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The present invention concerns a turbine assembly driven by a driving fluid to power a fluid lifting system to be placed in a well, comprising;
- a turbine comprising a turbine stator and a turbine rotor having blades rotatably mounted in the turbine stator about a rotation axis, the turbine rotor having a connection configured to be connected to a pump rotor of a pump;
- a driving fluid admitter located on one side of the turbine stator in reference to the rotation axis, the driving fluid admitter comprising a driving fluid admission inlet to be connected to an external pressurized driving fluid source and a driving fluid conveying passage connecting the driving fluid admission inlet to the turbine stator to feed driving fluid in the turbine stator and drive the turbine rotor in rotation about the rotation axis by expansion of the driving fluid,
- a driving fluid evacuation assembly located on a side of the turbine stator opposed to the driving fluid admitter in reference to the rotation axis.
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The turbine is in particular a gas turbine. The turbine is configured to be assembled to a fluid pump having at least a pump stator and a pump rotor, the pump rotor having an impeller which rotates to pump production fluid produced in the well from a reservoir. The rotor is driven in rotation by the turbine rotor.
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The fluid which is pumped is for example a multiphase fluid comprising various phases including liquid and gaseous hydrocarbons and/or water. The multiphase fluid may comprise a gas content which varies along time.
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During spontaneous fluid production in a well, without pumping the produced fluid, a change of phase composition of the produced fluid, in particular a decrease of the gas content may lead in some instances to an increase of pressure of the fluid column at the bottom of the well.
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Indeed, the liquids conveyed in the fluid column in the well have a higher weight contribution when the gas flow rate is smaller due to higher liquid hold-up in the fluid column.
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The productivity of the installation can thus be significantly affected. In some instances, below a critical gas flow rate, the liquid cannot longer be lifted by the gas. It then continuously accumulates in the fluid column, until the production eventually stops by installation self-killing.
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If such an accumulation of liquid in the fluid column occurs, a potential stop of production can be avoided by creating an artificial lift of the produced liquid. The artificial lift can be carried out through gas lift or/and through pumping.
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Gas lift is usually carried out by injecting gas from the annulus to the production tubing via a gas lift orifice. Injection of gas into the fluid column lightens the fluid column and enhances its circulation towards the surface of the well.
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Similarly, a fluid pump at the bottom of the well can be operated to pump fluid to the surface.
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These two solutions provide lift, but increase production costs.
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In order to decrease costs,
WO 2024/028626 discloses a fluid lifting system in which a turbine rotor mechanically connected to the pump rotor is driven in rotation by injecting gas in a gas expansion chamber of the turbine. The gas is provided from an annular space of the well located between the production tubing and the casing.
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Such a solution is very efficient, since it does not require an external source of energy to drive the pump.
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When the fluid lifting system is set up in the well, it has to be lowered through the production tubing, for example until the fluid lifting system reaches a side pocket having a gas injection inlet.
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At the side pocket, the fluid lifting device is tightly fixed in the well, and gas from the annular space is injected in the side pocket to reach a gas driving fluid admission inlet of the fluid lifting system.
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In many cases, the annular space and/or the side pocket initially comprise liquids and/or solids which are carried by the gas injected in the turbine. Consequently, the liquids and/or solids enter the turbine gas expansion chamber via the gas driving fluid admission inlet and the gas admission passage.
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The liquids and solids contained in the well may sometimes comprise larger particles which may get stuck between the turbine rotor and the turbine stator and between the blades, blocking or damaging the turbine.
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This is specially the case when the turbine is designed to rotate at very high speed under the effect of gas expansion.
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One aim of the invention is to provide a turbine assembly to be mounted on a well pump that can drive the well pump to enhance fluid production towards the surface, the turbine being configured to be safely and reliably driven in rotation by a driving fluid arising from an annular space of the well.
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To this aim, the invention concerns a turbine assembly for a fluid lifting system as described above, characterized by:
- a strainer, positioned in the driving fluid admission inlet or between the driving fluid admission inlet and the turbine, the strainer being configured to filter the whole of the driving fluid admitted in the turbine.
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The turbine assembly according to the invention may comprise one or more of the following features, taken solely or according to any technical feasible combination:
- the strainer defines filtering passages, a maximum transverse dimension of each filtering passage being less than 1 mm, advantageously being comprised between 500 µm and 50 µm, in particular between 250 µm and 80 µm;
- the driving fluid admitter comprises an outer sleeve having an axis extending along the rotation axis, the outer sleeve defining the driving fluid admission inlet, the driving fluid admission inlet and the strainer being annular;
- the driving fluid admission inlet is located on the side of the turbine stator opposed to the connection;
- the driving fluid admitter has a safety valve connected to the driving fluid conveying passage, the safety valve being configured to open at a predetermined pressure, the safety valve advantageously emerging axially along the rotation axis;
- the driving fluid conveying passage comprises a driving fluid flow limiter, configured to limit the driving fluid flow circulating in the fluid conveying passage at a predetermined maximum flow rate;
- the evacuation assembly is located between the turbine stator and the connection;
- the evacuation assembly comprises at least an evacuation opening;
- the or each evacuation opening opens at least partially upwardly, the evacuation assembly comprising an axial section directed downwardly towards the evacuation opening and a flow direction inversion section connecting the axial section to the or each evacuation opening;
- the evacuation opening is annular, or the evacuation assembly comprises a plurality of separate evacuation openings;
- the or each evacuation assembly comprises at least a flapper movable between a rest closed position closing at least one evacuation opening and an opened fluid evacuation position in which the at least one evacuation opening is at least partially open, the at least one flapper being biased toward the rest closed position.
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The invention also concerns a fluid lifting system comprising a turbine assembly as defined above and a fluid pump having a pump stator and a pump rotor being connected to the turbine rotor via the connection.
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The fluid lifting system according to the invention may comprise one or more of the following features, taken solely or according to any technical feasible combination:
- the pump rotor is connected to the turbine rotor without a mechanical seal;
- the fluid lifting system is retrievable, in particular retrievable by or using a slickline, an electrical line, a coiled tubing, the fluid lifting system comprising at least an upper lock mandrel, a lower lock mandrel and a stinger, to fix the position of the fluid lifting system in the well.
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The invention also concerns a method to pump fluid in a well comprising the following steps:
- providing a fluid lifting system as defined above in the well,
- admitting a driving fluid from an external pressurized gas source via the driving fluid admission inlet of the driving fluid admitter, and conveying the driving fluid to the turbine stator through the driving fluid conveying passage;
- expanding the driving fluid to drive the turbine rotor in rotation about the rotation axis, and evacuating the driving fluid via the driving fluid evacuation assembly;
- jointly rotating the turbine rotor using the turbine stator to pump fluid through the pump;
characterized by filtering the whole of the driving fluid feeding the turbine stator through the strainer, in the driving fluid admission inlet or between the driving fluid admission inlet and the turbine.
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The invention also concerns a fluid lifting system, powered by a driving fluid, to be placed in a well, comprising:
- a turbine assembly comprising:
- * a turbine comprising a turbine stator and a turbine rotor having blades rotatably mounted in the turbine stator about a rotation axis, the turbine rotor having a connection;
- * a driving fluid admission inlet connected to the turbine stator on one side of the turbine stator in reference to the rotation axis, to feed driving fluid in the turbine stator and drive the turbine rotor in rotation about the rotation axis by expansion of the driving fluid,
- * a driving fluid evacuation assembly located on a side of the turbine stator opposed to the driving fluid inlet in reference to the rotation axis,
- the fluid lifting system comprising a fluid pump having a pump stator and a pump rotor being connected to the turbine rotor via the connection, on the side of the turbine stator opposed to the driving fluid inlet in reference to the rotation axis ;
- characterized by a coiled tubing connected to the driving fluid admission inlet, the coiled tubing defining a driving fluid inner feed passage, to be connected to an external pressurized driving fluid source, preferably located at the surface, to feed driving fluid from the external source in the driving fluid admission inlet.
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The turbine assembly is preferably without a strainer positioned in the driving fluid admission inlet or between the driving fluid admission inlet and the turbine.
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The turbine assembly may comprise one or more of the above features, taken solely or according to any technical feasible combination.
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Preferably, the driving fluid evacuation assembly is located between the turbine and the pump, in particular between the turbine stator and the connection.
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The invention will be better understood, based on the following description, given solely as an example, and made in reference to the following drawings, in which:
- Figure 1 is a schematic view, partially in section, of a fluid lifting system according to the invention, positioned in a side pocket of a well production tubing;
- Figure 2 is a partially cut-down view in perspective of the turbine and pump of the fluid lifting system according to the invention;
- Figure 3 is an elevation view, partially in section of the turbine and the pump of the fluid lifting system of figure 1;
- Figure 4 is a partially cut-down view in perspective of an upper part of the turbine according to the invention, depicting a strainer at the driving fluid admission inlet of the turbine;
- Figure 5 is a partially cut-down view in perspective of a first embodiment of a driving fluid evacuation outlet of the turbine;
- Figure 6 is a view similar to figure 5 showing a variant of figure 5;
- Figure 7 is a cross section, taken in the plane VII of figure 2, of the strainer located around an outer sleeve of the gas turbine.
- Figure 8 is a view similar to figure 1 of a variant of fluid lifting system.
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In the following description, the terms "upper", "upwards", "upwardly", "uphole", "lower", "downwards", "downwardly", "downhole" are given relative to their orientation from the top of the installation to the bottom of the installation.
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The terms "inward", "inside", "outward", "outside" are given relative to a local central axis of the installation. The term "inside" generally means closer or oriented towards the central axis, whereas the term "outside" generally means further away or oriented away from the central axis.
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A first fluid production installation 10 according to the invention is shown partially in figure 1.
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The fluid production installation 10 comprises at least one well 12 bored in a subsoil 14, an outer casing 19, and a production tubing 18 inserted in the casing 19.
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The fluid production installation 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 feed gas to the fluid lifting system 20 through the annular space 24.
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In the region shown in figure 1, the well 12 extends along a local central axis A-A' which is here shown vertical. In a variant, the well 12 has inclined regions, and/or horizontal regions.
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The well 12 extends from the surface of the subsoil 14 (not shown), which can be located on the ground or at the bottom of a body of water, to a lower formation including a fluid reservoir 28. As known in the art, the well 12 is closed by a wellhead (not shown) located at the top of the well 12.
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The 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.
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The casing 19 or an alternative lower liner (not shown) is in communication with a reservoir 28 geological formation of the subsoil 14, containing hydrocarbons and/or water. Thus, a multiphase fluid stream, which can comprise liquid hydrocarbons, gas and water, is produced through perforations 27 emerging in the well 12, downhole of the lower end of the production tubing 18.
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In this example, the reservoir 28 geological formation produces gas in particular, hydrocarbons such as methane. It also produces liquids, for example water and/or liquid hydrocarbons called oil or condensates.
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The multiphase fluid stream produced from the reservoir 28 is under pressure, for example at a pressure greater than 10 bars. The liquid is dispersed in the gas in the form of droplets ("mist flow"), or at intervals in the form of liquid pockets, ("slug flow"). In variant, the gas is dispersed in the liquid, in the form of droplets or in the form of gas pockets.
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The production tubing 18 is surrounded at its lower end with an annular outer packer 30, interposed between the casing 19 and the production tubing 18.
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The packer 30 seals the annular space 24 at the bottom of the production tubing 18. Hence, the fluid produced from the reservoir 28 necessarily flows to the production tubing 18 without entering the annular space 24 uphole of the outer packer 30.
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The production tubing 18 defines an internal production canal 32, which extends from the bottom of the production tubing 18, in the vicinity of the reservoir 28, to the wellhead at the surface. The annular space 24 is radially delimited towards the axis A-A' by the production tubing 18 and the casing 19.
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The production tubing 18 delimits at least an axial or radial gas injection inlet 34 which extends through the production tubing 18 to connect the annular space 24 to the internal production canal 32. The gas injection inlet 34 is configured to let a flow of driving fluid, in particular gas received from the gas source 22, pass from the annular space 24 to the fluid lifting system 20 located in the internal production canal 32, as will be described below.
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The gas injection inlet 34 is here located in a side pocket mandrel 36 defining a radially protruding region of the production tubing 18, protruding externally from the axis A-A'. The side pocket mandrel 36 internally defines a side pocket 37 where a gas lift valve 38 is present.
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As shown in figure 1, the fluid lifting system 20 is anchored in the production canal 32 at a longitudinal position overlapping the side pocket 37.
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The fluid lifting system 20 is preferably retrievable. It is thus configured to be introduced reversibly in the production tubing 18 of the well 12 using a wireline such as an electrical line, a slickline, and/or a coiled tubing and to be removed from the production tubing 18 also using a wireline.
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In a variant, not shown, the downhole fluid lifting system 20 is permanently assembled in the production tubing 18 and is not retrievable by a wireline without removing the production tubing 18.
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In the example of figures 1 to 5, the fluid lifting system 20 comprises a fluid pump 40, to pump the multi-phase fluid flowing upwardly in the internal production canal 32, and a gas turbine 42, coaxially connected to the fluid pump 40, above the fluid pump 40, to drive the fluid pump 40 exclusively with a driving fluid, in particular a gas injected from the gas source 22.
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As shown in figures 1 and 2, the fluid lifting system 20 further comprises an upper sleeve 44 defining part of a turbine driving fluid admitter 46, located above the gas turbine 42, and advantageously a lower sleeve 48 to cover the fluid turbine 42 and the fluid pump 40.
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The fluid lifting system 20 also includes an anchoring and sealing system comprising lock mandrels (which will be described further below) to maintain the fluid lifting system 20 in position in the production tubing 18, overlapping the side pocket mandrel 36.
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As shown in figure 4, the upper sleeve 44 comprises an upper sleeve part 60 to connect to the anchoring and sealing system 50, and a lower sleeve part 62 to connect to the lower sleeve 48. The upper sleeve part 60 is generally referred to as a « cross-over ».
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In addition to the upper sleeve 44, the turbine driving fluid admitter 46 also comprises a central hub 64 to which an upper end of the turbine 42 is assembled, and at least a connection arm 66 to connect the lower sleeve part 62 to the central hub 64.
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The turbine driving fluid admitter 46 further comprises a connection sleeve 65, mounted around a lower part of the central hub 64, an upper tapping 68 and a fluid flow limiter 70.
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The turbine driving fluid admitter 46 includes at least one, in particular several driving fluid admission inlets 72, defined in the upper sleeve 44 to receive driving fluid from the side pocket 37, and a strainer 74, covering the driving fluid admission inlet 72 to filter liquids and/or solids potentially contained in the driving fluid.
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The or each driving fluid admission inlet 72 is here defined between the upper sleeve part 60 (or cross-over) and the lower sleeve part 62. In the example of figures 2, 4 and 7, it has an annular shape around the central axis A-A'.
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The strainer 74 has filtering passages, for example holes or/and slots, to filter liquids and/or solids within the driving fluid. The filtering passages have a maximum transverse dimension which is less than 1 mm, in particular comprised between 500 µm and 50 µm, in particular between 250 µm and 80 µm.
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The strainer 74 totally covers the driving fluid admission inlet 72, such that the driving fluid admitted in the driving fluid admitter 46 necessarily passes through the strainer 74. In the example of figures 2, 4 and 7, the strainer 74 is annular.
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In the example of figures 2 and 4, the strainer 74 is tightly mounted in the driving fluid admission inlet 72 via at least two annular gaskets 76, which are positioned at its lower and upper edges.
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In reference to figure 7, the strainer 74 comprises inner radial protrusions 78, which lay on the outer surface of the upper sleeve 44, and define an interspace 80 between the outer surface and the strainer 74.
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As shown in figure 4, the central hub 64 extends axially within the lower part 62. It defines a central lumen 82 extending from the tapping 68 to the fluid flow limiter 70.
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In the example shown in figures 2 and 4, the driving fluid admitter 46 comprises at least one connection arm 66, for example three connection arms 66 connecting the outer sleeve 44 to the central hub 64.
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The or each connection arm 66 defines a radial lumen 84, connecting the interspace 80 to the central lumen 82.
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The connection sleeve 65 extends about the lower part of the central hub 64. It defines, with the lower end of the central hub 64, an intermediate space 86 connected to the central lumen 82 via radial through holes 88.
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The radial lumen 84, the central lumen 82, the radial through holes 88 and the annular space 86 define a fluid conveying passage 90 which connects the driving fluid admission inlet 72 to the turbine 42 to feed the turbine 42 with driving fluid flowing through the driving fluid admission inlet 72.
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The upper tapping 68 at least partially protrudes from the central hub 64 along the central axis A-A'.
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It comprises a driving fluid diffusion nozzle 92, and a safety valve 94 separating the diffusion nozzle 92 from the fluid conveying passage 90. The safety valve 94 is here formed of a rupture disc or a relief valve which is configured to open at a predetermined pressure to allow the driving fluid to bypass the turbine 42.
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The fluid flow limiter 70 comprises a sliding sleeve 96, mounted sliding within the central lumen 82 along the central axis A-A', and a biasing member 98, interposed between a transverse stop surface 100 of the central hub 64 and the sliding sleeve 96.
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The sliding sleeve 96 defines through apertures 102, which extend through the sleeve 96 and open radially. Depending on the position of the sliding sleeve 96 along the axis A-A', the percentage of overlap between the radial through holes 88 and the through apertures 102 varies.
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The biasing member 98 is for example formed of a helical spring.
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The biasing member 98 biases the sliding sleeve 96 away from the turbine 42 to maximize the overlap between the through apertures 102 and the radial through holes 88 at lower flows of the driving fluid. This maximizes the flowrate through the fluid conveying passage 90.
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At higher driving fluid flows, the biasing member 98 allows the sliding sleeve 96 to move towards the turbine 42, to lower the overlap between the through apertures 102 and the radial through holes 88. This limits the flowrate through the fluid conveying passage 90.
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The spring 98 is prestressed so the sleeve 96 moves only when the driving fluid flow is above a predefined maximum flow. Therefore, the overlap between the through apertures 102 and the radial through holes 88 get smaller, reducing both flow and pressure entrance of the turbine 42 and therefore, its power as well as its rotation speed.
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The turbine 42 is located downhole of the driving fluid admitter 46, here below the driving fluid admitter 46 in the vertical well 12, shown in figures 1 and 2.
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The turbine 42 comprises a turbine stator 110, connected to the driving fluid admitter 46, the turbine stator 110 defining an inner expansion chamber 112.
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The turbine 42 further comprises a turbine rotor 114, rotatably mounted within the turbine stator 110 about a rotation axis A-A', and a connection 116 to connect to the pump 40.
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The turbine 42 also has a driving fluid evacuation assembly 118, positioned at the bottom end of the turbine stator 110 to allow the evacuation of driving fluid out of the inner expansion chamber 112, without allowing production fluid to enter the inner expansion chamber 112.
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The turbine stator 110 comprises an outer sheath 120 whose upper end is tightly assembled on the connection sleeve 65 of the driving fluid admitter 46 (see figure 2). The outer sheath 120 has an upper end, which is here tapered toward the axis A-A' in an upwards direction. The outer sheath 120 radially delimits the inner expansion chamber 112 in a tight manner.
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The inner expansion chamber 112 is thus fluidly connected to the fluid conveying passage 90 of the driving fluid admitter 46 at the upper end of the turbine stator 110, to receive driving fluid from the fluid conveying passage 90. It emerges downwardly at the driving fluid evacuation assembly 118 located at the lower end of the turbine stator 110.
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The turbine rotor 114 is mounted in the inner expansion chamber 112. It comprises a central rotating shaft 122 and rotating blades 124 extending radially from the rotating shaft 122.
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The turbine rotor 114 is driven in rotation about the rotation axis A-A' exclusively via driving fluid introduced in the inner expansion chamber 112, by expansion of the driving fluid which acts on the blades 124.
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The lower end of the turbine stator 110 has a taper 126, from which a connecting flange 128 extends.
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The driving fluid admitter 46 is located on one side of the turbine stator 110 in reference to the rotation axis A-A', uphole of the turbine stator 110 along the rotation axis A-A'. The driving fluid evacuation assembly 118 is located on a side of the turbine stator 110, opposed to the driving fluid admitter 46 in reference to the rotation axis A-A', between the turbine stator 110 and the connection 116, downhole of the turbine stator 110 along the rotation axis A-A'.
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An example of driving fluid evacuation assembly 118 is shown in figure 5. It is mounted on the connecting flange 128 at the lower end of the turbine stator 110.
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The driving fluid evacuation assembly 118 comprises a central body 130 defining at least one opening 132 to evacuate the driving fluid, and a flapper 134, elastically movable between a rest closed position, in which it closes the opening 132, and an open position in which it lets driving fluid evacuate through the opening 132.
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The body 130 comprises at least a complementary flange 136, configured to mate with the connecting flange 128 of the turbine stator 110, and a central bore 138, extending along the rotation axis A-A', through which the turbine rotating shaft 122 protrudes.
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The body 130 defines an evacuation outlet with an annular axial section 140 directed downwardly, and a lower direction inversion section 142, connecting the downward axial section to the or each opening 132. In the example of figure 5, the body 130 defines a single annular opening 132 which extends about the rotation axis A-A'.
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The body 130 comprises connecting blades 144 connecting a central portion 146 of the body 134 with an outer peripheral section 148 of the body 134 through the annular axial section 140.
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The flow inversion direction section 142 allows the opening 132 to open at least partially upwardly. In the example of figure 5, it has a volute shape in cross section in at least a longitudinal median plane containing the rotation axis A-A'.
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The flapper 134 is here made of an elastic material. The elastic material is for example an elastomeric material such as rubber or an elastic alloy such as Ti6AI4V.
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The flapper 134 has a base 150 engaged below the body 130, and a shutter 152, elastically deformable, and positioned facing the opening 132.
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As mentioned above, the shutter 152 is biased against the opening 132 to close it in a rest position.
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The shutter 152 is configured to deform under the pressure of the driving fluid which is evacuated through the opening 132 to let the gas flow out of the inner expansion chamber 112 upwardly.
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Thanks to the upward orientation of the opening 132, the driving fluid, preferably in a gaseous form, evacuates upwardly and not towards the pump 40. It thus does not mix with the production fluid inside the pump 40, which would affect the pumping efficiency of the pump 40. On the contrary, the driving fluid contributes to lifting the production fluid emerging from opening 132, acting as jet-pump.
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The shutter 152 remains in the rest position when no driving fluid is evacuated. This closes the opening 132 and prevents production fluid to enter the inner expansion chamber 112 through the opening 132.
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As shown in figure 3, the pump 40 has a pump stator 160 defining an inner pumping chamber 162 and a pump rotor 164, mounted in the inner pumping chamber 162 downhole of the turbine rotor 114, below the turbine rotor 114.
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The pump stator 160 has an outer wall 166 having an inner surface defining the inner pumping chamber 162. In the example of figure 3, the inner pumping chamber 162 has a Venturi shape, at the outlet of the pump stator 160, to accelerate fluid pumped by the pump rotor 164.
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The pump rotor 164 is received within the inner pumping chamber 162. It comprises a pump shaft 170 and vanes 172 protruding radially from the pump shaft 170. The pump shaft 170 is made in one piece with the connection 116 or connected to the connection 116 through the turbine rotor 114.
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The pump shaft 170 is located below the central rotary shaft 122 of the turbine rotor 114. The pump shaft 170 and the central rotary shaft 122 of the turbine rotor 114 extend coaxially along the axis A-A'.
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In the example of figure 3, the pump shaft 170 is connected to the turbine rotor 114 without mechanical seal, and without a speed reducer.
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The connection 116 is configured such that the distance between the turbine rotor 114 and the pump rotor 164 is advantageously smaller than 1 m, preferentially below 0.5 m, thanks to the positioning of the driving fluid admitter 46 including the strainer 74 above the turbine 42.
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This prevents resonances to occur between the turbine rotor 114 and the pump rotor 164 when the turbine rotor 114 rotates at a speed greater than 5000 rpm, and preferentially comprised between 5000 rpm and 25 000 rpm and advantageously between 10 000 rpm and 15,000 rpm.
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The vanes 172 protrude downwardly. They advantageously have a helical shape.
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Under the effect of the driving fluid, the central rotating shaft 122 rotates about the axis A-A', and jointly drives in rotation the pump shaft 170 and the vanes 172.
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The rotation of the vanes 172 generates a pumping effect which pumps the production fluid located below the pump rotor 164 upwardly above the pump rotor 164 to the annular space between the turbine stator 110 and the lower sleeve 48, and then to the passage defined between the central hub 64 and the upper sleeve 44, in particular along the upper sleeve part 60 (or cross-over) and finally out of the fluid lifting system 20 through the upper lock mandrel 180 of the anchoring and sealing system 50.
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In reference to figure 1, the anchoring and sealing system 50 comprises an upper lock mandrel 180 mounted above the upper sleeve part 60 (or cross-over) of the driving fluid admitter 46, a lower stinger 182 mounted below the pump stator 160 and a lower lock mandrel 184.
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The upper lock mandrel 180 defines a central passage (not shown) to let the pumped production fluid flow upwardly from the upper sleeve part 60 (or cross-over).
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The lower stinger 182 is connected to the pump 40 by a tube 186.
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The operation of a fluid lifting system 20 to enhance fluid production in the well 12 of the fluid production installation 10 will now be described.
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Initially, the lower lock mandrel 184 is lowered and set in place just below the side pocket 37.
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Then, the fluid lifting system 20 with the stinger 182 at its bottom and the upper lock mandrel 180 at its top is lowered down to the lower lock mandrel 184. The upper lock mandrel 180 is set in place as well to immobilize the fluid lifting system 20 in position with the turbine 42 facing the top of the side pocket 37.
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When the pump 40 needs to be activated, driving fluid, in particular pressurized gas from the gas source 22, is injected through the annular space 24 between the production tubing 18 and the casing 19. The driving fluid enters the side pocket 37. If a residual liquid potentially containing solids particles is present in the side pocket 37, the driving fluid pushes the residual liquid towards the inlet 72 to be evacuated through the inner expansion chamber 112, and the evacuation assembly 118.
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The residual liquid, potentially containing solid particles is then filtered through the strainer 74, which prevents at least part of the solid particles to enter the expansion chamber 112 and block the turbine rotor 114, or damage it.
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The residual liquid initially present in the side pocket 37 can thus be drained very efficiently, without risk of damaging the turbine 42, even if the clearances between the turbine rotor 114 and the turbine stator 110 and/or between the blades are small.
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This allows a close fitting of the turbine rotor 114 in the turbine stator 110, and thus longer operation of the turbine rotor at higher rotation speeds in the turbine stator 110.
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Once the residual liquid has been evacuated, only driving fluid passes through the inlet 72. If the driving fluid collects some solids, the strainer 74 filters at least part of the solids, just as described above.
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The driving fluid flows through the inlet 72, and passes in the fluid conveying passage 90 in each radial lumen 84, in the central lumen 82, in the radial through holes 88 and through the apertures 102 before reaching the annular space 86 and the inner expansion chamber 112.
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The driving fluid then enters the inner expansion chamber 112 where it expands and interacts with the blades 124 to drive the turbine rotor 114 in rotation around the rotation axis A-A'. The rotation of the turbine rotor 114 drives in rotation the pump rotor 164 through the mechanical connection between the central rotary shaft 122, the connection 116, and the pump shaft 170.
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The rotation speed of the turbine rotor 114 may be greater than 5000 rpm, and is preferentially comprised between 5000 rpm and 25 000 rpm and advantageously between 10 000 rpm and 15,000 rpm.
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The production fluid, flowing downhole of the fluid lifting system 20 from the reservoir 28, enters the inner pumping chamber 162 and is pumped uphole by rotation of the vanes 172. It is ejected from the fluid lifting system 20 after passing in the intermediate space around and outside of the turbine stator 110, and around and outside the central hub 64.
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At the bottom of the inner expansion chamber 112, the driving fluid flows downhole through the annular axial section 140 of the driving fluid evacuation assembly 11. It changes direction in the inversion section 142 and flows out of the turbine stator 110 through the flapper 134 in an at least partially uphole direction.
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In particular, the driving fluid moves the shutter 152 towards the opening position of the flapper 134. It then flows upwardly to provide gas lift to the production fluid exiting the inner pumping chamber 162. The driving fluid remains above the inner pumping chamber 162 to avoid affecting the pumping efficiency.
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The fluid lifting system 20 which has been described can thus very easily and quickly/at low cost be installed at a bottom of a well 12, using a wireline and can also be removed easily quickly/at low cost if needed.
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The fluid lifting system 20 operates very efficiently, the turbine rotor 114 being rotated only under the effect of a driving fluid (in particular gas provided from a surface gas source 22), minimizing the production costs and the emission of greenhouse gases from the well 12.
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Additionally, the pump 40 can operate at very high speeds, without risk of overspeed thanks to the provision of the fluid flow limiter 70.
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In case the turbine rotor 114 is blocked, the overpressure existing in the fluid conveying passage 90 opens the safety valve 94, for example by rupturing it, which allows evacuation of gas through the diffusion nozzle 92. The gas evacuated through the diffusion nozzle 92 provides gas lift with a jet pump effect to the production fluid above the fluid lifting system 20. The fluid lifting system 20 is thus very safe, even under degraded conditions.
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In a variant shown in figure 6, the body 130 of the driving fluid evacuation assembly 118 delimits a plurality of openings 132, which are spread angularly about the axis A-A'. The driving fluid evacuation assembly 118 advantageously comprises an individual flapper 134 to close each opening 132, or a flapper 134 common to several openings 132 or to all the openings 132.
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In another variant, the production tubing 18 is without a side pocket mandrel 36. The production tubing 18 is then preferably punched at the location where the fluid lifting system 20 is anchored. The punched production tubing 18 allows an entry of driving fluid from the annular space 24 in the production tubing 18 to feed the driving fluid admitter 46.
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Another fluid lifting system 20 is shown in figure 8. The fluid lifting system 20 is also powered by a driving fluid which is fed via a coiled tubing 200 deployed from the surface.
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The fluid lifting system 20 comprises a turbine assembly with a gas turbine 42 as described above, comprising a turbine stator and a turbine rotor having blades rotatably mounted in the turbine stator about a rotation axis A-A'.
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The turbine assembly defines a driving fluid admission inlet 72 connected to the turbine stator on one side of the turbine stator in reference to the rotation axis A-A', uphole of the turbine stator, to feed driving fluid in the turbine stator and drive the turbine rotor in rotation about the rotation axis A-A' by expansion of the driving fluid.
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However, contrary to the fluid lifting system 20 of figure 1, the turbine assembly is preferably without a strainer positioned in the driving fluid admission inlet or between the driving fluid admission inlet and the turbine.
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The coiled tubing 200 is directly connected to the driving fluid admission inlet 72. It has a driving fluid feed inner passage 202 feeding driving fluid from the gas source 22 at the surface to the driving fluid admission inlet 72, and consequently to the turbine stator.
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Just as the turbine assembly shown in figure 1, the turbine assembly of figure 8 preferably has a driving fluid evacuation assembly 118 located on a side of the turbine stator opposed to the driving fluid inlet 72 in reference to the rotation axis, downhole of the turbine stator. The fluid evacuation assembly 118 is preferentially as described above in figures 5 or 6.
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The fluid lifting system 20 comprises a fluid pump 40 having a pump stator and a pump rotor being connected to the turbine rotor via a connection 116, on the side of the turbine stator opposed to the driving fluid admission inlet 72 in reference to the rotation axis A-A'.
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In operation, the fluid lifting system 20 is lowered in the well 12 via the coiled tubing 200 connected to the driving fluid admission inlet 72. It is set to an appropriate position in the well 12, advantageously by using at least a packer 184 or a stinger 182 connected to a packer 184 anchored prior to the fluid lifting system 20 run in hole.
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Driving fluid is fed from the gas source 22 through the inner passage 202 and the admission inlet 72. It reaches the turbine stator, where it expands to drive the turbine rotor in rotation about the rotation axis A-A'. Rotation of the turbine stator drives the pump rotor in rotation via the connection 116, hence pumping production fluid uphole, as described above.
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The driving fluid is evacuated via the fluid evacuation assembly 118, as described above.
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With the fluid lifting system of figure 8, the well 12 does not need to comprise a side pocket mandrel 36 or does not need to be punched at the position where the fluid lifting system 20 of figure 10 is positioned. In addition, the fluid lifting system 20 may be deployed directly in the casing 19 in an area where no production tubing 18 is present.