WO1995022003A1

WO1995022003A1 - Fluid pumping

Info

Publication number: WO1995022003A1
Application number: PCT/GB1995/000260
Authority: WO
Inventors: Frank Skilbeck
Original assignee: Baker Hughes Limited
Priority date: 1994-02-11
Filing date: 1995-02-09
Publication date: 1995-08-17
Also published as: GB9402708D0; NO963308L; GB2301401A; AU1585495A; NO963308D0; GB9616483D0

Abstract

A method and apparatus for pumping a first process fluid by means of a supply of a second power fluid under pressure, the second fluid being supplied with a tangential velocity component to one of a passageway such that the fluid swirls and forms a vortex around the axis of the passageway while flowing axially along the passageway to an outlet, whereby the vortex causes the formation of a low pressure zone within the flow, and a supply of the process fluid is exposed to the low pressure zone whereby the process fluid is drawn into the low pressure zone and entrained by the flow of power fluid with which it passes through the outlet.

Description

FLUID PUMPING

In the oil and other industries it is sometimes desirable to be able to pump a first liquid being processed by means of a supply of a second liquid under pressure, particularly when the pumping is to take place in inaccessible locations, such as downhole, where servicing of a mechanical pump with moving parts is most inconvenient. Such fluid pumping is conventionally carried out by means of a jet pump. As is well known a conventional jet pump passes the power or driving fluid through a small venturi which converts the pressure energy into kinetic energy and hence lowers the pressure around the throat of the venturi. The process fluid to be pumped is sucked through a suction inlet in the wall of the venturi into this low pressure region. A downstream divergent section is then usually provided to turn as much of the kinetic energy back into potential pressure energy. However, jet pumps have disadvantages, for example when oil and water mixtures are processed, the interaction between the mixture drawn radially in through the wall of the venturi with the high speed flow of power fluid passing axially through the venturi can result in liquid emulsification, making further liquid separation processes more arduous.

In accordance with the present invention, in a method of pumping a first process fluid by means of a supply of a second power fluid under pressure, the second fluid is supplied with a tangential velocity component to one end of a passageway such that the fluid swirls and forms a vortex around the axis of the passageway while flowing axially along the passageway to an outlet, whereby the vortex causes the formation of a low pressure zone within the flow, and a supply of the process fluid is exposed to the low pressure zone whereby the process fluid is drawn into the low pressure zone and entrained by the flow of power fluid with which it passes through the outlet. This method of pumping has in common with a jet pump the advantages that no moving parts are required. However, and particularly if the process fluid is supplied axially to the low pressure zone in the axial direction of flow of the power fluid, the entrainment of the process fluid is more gentle than in the case of a jet pump, with the commensurate additional advantage, particularly when the process fluid is an oil/water mixture, of reduced shearing and emulsification. The angular velocity of the vortex preferably increases up to the point at which the process fluid is introduced, to maximise the suction at this point in the low pressure zone, and/or reduces downstream of this point so that as much as possible of the energy is recovered as potential pressure energy. This can be achieved quite simply by causing the passageway to converge and/or then diverge.

A pump for use in carrying out the new method may comprise a body having an inner wall surface defining a passageway of substantially circular cross-section, at least one tangential inlet for power fluid at one end of the passageway and an outlet at the other end of the passageway, and an inlet nozzle for supplying process fluid axially in the downstream direction into the passageway substantially on the axis of the passageway and downstream of the inlet. For the reasons previously discussed, the inner wall surface preferably converges in between the inlet and a position adjacent to the tip of the process fluid inlet nozzle and/or diverges between this position and the outlet.

An example of a pump, for use in accordance with the present invention, and two uses for the pump, are illustrated diagrammatically in the accompanying drawings, in which:- Fig. 1 is an axial section through the pump;

Fig. 2 illustrates a use of the pump in a submarine oil field; and. Fig. 3 illustrates the use of the pump in an oil field well.

The pump shown in Figure 1 has a body having an internal wall with a convergent section 4 and a divergent section 5, defining a passageway. A tangential inlet 1 for power fluid is provided at the upstream end of the passageway and an outlet 3 is provided at the downstream end. A suction nozzle 2 extends through the upstream end wall of the body and opens at its end 6, adjacent to the discontinuity between the sections 4 and 5. In use, power fluid, such as water under pressure, is supplied through the inlet 1 setting up a vortex along the passageway. This vortex is accelerated as it passes along the convergent section 4 and the increase in rotational speed increases the centrifugal forces, creating a low pressure core. Process fluid is drawn in through the suction nozzle 2 and is entrained by the swirling flow of power fluid. The angular velocity is reduced along the divergent section 5, which acts as a pressure recovery section, before the mixture is discharged through the outlet 3.

If the power fluid is provided at a pressure P,, and a flow rate Q,, and the process fluid at a pressure P₂ is induced at a flow rate of Q₂, then the discharge mixture will be at a pressure P₃ and a flow rate Q_j, where P₁>P₃>P₂ and O^sQ^_j. In practice the geometry of the pump will be optimised to give the best hydraulic efficiency rfhile maximising Q₂ and P₃-P₂.

Figure 2 shows one possible use for the pump. Power fluid is provided under pressure from a host platform 7 along a line 8 to the inlet 1 of the pump P. The suction inlet 2 is connected to a remote production manifold 9 and the outlet 3 of the pump is connected through a further line 10 back to the host platform.

Used in this way, the pump could be used to increase production in satellite field developments to lower wellhead pressure and hence increase production. The main advantages of using the pump would be increased reliability over rotating equipment, and a potential to handle both gases, liquids and/or fluidised solids. Other benefits may arise through using water to reduce the viscosity of the pipeline fluids or heating the power fluid to preheat the crude oil. The production fluid could be separated from the power fluid on the host platform by pre-separator hydrocyclones or conventional gravity separators.

Figure 3 shows the pump P being used as a downhole oil well pump to increase production from a well. The pump is seen to be installed in the production tubing 11 just above a packer 12. Power fluid, usually in the form of water, would be pumped by a surface pump 13 down the annulus between the production tubing 11 and casing 14 to the pump inlet 1. Production fluid from a production zone 15 would then be induced in through the suction nozzle 2 and discharged along with the power fluid through the outlet 3 and up through the production tubing 11 to the wellhead 16. From here the fluids could be fed to a pre-separator cyclone 17 where the water would be knocked out for re-use as the power fluid and the separated production fluid would be fed along a line 18 for further processing. It is envisaged that this system would be particularly suited to high water cut production.

The main benefit of such a system over conventional pumping systems, such as electric submersible pumps and sucker rods, would be the increased reliability of the pump, the ability to remove the pump by wireline, and the possibility of well logging through the pump. Other potential advantages could be in heavy oil production where the power fluid could be heated to reduce viscosity and hence friction losses, and improve the subsequent oil/water separation.

As an alternative to water or other liquid, gas might also be used as the power fluid and this would also give a gas lift effect which might have some benefits.

Claims

1. A method of pumping a first process fluid by means of a supply of a second power fluid under pressure, the second fluid being supplied with a tangential velocity component to one end (1) of a passageway (4,5) such that the fluid swirls and forms a vortex around the axis of the passageway (4,5) while flowing axially along the passageway (4,5) to an outlet (3) , whereby the vortex causes the formation of a low pressure zone within the flow, and a supply of the process fluid is exposed to the low pressure zone whereby the process fluid is drawn into the low pressure zone and entrained by the flow of power fluid with which it passes through the outlet (3) .

2. A method according to claim 1, wherein the angular velocity of the vortex increases up to the point (6) at which the process fluid is introduced.

3. A method according to claim 1 or claim 2, wherein the angular velocity of the vortex reduces downstream of the point (6) at which the process fluid is introduced.

4. A method according to any one of the preceding claims, wherein the second power fluid is water.

5. A method according to any one of claims 1 to 3, wherein the second power fluid is a gas.

6. A method according to any one of the preceding claims, wherein the second power fluid is heated.

7. A method according to any one of the preceding claims, wherein the first process fluid is production fluid from an oil field.

8. A method according to claim 7, wherein the second power fluid is provided from a host platform (7) along a line (8) to the one end (1) of the passageway (4,5); the first process fluid is provided from a remote production manifold (9) ; and the outlet (3) is connected through a further line (10) back to the host platform (7) .

9. A method according to claim 7, wherein the pump is mounted downhole in an oilfield well.

10. A pump for pumping a first process fluid by means of a supply of a second power fluid under pressure, the pump comprising a body having an inner wall surface defining a passageway (4,5) of substantially circular cross-section, at least one tangential inlet (1) for power fluid at one end of the passageway (4,5) and an outlet (3) at the other end of the passageway (4,5), and an inlet nozzle (2) for supplying process fluid axially in the downstream direction into the passageway (4,5) substantially on the axis of the passageway (4,5) and downstream of the inlet (1).

11. A pump according to claim 10, wherein the inner wall surface converges between the inlet (1) and a position adjacent to the tip (6) of the process fluid inlet nozzle (2).

12. A pump according to claim 10 or claim 11, wherein the inner wall surface diverges between a position adjacent to the tip (6) of the process fluid inlet nozzle (2) and the outlet (3).