AU2017204375A1 - Improvements in relation to pumps and the operation of pumps - Google Patents

Abstract

with FIG. I A system 10 comprising a well bore 11 having a wellhead 12, a pump assembly comprising a progressive cavity pump 13, a hollow drive rod 14 connected to the pump, and as can be seen the pump forces liquid from the well hole at 15 as a stream up an annular space 16. Gas produced flows in a stream to the wellhead along a production casing defined annular space 17. The two streams are maintained separate in the wellhead, the stream from 16 carrying sand and solids is output to a desander 18. Solids are separated and relatively clean liquid is output from the desander at 19. Part of this is recycled along line 20 back to the hollow drive rod 14 where that liquid is delivered through the hollow rotor 21 of the pump 13 to the inlet side 22 of the pump to agitate the bottom of the well. -18- -2

Description

IMPROVEMENTS IN RELATION TO PUMPS AND THE OPERATION OF PUMPS TECHNICAL FIELD

[0001] THIS INVENTION relates to the operation of pumps and is concerned with liquids having solids entrained therein and more particularly to improve the pumping processes in well bores or the like employing submerged pumps.

BACKGROUND

[0002] Submerged pumps are used in the bottom of well bores. These are usually positive displacement pumps, one type being a progressive cavity pump. Liquids pumped are usually related to some commercial product as in oil, gas or water. The pump has to be able to cope with solid particles that are entrained in the liquid. The solid particles have been and continue to be a problem to varying extents in terms of pump wear and pumps becoming clogged. The gas and water are travel in separate streams to a wellhead. In coal seam gas operations, gas flows up a production casing, water is pumped from wells so that the production casing water level is below (or low enough to reduce water head pressure so gas can flow) perforations or an open-slotted liner. Once water head pressure is reduced then gas can flow freely up the production casing.

[0003] One common way of trying to overcome the problem of pumps being clogged is to simply use larger pumps but this can result in reductions in efficiency which can then affect the commercial viability of the well.

[0004] Over many years many inventors have sought to ameliorate this problem and while the present invention arose to provide an economic advantage and improved efficiency, albeit possibly at the margins, even small improvements in efficiency can have major commercial consequences. A search of the patent literature post the present invention reveals that the art of ameliorating the general problem of solids and their adverse effect on pumping has been around ever since well bores were drilled and consequently the art can be described as a "crowded art". Examples are set out in the following United States patents. • US2002134554A1 • US2002195254A1 • US2005167119A1 • US2006048934A1 • US2009090511A1 • US2011315387A1

• US3963073A

• US4140444A

• US5209293A • US6167960B1 • US6371206B1 • US6412563B1 • US8079753B2

• USRE35454E

• US7201222A

• US7905714A

[0005] The content of these patents is incorporated herein in their entirety. These patents include a whole range of general propositions for improving pump operation and efficiency ail the way from mechanical agitation of liquid in the bottom of the well bore, filtration upstream of the pump, pump bypass of large solids and pump purging. Disclosure of these patents should not be taken as an admission that any are part of the common general knowledge anywhere.

OUTLINE

[0006] The present invention arises without any particular problem being extant at the filing date of the present application but rather is the inventor's independent effort to improve efficiency and reduce the likelihood of major works being required to repair or replace pumps.

[0007] In one aspect the present invention resides in a method of preparing inlet liquid to an inlet of a pump in a wellbore, the method comprising the steps of, on a dynamic and continuous basis, creating a diluted liquid for pumping by: a. delivering a relatively clean liquid or at least a liquid having relatively low concentration of relatively small particles into the well bore, upstream of the pump; b. causing the relatively clean liquid to mix with relatively unclean liquid in the wellbore upstream of the pump, the relatively unclean liquid having a relatively high concentration of relatively large particles by comparison to the clean liquid; c. by a. and b., causing a major portion of the diluted liquid to continuously be generated adjacent the pump inlet so that the diluted liquid is continuously pumped by the pump [0008] Preferably, the method includes the step of agitating the liquid(s) adjacent the inlet to the pump. The agitation may be mechanical or hydraulic. In the case of hydraulic agitation, an agitator may employ the relatively clean liquid which may be used to drive the agitator or the relatively clean liquid may be employed directly, as in for example a jet or multiple jets, to agitate the bottom of the well. The purpose of the agitation is to break up larger particles and/or to more uniformly distribute particles in the liquid. Typically, hydraulic agitation is employed by the relatively clean liquid used to agitate the bottom of the well via jet flowing out of an outlet from a bore of a hollow progressive cavity pump rotor, the hollow progressive cavity pump rotor having an inlet adjacent to the outlet from the bore. The relatively clean liquid may delivered via a constriction adjacent the outlet to promote a jet outlet. The constriction may comprise a relatively narrower bore in the progressive cavity pump rotor. In this regard the method may include the further step of selecting a hollow rotor having a bore size according to predicted flow rates for particular well conditions. This can include the step of selecting a hollow rotor having a bore size in the range of between 1/4” and 3/4” diameter.

[0009] In another aspect there is provided a pump inlet dilution system for a subterranean borehole, well or the like, the system employing a submerged pump and comprising a bore hole, a well or borehole head, a pump drive, a pump inlet and a pump outlet, a pipe communicating between the head and the pump outlet a relatively clean liquid delivery tube between the head and pump and having an outlet adjacent the pump inlet for delivery of relatively clean liquid to a region at or adjacent the pump inlet for the purpose of reducing the load on the pump through introduction of the relatively clean liquid to mix with liquid already in the well to dilute it so that the diluted liquid travels through the pump.

[0010] The liquid may be introduced into the well by diffusion, injection, as one or more jets or by a regulated flow depending on the type and nature of the liquid already in the well that is to be diluted. Ideally, the system may be set to optimise operation of the pump. Optimisation may be over a range of dilutions. The pump typically comprises a progressive cavity pump having a hollow rotor and liquid is introduced into the well as one or more jets from the hollow rotor. Preferably the liquid is recycled relatively clear liquid originating as relatively unclear liquid pumped from the well by the pump, there being a first flow valve for regulating flow of the recycled liquid back to the well through the delivery tube, a bleed valve in parallel with the first valve, the valves being used to regulate the flow back to the well.

[0011] Preferably the system employs a separator downstream of the pump and more preferably downstream of the wellhead, the separator removing solids from pumped liquid to produce a relatively clean liquid and at least part the so produced relatively clean liquid from the separator is returned to the well thus recycling the liquid.

[0012] In one preferred arrangement there is provided a pump inlet dilution system according to any one of claim 8 to 11 comprising a wellbore having a wellhead, a pump assembly comprising a progressive cavity pump and a desander, a hollow drive rod connected to the pump, the pump having a hollow rotor which forces liquid from the well hole as a stream carrying sand and solids up an annular space, gas produced flows in a stream to the wellhead along a production casing defined annular space, the two streams being maintained separate in the wellhead, the stream carrying sand and solids being output to the desander, solids being separated and a relatively clean liquid being output from the desander, at least part of this is recycled back to the hollow drive rod where that liquid is delivered through the hollow rotor of the pump to an inlet side of the pump. In order to promote a jet outlet from the pump the hollow drive rod having a diameter and the hollow rotor has an internal diameter less than the diameter of the delivery tube. The hollow rotor may have an inside diameter less than 3/4”.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order that the present improvements may be more readily understood and put into practical effect reference will now be made to the accompanying drawings which illustrate preferred embodiments of the invention and wherein:-

Figure 1 is a schematic drawing illustrating the general principle of the invention in a wellbore;

Figure 2 is a is a drawing illustrating the arrangement in the bottom of the wellbore; Figures 3 is drawing showing typical hollow rotors;

Figure 4 is drawing illustrating a coupling arrange used to deliver liquid to the pump; Figure 5 is a an overall view of a conventional wellhead using the present invention Figure 5 is a drawing illustrating the application of the present invention to a coal seam gas well employing a desander for removal of solids and recycling of clarified water to the well.

METHOD OF PERFORMANCE

[0014] Referring to the drawings and initially to Figure 1 there is illustrated a system 10 according to one preferred embodiment of the present invention, the system comprising a well bore 11 having a wellhead 12, a pump assembly comprising a progressive cavity pump 13, a hollow drive rod 14 connected to the pump, and as can be seen the pump forces liquid from the well hole at 15 as a stream up an annular space 16. Gas produced flows in a stream to the wellhead along a production casing defined annular space 17. The two streams are maintained separate in the wellhead, the stream from 16 carrying sand and solids is output to a desander 18. Solids are separated and relatively clean liquid is output from the desander at 19. Part of this is recycled along line 20 back to the hollow drive rod 14 where that liquid is delivered through the hollow rotor 21 of the pump 13 to the inlet side 22 of the pump.

[0015] The desander 18 may typically be a desander sold under the unregistered trade mark “Steelhead”, the desanders being available from Steelhead Energy Services of Suite 6, Level 1,29 McDougall Street, Milton, QLD Australia 4064. Desanders are described in Australian patent specifications accompanying applications 2012370294 and 2014366820 (WO2015/089652) to Specialized Desanders Inc. These specifications are incorporated herein in their entirety by cross reference.

[0016] The relatively clean liquid perfuses and mixes with liquid in the well reducing viscosity thus creating a region around the inlet to the pump which has a relatively lower concentration of solids by reason of the diluting liquid travelling along line 20 and down the hollow drive rod 14.

[0017] The commercial gas is produced up the production casing in space 17. The fluid in the production at 16 is >95% liquid. There is no actual reduction of efficiency in terms of the gas carried but rather the load on the pump is reduced due to the dynamic and continuous reduction in the concentration of solids passing through the pump.

[0018] Control over the outlet from the hollow drive rod through the hollow rotor of the progressive cavity pump may be varied. In this case line 20 communicates with it rotating counterpart via a rotary swivel 23, and a flow control valve 24 and a flow meter 25. A bleed off valve 27 provides an extra means of regulating flow. Return flow from the desander to the hollow drive rods 14 may be regulated in accordance with the type of solids, concentration of solids and other factors in the environment at 26 in the bottom of the well adjacent the inlet to the pump thus by the use of flow control valves 24 and 27 all of the flow from the desander may be recycled, there may also be the inclusion of a pump in line 20 if it is desirable to cause a larger jet other than arises from the gravitational flow of liquid from the wellhead to the bottom of the well or as et by the bore diameter of the pump rotor.

[0019] Referring to Figure 2 there are pertinent features of the pump are described and in this case there comprises a hollow rotor 27, a stator 28 and between the helical rotor 27 there are cavities 29 which is in effect a helical cavity which travels along the pump as the rotor rotates. Pertinent to the present invention is the internal diameter shown at 30 which is selected to promote a jet of flow through the outlet of the pump so that the jet of flow serves to aid agitation of the liquid already in the well on a continuous basis to aid in the breakdown and mixing of the solids and dilution of the liquid immediately adjacent to the inlet of the pump.

[0020] The internal diameter for the hollow rotor can range from all diameters including and between 1/4” and 3/4”. The internal diameter is created by machining out the centre of the rotor. Another way of building a hollow rotor is by casting. Using a cast, there could be a standard hole diameter including and between 1/4” and 3/4” or the wall thickness of the rotor would be the same throughout. With standard wall thickness, the hollow area would have double helical geometry similar to the external surface of the rotor.

[0021] Flow rates into the well through the rotor can range from greater than 0 bbl/d and up to 1000 bbl/d. Flow rate is adjusted at surface using the flow control valve where the operator can dictate the optimal flow rate depending on local conditions. Typical flow rates may range from 50 to 300 bbl/d. The liquid that passes through the rotor agitates the well bore fluid and solids around the pump intake area. The jetting effect of the rotor acts to “fluidise” any solids before they enter the pump. Figure 3 illustrates three examples of different pump rotors 31,32 and 33 that could be employed depending upon the environment at the bottom of the well as another or complementary mechanism to control the environment at the pump inlet depending upon the circumstances.

[0022] Figure 4 illustrates adaptation of inline components of conventional form comprising the rotary swivel/union 23 which is connected to line 20 at one end and at it other end to coupling assembly 34 to the top drive rod at 14. Figure 5 shows an exemplary wellhead assembly of conventional form fitted with a pump inlet dilution system according to the present invention.

[0023] Figure 6 illustrates a further practical embodiment of the present invention wherein like numerals have been used to illustrate like features.

[0024] In the present specification and claims, the word "comprising" and its derivatives including "comprises" and "comprise" include each of the stated integers but does not exclude the inclusion of one or more further integers.

[0025] In compliance with the statute, the invention has been described in language more or less specific to structural or methodical features. It is to be understood that the invention is not limited to specific features shown or described since the means herein described comprises preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims appropriately interpreted by those skilled in the art. Accordingly, it will be appreciated that while the above has been given by way of illustrative example of the present invention many variations and modifications will be apparent to those skilled in the art without departing from the broad ambit and scope of the invention as set forth in the appended claims.

Claims (17)

1. A method of preparing inlet liquid to an inlet of a pump in a wellbore, the method comprising the steps of, on a dynamic and continuous basis, creating a diluted liquid for pumping by: a. delivering a relatively clean liquid or at least a liquid having relatively low concentration of relatively small particles into the well bore, upstream of the pump; b. causing the relatively clean liquid to mix with relatively unclean liquid in the wellbore upstream of the pump, the relatively unclean liquid having a relatively high concentration of relatively large particles by comparison to the clean liquid; c. by a. and b., causing a major portion of the diluted liquid to continuously be generated adjacent the pump inlet so that the diluted liquid is continuously pumped by the pump.

2. The method according to claim 1 wherein the method includes the step of agitating the liquid(s) adjacent the inlet to the pump.

3. The method according to claim 1 or claim 2 wherein hydraulic agitation is employed by the relatively clean liquid used to drive an agitator or the relatively clean liquid may be employed directly to agitate the bottom of the well.

4. The method according to claim 1 or claim 2 wherein hydraulic agitation is employed by the relatively clean liquid being employed directly to agitate the bottom of the well.

5. The method according to any one of the preceding claims wherein hydraulic agitation is employed by the relatively clean liquid used to agitate the bottom of the well via jet flowing out of an outlet from a bore of a hollow progressive cavity pump rotor, the hollow progressive cavity pump rotor having an inlet adjacent to the outlet from the bore.

6. The method according to any one of the preceding claims wherein the relatively clean liquid is delivered via a constriction adjacent the outlet to promote a jet outlet.

7. The method according to claim 7 wherein relatively clean liquid is delivered via a constriction adjacent the outlet to promote a jet outlet, the constriction comprising a relatively narrower bore in the progressive cavity pump rotor.

8. A pump inlet dilution system for a subterranean borehole, well or the like, the system employing a submerged pump and comprising a bore hole, a well or borehole head, a pump drive, a pump inlet and a pump outlet, a pipe communicating between the head and the pump outlet, a relatively clean liquid delivery tube between the head and pump and having an outlet adjacent the pump inlet for delivery of relatively clean liquid to a region at or adjacent the pump inlet for the purpose of reducing the load on the pump through introduction of the relatively clean liquid to mix with liquid already in the well to dilute it so that the diluted liquid travels through the pump.

9. A pump inlet dilution system according to claim 8 wherein the pump comprises a progressive cavity pump having a hollow rotor and liquid is introduced into the well as one or more jets from the hollow rotor.

10. A pump inlet dilution system according to claim 8 or claim 9 wherein the liquid is recycled relatively clear liquid originating as relatively unclear liquid pumped from the well by the pump, a first flow valve for regulating flow of the recycled liquid back to the well through the delivery tube, a bleed valve in parallel with the first valve, the valves being used to regulate the flow back to the well.

11. A pump inlet dilution system according to claim 8 or claim 9 wherein the liquid is recycled relatively clear liquid originating as relatively unclear liquid pumped from the well by the pump, a first flow valve for regulating flow of the recycled liquid back to the well through the delivery tube, a bleed valve in parallel with the first valve, the valves being used to regulate the flow back to the well, a separator downstream of the pump the separator removing solids from pumped liquid to produce a relatively clean liquid and at least part the so produced relatively clean liquid from the separator is returned to the well thus recycling the liquid.

12. A pump inlet dilution system according to any one of claim 8 to 11 comprising a wellbore having a wellhead, a pump assembly comprising a progressive cavity pump and a desander, a hollow drive rod connected to the pump, the pump having a hollow rotor which forces liquid from the well hole as a stream carrying sand and solids up an annular space, gas produced flows in a stream to the wellhead along a production casing defined annular space, the two streams being maintained separate in the wellhead, the stream carrying sand and solids being output to the desander, solids being separated and a relatively clean liquid being output from the desander, at least part of this is recycled back to the hollow drive rod where that liquid is delivered through the hollow rotor of the pump to an inlet side of the pump.

13. A pump inlet dilution system according to any one of claim 8 to 10 or 12 wherein control over the outlet from the hollow drive rod through the hollow rotor of the progressive cavity pump is variable, a flow control valve 24 and a bleed off valve being used as a means of regulating flow.

14. A pump inlet dilution system according to any one of claim 8 to 13 wherein the delivery tube has a diameter and the hollow rotor has an internal diameter less than the diameter of the delivery tube.

15. A pump inlet dilution system according to any one of claim 8 to 14 wherein the hollow rotor has an inside diameter less than 3/4”.

16. The method according to any one of the claims 1 -7 including the step of selecting a hollow rotor having a bore size according to predicted flow rates for particular well conditions.

17. The method according to any one of the claims 1-7 including the step of selecting a hollow rotor having a bore size in the range of between 1/4” and 3/4” diameter.