CONVEYING DEVICE FOR CONVEYING A LIQUID/GAS MIXTURE TAKEN FROM A BOREHOLE

Abstract

A conveying device for conveying a liquid/gas mixture, in particular a crude-oil/natural-gas mixture, taken from a borehole, having a multiphase-pumping device, which can be or is coupled to a feed line and a discharge line and to which the liquid/gas mixture can be fed as a feed flow, via the feed line and via which the mixture can be discharged under increased pressure as a conveyance flow, into the discharge line, and having a recirculation line, via which a sub-flow of the liquid contained in the conveyance flow can be returned to the feed flow. The recirculation line contains an injector, through which the sub-flow is conducted, with a negative pressure being generated in the process, and which can be or is coupled to a gas line, which conducts a gas taken from the borehole. The negative pressure causes the gas to be taken in by suction.

Claims

1. A conveying device for conveying a liquid/gas mixture, in particular a crude-oil/natural-gas mixture, taken from a borehole, having a multiphase-pumping device, which can be or is coupled to at least one feed line and a discharge line and to which the liquid/gas mixture can be fed, in the form of a feed flow, via the feed line and via which the mixture can be discharged under increased pressure, in the form of a conveyance flow, into the discharge line, and having a recirculation line, via which a sub-flow of the liquid contained in the conveyance flow can be returned to the feed flow, wherein the recirculation line contains an injector, through which the sub-flow can be conducted, with a negative pressure being generated in the process, and which can be or is coupled to at least one gas line, which conducts a gas, in particular natural gas, taken from the borehole, wherein the negative pressure can cause the gas to be taken in by suction.

2. The conveying device according to claim 1, wherein the multiphase-pumping device has arranged downstream of it a separator device, to which the recirculation line is coupled.

3. The conveying device according to claim 1, wherein the recirculation line has a first line portion, which is coupled to the multiphase-pumping device and via which a first sub-flow fraction can be fed to the multiphase-pumping device, and has a second line portion, which is coupled to the injector and via which a second sub-flow fraction can be fed to the injector.

4. The conveying device according to claim 1, wherein a throttle valve is provided in the recirculation line or in the first and in the second line portions.

5. The conveying device according to claim 1, wherein the feed line is connected to a plurality of separate lines which are associated with different boreholes and conduct a liquid/gas mixture, and/or in that the gas line is connected to a plurality of separate lines which are associated with different boreholes and conduct gas.

6. The conveying device according to claim 1, wherein the injector has a first connection, to which the recirculation line is connected and which is followed, in a nozzle housing, by a nozzle with a constricted nozzle cross section, and also has a second connection, to which the gas line is connected and which opens out in the nozzle housing, wherein the nozzle housing is followed by a mixing line, which is connected to the feed line.

7. A method which is intended for conveying a liquid/gas mixture, in particular a crude-oil/natural-gas mixture, taken from a borehole and in which, by means of a multiphase-pumping device, which is coupled to a feed line and a discharge line, the liquid/gas mixture fed in the form of a feed flow via the feed line is conveyed under increased pressure, in the form of a conveyance flow, into the discharge line, wherein a recirculation line is used to return a sub-flow of the conveyance flow to the feed flow, wherein the sub-flow flows through an injector, which is provided in the recirculation line, this generating a negative pressure which causes a gas conducted in a gas line and taken from the borehole to be taken in by suction.

8. The method according to claim 7, wherein the sub-flow is taken from a separator device, which is arranged downstream of the multiphase-pumping device and to which the recirculation line is coupled.

9. The method according to claim 7, wherein a first sub-flow fraction is fed to the multiphase-pumping device via a first line portion of the recirculation line, and a second sub-flow fraction is fed to the injector via a second line portion.

10. The method according to claim 7, wherein the pressure at which the sub-flow or the sub-flow fraction is conveyed is reduced via a throttle valve, which is provided in the recirculation line or in the first and in the second line portions.

11. The method according to claim 7, wherein the liquid/gas mixture is fed in the form of a feed flow by a plurality of separate lines which conduct a liquid/gas mixture, are associated with a plurality of separate, different boreholes and are connected to the common feed line, which is coupled to the multiphase pump, and/or in that the gas is taken in by suction by a plurality of separate lines which conduct gas, are associated with a plurality of separate, different boreholes and are connected to the common gas line, which is coupled to the injector.

12. The method according to claim 7, wherein use is made of an injector which has a first connection, to which the recirculation line is connected and which is followed, in a nozzle housing, by a nozzle with a constricted nozzle cross section, and also has a second connection, to which the gas line is connected and which opens out in the nozzle housing, wherein the nozzle housing is followed by a line which is connected to the feed line.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0022] FIG. 1 shows a schematic diagram of a conveying device according to the invention coupled to a borehole,

[0023] FIG. 2 shows a schematic diagram of an injector, and

[0024] FIG. 3 shows a schematic diagram, in section, of one embodiment of an injector.

DETAILED DESCRIPTION OF THE INVENTION

[0025] FIG. 1 shows a schematic diagram of a conveying device 1 according to the invention, along with its essential functional components, which serves to convey a liquid/gas mixture taken from a borehole 2. The borehole 2 is realized by a well 3, having an external well casing 4 and an internal line 5. For example a crude-oil/natural-gas mixture is taken from the borehole 2, wherein a corresponding mixture of crude oil and natural gas with a predominant crude-oil fraction is conveyed in the line 5, whereas natural gas is drawn off in the external well casing 4. The conveying device 1 is suitably connected to the external well casing 4 and the line 5 via corresponding lines 6, 7.

[0026] The conveying device 1 has a multiphase-pumping device 8, which is connected via a feed line 9 to the line 7, which in turn is coupled to the line 5 of the borehole 2. Via the multiphase-pumping device 8, the liquid/gas mixture is taken in by suction in the form of a feed flow and conveyed onward at higher pressure, in the form of a conveyance flow, via a discharge line 10. The pressure on the suction side, that is to say the pressure of the feed flow, is for example 4-5 bar, whereas the pressure on the pressure side, that is to say the pressure of the conveyance flow, is for example 30-35 bar.

[0027] The multiphase-pumping device 8 has arranged downstream of it a separator device 11, in which phase separation takes place, i.e. a liquid flow is branched off there. The rest of the crude-oil/natural-gas mixture is fed to a pipeline 12.

[0028] Also provided is a recirculation line 13, which in the example shown is guided away from the separator device 11 or the appliance part in which the separated-off liquid, that is to say the crude oil/water, is present. It has a first line portion 13a, which leads directly to the multiphase-pumping device 8, so that a fraction of the sub-flow which is drawn off from the separator device 11, and contains just liquid, is fed directly to the multiphase-pumping device 8, in order to provide, via this returned liquid fraction, for gap sealing and pressure build-up and cooling there. The recirculation line 13 also has a second line portion 13b, which serves for the feed line 9, so that a further sub-flow fraction which is conducted in the line portion 13b, and contains only liquid, is returned to the feed flow again.

[0029] An injector 14 is incorporated in the second line portion 13b, the sub-flow fraction being fed to the injector and guided through the same before being mixed in with the feed flow again. This injector 14, in turn, is connected to a gas line 15, which for its part is connected to the line 6, via which the natural gas is drawn off out of the external well casing 4. The injector 14 hasand this will be discussed in more detail hereinbelowa nozzle arrangement, through which the sub-flow fraction flows, so that a negative pressure is generated in the injector, the negative pressure causing the natural gas to be sucked out of the external well casing 4 via the gas line 15 and the line 6. This reduces the pressure in the external well casing 4 and therefore the pressure to which the crude-oil reservoir is subjected, which makes possible an increase in the conveyance quantity.

[0030] This results in the formation, in the injector, of a mixture of the sub-flow fraction, that is to say of a purely liquid phase, and the natural gas taken in by suction, that is to say of a gaseous phase, so that the feed flow in the feed line 9, once again, is fed a liquid/gas mixture or, specifically, a crude-oil/natural-gas mixture. The two sub-flows, that is to say the actual feed flow and the flow coming from the injector 14, are then pumped once again via the multiphase-pumping device 8.

[0031] As FIG. 1 also shows, the two line portions 13a, 13b contain two throttle valves 16, 17, via which it is possible to set a setting of the volume fraction of the respective sub-flow fraction conveyed in the line portion 13a, 13b, depending on the pressure at which the respective sub-flow fraction is to be fed, on the one hand, to the multiphase-pumping device 8 and, on the other hand, to the injector 14.

[0032] FIG. 1 also shows the possibility of the conveying device 1 according to the invention, rather than serving just one borehole 2, serving further boreholes 2, of which, in the example shown, the respective lines 6a, 6b, 6c which conduct gas, and via which the natural gas is respectively removed by suction, and also the lines 7a, 7b, 7c which conduct a liquid/gas mixture, and via which the crude oil is respectively pumped off, are shown. The lines 6, 6a, 6b, 6c and 7, 7a, 7b, 7c are bundled and connected to the gas line 15 and the feed line 9, respectively, so that the multiphase-pumping device 8 can therefore be used to pump off crude oil from a plurality of boreholes 2, as can the injector 14 be used to remove natural gas by suction from a plurality of boreholes 2 or external well casings.

[0033] FIG. 2 shows a schematic diagram of the injector 14. The figure shows a nozzle housing 18, which accommodates a nozzle 19 of decreasing cross section. The nozzle housing 18 has a first connection 20, to which in the example according to FIG. 1 the line portion 13b is connected, so that the sub-flow fraction 23a, as shown by the arrow P1, is fed directly to the nozzle 19. The liquid sub-flow 23b, that is to say the crude oil taken for example according to FIG. 1 from the separator device 11, exits at the nozzle exit 21, which has a considerably reduced cross section, the flow speed of this liquid sub-flow having increased, but its pressure having decreased, so that a negative pressure is established in the interior of the nozzle housing 18.

[0034] The nozzle housing 18 has a second connection 22, to which in the example shown according to FIG. 1 the gas line 15 is connected. The negative pressure prevailing in the interior of the nozzle housing 18 causes natural gas to be taken in by suction via the gas line 15, as shown by the arrow P2, and this results in a pressure reduction in the external well casing and therefore in the deposit itself. The natural gas taken in by suction mixes with the crude-oil sub-flow fraction 23b, and this results in the formation of a crude-oil/natural-gas mixture 24, as illustrated in FIG. 2. In a continuing line 25, which can widen in cross section, the crude-oil/natural-gas mixture 24 flows onwardas is illustrated by the arrow P3until the mixture 24, at an interface to the feed line 9, is mixed in with the actual feed flow. Depending on the ratios of the cross section of the nozzle 19 and of the pressure at which the sub-flow fraction 23a is fed, a higher or lower negative pressure is established, that is to say that the design of this Venturi-nozzle arrangement can set the suction-intake operation correspondingly.

[0035] FIG. 3 shows a sectional view of one embodiment of the injector 14. The figure shows the nozzle housing 18 with the nozzle 19 and the two connections 20, 22, which are designed in the form of corresponding connection flanges and in the example shown are located orthogonally in relation to one another. The figure also shows the line 25, which is connected to the nozzle housing 18 via a flange connection 26. The line 25 communicates with the interior 27 of the nozzle housing 18, in which forms the crude-oil/natural-gas mixture 24, which is conducted away via the line 25.

[0036] The embodiment of the injector 14 shown is merely by way of example; other designs are, of course, conceivable, as long as they provide for the suction-intake operation according to the invention.

[0037] While specific embodiments of the invention have been shown and described in detail to illustrate the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.