Mechanical-Hydraulic Pumping System

Abstract

Devices and methods for recovering production fluid from a subterranean formation using a mechanical-hydraulic production system. A mechanical-hydraulic production system is described that includes a power fluid pump, a production fluid pump and a hydraulically-actuated motor that is associated with the production fluid pump to actuate the production fluid pump. The power fluid pump is mechanically driven from the surface to fluid hydraulic power fluid to the motor, thereby driving the production fluid pump to pump production fluid.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to systems and methods for operating fluid pumps for subterranean production fluid recovery.

2. Description of the Related Art

Enhanced oil recovery techniques often utilize downhole pumps, such as electrical submersible pumps (ESPs) or progressive cavity pumps (PCPs), to increase the flow rate of hydrocarbons from a well. However, it is difficult to use these devices in many lateral or deviated wellbores having tight radius lateral bends. These bends can damage electrical cables and preclude the use of rigid drive rods for operation of the pumps.

SUMMARY OF THE INVENTION

The invention provides devices and methods for the operation of fluid pumps used for recovery of fluids from subterranean formations. The systems and methods of the present invention are particularly suited to operation of fluid pumps in lateral or deviated wellbores.

An exemplary mechanical-hydraulic pumping system is described that includes a mechanically-actuated power fluid pump that is preferably located within a proximal area of the wellbore and a mechanically-actuated production fluid pump that is preferably located in a distal portion of the wellbore. Mechanical operation of the power fluid pump produces a hydraulic output that is used to power a downhole motor that mechanically drives the production fluid pump. In a described embodiment, flexible power fluid transmission conduits extend between the power fluid pump and the downhole motor and serve to transmit power fluid between the power fluid pump and the downhole motor. In a described embodiment, the power fluid transmission conduits are coaxial. The described transmission conduits also transmit power fluid that has been exhausted by the downhole motor back to the power fluid pump from the motor. Also in a described embodiment, a shroud defines a further fluid transmission conduit that extends between the power fluid pump and the downhole motor to transmit hydrocarbon production fluid from a formation to be produced into production tubing. The production fluid may be transmitted toward the surface via the production tubing.

In exemplary operation, mechanical power is transmitted from a surface-based mechanical driver, such as a rod drive unit, to the power fluid pump which is preferably located in a proximal portion of a wellbore or other subterranean region. The power fluid pump generates an output of power fluid which drives the downhole motor. The downhole motor mechanically drives the production fluid pump which is preferably located in a distal portion of the wellbore or other subterranean region. In particular embodiments, the proximal portion is a substantially vertical portion of a wellbore while the distal portion is a deviated or lateral portion of the wellbore.

According to some embodiments of the invention, the exemplary mechanical-hydraulic pumping system includes a fluid accumulator to accommodate thermal expansion/contraction of the power fluid. Also according to some embodiments of the invention, the motor includes a speed increaser which increases the rate of rotation provided by the motor to the production fluid pump.

BRIEF DESCRIPTION OF THE DRAWINGS

For a thorough understanding of the present invention, reference is made to the following detailed description of the preferred embodiments, taken in conjunction with the accompanying drawings, wherein like reference numerals designate like or similar elements throughout the several figures of the drawings and wherein:

FIG. 1 is a side, cross-sectional view of a wellbore containing an exemplary mechanical-hydraulic pumping system constructed in accordance with the present invention.

FIG. 2 is a cross-sectional view taken along lines 2-2 in FIG. 1.

FIG. 3 is a cross-sectional view of an exemplary accumulator bellows that could be used within the pumping system shown in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 depicts an exemplary wellbore 10 that has been drilled from the surface 12 down through the earth 14 to a hydrocarbon-bearing formation 16. The wellbore 10 has a substantially vertical portion 18 and a lateral, deviated portion 20 which are interconnected by angular bend 22. The substantially vertical portion 18 is proximate the opening 17 at the surface 12 (i.e., a proximal portion of the wellbore 10), while the lateral portion 20 is in a distal portion of the wellbore 10. Perforations 24 extend outward from the lateral portion 20 into the formation 16. Although perforations 24 are shown in the described embodiment, it will be understood that these are depicted as an example of a wellbore and are not necessary to the invention. The systems and methods of the present invention may be used in open hole wellbores or other wells which do not have perforations. In particular embodiments, at least the substantially vertical portion 18 of the wellbore 10 is lined with casing 19, of a type well known in the art. Also in particular embodiments, the casing 19 is provided with a gas removal port 21 which permits gas within the casing 19 to escape the casing 19.

An exemplary mechanical-hydraulic pumping system, generally indicated at 26, is disposed within the wellbore 10. The system 26 includes a mechanically-driven power fluid pump 28 which is disposed within the substantially vertical portion 18 of the wellbore 10. The power fluid pump 28 includes a lower pump section 30 and an upper seal section 32, as is known in the art. In one embodiment, the exemplary power fluid pump 28 is actuated by rotation of drive rod 34. Drive rod 34 extends from the seal section 32 to the surface 12 within production tubing 35 and is rotated at the surface 12 by a mechanical driver in the form of a rod drive unit 36. In an alternative embodiment, the power fluid pump 28 is actuated by axial reciprocation of rod 34 by the rod drive unit 36. Suitable pumps for use as the power fluid pump 28 include any of a number of electrical submersible pumps or progressive cavity pumps which are available commercially from Baker Hughes Incorporated of Houston, Tex. In particular embodiments, the rod drive unit 36 is operable to rotate (or axially reciprocate) the rod 34 at variable speeds.

A production fluid pump, mechanically-actuated fluid pump 38, is disposed within the lateral portion 20 of the wellbore 10. The production fluid pump 38 includes fluid intake openings 40 and fluid discharge openings 42. The production fluid pump 38 may be an ESP or a PCP style pump. Suitable fluid pumps for use as the production fluid pump 38 include a number of ESP or PCP pumps which are available commercially from Baker Hughes Incorporated. A downhole hydraulic motor 44 is affixed to the production fluid pump 38. The motor 44 uses the power fluid supplied by the power fluid pump 28 to cause rotational energy. In particular embodiments, the motor 44 includes a speed increaser which will increase the rate of rotation that is transmitted from the motor 44 to the second fluid pump 38. In particular embodiments, the speed increaser of the motor 44 is a gearing arrangement that converts rotation at a lower speed to rotation at a higher speed. A suitable component for use as the speed increaser is a device known in the industry as a gear box. For example, if the power fluid provided by the motor 44 generated a rotational speed of about 500 RPM, the speed increaser might use gears having a ratio of 7:1 to increase the rate of rotation applied to the production fluid pump 38 to 3500 RPM. Suitable motors for use as the hydraulic motor 44 any of a number of motors for driving downhole pumps which are available commercially from Baker Hughes Incorporated. In operation, the hydraulic motor 44 uses hydraulic power fluid as a power input to drive the production fluid pump 38 mechanically. The production fluid pump 38 draws hydrocarbon production fluid into the intake openings 40 and expels the production fluid through the discharge openings 42. Gas that is within the casing 19 is removed from the casing annulus by gas removal port 21. Some gas, or substantially all gas, may also be produced through the production fluid pump 38 and through the production tubing 35, depending upon the application and the selection of pump 38.

Flexible hydraulic power fluid conduits 46, 48 extend between the power fluid pump 28 and the hydraulic motor 44 that is associated with the production fluid pump 38. In the embodiment depicted in FIGS. 1 and 2, these conduits 46, 48 are coaxial. However, in an alternate embodiment, the conduits 46, 48 are not coaxial but are, instead, separate, parallel conduits. In the exemplary embodiment, the coaxially inner conduit 46 is a power fluid supply conduit that transmits hydraulic power fluid exiting the first fluid pump 28 to the motor 44. Also in the exemplary embodiment, the outer coaxial conduit 48 is a power fluid return conduit that returns hydraulic power fluid from the motor 44 to the first fluid pump 28.

A flexible shroud 50 radially surrounds the power fluid pump 28, the hydraulic power fluid conduits 46, 48, the hydraulic motor and speed increaser 44, and the discharge openings 42 of the production fluid pump 38. At its proximal end, the shroud 50 is interconnected with the production tubing 35. At its distal end, the shroud 50 is affixed to the production fluid pump 38. In particular embodiments, the shroud 50 is formed of resilient steel, polymer or composite material and has sufficient pressure capability and integrity to handle the full discharge pressure of the production fluid pump 38.

In operation, the rod drive unit 36 rotates the drive rod 34 to mechanically operate the power fluid pump 28. In an alternative embodiment, the drive rod 34 is axially reciprocated to operate the power fluid pump 28. The power fluid pump 28 flows hydraulic power fluid as an output through the power fluid supply conduit 46 to the hydraulic motor and speed increaser 44. Power fluid that is exhausted by the hydraulic motor and speed increaser 44 is returned to the power fluid pump 28 through the power fluid return conduit 48. The hydraulic power fluid causes the production fluid pump 38 to draw hydrocarbon production fluid in through the intake openings 40 and expel it through the discharge openings 42. Expelled hydrocarbon production fluid is flowed through the shroud 50 to production tubing 35. The production fluid will then flow through the production tubing 35 upwardly toward the surface 12 wherein it will exit the production tubing 35 into production line 52.

In particular embodiments, a fluid accumulator 54, of a type known in the art, is associated with the power fluid conduits 46, 48 to accommodate increases and decreases in fluid volume due to thermal expansion and contraction. FIG. 3 depicts an exemplary fluid accumulator 54 that is incorporated into the production fluid pump 28 below the pump section 30. The exemplary fluid accumulator 54 includes an outer housing 55 which houses an expandable elastomeric bladder 56 that interconnects with the lower pressure power fluid return conduit 48. It is noted that the passage of production fluid past the power fluid pump 28 will help to cool the power fluid pump 28 and associated gear box speed increaser.

The systems and methods of the present invention permit a mechanical drive means at surface 12, such as rod drive unit 36 to mechanically operate a power fluid pump 28 which, in turn, operates a production fluid pump 38 that is driven by hydraulic power fluid. Thus, the invention provides a power transmission system that can operate efficiently and reliably in deviated wells. Systems constructed in accordance with the present invention are capable of producing hydrocarbon fluid through any reasonable radius lateral bend 22 without conventional concerns relating to side loading of sucker rods or ESP cables being damaged. In addition, the systems and methods of the present invention allow for the intake openings 40 of the second pump 38 to be placed anywhere within the lateral section 20 of the wellbore 10.

According to exemplary methods of the present invention, a mechanical-hydraulic pumping system 26 constructed in accordance with the present invention is disposed within the wellbore 10 such that the power fluid pump 28 is located within a proximal portion of the wellbore 10, and, in particular, the substantially vertical portion 18. The production fluid pump 38 is disposed within a distal portion of the wellbore 10, and in particular, the lateral deviated portion 20. Thereafter, the rod drive unit 36 mechanically drives the power fluid pump 28 via rotation or axial reciprocation of the drive rod 34. Actuation of the power fluid pump 28 in this manner will flow hydraulic power fluid along the power fluid supply conduit 46 to operate the downhole motor 44. The motor 44, in turn, drives the production fluid pump 38 to draw production fluid into the shroud 50.

Those of skill in the art will recognize that numerous modifications and changes may be made to the exemplary designs and embodiments described herein and that the invention is limited only by the claims that follow and any equivalents thereof.

Claims

1. A mechanical-hydraulic pumping system for use in flowing fluid from a subterranean formation, the system comprising:

a power fluid pump to be placed in a proximal portion of a wellbore;

a production fluid pump to be placed in a distal portion of a wellbore;

a hydraulically-actuated motor associated with the production fluid pump to actuate the production fluid pump; and

the power fluid pump flowing hydraulic power fluid to the motor to drive the motor and production fluid pump.

2. The pumping system of claim 1 further comprising a fluid transmission conduit for flowing production fluid pumped by the production fluid pump from the formation.

3. The pumping system of claim 1 wherein the power fluid pump is associated with the motor by:

a power fluid supply conduit to transmit hydraulic power fluid from the power fluid pump to the motor; and

a power fluid return conduit to transmit power fluid from the motor to the power fluid pump.

4. The pumping system of claim 3 wherein the power fluid supply conduit and the power fluid return conduit are coaxial.

5. The pumping system of claim 1 further comprising a fluid accumulator to accommodate thermal expansion and contraction of the hydraulic power fluid.

6. The pumping system of claim 3 further comprising a fluid reservoir associated with the power supply and return conduits to permit cooling of power fluid.

7. The pumping system of claim 1 further comprising a mechanical driver for operation of the power fluid pump.

8. The pumping system of claim 7 wherein the mechanical driver comprises a rod drive unit to rotate a drive rod that actuates the power fluid pump.

9. The pumping system of claim 7 wherein the mechanical driver comprises a rod drive unit to axially reciprocate a drive rod that actuates the power fluid pump.

10. The pumping system of claim 1 wherein the power fluid pump comprises an electrical submersible pump.

11. The pumping system of claim 1 wherein the power fluid pump comprises a progressive cavity pump.

12. The pumping system of claim 4 further comprising a transmission conduit for flowing production fluid pumped by the production fluid pump from the formation, the transmission conduit being defined within a shroud that radially surrounds the power fluid supply conduit and power fluid return conduit.

13. A mechanical-hydraulic pumping system for use in flowing fluid from a subterranean formation, the system comprising:

a power fluid pump to be placed in a proximal portion of a wellbore;

a production fluid pump to be placed in a distal portion of a wellbore;

a hydraulically-actuated motor associated with the production fluid pump to actuate the production fluid pump;

the power fluid pump flowing hydraulic power fluid to the motor to drive the motor and production fluid pump; and

a fluid transmission conduit for flowing production fluid pumped by the production fluid pump from the formation.

14. The pumping system of claim 13 wherein the power fluid pump is associated with the motor by:

a power fluid supply conduit to transmit hydraulic power fluid from the power fluid pump to the motor; and

a power fluid return conduit to transmit power fluid from the motor to the power fluid pump.

15. The pumping system of claim 14 wherein the fluid transmission conduit is defined within a shroud that radially surrounds the power fluid supply conduit and power fluid return conduit.

16. A method of recovering production fluid from a subterranean formation comprising the steps of:

a) disposing a mechanical-hydraulic pumping system within a wellbore formed down to the formation, the pumping system having a power fluid pump, a production fluid pump, a hydraulically-actuated motor associated with the production fluid pump to actuate the production fluid pump;

b) mechanically driving the power fluid pump with a mechanical driver to output hydraulic power fluid;

c) flowing the hydraulic power fluid from the power fluid pump to the motor to drive the motor and production fluid pump, the production fluid pump drawing production fluid from the subterranean formation.

17. The method of claim 16 wherein the step of mechanically driving the power fluid pump further comprises rotating a drive rod by a rod drive unit to actuate the power fluid pump.

18. The method of claim 16 wherein the step of mechanically driving the power fluid pump further comprises axially reciprocating a drive rod by a rod drive unit to actuate the power fluid pump.

19. The method of claim 16 further comprising the step of transmitting production fluid from the production fluid pump to a surface location.

20. The method of claim 16 wherein the step of disposing a mechanical-hydraulic pumping system within a wellbore further comprises:

disposing the power fluid pump in a proximal portion of the wellbore, and

disposing the production fluid pump in a distal, deviated portion of the wellbore.