HYDRAULICALLY DRIVEN OIL WELL PUMP

POMPE A MOTEUR HYDRAULIQUE POUR PUITS DE PETROLE

English Abstract

A down hole rotary pump in a well is driven by a down hole hydraulic
motor. The motor is mounted in the production string using a motor mount. 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. This arrangement
eliminates the sucker rod drive that causes power loss and tubing wear and
mitigates problems in completing directional and deviated wells.

French Abstract

Pompe rotative de fond dans un puits entraînée par un moteur hydraulique de fond. Le moteur est monté dans la colonne de production au moyen d'un support de moteur. Le support de moteur comporte des ouvertures pour permettre l'écoulement du fluide produit au-delà du moteur et à travers le support vers le tube de production situé au-dessus du moteur. Cette disposition permet d'éliminer la nécessité d'un entraînement des tiges de pompage qui cause une perte de puissance et l'usure des tubes, et elle atténue les problèmes liés à la réalisation de puits par forage dirigé et dévié.

Claims

CLAIMS
1. A pump system for a well having a well bore extending into the
ground from a well head, said system comprising:
a rotary pump in the well bore for pumping fluid up the well bore, to
the well head;
an hydraulic motor in the well bore, adjacent the rotary pump, the
motor having hydraulic fluid supply and return ports;
coupling means coupling the hydraulic motor to the pump for
operating the pump;
an hydraulic fluid supply line extending along the well bore from the
well head and coupled to the hydraulic fluid supply port of the motor;
an hydraulic fluid return line extending along the well bore from the
well head and coupled to the hydraulic fluid return port of the motor; and
pump means 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 well includes a
production tubing string coupled to the pump for delivering fluid from the pump to
the well head and the pump drive system includes a motor mount mounting the
hydraulic motor in the production tubing and fluid passage means through the
motor mount for passing fluid along the production tubing string from below the
motor mount to above the motor mount.
3. A system according to Claim 2 wherein the motor mount comprises a
mounting block secured to an upper end of the motor, a supply passage
connecting the supply line to the supply port of the motor and a return passage
connecting the return line to the return port of the motor.

4. A system according to Claim 3 wherein the supply and return lines
are concentric.
5. A system according to Claim 2, 3 or 4 wherein the fluid passage
means comprise ports through the motor mount.
6. A system according to any one of Claims 1 through 5 wherein the
production string comprises coiled tubing.
7. A system according to any preceding Claim wherein the coupling
means comprise a drive shaft assembly coupling the hydraulic motor to the pump;
8. A motor assembly for operating a rotary pump in a well, the motor
assembly comprising:
an hydraulic motor with a supply port and a return port and drive
means for driving a pump rotor;
a tubular motor casing with coupling means at each end for
connecting the motor casing into a production tubing string in the well;
a motor mount mounted on the motor and mounted in the motor
casing, the mount having:
production fluid passages therethrough for delivering fluid
along the production tubing string past the motor mount, and
supply and return passages through the mount communicating
with the supply and return ports respectively of the motor.
9. An assembly according to Claim 8 wherein the motor mount
comprises a mounting block, a supply passage connecting the supply line to the
supply port of the motor and a return passage connecting the return line to the
return passage of the motor.
10. An assembly according to Claim 9 wherein the supply and return
lines are concentric.

Description

CA 02209803 1997-07-04
.
HYDRAULICALLY DRIVEN OIL WELL PUMP
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.
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 thesucker 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.
According to one aspect of the present invention there is provided a
pump system for a well having a well bore extending into the ground from a well
head, said system comprising:
a rotary pump in the well bore for pumping fluid up the well bore, to
the well head;
an hydraulic motor in the well bore, adjacent the rotary pump, the
motor having hydraulic fluid supply and return ports;
coupling means coupling the hydraulic motor to the pump for
operating the pump;
an hydraulic fluid supply line extending along the well bore from the
well head and coupled to the hydraulic fluid supply port of the motor;

CA 02209803 1997-07-04
an hydraulic fluid return line extending along the well bore from the
well head and coupled to the hydraulic fluid return port of the motor; and
pump means 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.
The invention thus uses a down hole hydraulic motor for driving a
rotary pump. This eliminates the friction involved in a sucker rod drive, with
consequent reduction of power losses and elimination of tubing wear.
According to another aspect of the present invention there is
10 provided a motor assembly for operating a rotary pump in a well, the motor
assembly comprising:
an hydraulic motor with a supply port and a return port and drive
means for driving a pump rotor;
a tubular motor casing with coupling means at each end for
15 connecting the motor casing into a production tubing string in the well;
a motor mount mounted on the motor and mounted in the motor
casing, the mount having:
production fluid passages therethrough for delivering fluid
along the production tubing string past the motor mount, and
supply and return passages through the mount communicating
with the supply and return ports respectively of the motor.
The present invention 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
25 legs are mitigated. The production pump can even be laid in a horizontal section

CA 02209803 1997-07-04
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 present
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 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
10 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
15 supply oil prior to injection. This heats the produced fluid to eliminate wax formation or to thin heavy oil.
The present system allows the pumps to be automatically controlled
to eliminate dry running of the pump, thus reducing wear. Control of the pump
can be carried out remotely.
In the accompanying drawings, which illustrate exemplary
embodiments 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
25 driver section of the installation;
Figure 3 is an end view of a motor mount;

CA 02209803 1997-07-04
- Figure 4 is the opposite end view of the motor mount; and
Figure 5 is a cross section along line 5-5 of Figures 3 and 4.
Referring to the accompanying drawings, Figure 1 illustrates a well
system 10 including a well bore 12 lined with a production casing 14. The bore
5 extends into the ground into a production formation 16 in the usual way.
A conventional rotary production pump 18 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
10 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 14 to a well head 34 which includes a surface
15 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
20 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
25 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

CA 02209803 1997-07-04
an optional iine heater 48 for heating the hydraulic fluid entering the supply
tubing .
As iliustrated 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
5 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 ofthe 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 ofthe 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.

CA 02209803 1997-07-04
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 rnuch flow cross section as possible.
While one particular embodiment of the present invention has been
5 described in the foregoing, it is to be understood that other embodiments are
possible within the scope of the invention and are intended to be included herein.
The invention is to be considered limited solely by the scope of the appended
claims.

Representative Drawing