Fluid lifting system to be placed in fluid production well, associated fluid production apparatus and method

Abstract

A fluid lifting system (20) comprising:-a fluid pump (40) having a pump stator (72) and a pump rotor (70) rotatable about a longitudinal axis of rotation (A-A '); -a gas turbine (42) comprising a turbine stator (50) and a turbine rotor (52) defining a gas expansion chamber (58); -a gas injection conduit (54) for introducing a gas flow in the gas expansion chamber (58) to drive the turbine rotor (52) in rotation. The turbine rotor (52) is rotatable about an axis of rotation (A-A '), the turbine rotor (52) and the pump rotor (70) are mechanically coupled such that rotation of the turbine rotor (52) resulting from gas injection from the gas injection conduit (54) drives rotation of the pump rotor (70). The projections of the turbine rotor (52) and the pump rotor (70) on the axis of rotation (A-A') at least partially overlap longitudinally.

Description

Technical Field

[0001] The present invention relates to a fluid lifting system to be placed in a fluid production well, comprising:

[0002] a fluid pump having a pump rotor and a pump stator defining an intermediate fluid pumping space, the pump rotor having an impeller received in the intermediate fluid pumping space, the pump rotor being rotatable about a longitudinal rotation axis,

[0003] a gas turbine comprising a turbine rotor having blades and a turbine stator defining together with the turbine rotor a gas expansion chamber,

[0004] a gas injection conduit configured to receive a gas flow from an external gas source and introduce the gas flow into the gas expansion chamber to drive the turbine rotor in rotation about the longitudinal rotation axis,

[0005] The turbine rotor is rotatable about the longitudinal rotation axis, the turbine rotor and the pump rotor being mechanically coupled such that rotation of the turbine rotor resulting from gas injection from the gas injection conduit drives rotation of the pump rotor. Background Art

[0006] The fluid is, for example, a multiphase fluid comprising various phases, including hydrocarbons and / or water in liquid and gaseous states. The multiphase fluid may include a gas content that varies with time, such as a gas content that gradually decreases with time.

[0007] During production, changes in the phase composition of the produced fluid, in particular a decrease in gas content, may in some cases lead to an increase in the pressure of the fluid column at the bottom of the well.

[0008] In fact, when the gas flow rate is small, the liquid transported in the fluid column in the well has a higher weight contribution due to the higher liquid holdup in the fluid column.

[0009] As a result, the productivity of the equipment may be significantly affected. In some cases, below a critical gas flow rate, the liquid can no longer be lifted by the gas. It then continues to accumulate in the fluid column until production eventually stops due to self-killing of the equipment.

[0010] If such liquid accumulation occurs in the fluid column, a potential production stop can be avoided by establishing an artificial lift of the produced liquid as required. The artificial lift can be performed by gas lift or / and by pumping. Such a solution increases production costs.

[0011] Gas lift is typically performed by injecting gas from the annular space into the production tubing system through gas lift orifices. Injecting gas into the fluid column lightens the fluid column and enhances its circulation to the well surface.

[0012] Likewise, a fluid pump at the bottom of the well can pump the fluid to the surface. As described above, both of these solutions can provide lift, but increase production costs.

[0013] To alleviate this problem, WO2015 / 065574 discloses a fluid lift system in which the gas injected for gas lift is injected into a gas turbine installed in series with a pump. The expansion of the gas in the gas turbine drives the rotor of the pump to rotate, which pumps the liquid upward. At the same time, the gas expanded in the turbine is injected into the fluid column above the fluid lift system to lighten the fluid column.

[0014] This solution is not entirely satisfactory. In fact, the combined length of the gas turbine and the pump in the fluid lift system may not facilitate the insertion of the fluid lift system in the well, especially when the well includes a curved area. In severe cases, a bending of the fluid lift system may occur, which may cause the fluid lift system to become stuck in the well.

[0015] In addition, the delivery of gas to the gas turbine must be isolated from the passage of the fluid pumped by the pump. This means providing a specific pipe through the fluid passage in the fluid lift system, which makes manufacturing more complicated and leads to increased pressure losses. Summary of the invention

[0016] It is an object of the present invention to provide a fluid lift system in a fluid producing well which increases the production of fluid as the fluid column becomes heavier, which fluid lift system is easy to put in place and is very efficient in operation.

[0017] For this purpose, the subject matter of the invention is characterized in that the turbine rotor and the pump rotor at least partially overlap longitudinally in a projection onto the axis of rotation.

[0018] The lifting system according to the invention may include one or more of the following features, taken alone or in any technically feasible combination:

[0019] - the fluid pump is engine-less, the rotation of the pump rotor being driven solely by the rotation of the turbine rotor;

[0020] - the turbine rotor and the pump rotor are directly mechanically coupled, so that a rotation of the turbine rotor about the longitudinal rotation axis at a given angular rotation speed drives the pump rotor in rotation about the rotation axis at the same angular rotation speed;

[0021] - the fluid pump comprises a mechanical separator interposed between the pump rotor and the turbine rotor, the rotation of the turbine rotor at a given first angular rotational speed driving the pump rotor in rotation at a given second angular rotational speed different from the first angular rotational speed, the second angular rotational speed being advantageously lower than the first angular rotational speed;

[0022] - the mechanical separator comprises a non-Newtonian fluid, an epicyclic gear or / and a magnetic coupling interposed between the turbine rotor and the pump rotor;

[0023] - said fluid comprises radial gas passages fluidically connecting said expansion chamber to said intermediate fluid pumping space;

[0024] - the impeller of the pump rotor defines a gas mixing through hole;

[0025] - the turbine rotor and the pump rotor completely overlap longitudinally in their projection onto the axis of rotation;

[0026] - the pump rotor is received within the turbine rotor;

[0027] - the turbine stator receives the turbine rotor, the turbine rotor receives the pump rotor and is mechanically coupled to the pump rotor, the pump rotor receives the pump stator;

[0028] The impeller of the pump rotor has blades which project radially towards the longitudinal axis of rotation, and the blades of the pump rotor project radially away from the axis of rotation.

[0029] The present invention also relates to a fluid production device comprising a fluid production well, wherein the fluid production well has:

[0030] a production tubing system internally defining an inner production tubing and externally defining an outer annular space connected to a gas source at the surface of the well, the production tubing system defining a gas injection inlet extending between the outer annular space and the production tubing,

[0031] - A fluid lifting system as described above, wherein the gas injection conduit is connected to the gas injection inlet.

[0032] The present invention also relates to a fluid lifting method, which comprises the following steps:

[0033] - providing a fluid lifting system as described above in a fluid producing well;

[0034] - providing a gas flow from an external gas source to the gas injection conduit and introducing the gas flow into the gas expansion chamber to drive the turbine rotor in rotation about the longitudinal rotation axis,

[0035] - jointly driving the pump rotor with the turbine rotor to pump fluid through the intermediate fluid pumping space.

[0036] The fluid lifting method according to the invention may include one or more of the following features, taken alone or in any technically feasible combination:

[0037] - it comprises transferring the expanded gas from said expansion chamber to said intermediate fluid pumping space in order to mix said expanded gas with the pumped liquid;

[0038] -It comprises: generating a negative first thermal power in the gas turbine by expansion of the gas in the gas chamber, generating a positive second thermal power in the fluid pump by pumping the fluid through the intermediate pumping space, and providing heat exchange between the gas turbine and the fluid pump to at least partially compensate the second thermal power with the first thermal power. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The invention will be better understood based on the following description given by way of example only and with reference to the accompanying drawings, in which:

[0040] -[ Figure 1 ] Figure 1 is a schematic cross-section of the bottom of a well equipped with a fluid lifting system according to the invention;

[0041] -[ Figure 2 ] Figure 2 is a schematic functional view of a fluid lifting system according to the present invention;

[0042] -[ Figure 3 ] Figure 3 yes Figure 2 Structural diagram of the fluid lifting system. DETAILED DESCRIPTION

[0043] In the following description, the terms "upper", "upward", "upwardly", "uphole", "lower", "downward", "downwardly", "downhole" are given relative to their orientation from the top of the equipment to the bottom of the equipment.

[0044] The terms "inner", "medial", "external", "outer" are given relative to the local central axis of the device. The term "inner" generally refers to being closer to or oriented toward the central axis, while the term "outer" generally refers to being farther from or oriented away from the central axis.

[0045] exist Figure 1 A first fluid production device 10 according to the present invention is partially shown in FIG.

[0046] The fluid production facility 10 includes at least one well 12 drilled in a foundation 14 , an outer casing 19 , and a production tubing system 18 inserted into the casing 19 .

[0047] The fluid production facility 10 further comprises a downhole fluid lifting system 20 according to the invention. It comprises a surface gas source 22 connected to an annular space 24 between the casing 19 and the production tubing 18 to supply gas to the fluid lifting system 20 through the annular space 24.

[0048] exist Figure 1 In the region shown, the well 12 extends along a local central axis AA', which is shown here as vertical. In a variant, the well 12 has inclined regions and / or horizontal regions.

[0049] Well 12 extends from the surface of a foundation 14 (not shown), which may be located on the ground or at the bottom of a body of water, to a lower formation including a fluid reservoir 28. Well 12 is closed by a wellhead (not shown) located at the top of well 12, as is known in the art.

[0050] Casing 19 lines the well 12. In this example, the casing 19 comprises an assembly of cylindrical metal strings which are advantageously held in place with cement.

[0051] The casing 19 or an alternative lower liner (not shown) communicates with a reservoir geological formation 28 containing hydrocarbons and / or water. Thus, a multiphase fluid flow, which may contain hydrocarbons, is generated through perforations 27 present in the well 12 below the lower end of the production tubing system 18.

[0052] In this example, the reservoir geological formation 28 produces, in particular, gases, hydrocarbons such as methane. It also produces liquids, such as water and / or liquid hydrocarbons called oil or condensate.

[0053] The multiphase fluid flow generated from the formation 28 is under pressure, for example, at a pressure greater than 10 bar. Preferably, the liquid is dispersed in the gas in the form of droplets ("mist flow") or in the form of pockets at intervals in the gas ("slug flow"). In a variant, the gas is dispersed in the liquid in the form of droplets or in the form of cavitations.

[0054] The production tubing 18 is surrounded at its lower end by an annular outer packer 30 which is inserted between the casing 19 and the production tubing 18 .

[0055] The packer 30 seals the annular space 24 at the bottom of the production tubing 18. Therefore, fluid produced from the reservoir 18 must flow to the production tubing 18 without entering the annular space 24 above the outer packer 30.

[0056] The production tubing 18 defines an internal production tubing 32 that extends from the bottom of the production tubing 18 near the reservoir 28 to the wellhead at the surface. The annulus 24 is radially bounded by the production tubing 28 toward the axis AA'.

[0057] The production tubing system 18 defines at least one radial gas injection inlet 34 that extends through the production tubing system 18 to connect the annular space 24 to the inner production tubing 32. The gas injection inlet 34 allows gas received from the gas source 22 to be supplied through the annular space 24 to the fluid lift system 20 located in the inner production tubing 32, which will be described below.

[0058] like Figure 2 As shown, the fluid lift system 20 is anchored in the production tubing 32 at a longitudinal location facing the gas injection inlet 34 .

[0059] The fluid lift system 20 includes an internal fluid pump 40 for pumping a multiphase fluid flowing upward in the internal production tubing 32 , and an external gas turbine 42 coaxially receiving the internal fluid pump 40 and driving the fluid pump 40 to rotate.

[0060] The fluid lift system 20 also includes an anchoring system 44 for longitudinally anchoring the external gas turbine 42 in the production tubing 18 , and a sealing system 46 for directing gas received from the gas injection inlet 34 only to the gas turbine 42 .

[0061] like Figure 2 and Figure 3 As shown, according to the invention, the external gas turbine 42 and the internal fluid pump 40 overlap longitudinally in a projection onto the axis AA′ over the entire length of the external gas turbine 42. In this example, the internal fluid pump 40 is received completely in the center of the external gas turbine 42.

[0062] Reference Figure 3 The external gas turbine 42 includes an external turbine stator 50 and a turbine rotor 52 in a radial direction toward the axis A-A', the external turbine stator 50 being fixed to the production piping system 18 via the anchoring system 44, and the turbine rotor 52 being rotatably mounted in the turbine stator 50 around the rotation axis A-A', and the rotation axis A-A' corresponds to the central longitudinal axis A-A' of the production piping system 18.

[0063] The external gas turbine 42 also includes a gas injection conduit 54 to supply the turbine rotor 52 with gas from the gas injection inlet 34 .

[0064] The turbine stator 50 comprises a sleeve 56 defining an outer wall of the gas turbine. The sleeve 56, together with the turbine rotor 52, internally delimits a gas expansion chamber 58 which receives gas from the gas injection conduit 54 to drive the turbine rotor 52 in rotation.

[0065] The turbine rotor 52 includes, for example, a rotating hub 60 and rotating blades 62 protruding from the hub 60 toward the sleeve 56 in the expansion chamber 58. The expansion of the gas received from the gas injection inlet 34 in the expansion chamber 58 acts on the rotating blades 62 to jointly drive the blades 62 and the hub 60 of the turbine rotor 52 to rotate relative to the turbine stator 50 about the axis A-A'.

[0066] The pump 40 includes an outer pump rotor 70 mechanically connected to the inner turbine rotor 52 to be driven in rotation by the turbine rotor 52 and an inner pump stator 72 placed at the center of the pump rotor 70 to guide the pump rotor 70 to rotate about the axis AA′.

[0067] The pump rotor 70 includes an inner impeller 74 having blades protruding toward the pump stator 72 in an intermediate fluid pumping space 76 defined between the pump rotor 70 and the pump stator 72 .

[0068] The intermediate fluid pumping space 76 opens downwardly and upwardly in the inner production tubing 32 to allow fluid to be sucked in from below the fluid lifting system 20 and to allow the pumped fluid to be ejected above the fluid lifting system 20 after being pumped by the outer pump rotor 70 .

[0069] The outer pump rotor 70 is rotatably mounted relative to the inner pump stator 72 about the axis AA′.

[0070] exist Figure 3 In the example shown, the pump rotor 70 is directly mechanically connected to the turbine rotor 52 , so that a rotation of the turbine rotor 52 about the axis AA′ at a given angular rotational speed provides a concomitant rotation of the pump rotor 70 about the axis of rotation AA′ at the same angular rotational speed.

[0071] exist Figure 3 In a variant shown in dashed lines in FIG. 8 , a mechanical separator 68 is provided between the turbine rotor 52 and the pump rotor 70 .

[0072] The mechanical separator 68 comprises, for example, a non-Newtonian fluid to adjust the separation based on the angular rotational speed of the pump rotor 70 as a function of the speed of the turbine rotor 52. Alternatively, the mechanical separator 68 comprises an epicyclic gear or a magnetic coupling with magnets. Preferably, the mechanical separator 68 comprises at least one bearing 79 to keep the turbine rotor 52 and the pump rotor 70 well centered and supported for rotation.

[0073] Typically, when the turbine rotor 52 is driven to rotate at a given first angular rotation speed, the mechanical separator 68 allows the pump rotor 70 to be driven to rotate at a given second angular rotation speed. The given second angular rotation speed is, for example, greater than or lower than the given first angular rotation speed. Advantageously, the mechanical separator 68 comprises a gearbox (not shown) capable of varying the ratio of the given second angular speed to the given first angular speed.

[0074] In any case, the pump rotor 70 is driven in rotation about the axis AA′ only by the turbine rotor 52 , without rotational drive being provided by a hydraulic or electric motor.

[0075] The pump stator 72 extends along the axis AA' in the middle of the outer pump rotor 70. It comprises a cylindrical base and arms (not shown) connected to the turbine stator 50. The arms define between them through openings for the flow of the fluid.

[0076] The anchoring system 44 includes at least one anchor 80 that radially projects from the sleeve 56 of the turbine stator 50 for attachment to the production tubing 18. The production tubing 18 preferably includes a corresponding receptacle that receives the anchor 80.

[0077] The anchor 80 radially spaces the turbine stator 50 from the production tubing 18 such that an outer peripheral space 82 is defined around the turbine stator 50 between the turbine stator 50 and the production tubing 18 .

[0078] The sealing system 46 includes at least one upper seal 84 for tightly closing the peripheral space 82 in the uphole direction, and at least one lower seal 86 for tightly closing the peripheral space 82 in the downhole direction.

[0079] Thus, peripheral space 82 communicates only with gas injection inlet 34 on one side and with gas injection conduit 54 on the other side. Gas from the source flowing from annular space 24 through gas injection inlet 34 flows directly and exclusively through gas injection conduit 54 to expansion chamber 58.

[0080] In a preferred embodiment, the hub 60 of the turbine rotor 52 , the mechanical separator 68 (if present) and the pump rotor 70 define at least one radial gas through channel connecting the expansion chamber 58 to the intermediate fluid pumping space 76 .

[0081] Preferably, the blades of the impeller 74 define a through longitudinal through hole 75 , through which the gas flowing out of the radial passage is discharged and mixed.

[0082] Thus, the gas expanded in the intermediate chamber 58 is discharged through the radial through passages to the intermediate fluid pumping space 76 and mixes with the fluid pumped in the intermediate fluid pumping space 76. Further mixing and gas lift effects are advantageously provided by the passage of the gas through the holes 75 formed in the blades of the impeller 74.

[0083] The operation of fluid lift system 20 to increase fluid production in apparatus 10 will now be described.

[0084] During production, fluid from the reservoir 28 enters the well 12 beneath the fluid lift system 20 and flows upward in the production tubing 18 .

[0085] Simultaneously, gas from gas source 22 is injected into well annulus 24 and flows downhole toward gas injection inlet 34. Gas enters peripheral space 82 around turbine stator 50 and is longitudinally confined therein by seals 84, 86 of sealing system 46.

[0086] Thus, the gas flows to the gas injection conduit 54 and enters the expansion chamber 58. In the expansion chamber 58, the gas expands and interacts with the blades 62 to drive the turbine rotor 52 in rotation about the rotation axis AA'.

[0087] The rotation of the turbine rotor 52 in turn drives the pump rotor 70 to rotate about the pump stator 72 .

[0088] Thus, fluid flowing below the fluid lift system 20 enters the intermediate fluid pumping space 76 and is pumped uphole to be ejected from the fluid lift system 20 toward the surface.

[0089] Preferably, the gas expanding in the chamber 58 flows through the or each radial passage into the intermediate fluid pumping space 76 and mixes with the pumped fluid. When the gas circulates into the through holes 75 formed on the blades of the impeller 74, a jet effect is advantageously produced.

[0090] Due to the arrangement of the fluid lifting system 20, fluid can be lifted with low energy consumption, with the internal pump 40 received in and driven in rotation by the external gas turbine 42. The fluid lifting system 20 is also very compact, which facilitates its introduction into the well 12.

[0091] The gas supplied to the external gas turbine 42 is completely separated from the fluid pumped in the internal pump 40, which simplifies the structure and piping system within the fluid lifting system 20. However, further mixing of the gas expanded in the external gas turbine 42 with the pumped fluid can be performed in the uphole stage of the internal pump 40. In some cases, a jet pump effect can be obtained, especially when through holes are provided on the blades of the pump impeller 74.

[0092] Thus, fluid management within the fluid lift system 20 is simplified and less pressure drop occurs.

[0093] Another advantage of the arrangement of the fluid lifting system 20 according to the invention is the compensation of thermal effects occurring in the fluid lifting system 20. In fact, the expansion of the gas in the expansion chamber 58 of the external gas turbine 42 generates negative thermal power. Conversely, the compression of the fluid in the internal pump 40 provides positive thermal power. Since the internal pump 40 has at least a longitudinal overlap with the external gas turbine 42, thermal power can be exchanged between the internal pump 40 and the external gas turbine 42 to compensate for the above-mentioned thermal effects.

Claims

1. A fluid lifting system (20) to be placed in a fluid production well (12), comprising: a fluid pump (40) having a pump rotor (70) and a pump stator (72) defining an intermediate fluid pumping space (76), the pump rotor (70) having an impeller (74) received in the intermediate fluid pumping space (76), the pump rotor (70) being rotatable about a longitudinal rotation axis (A-A'), a gas turbine (42) comprising a turbine rotor (52) having blades (62) and a turbine stator (50) which defines, together with the turbine rotor (52), a gas expansion chamber (58), a gas injection conduit (54) configured to receive a gas flow from an external gas source (22) and to introduce the gas flow into the gas expansion chamber (58) to drive the turbine rotor (52) in rotation about the longitudinal rotation axis (A-A'), The turbine rotor (52) is rotatable about the longitudinal rotation axis (AA'), the turbine rotor (52) and the pump rotor (70) being mechanically coupled such that rotation of the turbine rotor (52) caused by gas injection from the gas injection conduit (54) drives rotation of the pump rotor (70), It is characterized in that the turbine rotor (52) and the pump rotor (70) at least partially overlap longitudinally in a projection onto the axis of rotation (AA').

2. The fluid lift system (20) of claim 1, wherein the fluid pump (40) is engine-less, the rotation of the pump rotor (70) being driven solely by the rotation of the turbine rotor (52).

3. The fluid lifting system (20) according to any one of claims 1 to 2, wherein the turbine rotor (52) and the pump rotor (70) are directly mechanically coupled so that rotation of the turbine rotor (52) about the longitudinal rotation axis (A-A') at a given angular rotation speed drives the pump rotor (70) to rotate about the rotation axis (A-A') at the same angular rotation speed.

4. A fluid lifting system (20) according to any one of claims 1 to 2, comprising a mechanical separator (68) inserted between the pump rotor (70) and the turbine rotor (52), wherein the rotation of the turbine rotor (52) at a given first angular rotation speed drives the pump rotor (70) to rotate at a given second angular rotation speed, which is different from the first angular rotation speed and is advantageously less than the first angular rotation speed.

5. The fluid lift system (20) of claim 4, wherein the mechanical separator (68) comprises a non-Newtonian fluid, an epicyclic gear, or / and a magnetic coupling interposed between the turbine rotor (52) and the pump rotor (70).

6. The fluid lift system (20) according to any one of the preceding claims, comprising a radial gas passage fluidly connecting the expansion chamber (58) to the intermediate fluid pumping space (76).

7. The fluid lifting system (20) according to any one of the preceding claims, wherein the impeller (74) of the pump rotor (70) defines a gas mixing through hole (75).

8. The fluid lifting system (20) according to any of the preceding claims, wherein the turbine rotor (52) and the pump rotor (70) completely overlap longitudinally in a projection onto the rotation axis (AA').

9. The fluid lift system (20) of any preceding claim, wherein the pump rotor (70) is received within the turbine rotor (52).

10. The fluid lift system (20) of claim 9, wherein the turbine stator (50) receives the turbine rotor (52), the turbine rotor (52) receives the pump rotor (70) and is mechanically coupled to the pump rotor (70), the pump rotor (70) receiving the pump stator (72).

11. A fluid lifting system (20) according to any of the preceding claims, wherein the impeller (74) of the pump rotor (70) has blades that protrude radially toward the longitudinal rotation axis (A-A'), and the blades (62) of the pump rotor (70) protrude radially away from the rotation axis (A-A').

12. A fluid production device (10), comprising a fluid production well (12), wherein the fluid production well has: a production piping system (18) which internally defines an internal production piping (32) and externally defines an outer annular space (24), the outer annular space (24) being connected to a gas source (22) at the surface of the well (12), the production piping system (18) defining a gas injection inlet (34) extending between the outer annular space (24) and the production piping (32), - The fluid lifting system (20) according to any of the preceding claims, the gas injection conduit (54) being connected to the gas injection inlet (34).

13. A fluid lifting method comprising the following steps: - providing a fluid lifting system (20) according to any one of the preceding claims in a fluid production well (12); - providing a gas flow from an external gas source (22) to the gas injection conduit (54) and introducing the gas flow into the gas expansion chamber (58) to drive the turbine rotor (52) in rotation about the longitudinal rotation axis (A-A'), - using the turbine rotor (52) to jointly drive the pump rotor (70) to pump fluid through the intermediate fluid pumping space (76).

14. A fluid lifting method according to claim 13, comprising transferring expanding gas from the expansion chamber (58) to the intermediate fluid pumping space (76) to mix the expanding gas with the pumped liquid.

15. The fluid lifting method according to any one of claims 13 or 14, comprising: A negative first thermal power is generated in the gas turbine (42) by expansion of the gas in the gas chamber (58), and a positive second thermal power is generated in the fluid pump (40) by pumping the fluid through the intermediate pumping space (76), and heat exchange is provided between the gas turbine (42) and the fluid pump (40) to at least partially compensate the second thermal power with the first thermal power.

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