GB2360302A

GB2360302A - Submersible pumps

Info

Publication number: GB2360302A
Application number: GB0005330A
Authority: GB
Inventors: Philip Head
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-03-04
Filing date: 2000-03-04
Publication date: 2001-09-19
Anticipated expiration: 2020-03-04
Also published as: GB2360302B; GB0005330D0

Abstract

Electric submersible pumps or other modules (100) are located by projecting slips (103) in docking ports in oil production tubing, and powered inductively by coils supplied by fixed power lines and arranged around each docking port (20) Fig 3. Each pump preferably comprises a rotor incorporating permanent magnets, which together with the fixed coils forms a brushless DC motor. Alternatively linear motors may be employed. A module is removed from its docking port by retracting its slips (103) and closing a valve in the oil flow path at the base of the module. It is then pumped out from the borehole under pressure from hydraulic fluid passed down a fixed hydraulic line (19) Fig 6 or between twin walls of the tubing, or alternatively from the production fluids, and acting against the valve and a dynamic seal (103') between the module and the tubing. A pump out seal module (32) has a non-return valve (35) which is kept open by a fixed spigot (101) at the bottom of the tubing. The valve is closed by passing hydraulic fluid down the fixed line (19) to raise the seal module from the spigot, trapping the fluid between the valve (35) and a non-return valve (30) at the base of the tubing. The seal module may then be pumped to the surface to retrieve all modules. The invention provides for reduced cost maintenance of electrical and nonelectrical well equipment. The pump may have its own valve so that it can be pumped in or out by itself in a controlled manner.

Description

2360302 Submersible Pumps This invention relates to submersible pumps and

the like, in particular the deployment and retrieval of semi-permanent assemblies into wells and io pipelines, especially electrically powered assemblies such as electric submersible pumps (ESPs) and flow regulators based on permanent magnet brushless motors.

A conventional electrical submersible pump installation for oil wells is deployed at the end of a production tubing, the tubing being used to conduct the pumped fluids to surface. The tubing consists of jointed sections, to which the electrical power cable is externally strapped. The motor and centrifugal or positive displacement pump are assembled at the bottom of the tubing, normally with the pump above the motor, so it can lift fluids via a discharge head directly into the tubing.

The ESP must be maintained from time to time. This requires a so-called work-over rig and crew which can pull up and dismantle the sections of tubing from the well and detach the cable to retrieve the pump. The repaired or replaced pump is deployed back into the well as for a new installation, remaking the tubing and affixing the cable. Since there is a high likelihood of damaging the cable and its connectors, these are often replaced during the work-over. This type of work-over is a time consuming and expensive exercise, and it is often done to a fixed schedule that leaves failed installations 1 until the next scheduled slot, with consequent lengthy periods without production.

An alternative known method of ESP installation disclosed in GB 2 318 167 uses coiled tubing. In this the power cable is pre-installed into the continuous io tubing and makes on to the motor, which is now above the pump. The fluids are lifted in the annulus between the tubing and the well casing. Since the ESP is reeled into and out of the well, work-over costs are significantly reduced compared to the conventional means of installation. Nevertheless the method requires the use of a reeled tubing rig and remains expensive.

It is an objective of this invention to allow convenient recovery of components disposed in a well or pipeline.

According to the present invention there is provided an oil flow line and powered device system comprising: a tube for the transportation of oil, and at least one powered device, the powered device being disposable in the tube, and including a locating means upon it for arresting particular position in the tube, the tube having an electrical power transmission means disposed along at least some of its length, the tube and the powered device both having co- operating power transfer means.

2 Preferably the powered device is a pump. The location means preferably includes a dynamic seal. Preferably the location means is activatable between a first state in which the powered device may pass through the tube, and a second state in which the powered device is arrested.. The location means may include projecting io members which frictionally engage the inner bore of the tube. Alternatively or additionally, the location means may include projecting members to interlock with co-operating parts on the tube.

These projecting members may be rotationally unsymmetrical such that rotation of the powered device in the tube is reduced.

Preferably the tube is disposed in a borehole.

Preferably the power transfer means is by electrical induction. The tube and the powered device preferably both have co-operating signal transfer means.

The tube may have a plurality of locating means upon its inner surface, and there may be a plurality of powered devices are disposed in the tube.

According to another aspect of the present invention, there is provided a method of installing a powered device in a system as defined above, at least part of the delivery or retrieval of the powered device to or from a position in the flow line is achieved by fluid pressure in the flow line.

3 At least part of the delivery or retrieval of the powered device to or from a position in the flow line may be achieved by a traction means interacting between the tube and the powered device.

According to a further aspect of the present invention, there is provided a tube io for an oil flow line and powered device system as defined above.

According to a further aspect of the present invention, there is provided a powered device for an oil flow line and powered device system as defined above.

The powered device may include a traction means which interacts between the tube and the powered device so as move the powered device along the flow line.

The docking ports may be addressable when required to permit individual control.

In this way, the electrical power cable, its connectors, and production tubing remains in the well during an entire ESP work-over. Docking ports are used to station and operate modular pumps, valves, sensors and/or other actuators at one or more locations, said docking ports possibly being addressable when required to pennit individual control.

The modules may be recovered by the production fluids themselves as an 30 alternative or in addition to special hydraulic fluids. These modules are 4 recovered by re-circulating the said fluids using a permanent flow path in or attached to the production tubing. The modules are also recoverable by a wireline or slickline operation for back-up or primary means of recovery, and by electric powered traction tools.

io Electrical connections between said modules and docking ports are not required. Rotary or linear motor action be developed using stator coils mounted in or on the fixed part of the downhole assembly and permanent magnets mounted in or on the said modules. The said modules may be individually controlled from the same power supply.

The invention will now be described, by way of example, reference being made to the accompanying drawings, in which:

Figure 1 shows a side view of a well with an ESP installed using coiled tubing 2o deployment; Figure 2 shows a side view of a well with an ESP installed using conventional jointed tubing and externally strapped power cable deployment; Figure 3 shows a side view of a well with jointed tubing and externally strapped power cable connected to full bore docking ports incorporating electrical power coils; Figure 4 shows a side view of a well with coiled tubing with internal power cable (not shown) connected to full bore docking ports incorporating electrical power coils; Figure 4a shows a 3 dimensional perspective of twin-wall coiled tubing used in io figure 4, forming a conduit for internal power and other cables; Figure 4b shows a 3 dimensional perspective of the twin-wall coiled tubing used in figure 4, forming a conduit for the power transfer electrical coils.

is Figure 5 shows a side view of a more detailed view of figure 4 of the lower section of the well with pump modules located in their docking stations and a pump out seal positioned, not in operation, at the lower most end of the tubing; Figure 6 shows a similar view to figure 6 with the pump out seal conveying 20 one pump module out of the well; Figure 7 shows a similar view to figure 6 with the different type of pump being lowered into the well.

Figure 8 shows a side view of a first embodiment of a pumping module; Figure 9 shows a side view of a second embodiment of a pumping module; Figure 10 shows a side view of a docked electrically actuated flow control 30 module; 6 Figure 11. shows a side view of a floating production vessel in the ocean with a flow line linking it to subsea wellheads, said flow line containing docking ports, and jo Figure 12 shows a schematic view of the wiring topology supplying a docking station.

Referring to figures 1 and 2, these show the existing state of the art. Figure 1 shows a coiled tubing deployed ESP. Well casing 1 provides a passage from is the reservoir to the surface. A sealing device 2, generally referred to as a packer, separates the pump inlet 3 from pump discharge port 4. The ESP is supported by coiled tubing 5 which has a power cable 6 installed inside its bore, terminating directly into the electrical motor 7. The electric motor output shaft connects to the pump input shaft near 8, around which is the pump discharge port 4.

Figure 2 shows the jointed tubing conveyed version of the electrical submersible pump. In this embodiment the jointed tubing 9 has an externally strapped power cable 10. The power cable is fed through the packer 2 by a penetrator (or electrical bulkhead) 11, the cable being terminated at either end of the penetrator by electrical cable terminations 12. The cable passes down the side of the pump section 13 and attaches to the electrical motor 14 via an electrical pot head connector 15.

7 It is clear from both of these embodiments that once any part of the ESP has failed the entire assembly has to be removed to be repaired or replaced. The most likely failures are of rotary seals, bearings and pump stages, which are moving parts unlike the cable, its connectors, and the motor windings.

io Referring to figures 3, 4, 4a and 4b, there are shown two embodiments of the present invention's well infrastructure. Figure 3 shows jointed tubing, with an externally strapped power cable 10 terminated at one or more power transfer ports 20, and actuator fluid conduit 19. The docking ports contain electrical coils 2 1. These items are permanently installed and not disturbed during workover operations. The coils may be permanently scaled in an insulating environment, such as oil, polyamide varnish, epoxy or elastomer filling.

Figure 4 shows a similar view to figure 3. In this embodiment the power cables are integral with the coiled tubing 23 and have not been shown for clarity. Figure 4a shows two concentric coiled tubing skins 26,27. The annular space thereby formed houses the integral power wiring 28 and other well support infrastructure such as fibre optics 28' and hydraulic control lines 2V. Free space in the annulus 29 may be used as a means of passing actuator fluid in place of a special line or the externally strapped flow tube 19 shown in figure 3.

In both embodiments there is full bore access 25 to the reservoir when no tool modules are installed. This is beneficial for well operations which require the passage of, for example, higher flows, drilling and de-scaling equipment, and large modules. It will be apparent that these permanently wired docking 8 stations can be used with other modules and are not restricted to pumping. A plurality of docking stations can be installed, with a mix of modules performing different functions simultaneously. Retrieval and deployment of modules according to the invention will be io explained with reference to figures 5, 6 and 7. By way of example, these show a pumping module installed in the coiled tubing completion of figure 4, but it will be apparent that the method to be explained will work in the jointed pipe completion of figure 3 and with any mix of module types. It will also be apparent that the non-retum valves 30 and 35 may be of different types known is in the art. Figure 5 shows a pump module anchored sealed with slips 103 and seal 103' at the power transfer port 20. At the lower-most end of the tubing is a springloaded non-retum valve 3 0, and a mechanical docking port 3 1 for a pump out 20 seal 32. The seal fits over a hollow spigot 10 1 that is part of the docking port. The resultant small trapped volume 3 1% between 31 and 32 is connected via an inlet 3 1 " to the aforementioned flow line 19 or 29. The seal carries a springloaded non- retum valve 3 5 which is held open by the spigot 10 1 when in the docked position. 25 In normal operation flow in the well holds valve 30 open. To recover the pump modules, electrical power is first preferably turned off. Control fluid is pumped down the flow path inside the coiled tubing 29 and pressurises the trapped volume 3 P, forcing the seal 32 to rise, as shown in figure 6. When the 30 seal eventually rises off the spigot 101, the valve 35 springs closed and blocks 9 production flow. This equalises pressure across valve 30, so that it springs shut, leaving a trapped volume 33 between the two valves 30 and 35. This volume is a large extension of the original volume 3 P, so that continued control fluid flow will now continue to move the seal up the tubing bore. When it reaches the lower pumping module 100 it removes the hanging weight io from slips 103 and seal lOY, which disconnects the pump module 100 from the inner surface of the tubing. By continuing to pump fluid down flow path 29 the pump module 100 is displaced up tubing. Continued displacement unlatches this second module (not shown), and thence both back to surface. After a short period of time determined by the flow rate in 29 the modules are all recovered back to surface where they can be either repaired or replaced.

To reinstall the pump modules the reverse operation is performed. A new pump out seal is first installed. This allows the lowering of all the pump out modules at a controlled descent rate. It will be appreciated that if a lower pumping module is still operating correctly, this could be used to pump out the pump modules above it.

If pumping out is not preferred, or the pump out seal fails, a wire-line or slickline could be lowered which would connect to a fishing profile 104 on top of each module to allow their recovery one by one. Alternatively, particularly in horizontal sections, the modules could be deployed and retrieved using autonomous or wireline powered tractors.

The mechanical slips 103 may be varied according to particular requirements.

For example, it may need splines to prevent rotation, as when supporting torque reaction from a pump. The details of such embodiments are covered by the present invention which discloses the principle of the power transfer port, and slips and seals used on the power transfer module.

Figure 7 shows a module where the pump inlet contains a valve 80, which io without power is held closed by a spring 81. The sleeve 82 is either electrically or hydraulically powered to keep the valve open. When closed, and the slips 103 released, hydraulic pressure can be applied below the valve via the port 31 which works as indicated by the arrows 83. This also works against the large moving seal 103' situated at the upper end of the module. Therefore rather than Is use a pump out seal, each individual pumping module could be pumped out, and lowered with full control. In a more sophisticated mode of operation the valve 80 could be used to lower the pump into the well. A battery operated control system fitted to the valve could monitor the rate of decent of the pump assembly and adjust the volume of fluid passed through the valve by alternately opening and closing the valve 80. Each pump and docking station would also have identification tags so that when the pump reaches the correct power transfer station its locating slips 103 will only b ecome active to allow the pump to be located.

The permanent electrical wiring of the docking stations depends on the module technology to be deployed. In the embodiments disclosed below, permanent magnet brushless motor technology is preferred. Typically the wiring to a docking station operated in isolation will be as shown in figure 12. In this case 11 the motor is wound for three-phase AC power, and the three windings are joined to form a so-called star point. Several such docking stations may be connected together in this way on the same three power lines if the motors are run synchronously. However greater flexibility is obtained by using permanently installed, conservatively rated, power electronics to commutate i o the motors individually at each station. Where only a few pumps are required it may be feasible to wire the docking stations separately back to surface.

Referring to figures 8, and 9, there are shown various embodiments of the pumping modules. Each of these will be described in more detail as follows.

Figure 8 shows the power transfer station 22 and embedded coils 2 1. The pump, of centrifugal type, comprises an inner stator 40 and an outer rotor 4 1. The module locates using an ID tag 1000 in the tool housing and tag 100 1 in the deployed module, and slips 103 and seal 103' hold the pump stationary against the tubing and withstand reactive torque and thrust loads that the module is subjected too. Flow passes through from outside the tubing via ports 60. The pump rotor 41 sits in a thrust bearing housing 43 and is supported by bearings C. The stator 40 is stabilised at the top by a support 40%.

Permanent magnets 4 1' are mounted on the circumference of the rotor, and in conjunction with the coils 21 form a brushless dc motor whose operating principles are well known in the art. The magnets are protected from the well fluids by means of a thin non-magnetic sleeve made for example from stainless steel or composite material. The inner bore of the docking port opposite the 12 s coils 21 is similarly protected, with the structural strength of the tubing being maintained by the coil core and outermost housing. It is an advantage of this type of motor and other permanent magnet motor types and their associated electrical drives that they may be designed with a relatively large gap between magnets 4Pand coils 21. This permits robust construction with good electro- io mechanical performance. By contrast the most widely-used downhole pump motors are of the well-known induction motor type. This requires transformer action between coils 21 and coils on the stator. This transformer action is gravely weakened with large gaps and renders induction motors non-preferred for the purposes of the present invention.

The pump vanes may be made metallic as commonly found, or made of damage resistant composite material. It will be apparent that the concentric motor-pump arrangement is applicable to other pump types that may be used in this application such as but not restricted to positive displacement pumps, turbine pumps, impeller pumps.

Where the tubing diameter restricts the concentric design lift or flow rate capacity or where it is preferred to ineorporate a conventional pump product, or it is preferred to have the pump rotate internal to its stator then the motor and pump can be separated along the axis of the tubing, with the pump above or below the motor. Figure 9 shows an embodiment of such a pumping module with stator coils 21 and rotor magnets 4 1.

Remaining with figure 9, the pump inlet contains a valve 80, which without power is held closed by a spring 8 1. The sleeve 82 is either electrically or 13 hydraulically powered to keep the valve open. When closed, and the landing profile 22 released, hydraulic pressure can be applied below the valve via the port 31 which works as indicated by the arrows 83. This also works against the large moving seal 85 situated at the upper end of the module. Therefore rather than use a pump out seal, each individual pumping module could be pumped io out, and lowered with full control. In a more sophisticated mode of operation the valve 80 could be used to lower the pump into the well. A battery operated control system fitted to the valve could monitor the rate of decent of the pump assembly and adjust the volume of fluid passed through the valve by alternately opening and closing the valve 80. Each pump and docking station 15 would also have identification tags so that when the pump reaches the correct docking station its locating dogs will only become active to allow the pump to belanded. In the case of a gas pipeline the pumps, concentrically or axially disposed with 20 respect to the motor, can be turbine impellers rotated at very high rpm to compress gas to assist in transporting it along the pipeline or to re-inject it back into the oil production path to assist in reducing the hydrostatic pressure or reenergise the reservoir. 25 Next referring to figure 10 there is shown a further application of the tubing power transfer stations. Figure 10 shows a flow regulator in split view. The left side shows the throttle sleeve 202 fully open and the right side shows it fully closed. Flow control port 60 is opened and closed by an on/Off Solenoid shuttle valve 200. Flow passes through the port 60 and passage 201 into the 30 main bore 2 5. At the exit of the flow passage 20 1, a variable flow are can be 14 achieved by moving the sleeve 202 towards the passage opening 201 or away from the passage opening. The precise position of sleeve 202 is maintained by the motor formed from permanent stator coils 203 and rotor magnets on the threaded sleeve 204. Threaded sleeve 204 engages in threads on sleeve 202, so converting motor rotation to linear actuation of sleeve 202. When it is necessary to recover this valve to surface. solenoid valve 60 is closed and motor 203/204 is deactivated. A pump out seal 32 can be used to recover this assembly to surface as previously disclosed herein. Alternatively, an internal fishing profile 205 may be machined into 202, so a wireline or coiled tubing recovery method can be employed.

Is Linear sleeve motion may also be obtained by direct use of a linear motor, in which the rotor magnet poles are disposed along the length of sleeve 204 instead of circumferentially, and the winding 203 topology is modified accordingly as is known in the art. Then sleeve 204 and throttle 205 move axially together and need not be separate parts. Linear motors may be used where the forces involved are not very high, and end-stops may be used to restrain motion in the case of unexpected flow surges.

Instead of (or in addition to) the technique disclosed herein of using pressurised fluid to deploy and retrieve the powered modules, other methods could be employed. As mentioned, a wireline and fishing tool could be used in part of the installation or removal operation. A traction means, either integral with the module, or discrete from the module and able to traverse the tube, may be used to move modules along the tube.

The foregoing embodiments have emphasised the application to wells. Figure 11 depicts the use of the invention in flow-lines connecting subsea wellheads 500 back to a floating production vessel 501. Because of the horizontal and vertical distances involved it is advantageous to install booster pumps along the flow-lines' length. These are indicated by circles 502. At each of these io locations is an internal docking port 22 and an electrically driven pump similar to the devices described earlier. A further benefit of the retrievable module approach is to avoid very expensive diver and remotely operated vehicle (ROV) intervention.

The invention's main objective is to provide an economical means of performing advanced well electrical completions with greatly reduced maintenance costs and enhance flexibility. The deployment and recovery means disclosed can also be applied to non-electrical equipment such as hydraulic submersible pumps.

16

Claims

1. An oil flow line and powered device system comprising: a tube for the transportation of oil, and at least one powered device, the powered device being disposable in the tube, io and including a locating means upon it for arresting the powered device at a particular position in the tube, the tube having an electrical power transmission means disposed along at least some of its length, the tube and the powered device both having co-operating power transfer means.

2. An oil flow line and powered device system according to claim 1, wherein the powered device is a pump.

3. An oil flow line and powered device system according to either previous claim, wherein the powered device includes a seal which acts against the inner bore of the tube.

4. An oil flow line and powered device system according to any previous claim, wherein the location means is activatable between a first state in which the powered device may pass through the tube, and a second state in which the powered device is arrested..

17 5. An oil flow line and powered device system according to any previous claim, wherein the location means includes projecting members which frictionally engage the inner bore of the tube.

6. An oil flow line and powered device system according to any previous io claim, wherein the location means includes projecting members to interlock with co-operating parts on the tube.

7. An oil flow line and powered device system according to any previous claim, wherein the projecting members are rotationally unsymmetrical such that rotation of the powered device in the tube is reduced.

8. An oil flow line and powered device system according any previous claim, wherein the tube is disposed in a borehole.

9. An oil flow line and powered device system according to any previous claim, wherein the power transfer means is by electrical induction.

10. An oil flow line and powered device system according to any previous claim, wherein the tube and the powered device both have co-operating signal transfer means.

11. An oil flow line and powered device system according to claim 10, wherein a plurality of powered devices are disposed in the tube.

18 12. A method of delivering or retrieving a powered device in a powered device and flow line system according to any previous claim, wherein at least part of the delivery or retrieval of the powered device to or from a position in the flow line is achieved by fluid pressure in the flow line.

13. A method of delivering or retrieving a powered device in a powered device and flow line system according to any previous claim, wherein at least part of the delivery or retrieval of the powered device to or from a position in the flow line is achieved by a traction means interacting between the tube and the powered device.

14. A tube for an oil flow line and powered device system according to any previous claim.

15. A powered device according to any of claims 1 to 10.

16. A powered device for an oil flow line and powered device system including a traction means which interacts between the tube and the powered device so as move the powered device along the flow line.

17. A powered device for an oil flow line and powered device system, wherein the powered device is a pump.

18. An oil flow line and powered device system substantially as described.

19 19. Any novel or inventive feature or combination of features specifically disclosed herein within the meaning of Article 4H of the International Convention (Paris Convention).