GB2254659A - Jet pump with annular nozzle and central plug - Google Patents

Abstract

A jet pump unit which is adapted to be installed in a production pipe extending from an underground reservoir is operable by application of a fluid pressure driving medium thereto said pump comprising; a housing 101 positionable in the pipe and arranged to allow upward movement of liquid through the housing 101: a fluid inlet 102 provided on the housing 101 to admit a fluid pressure driving medium: a liner 103 mounted within the housing 101: an annular nozzle 104 arranged at the lower end of the liner 103 communicating with the fluid inlet 102, said nozzle 104 surrounding a central inlet passage 106 for liquid flowing upwardly through the pipe. A nozzle section 107 is mounted in the liner 103 defining an annular through-flow passage 108 which communicates with said central inlet passage 106, and an internal seating 111 in the interior of the nozzle section 107 to receive a removable plug 112 which can be introduced into and removed from the internal seating 111 by a wireline technique. <IMAGE>

Description

JET PUMP FOR UPLIFTING LIQUID FROM UNDERGROUND RESERVOIR This invention relates to a jet pump for use in uplifting liquid from an underground reservoir.

In this specification. an underground reservoir should include reservoirs located below the seabed. such as North Sea oilfields.

In the extraction of crude oil from a reservoir, the oil passes upwardly through an oil production pipe, and then is directed to a pipeline or storage facility, usually after completion of preliminary treatment of the extracted liquid e.g. separation of any gas contained in the upwardly flowing stream of crude oil.

In the case of underground oil reservoirs containing natural gas under pressure, the oil is forced up through the production pipe by this gas pressure and no assistance is required for as long as this natural pumping source remains available and effective. However, over a period of time, as the quantity of oil remaining in the reservoir reduces, the pumping pressure will reduce and eventually it becomes necessary to employ a pump to assist the extraction of oil from the reservoir.

Also, in the case of an oilfield which is "marginal" at the outset, it is necessary to employ a pump throughout the period of extraction of oil from the marginal field.

Therefore, in situations in which reservoir energy is low, it is known to install a pump "downhole" to enable production, or to enhance production rates. Generally, this applies to oil wells, but could also apply to water source wells. It is necessary to locate the pump at great depth, often just above the reservoir, in order to develop sufficient head to enable high offtake rates to be achieved.

One possible jet pumping arrangement is shown schematically in Figure 1 of the drawings, and designated generally by reference 10. A production pipe assembly 13 comprises a central oil production pipe 12, and an annulus 14 surrounding the central pipe 12. The pump unit is shown schematically by reference 15, and is installed in, or removed from the production pipe 12 by known wireline techniques. Driving fluid, generally water or crude oil, can be supplied via the annulus 14 and is routed to the interior of the pump unit 15 via inlet ports 16 formed in the wall of an outer housing of the unit 15. Energy transfer takes place between the driving fluids and the uplifted (pumped) oil which passes upwardly from the reservoir through the oil production pipe 12.The net effect is that oil is pumped up from the reservoir and the commingled fluids are then transported to the surface via the pipe 12 by virtue of the pressure which is developed at the pump discharge. This arrangement, whereby driving fluid is routed via the annulus 14 while the commingled driving / reservoir fluids are returned up the production pipe is referred to as "reverse circulation".

A detailed example of a jet pump is shown in Figure 2 of the accompanying drawings, and which can be operated by the supply of a gaseous driving pressure medium, which is described in more detail and which comprises a preferred embodiment of an invention which forms the subject of our co-pending UK patent application No 9101058.7 filed 17th January 1991.

The jet pump arrangement shown in Figure 2 comprises a twin pipe arrangement having an inner oil production pipe 12 which is arranged centrally within an outer pipe (not shown) which will comprise a usual liner of a bore hole.

The outer pipe therefore defines an annulus surrounding the inner pipe 12 and through which a fluid pressure driving medium can be supplied to operate the jet pump. An outer housing 17 of the jet pump arrangement forms an integral part of the production pipe 12, and the jet pump arrangement is sealed within the outer housing 17 between upper and lower seals 18 and 19, and comprises a nozzle section 20, a throat section 21 and a diffuser section 22.

The fluid pressure driving medium is conveyed to the nozzle section 20 via an aperture 23 in the outer housing 17, and an inlet 24 to the nozzle section 20, and then a high speed jet is formed which issues into the throat section 21 and then subsequently into the diffuser section 22. As the jet travels along the throat section 21 and diffuser section 22. its velocity decreases. However. the upwardly moving column of oil in production pipe 12 is guided in by-pass manner around the nozzle section 20, as shown' by arrow 25. and into an annular chamber 26 surrounding the outlet of nozzle section 20. The oil is relatively slower moving than the high speed jet, and energy is therefore transferred from the jet to the slower moving reservoir fluid which flows in the annular space created between the jet and the walls of the throat and diffuser sections 21, 22.As a result, the production rate from the reservoir is increased, and the commingled driving fluid and reservoir fluids then flow upwardly to the wel lhead.

Accordingly, as the commingled fluids pass along the diffuser section, the pressure rises steadily until at the pump outlet sufficient pressure has been developed to transport the fluids to the surface.

However, while the jet pumping arrangements shown in Figures 1 and 2 can operate satisfactorily in order to "lift" liquid e.g. oil from an underground reservoir to the surface, these arrangements do not permit use of "wireline access" to the reservoir. which is a technique employed to perform production logging or to perforate another part of a reservoir while simultaneously flowing the well. To date, in all known jet pumped wells, this has not been possible because the internal arrangement of the pump does not permit this, as will be appreciated from review of Figure 2.

The present invention has therefore been developed with a view to providing an improved design of jet pump unit which can be installed in a production pipe, and yet which allows use of wireline techniques.

According to the invention there is provided a jet pump unit which is adapted to be installed in a production pipe extending upwardly from an underground reservoir, said pump unit being operable by application of a fluid pressure driving medium thereto in order to pump liquid up the pipe from the reservoir, and said pump unit comprising:: a housing which is positionable at a required height in the pipe and which is arranged to allow upward movement of liquid through the housing; a fluid inlet provided on the housing to admit a fluid pressure driving medium to operate the pump unit; a liner mounted within the housing; an annular nozzle arranged at a lower end of the liner and communicating with the fluid inlet, said nozzle surrounding a central inlet passage for liquid flowing upwardly through the pipe from the reservoir; a nozzle section mounted in the liner and arranged to define an annular through-flow passage which communicates with said central inlet passage, said annular passage being defined between an outer wall of the nozzle section and an inner wall of the liner; and, an internal seating arranged in the interior of the nozzle section to receive a removable plug which can be introduced into and removed from the internal seating by a wireline technique.

The removable plug which is used in conjunction with the pump unit may comprise a solid plug of a type suitable to close the interior of the nozzle section and allow normal production lift of liquid from the reservoir through the annular through-flow passage of the pump unit.

However, the solid plug may be replaced by a so-called logging plug when it is required to carry out liquid flow logging operations during operation of the pump unit.

The logging plug preferably has a through passage through which a wire can be taken and which carries a logging tool below the plug which can be located in the pipe below the central inlet passage in order to monitor liquid flow.

The logging tool may comprise an impeller type of gauge.

Preferably, the shaping of the inner wall of the liner and the outer wall of the nozzle section is such as to define a first cylindrical portion which communicates with and which is substantially in line with the annular nozzle and which also communicates with the central inlet passage, and a second diverging portion downstream of the first portion and which forms a diffuser section.

One embodiment of a jet pump unit according to the invention will now be described in detail, by way of example only, with reference to Figures 3 and 4 of the accompanying drawings.

Referring now to Figures 3 and 4 of the drawings, a jet pump unit according to the invention is designated generally by reference 100 and is adapted to be installed in a production pipe (not shown) which extends upwardly from an underground reservoir. The pump unit 100 is operable by application of a fluid pressure driving medium thereto in order to pump liquid up the pipe from the reservoir.

The pump unit 100 comprises a housing 101 which is positionable at a required height in the pipe and which is arranged to allow upward movement of liquid through the housing. A fluid inlet is provided on the housing 101 and takes the form of a series of circumferentially spaced inlet apertures 102 which serve to admit a fluid pressure driving medium to operate the pump unit 100.

A liner 103 is mounted within the housing 101, and an annular nozzle 104 is arranged at a lower end of the liner 103, and communicates with the fluid inlets 102. The annular nozzle 104 defines a circular nozzle outlet 105 through which an upwardly flowing cylindrical jet of the driving pressure medium can be formed. The annular nozzle 104 also has a central inlet passage 106 which is surrounded by the circular nozzle 105, and which communicates with the oil production pipe in order to allow upward flow of oil through the pump unit 100.

A nozzle section 107 is mounted in the liner 103 and is arranged to define an annular through-flow passage which communicates with the central inlet passage 106. The annular passage is designated generally by reference 108, and is defined between an outer wall 109 of the nozzle section 107 and an inner wall 110 of the liner 103.

An internal seating 111 is arranged in the interior of the nozzle section 107 and is adapted to receive a removable plug which can be introduced into and removed from the internal seating by a wireline technique.

As shown in Figure 3, the removable plug which is used in conjunction with the pump unit 100 comprises a solid plug 112 drawn by a wire 113 to a position in which it closes the interior of the nozzle section 111, but allows normal production lift of liquid from the reservoir through the annular throughflow passage 108. Figure 3 therefore shows detail of a jet pump unit 100 which allows wireline access of a solid plug set during normal production operations.

However, as shown in Figure 4, the solid plug 112 of Figure 3 can be replaced by a so-called logging plug 114 when it is required to carry out liquid flow logging operations during operation of the pump unit 100. The logging plug 114 has a through-passage 115 which is oversized relative to the diameter of wire 113, which is taken through passage 115, and which carries a logging tool below the plug 114 which can therefore be located in the pipe below the central inlet passage 106 in order to monitor liquid flow. In the illustrated arrangement, there is shown schematically a logging tool in the form of an impeller type of gauge 116.

Accordingly, the jet pump unit described above with reference to Figures 3 and 4 provides an arrangement which allows wireline access whilst simultaneously jet pumping a well. Thus. by displacing the nozzle / throat / diffuser components from the centre line, as shown in the arrangement of Figure 2, to the perimeter as shown in Figures 3 and 4, wireline access of removable plugs can be achieved.

This lateral displacement of the components can take a number of forms. For example, a number of conventionally shaped (circular) nozzle / throat / diffusers can be arranged around the circumference. Alternatively, the throated diffuser could take the form of a continuous annulus as shown in Figures 3 and 4. The nozzle has the shape shown in the Figures, and the jet formed by such a nozzle will be cylindrical in form.

As described above, during normal production plug 112 (which can be set or retrieved by wireline means) is located within the central passage of the nozzle section 107 of the jet pump unit 100. This effectively isolates the suction and discharge parts of the pump. However.

wireline access can be achieved by using a plug (the logging plug 114 of Figure 4), which has a hole drilled through its centreline. The diameter of this hole is slightly larger than the diameter of the wireline 114, so that the latter is free to move through the plug unimpeded during jet pumping operations and with the desired tool (production logging tool 116) attached to the end of the wire.

A typical operating sequence would be as follows: 1. Retrieve the plug 112 of Figure 3 by normal wireline means.

2. Feed the wire through the logging plug 114 on the surface and attach the desired tool e.g. production logging tool 116) to the end of the wire.

3. Run the assembly into the well suspended on the wire. As the assembly passes through the jet pump unit 100, the logging plug 114 locates on the seating 111 within the machined bore. whilst the tool 116 continues its passage down the well.

4. Supply driving fluid to operate the pump unit 100 thereby causing the well to flow, and logging operations can then proceed unimpeded.

The novel design of jet pump unit 100 disclosed herein, by way of preferred embodiment shown in Figures 3 and 4, is believed to provide unique wireline access to a jet pump installation. and also to have a novel arrangement of nozzle / throat / diffuser design which, in particular, is off-set from the centreline. (as in conventional jet pumps). to the perimeter. In addition. there is unique provision of throat and diffuser sections having annular cross sections, whilst the nozzle is shaped so as to produce a cylindrical jet. Also. a number of conventionally shaped nozzle I throat / diffuser units can be arranged around the perimeter of the pump.

Claims (9)

1. A jet pump unit (100) which is adapted to be installed in a production pipe (12) extending upwardly from an underground reservoir. said pump unit being operable by application of a fluid pressure driving medium thereto in order to pump liquid up the pipe from the reservoir, and said pump unit comprising:: a housing (101) which is positionable at a required height in the pipe and which is arranged to allow upward movement of liquid through the housing; a fluid inlet (102) provided on the housing to admit a fluid pressure driving medium to operate the pump unit; a (103) liner mounted within the housing; an annular nozzle (104) arranged at a lower end of the liner (103) and communicating with the fluid inlet (102), said nozzle surrounding a central inlet passage (106) for liquid flowing upwardly through the pipe from the reservoir; a nozzle section (107) mounted in the liner (103) and arranged to define an annular through-flow passage (108) which communicates with said central inlet passage (106), said annular passage being defined between an outer wall (109) of the nozzle section (107) and an inner wall (110) of the liner (103); and.

an internal seating (111) arranged in the interior of the nozzle section to receive a removable plug (112, 114) which can be introduced into and removed from the internal seating by a wireline technique.

Amendments to the claims have been filed as follows 1. A jet pump unit which is adapted to be installed in a production pipe extending upwardly from an underground reservoir. said pump unit being operable by application of a fluid pressure driving medium thereto in order to pump liquid up the pipe from the reservoir. and said pump unit comprising: a housing which is positionable at a required height in the pipe and which is arranged to allow upward movement of liquid through the housing: a fluid inlet provided on the housing to admit a fluid pressure driving medium to operate the pump unit:: a liner mounted within the housing; an annular nozzle arranged at the lower end of the liner and communicating with the fluid inlet, said nozzle surrounding a central inlet passage for liquid flowing upwardly through the pipe from the reservoir; a nozzle section mounted in the liner and arranged to define an annular through-flow passage which communicates with said central inlet passage. said annular passage being defined between an outer wall of the nozzle section and an inner wall of the liner; and.

an internal seating arranged in the interior of the nozzle section to receive a removable plug which can be introduced into and removed from the internal seating by a reline technique.

2. A jet pump unit as claimed in claim 1. including a removable plug.

3. A jet pump unit as claimed in claim 2, in which the removable plug comprises a solid plug of a type suitable for closing the interior of the nozzle section and allow normal production lift of liquid from the reservoir through the annular through-flow passage of the pump unit.

4. A jet pump unit as claimed in claim 2. in which the removable plug comprises a logging plug to carry out liquid flow logging operations during operation.

5. A jet pump unit as claimed in any one of claims 2 to 4, in which the removable plug has a through-passage through which a wire can be taken.

6. A jet pump unit as claimed in claim 5, including a wire passing through the through-passage and carrying a logging tool below the plug which can be located in the pipe below the central inlet passage in order to monitor liquid flow.

7. A jet pump unit as claimed in claim 6, in which the logging tool comprises an impeller type gauge.

8. A jet pump unit as claimed in any one of claims 1 to 7, in which the shaping of the inner wall of the liner and the outer wall of the nozzle section is such as to define a first cylindrical portion which communicates with and which is substantially in line with the central inlet passage. and a second diverging portion downstream of the first portion and which forms a diffuser section.

9. A jet pump unit as claimed in claim 1 and substantially as hereinbefore described with reference to, and as shown in Figure 3 or 4 of the accompanying drawings.