WO1999001667A1

WO1999001667A1 - Hydraulically driven oil well pump

Info

Publication number: WO1999001667A1
Application number: PCT/CA1998/000635
Authority: WO
Inventors: Winston Smith
Original assignee: Proalta Machine & Manufacturing Ltd.
Priority date: 1997-07-04
Filing date: 1998-07-03
Publication date: 1999-01-14
Also published as: AU8098398A

Abstract

A down hole rotary pump (18) in a well (16) is driven by a down hole hydraulic motor (26). This arrangement eliminates the sucker rod drive that causes power loss and tubing wear and mitigates problems in completing directional and deviated wells. In one embodiment, the motor (26) is mounted in the production string using a motor mount. In one embodiment the motor mount is ported to allow the flow of produced fluid past the motor and through the mount to the production tubing above the motor. In another embodiment, the motor has a hollow shaft that passes fluid through both the motor and the motor mount. This arrangement provides a high torque down hole drive system.

Description

HYDRAULICALLY DRIVEN OIL WELL PUMP FIELD OF THE INVENTION

The present invention relates to the production of liquid from wells and more particularly to the driving of a rotary production pump in a well. BACKGROUND

The invention has particular application to oil wells and will be described in connection with that application. It is to be understood, however, that the invention is not limited to that application.

Production pumps used in oil wells are conventionally driven by a motor at the surface, through a sucker rod extending along the well. This has a number of disadvantages, including the significant wear caused by rubbing of the sucker rod on the production tubing. This problem is especially severe in directional or horizontal wells.

The present invention is concerned with an alternative drive system that will eliminate the sucker rod drive. SUMMARY

According to one aspect of the present invention there is provided a pump system for an oil well having a well bore extending into the ground from a well head, said system comprising: a production tubing string extending along the well bore to the well head; a progressive cavity pump in the well bore for pumping fluid up the production tubing string, to the well head; an hydraulic motor in the well bore; a pump drive including: a tubular motor casing; means securing the motor casing to an end of the pump stator; an hydraulic motor having hydraulic fluid supply and return ports and a drive shaft; a motor mount securing the hydraulic motor to the casing; and drive coupling means extending long the casing and coupling the motor drive shaft to the pump rotor for operating the pump; hydraulic fluid supply and return lines extending along the well bore from the well head and coupled to the hydraulic fluid supply and return ports of the motor; and a pump at the well head for delivering hydraulic fluid under pressure to the hydraulic fluid supply line and for receiving hydraulic fluid from the hydraulic fluid return line.

This system thus uses a down hole hydraulic motor for driving a rotary progressive cavity pump. This eliminates the friction involved in a sucker rod drive, with consequent reduction of power losses and elimination of tubing wear.

The system eliminates rod failures and rod induced tubing failures, and thus reduces the frequency with which pumps must be pulled and replaced. Production problems with directional wells or wells with severe dog legs are mitigated. The production pump can even be laid in a horizontal section of a well. By eliminating the sucker rod, rotary pumps can be used at greater depths.

Most standard well head equipment can be used with the system so that the system may be installed quickly and at reasonable cost. When coiled tubing units are used for installing the pump, a number of additional advantages are achieved. Fewer people are on location than in conventional field operations, thus providing safer and more economic operations. Service rigs and accessories are eliminated so that the system is more suitable for use in environmentally sensitive areas, for example irrigated farm properties and government land. The reduced quantity and size of the surface insulation makes the system visually less obtrusive than prior art systems. The cost of abandonment is reduced because of the smaller, lighter and less intrusive surface equipment.

Where desired, a line heater can be installed to heat the hydraulic supply oil prior to injection. This heats the produced fluid to eliminate wax formation or to thin heavy oil.

The system allows the well head pump to be automatically controlled to eliminate dry running of the downhole pump, thus reducing wear. Control of the pumps can be carried out remotely.

The motor mount may have production fluid passages therethrough for delivering fluid along the production tubing string past the motor mount. In an alternative embodiment, the motor has a drive shaft extending through the motor and the motor mount and a produced fluid bore extends along the motor drive shaft, with an inlet opening between the motor and the pump and an outlet opening between the motor and the well head.

This arrangement allows the use of the largest diameter portions of the motor to provide the most torque available. The manufacture of the motor mount is simplified as it need not be ported to pass the production fluid. At the same time, the flow cross section may be equal to or greater than that in the system of the co-pending application. BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings, which illustrate an exemplary embodiment of the present invention:

Figure 1 is an illustration of a well installation according to the present invention;

Figure 2 is a detail view, partially broken away showing the pump driver section of the installation;

Figure 3 is an end view of a motor mount;

Figure 4 is the opposite end view of the motor mount;

Figure 5 is a cross section along line 5-5 of Figures 3 and 4; and

Figure 6 is a detail view, partially broken away showing the pump driver section of an alternative embodiment. DETAILED DESCRIPTION

Referring to the accompanying drawings, Figure 1 illustrates a well system 1 0 including a well bore 1 2 lined with a production casing 1 4. The bore extends into the ground into a production formation 1 6 in the usual way.

A conventional rotary production pump 1 8 is installed in the production casing. This includes a stator 20 and a rotor 22. Immediately above the pump in the well is the pump driver 24. This includes a driver casing 26 connected to the stator 20 of the pump and to production tubing 28 extending along the production casing from the pump driver.

Concentrically within the production tubing 28 is an hydraulic fluid return tubing string 30. Within the return tubing 30 is an hydraulic supply tubing string 32. The production tubing 28, return tubing 30 and supply tubing 32 all extend with the production casing 1 4 to a well head 34 which includes a surface casing 36 around the production casing.

At the top of the well, the gas coming up the annulus between the production casing and the production tubing is vented through the well head by gas vent 38.

The production tubing is hung in slips in a dog nut 40 to hold the pump at the desired height. The production tubing is cut off just above the slips, allowing the production fluid to be delivered from the well head body through a valve 42. The area between the production tubing and the well head is sealed by a pack off to prevent leaks around the tubing from the well head. The hydraulic fluid supply and return tubings extend through the bonnet 44. They are connected to a surface hydraulic pump 46 to supply the down hole power unit with the oil required to drive it in a closed loop system. Figure 1 also illustrates an optional line heater 48 for heating the hydraulic fluid entering the supply tubing.

As illustrated in Figure 2, the pump driver casing includes a tubular housing section 49 with a thread 50 at its bottom end screwed onto the end of a tube section 52. The bottom end of the tube section 52 is in turn threaded into the top of the pump stator 20. At its top end, the motor housing 49 has a threaded counter bore 56 ending at a land 58. The upper end of this counter bore is threaded onto the bottom end of a cross-over that is screwed into the bottom end of the production tubing string.

Inside the pump driver assembly is a drive shaft 62 with two constant velocity joints 64. This is connected at the bottom end to the pump rotor 22 and at the end top end to the output shaft 66 of an hydraulic motor 68. The motor is a small diameter, high displacement orbital motor delivering high torque at low speed. The motor has a supply port and a return port at the end of the motor opposite the drive shaft 66.

The upper end of the motor is coupled to a motor mount 74 including a cylindrical mounting block 76 that engages the upper end of the motor and a larger diameter head 78 that screws into the counter bore 56 at the upper end of the motor housing.

As illustrated most particularly in Figures 3, 4 and 5, there is a center blind bore 80 extending into the upper end of the mount 74. This is threaded to receive the bottom end of the hydraulic supply tubing 32. The bore 80 has a threaded counter bore 82 that is connected to the bottom end of the hydraulic return tubing 30. A supply passage 84 through the mount 74 leads from the end of the center bore 80 to the supply port of the motor. Similarly, a return passage 86 in the mount leads from the counter bore 82 to the return port of the motor.

To allow production fluid to pass along the production tubing string from the pump, past the motor and motor mount, a series of oval ports 88 extend through the mount to provide as much flow cross section as possible.

An alternative embodiment of the invention is illustrated in Figure 6. In this embodiment, the upper end of the motor 90 is coupled to a motor mount 92 including a cylindrical mounting block 94 that engages the upper end of the motor and a larger diameter head 96 that screws into the counter bore 56 at the upper end of the motor housing. The motor mount 92 has a large central through bore 96. The drive shaft 98 of the motor 90 passes through the motor and through the bore 96. It is hollow, with an axial bore 1 00 with inlet ports 1 02 at the lower end, below the motor and an open upper end 1 04. This bore 1 00 serves as the production fluid passage through the motor and the mount. The supply tubing 32 and the return tubing 30 are connected to supply and return passages 1 06 and 1 08 respectively through the mount 92, communicating with the supply and return ports of the motor 90.

This arrangement allows the use of the largest diameter portions of the motor to provide the most torque available. The motor mount is simple in construction. A large flow cross section for the production fluid is provided, unrestricted by sharp or numerous changes in the flow direction.

While specific embodiments of the present invention have been described in the foregoing, it is to be understood that other embodiments are possible within the scope of the invention. For example, the motor may be mounted below the pump, in which case the hydraulic fluid lines will pass through the annulus around the pump stator, and may extend through the annulus to the wellhead. These and other modifications are intended to be included within the present invention. The invention is to be considered limited solely by the scope of the appended claims.

Claims

1 . A pump system for an oil well having a well bore extending into the ground from a well head, said system comprising: a production tubing string extending along the well bore to the well head; a progressive cavity pump in the well bore for pumping fluid up the production tubing string, to the well head; an hydraulic motor in the well bore; a pump drive including: a tubular motor casing; means securing the motor casing to an end of the pump stator; an hydraulic motor having hydraulic fluid supply and return ports and a drive shaft; a motor mount securing the hydraulic motor to the casing; and drive coupling means extending long the casing and coupling the motor drive shaft to the pump rotor for operating the pump; hydraulic fluid supply and return lines extending along the well bore from the well head and coupled to the hydraulic fluid supply and return ports of the motor; and a pump at the well head for delivering hydraulic fluid under pressure to the hydraulic fluid supply line and for receiving hydraulic fluid from the hydraulic fluid return line.

2. A system according to Claim 1 wherein the motor mount comprises a mounting block secured to the motor, a supply passage through the mounting block connecting the supply line to the supply port of the motor and a return passage through the mounting block connecting the return line to the return port of the motor.

3. A system according to Claim 2 wherein the supply and return passages have concentric inlet ends connected to the supply and return lines respectively.

4. A system according to Claim 1 , 2, or 3 including fluid passage means through the motor mount for passing fluid along the casing from below the motor mount to above the motor mount for supply to the production tubing string.

5. A system according to any one of Claims 1 through 4 wherein the production string comprises coiled tubing.

6. A system according to any preceding Claim wherein the drive coupling means comprise a drive shaft assembly including constant velocity joints coupling the hydraulic motor output to the pump rotor;

7. A system according to any preceding Claim wherein the motor includes a motor drive shaft extending through the motor and the motor mount and a produced fluid bore extending along the motor drive shaft, with an inlet opening between the motor and the pump and an outlet opening between the motor and the well head.

8. A system according to any preceding claim wherein the production tubing string comprises coiled tubing.