dissous en solution,
sans permettre ainsi à un dégagement de gaz de se produire pendant que le flux passe
à travers la première pompe, le dispositif séparateur, et jusque dans la seconde pompe.