Well Fluid Extraction System

Description

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority to patent application GB 2413315.9 filed on Sep. 11, 2024. The contents of that application are incorporated herein in their entirety.

FIELD OF THE INVENTION

The present invention relates to a well fluid extraction system and in particular including torque measuring means. In one specific aspect it relates to a method of measuring the instantaneous torque exerted on the drive shaft of a rotating body. In another specific aspect it relates to apparatus for computing the instantaneous torque exerted on the drive shaft of the rotating rod of a rod well pumping unit.

BACKGROUND OF THE INVENTION

The rotating rod well pumping unit is a mechanical system that is quite elastic in structure. Such a system includes a string of small diameter connecting rods extending long distances the surface of the earth to an impeller and rotated by a motor located at the surface.

These are to be distinguished from beam pumps to sucker rods attached to a plunger pump which is actuated by suitable surface equipment comprising a walking beam, counterweights, a rotating crank arm, a pitman connecting said crank arm with said walking beam, a prime mover, and driving means connecting said crank arm with said prime mover.

Although sucker rod and rotating rod pumping units have been employed in oil fields for many years, due to the elasticity of the system, satisfactory methods of dynamic analysis have not been available which can serve to predict the numerous possibilities as to variance in peak and average loads with regard to pumping speed or viscosity or the fluid being pumped.

Progressive cavity pumps are a form of positive displacement pumps based on the Moineau principle. They are often used for the extraction of water and oil from underground reservoirs. They are installed downhole and driven from surface by a rotary drive mechanism that is connected to the pump by slender rotating rods. The speed of rotation of the pump controls the flow rate and the differential pressure across the pump.

Positive displacement pumps work well with liquid but can be damaged, or can wear prematurely, if a gaseous medium gets into the flow stream, or if abrasive particles are entrained in the fluid. Either of these events can damage the pump and make it less efficient, or cause it to fail completely due to wear.

Even under normal usage, with no gas or entrained solids, the sealing elements of the pump will eventually fail, and the pump will need to be replaced. Typically this might be after a period of two years constant usage but this lifetime is very variable and difficult to predict. Replacing the pump involves retrieving the drive rods and then retrieving the pump on the bottom of the tubing. This can be expensive and time consuming. It is activity that is best postponed as long as possible and over the years, pump manufacturers have found ways to adjust the sealing dimensions of the pump to provide the best lifetime without impairing pump efficiency.

Although the rotation speed of the pump can be used to control pressure and flow rate down hole, it can be difficult to adjust pressure with any degree of precision without making a direct pressure measurement.

SUMMARY OF THE INVENTION

The present invention provides a well fluid extraction system with a torque sensor which overcomes these difficulties.

According to the present invention, there is provided a well fluid extraction system using a progressive cavity pump; wherein the progressive cavity pump comprises: a stator, a rotor, a rotating drive rod, and a drive motor; the rotor is installed in the stator and has an external threaded curve surface; and the rotating rod is connected to the rotor; the drive motor, and the rotating rod are connected in sequence; a fluid outlet of the progressive cavity pump is connected to an input end of a tank or a fluid pipeline; a contactless strain based torque sensor; the torque sensor measures the torque of the rotating rod; and comprises a housing and, located in the housing, and which is located circumferentially with respect to the cross section of the rotating rod when the torque sensor is located in a position in close proximity in relation to the rotating rod, but without needing to be in physical contact with it, to provide an indication of the torque present in the rotating rod whilst the rod is rotating.

Further contactless torque sensors may be located in positions that are spaced circumferentially around the cross section of the rotating rod.

The housing preferably comprises an opening through which the rotating rod extends. The opening may be U-shaped to permit the housing to be located laterally with respect to the rotating rod and secured to an adjacent frame.

The housing may be formed in a first half and a second half which are connected together such that when the first and second halves are connected together the housing surrounds the rotating rod with the rotating rod extending though the opening.

Preferably the sensor housing is located around the rotating rod at surface and connected to the controller by means of a cable.

Preferably the continuous measurements are taken whilst pumping is in progress.

BRIEF DESCRIPTION OF THE FIGURES

Embodiments of the present invention will now be described in more detail, with reference to the attached drawings in which:

FIG. 1 shows a side elevation of a production well with the well fluid extraction system of the invention installed,

FIG. 2 shows an enlarged side elevation view of the pump portion,

FIG. 3 shows an enlarged side elevation view of the drive head,

FIG. 4 shows a perspective view of a torque sensor housing in an installed position,

FIG. 5 shows a block diagram of the data processing steps,

FIG. 6 shows an enlarged side elevation of the well drive head with a further embodiment of the sensor housing and sensor housing support of the invention,

FIG. 7 shows an enlarged view of a further embodiment of the sensor housing support of the invention,

FIG. 8 shows an enlarged view of the sensor housing and top part of the sensor housing support of the embodiment of FIG. 7 of the invention,

FIG. 9 shows an enlarged underside view of a sensor housing of FIG. 8,

FIG. 10 shows a longitudinal cross section of the sensor housing of FIG. 9, and

FIG. 11 shows an enlarged side elevation of the well drive head with the embodiment of the sensor housing and sensor housing support of FIGS. 7 to 10.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1 to 4, a well fluid extraction system 1 using a progressive cavity pump 7 is shown; wherein the progressive cavity pump 7 comprises: a stator 8, a rotor 9, a rotating drive rod 3, and a drive motor 6. The stator 8 has an internal uniform tubular surface; the rotor 9 is installed in the stator 8 and has an external helical curved surface 5. The rotating rod 3 is connected to the rotor 9. The drive motor 6 and the rotating rod 3 are connected via a drive head 6a; a fluid outlet 9b is connected to an input end of a tank or a fluid pipeline; the external threaded curve surface 8 is a tapered spiral structure with equal tapers which urges the fluid upwards as the rotating rod rotates inside the tubing 4 through inlet 9a. The well fluid extraction system 1 further comprises a monitoring and control system 10, and the monitoring and control mechanism 10 comprises a controller 11 and a torque sensor housing 12. The controller 11 is electrically connected to the torque sensor housing 12, and the drive motor 6. The torque sensor housing 12 monitors pumping torque in the rotating rod 3; and comprises a housing 13 which includes support means 14 to locate the torque sensor housing 12 in the desired position in relation to the rotating rod 3, without being in contact with it, so permitting the rotating rod to rotate. The housing means 13 is attached to a frame of the drive head 6a by support means 14, which in this embodiment are in the form of springs although other embodiments of housing support are described in more detail below.

At the end at the region of the drive head 6a the rotating rod 3 includes a polished portion 2 around which the torque sensor housing 12 is located in a non-contacting manner. The spring supports 14 protect the torques sensor housing 12 by preventing vibration in the system during use being transmitted to the torque sensor. Incidental contact of the torque housing 12 with the polished portion 2 may occur as the system vibrates during use, but contact is not required for the torque sensor 15 to detect the torque within the rod 3.

The rotating drive rod 3 is conveniently made from a suitably strong material having the ability to transmit torque and may or may not be ferro magnetic material.

The contactless torque sensor housing 12 is located in close proximity to the outside diameter of the rotating rod 3 but without out being in contact with the rod 3 to provide an indication of the torque being experienced in the rotating rod whilst the rotating rod 3 is rotating.

Further sensors may be provided to aid in the elimination of induced bending loads impacting the accuracy of the resulting torque measurements. The senses or preferably located circumferentially around the rotating rod 3 at regular radial intervals and at the same spacing in relation to the outside diameter of the rotating order 3.

The housing portion 13 comprises an opening 16 through which the rotating rod 3 extends.

In this embodiment the opening 16 is C-shaped to permit the sensors 15 in each housing portion 13 to be located laterally with respect to the rotating rod 3 and secured to an adjacent frame or mounting.

In an alternative embodiment the housing portion 13 is formed in a first housing portion 17 and a second housing portion 18 which are connected together such that the first and second housing portions 17, 18 surround the rotating rod 3 with the rotating rod 3 extending though the opening 16 formed between the two housing portions 17, 18.

In this embodiment the sensor housing portion 13 is located around the rotating rod 3 at surface and connected to the controller by means of a cable 19.

Referring now to FIG. 5 the data output of the torque sensor is connected to a torque sensor interface 22 which in turn is connected to a demodulator and processor 30 which produces a system output 31 of data which may be used to control the motor or to manage the pumping activity in other ways such as to identify changes in performance in order to inform preventative maintenance strategies.

Common parts may have the same identifying numbers across each embodiment.

FIG. 6 shows an enlarged side elevation of the well drive head 1 with an embodiment of the sensor housing 12 and sensor housing support in the form of axial sprung struts 14 arranged between the sensor housing and the well head 6a. The axial struts 14 serve to optimally align the sensor housing 12 concentrically with the rotating rod 3 and to maintain the alignment during the continuous operation of the pump 7.

FIGS. 7 to 10 show detailed views of a further embodiment of a mounting assembly 20 comprising a support plate 21 configured to support a pair of torque sensors 15 in a central and stable position relative to the rotating rod (not shown). The support plate 21 is U-shaped and includes a pair of wing arms 23 and each wing arm 23 is connected to an axial support 24 on an outside surface of each wing arm 23. Each axial support 24 extends radially and is connected at an opposite end to a lower support 25 which is in the form of a C-shaped bracket, and which is securely attachable to the drive head or casing. This lower support 25 ensures concentricity of the mounting assembly 30, and thus the sensors 15, in relation to the rotating rod and restrains the mounting assembly from rotating. The axial supports 24, which may be in the form of springs, as in the previous embodiment, or flat strips as shown in this embodiment, and extend axially from the support plate 21 to the lower support 25 and are used to support the offset the sensors 15 axially, and usually vertically as shown, allowing alignment with respect to the rotating rod without contact therewith. At the upper end of the mounting assembly 20, the sensor housing portions 17, 18 are attached to the support plate 24 by fixing means in the form of a socket 27 on each sensor housing portion 17, 18 and a corresponding tongue 28 on each wing arm 23. A pair bolts (not shown) finally secure the sensor housing portions 17, 18 to the support plate 21. The lower support 25 interfaces with the main drive head casing. This connection is achieved through a mechanical fixing method, such as bolting or by the resilient clips 26 which are arranged at the external circumferential edge of the lower support 25 as shown.

The individual supports may be joined through various conventional fastening methods, including welding or threaded fasteners, depending on material selection and required mechanical properties.

Reference is now particularly made to FIGS. 8 to 10 in which further details of the first and second sensor housing portions 17, 18 are shown connected together to form an integral sensor housing 33 by means of a connecting plate 29. The first and second housing portions 17, 18 each comprise a cylindrical casing 32 and inner and outer end caps 36, 34 which are all comprised of a thick resilient material and which completely surround the disc-shaped sensors 15. This provides ruggedized protection for the sensors 15 to prevent physical or chemical damage at the well head environment.

Circumferential seal means 35 are provided which ensure a sealed connection between the end caps 34, 36 and the internal surface of the cylindrical casing 32. Power and date conduits 37 pass from the sensor through the cylindrical casings 32 into a common connector (not show) on an exterior side of the connecting plate 29.

FIG. 11 shows the embodiment of FIG. 7 to 10 installed in position in the well head with the sensor housing 33 supported in such a way that the first and second sensor housings 17, 18 and thus the sensors are aligned with respect to each other and along an axis which is orthogonal to the axis of the rotating rod 3 and are positioned in close proximity to the rotating rod 3 but do not make contact with it.

The method and apparatus disclosed herein may be used, in isolation or in conjunction with existing sensor technologies, to overcome these drawbacks and to provide high resolution transfer of data from anywhere in the well hole to the surface.

This invention provides real-time, high-resolution measurement whilst pumping allows the well operation to be more effectively managed, with the obvious consequential benefits of increases in production and decrease in equipment failure.

Components

• • 1. Well fluid extraction system
  • 2. Polished portion
  • 3. Rotating drive rod
  • 4. Tubing
  • 5. External helical surface
  • 6. Drive motor
  • 6a. Well head
  • 7. Progressive cavity pump
  • 8. Stator
  • 9. Rotor
  • 9a. Fluid inlet
  • 9b Fluid outlet
  • 10. Monitoring and control system
  • 11. Controller
  • 12. Torque sensor housing
  • 13. Sensor housing portion
  • 14. Support means
  • 15. Contactless torque sensor
  • 16. Opening
  • 17. First housing portion
  • 18. Second housing portion
  • 19. Cable
  • 20. Mounting assembly
  • 21. Support plate
  • 22. Torque sensor interface
  • 23. Wing arm
  • 24. Axial support
  • 25. Lower support
  • 26. Resilient clips
  • 27. Socket
  • 28. Tongue
  • 29. Connecting plate
  • 30 Demodulator and processor
  • 31 System output
  • 32 Cylindrical casing
  • 33 Sensor housing
  • 34 End cap
  • 35 Seal
  • 36 End cap
  • 37 Conduit