Gas Powered Subsurface Pump Drive System

Description

FIELD OF THE INVENTION

The present invention relates generally to artificial lift systems for low producing hydrocarbon wells, and more particularly, relating to a pneumatic system for driving a lift pump positioned downhole in a producing gas and/or oil well.

BACKGROUND OF THE INVENTION

When a hydrocarbon well ceases to produce naturally, an artificial lift system may be utilized to continue well production. Artificial lift systems include some sort of mechanical device that is inserted into the well to lift fluid from the bottom of the well to the surface. Most commonly, a subsurface pump is installed in the well at a position that submerges the pump within formation fluid that has accumulated within the well casing. The subsurface pump is driven by reciprocating a string of interconnected sucker rods that are connected to the subsurface pump and extend the length of the well from the subsurface pump to the ground surface. Traditionally, a device referred to as a pump jack is installed at the surface that is connected to the string of sucker rods and operates to reciprocate the string of sucker rods, and thus produce products from the well. The pump jack is powered by either an electric motor or a combustion engine. While pump jacks remain the primary method for extracting products from a well, they suffer from many disadvantages and inefficiencies that include their size and weight, noise pollution, visual pollution, the costs associated with their operation and maintenance.

To overcome the disadvantages and inefficiencies of pump jacks, various hydraulic and pneumatic drive mechanisms have been devised to meet various needs such as eliminating the need for the pump jack, the use of sucker rods and reducing operating and maintenance costs. While these devices meet their respective objectives and requirements drawback remain.

Further existing technology requires a source of energy to operate a prime mover to drive the artificial lift system. The prime mover may be an electric motor or combustion engine. Use of an electric motor requires an electric utility line to be run to the well site or an onsite electrical generator powered by a combustion engine. In most instances the costs to run a dedicated electric utility line outweigh the benefit and in some areas it is not possible to run an electric utility. Accordingly, most artificial lift systems whether it is a pump jack or a hydraulic or pneumatic system utilize a combustion engine requiring a source of fuel that must be periodically replenished. Gas produced from the well may be used to fuel the engine but servicing is still required.

Many wells are located in remote locations that may be inaccessible during different times of the year depending on the region in which the is well located which makes operator visits to inspect the well and replenish fuel difficult, expensive and in some circumstances impossible during certain weather seasons.

Accordingly, there is a need for a new artificial lift system that overcomes the disadvantages as discussed above and inherent in existing technology.

SUMMARY OF THE INVENTION

Embodiments of the present invention address this need by providing an artificial lift system which eliminates the use of a pump jack and associated string of sucker rods.

Embodiments of the present invention also provide an artificial lift system which eliminates the requirement of a stuffing box, and thus eliminates the operational and maintenance costs associated therewith.

Embodiments of the present invention further provide an artificial lift system including coiled tubing.

Embodiments of the present invention further provide an artificial lift system that does not require a combustion engine or an electric utility line for operation by employing a pneumatically operated pump driver that that is driven by pressurized gas that can be routed to the well from downstream of the sales gas compressor.

To achieve these and other advantages, in general, in one aspect, a gas powered subsurface pump drive system for use with a well having a wellhead located at the ground surface, a length of completion tubing extending downwardly from the wellhead and a subsurface pump connected to a lower end of the completion tubing by which formation fluid can be pumped upward through the tubing to the wellhead is provided. The system includes a pressure vessel supported above the wellhead and sealing connected to the wellhead establishing a fluidic connection between the internal space of the pressure vessel and the completion tubing extending downwardly from the wellhead. A pneumatic cylinder is supported above the pressure vessel and has a vertically positioned and reciprocal piston rod sealing extending into the internal space of the pressure vessel. An intermediate drive member extends through the production tubing and couples the piston rod of the pneumatic cylinder and a piston rod of the subsurface pump for conjoint reciprocation. A pneumatic drive system alternately provides pressurized gas to an instroke port of the pneumatic cylinder and to the pressure vessel to vertically reciprocate the piston rod, the intermediate drive member and the piston rod of the subsurface pump to pump formation fluid upwardly through the tubing.

There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood and in order that the present contribution to the art may be better appreciated.

Numerous objects, features and advantages of the present invention will be readily apparent to those of ordinary skill in the art upon a reading of the following detailed description of presently preferred, but nonetheless illustrative, embodiments of the present invention when taken in conjunction with the accompanying drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of descriptions and should not be regarded as limiting.

As such, those skilled in the art will appreciate that the conception, upon which this disclosure is based, may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.

For a better understanding of the invention, its operating advantages and the specific objects attained by its uses, reference should be had to the accompanying drawings and descriptive matter in which there are illustrated embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings illustrate by way of example and are included to provide further understanding of the invention for the purpose of illustrative discussion of the embodiments of the invention. No attempt is made to show structural details of the embodiments in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice. Identical reference numerals do not necessarily indicate an identical structure. Rather, the same reference numeral may be used to indicate a similar feature of a feature with similar functionality. In the drawings:

FIG. 1 is a diagrammatic illustration of a gas powered subsurface pump drive system in accordance with an embodiment of the invention;

FIG. 2 is a diagrammatic illustration of a subsurface pump positioned downhole a well and connected to a drive member in accordance with an embodiment of the invention;

FIG. 3 is a diagrammatic illustration of a pneumatic cylinder and pressure vessel with the drive member connected to the pneumatic cylinder in accordance with an embodiment of the invention; and

FIG. 4 is ladder diagram of a control circuit of a pneumatic drive system of the gas powered subsurface pump drive assembly in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Initially referring to FIG. 1 of the drawings, there is diagrammatically illustrated a gas powered subsurface pump drive system 10 according to an embodiment of the invention for pumping formation fluid from a well, such as the representatively illustrated well 12.

Well 12 is a conventional hydrocarbon that produces oil and/or gas and has the usual borehole, or well-bore 14 having casing 16, formed into the Earth. The borehole 14 extends from the surface, down through a hydrocarbon producing formation 18 from which fluid flows through casing perforations 20 into the casing annulus 22. While specific discussion is made herein with respect to an oil and/or gas well, the well could be a water well. Well 12 has a conventional wellhead 24 attached to the surface end of the well casing 16 and including a blowout preventer (BOP) 26. The wellhead 24 configuration can include different components suited for the requirements and/or operation conditions of each particular well.

System 10 includes a production tube 28 extending from the wellhead 24 down the well casing 16 to a downhole position. The production tube 26 may be retained or secured to the wellhead 24 by a conventional tubing hanger (not shown), which is well known in the art. Preferably, the production tubing 26 is a length of coiled tubing for specific advantages over segmented sections of rigid tubing, including being capable of being run into the well without killing the well.

A subsurface pump 30 is connected at a bottom 32 of the production tubing 28. Subsurface pump 30 is a conventional subsurface rod type pump (also may be called a sucker rod pump) that is connectable to the production tubing 26 at the surface to be run into the well along with the production tubing. As best seen in FIG. 2, subsurface pump 30 includes an internally disposed piston 34 that is connected to a piston rod 36 that extends vertically upward from the casing of the pump. Reciprocation of piston rod 36 results in reciprocation of the piston 34 and thus pumping of fluid into and out of the pump. The specific construction of the subsurface pump 30 forms no part of this invention and one of ordinary skill in the art will readily recognize numerous pump designs are suitable for use herein. Accordingly, and because such pumps are well known in the art, a complete technical description of the construction of the subsurface pump 30 is not warranted here for the understanding and implementation of the embodiments of the invention.

System 10 further includes a pressure vessel 38 having a sealed internal volume or space 40. The pressure vessel 38 is supported above and sealing connected to the wellhead 24 with the production tubing 28 in fluidic communication with the internal space 40 of the pressure vessel, as best seen in FIG. 3. Pressure vessel 38 serves to eliminate the use of a stuffing box and several additional purposes that will become readily apparent below. The pressure vessel 38 includes a hand port 42 that may be unsealed to permit access to the internal space 40.

System 10 further includes a pneumatic cylinder 44. Like conventional pneumatic cylinders, pneumatic cylinder 44 includes a piston 46 that is internally disposed for reciprocation therein by gas pressure alternately applied to opposite sides of the piston. A piston rod 48 is connected to the piston 46, and in turn reciprocates with the piston. The piston rod 48 extends from the housing of the pneumatic cylinder between outstroke and instroke positions where the piston rod is fully extend and fully retracted, respectively. An instroke port 50 is configured to receive gas pressure on one side of the piston 46 to retract the piston rod 48. However, in embodiments of the invention outstroke port 52 may be utilized to vent gas pressure from the pneumatic cylinder 44.

The pneumatic cylinder 44 is supported vertically above the pressure vessel 38 with the piston rod extending downwardly and into the internal space 40 of the pressure vessel and in alignment with the production tubing 28. As illustrated, the lower end 54 is threadably and sealing connected to a port of the pressure vessel opposite of the wellhead 24. Of course other connections are possible that provide a sealing connection between at least the piston rod 48 of the pneumatic cylinder 44 and the pressure vessel 38, and which may also support the pneumatic cylinder.

An intermediate drive member 56 extends the length of the production tubing 28 and internally therewithin. The intermediate drive member 56 is connected at a top end to piston rod 48 within the pressure vessel 38 and is connected at a bottom end to the piston rod 36 of the subsurface pump 30. While it is possible for the intermediate drive member 56 to comprise a string of sucker rods, it is preferred that the intermediate drive member is a flexible cable. The flexible cable is preferred because an assembly comprising the coiled production tubing 28, the subsurface pump 30 and the intermediate drive member 56 may be constructed at the surface and then run into the well without killing the well.

System 10 further includes a pneumatic drive system 58, as best seen in FIG. 1. The pneumatic drive system 58 utilizes the existing crude formation fluid pipeline 60 installed at the wellsite for receiving and transporting formation fluid produced by the well to a location remote from the wellsite. The pneumatic drive system 58 also utilizes a sales gas pipeline 62 installed at the wellsite for transporting compressed natural gas to the wellsite from a location remote of the wellsite. The pneumatic drive system 58 utilizes the relatively higher pressure gas in pipeline 62 (for example 200 PSI) and relatively lower pressure in pipeline 60 (for example, less than 50 PSI) in driving the pneumatic cylinder 44, and thus, the subsurface pump 30 to pump formation fluid from the well. To this end, the pneumatic drive system 58 is configured to alternately providing pressurized gas to the instroke port 50 of the pneumatic cylinder 44 and to the pressure vessel 38 and to alternately vent the pressurized gas from the pneumatic cylinder 44 and the pressure vessel 38 to vertically reciprocate the piston rod 48, the intermediate drive member 56 and the piston rod 36 of the subsurface pump 30 to pump formation fluid upwardly through the tubing.

More specifically, an in an embodiment, the pneumatic drive system 58 operates to provide relatively high gas pressure at the instroke port 50 of the pneumatic cylinder 44 from pipeline 62 and to simultaneously connect the internal space 40 of the pressure vessel 38 to the relatively low pressure of pipeline 60 to cause an instroke action on the piston rod 48 of the pneumatic cylinder, and thus, also stroke the intermediate drive member 56 and the piston rod 36 of the subsurface pump. Once the instroke action is completed, the pneumatic drive system 58 then operates to provide relatively high gas pressure to the internal space 40 of the pressure vessel 38 to pressurize the column of formation fluid (which is relatively incompressible fluid) in the production tubing 28 and to simultaneously connect the instroke port 50 of the pneumatic cylinder 44 to the relatively low pressure of pipeline 60 to vent the gas pressure therefrom to cause reset or an outstroke action on the piston rod 48 of the pneumatic cylinder by downwardly stroking the piston rod 36 of the subsurface pump 30 as a result of the head pressure on the column of formation fluid acting on the subsurface pump. This process is repeated until a desired amount of formation fluid is pumped from the well 12.

In an embodiment of the pneumatic drive system 58, fluid line 64 conventionally connects the wellhead 24 to the pipeline 60 to receive produced (pumped) formation fluid from the production tubing 28. Fluid line 64 is illustrated diagrammatically and in a simplified form and may contain many different systems installed along fluid line from the wellhead to the pipeline 60. The instroke port 50 of the pneumatic cylinder 44 is alternately connected to pipeline 62 receive gas pressure therefrom and to pipeline 60 to vent gas pressure from the instroke port side of the pneumatic cylinder to the lower pressure pipeline 60 to recover the natural gas. An instroke port valve 66 is fluidically connected by line 68 to the instroke port 50, is fluidically connected to pipeline 60 by line 70 and is fluidically connected to pipe line 62 by line 72. Instroke port valve 66 is configured and operated to selectively establish a fluid flow between lines 68 and 72 to connect the instroke port 50 to pipeline 62 to receive gas pressure therefrom, and to establish a fluid flow between lines 68 and 70 to connect the instroke port 50 to pipeline 60 to vent gas pressure from instroke port to pipeline 60. The pressure vessel 38 is likewise alternately connected to pipeline 62 receive gas pressure therefrom and to pipeline 60 to vent gas pressure from the pressure vessel to the lower pressure pipeline 60 to recover the natural gas. A pressure vessel valve 74 is fluidically connected by line 76 to the internal space 40 of the pressure vessel 38, is fluidically connected to pipeline 60 by line 78 and is fluidically connected to pipe line 62 by line 80. Pressure vessel valve 74 is configured and operated to selectively establish a fluid flow between lines 76 and 80 to connect the internal space 40 of the pressure vessel 38 to pipeline 62 to receive gas pressure therefrom, and to establish a fluid flow between lines 76 and 78 to connect the internal space of the pressure vessel to the lower pressure pipeline 60 to vent gas pressure therefrom.

In the same embodiment, the pneumatic drive system further includes a first pressure switch or sensor 82 that is connected to the pressure vessel 38 via line 76 to measure the gas pressure in the internal space 40. A second pressure switch or sensor 84 is connected to the instroke port 50 via line 68 to measure the gas pressure of the pneumatic cylinder 44 at the instroke port thereof. Pressure switch 82, pressure switch 84, valve 66 and valve 74 are connected to a control circuit 86 which operates to control valves 66 and 74 based upon pressure at pressure switches 82 and 84 to alternately provide pressurized gas from pipeline 62 to the instroke port 50 of the pneumatic cylinder 44 and to the pressure vessel 38 to vertically reciprocate the piston rod 48, the intermediate drive member 56 and the piston rod 36 of the subsurface pump 30 to pump formation fluid upwardly through the tubing.

With reference to FIG. 4, there is illustrated a ladder diagram according to an embodiment of the control circuit 86. In this embodiment, the control circuit includes a 12V power source 88 (such as a small battery that may be recharged by solar energy), a main power switch 90, a timer 92, a first control relay 94, a second control relay 96, a solenoid operator 98 of valve 66, a solenoid operator 100 of valve 74, the first pressure switch 76 and the second pressure switch 84.

With continued reference to FIG. 4, in an embodiment, the timer 92 is programmed to operate the control circuit 86 at desired times and days depending upon the requirements of the well. The timer may be modified as well requirements change. Initially, the following control sequency starts from the piston rod 48 of the pneumatic cylinder 44 in the extended or outstroked position. Upon wakeup of the timer 92, control relay 96 operates to energize solenoid operator 100 of valve 66 to establish a fluid connection between lines 68 and 72, and thereby provide gas pressure at instroke port 50 of the pneumatic cylinder 44. Valve 74 is normally set to establish a fluid connection between lines 76 and 78, and thus is at low pressure relative to the gas pressure of pipeline 62. Gas pressure at instroke port 50 causes the piston rod 48 of the pneumatic cylinder 44 to instroke which results in stroking of the intermediate drive member 56 and the piston rod 36 of the subsurface pump 30. A completed instroke of piston rod 48 is determined by a pressure rise at instroke port 50 which is measured by pressure switch 84. Once the pressure at instroke port 50 reaches a predetermined pressure, pressure switch 84 is activated which results in control relay 94 operating to de-energize solenoid operator 100 of valve 66, thereby connecting lines 68 and 70 to permit venting of gas pressure from the pneumatic cylinder 44 through instroke port 50 and into pipeline 60. Activation of pressure switch 84 also results in control relay 96 energizing the solenoid operator 98 of valve 74 to establish a fluid connection between lines 76 and 80, and thus pressurize the internal space 40 of the pressure vessel 38 by pressurized gas from pipeline 62. Pressurization of internal space 40 increases the head pressure of the column of formation fluid in the production tubing 28 causing a reset or an outstroke action on the piston rod 48 of the pneumatic cylinder by downwardly stroking the piston rod 36 of the subsurface pump 30 as a result of the head pressure on the column of formation fluid acting on the subsurface pump. A completed reset or outstroke of piston rod 48 is determined by a pressure rise in the internal space 40 which is measured by pressure switch 82. Once the pressure of the internal space 40 reaches a predetermined pressure, pressure switch 82 is activated which results in control relay 96 operating to de-energize solenoid operator 98 and control relay 92 once again operating solenoid operator 100 to start the process over again. This process continues until timer 92 enters a sleep mode.

In embodiments, port 52 of the pneumatic cylinder 44 may be connected to pipeline 60 by connection to vent any well gas that may have migrated across the piston 46 of the pneumatic cylinder to the pipeline to prevent air pollution from a sour well. In other embodiments, port 52 is vented to atmosphere.

A number of embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.