CA2961634A1 - Gas compressor - Google Patents

Abstract

A gas compressor system is disclosed which may have a driving fluid cylinder has a driving fluid chamber adapted for containing a driving fluid therein. The driving fluid cylinder may also have a driving fluid piston movable within the driving fluid chamber. The system may also include a gas compression cylinder having a gas compression chamber adapted for holding a gas therein and a gas piston movable within the gas compression chamber. A buffer chamber may be located between the driving fluid chamber and the gas compression chamber, and may be adapted to inhibit movement of at least one non-driving fluid component, when gas is located within the gas compression chamber, from the gas compression chamber into the driving fluid chamber. The buffer chamber may include a buffer gas which may be maintained at a pressure higher than the pressure reached in the gas compression chamber.

Description

GAS COMPRESSOR
TECHNICAL FIELD
[0001] The present disclosure relates to gas compressors driven by a driving fluid such as a hydraulic fluid, including hydraulic gas compressors driven by hydraulic fluid that are used in oil and gas field applications.
BACKGROUND

[0002] Various different types of gas compressors to compress a wide range of gases are known. Hydraulic gas compressors in particular are used in a number of different applications. One such category of, and application for, a is a gas compressor employed in connection with the operation of oil and gas producing well systems. When oil is extracted from a reservoir using a well and pumping system, it is common for natural gas, often in solution, to also be present within the reservoir.
As oil flows out of the reservoir and into the well a wellhead gas may be formed as it travels into the well and may collect within the well and /or travel within the casing of the well. The wellhead gas may be primarily natural gas and also includes impurities such as water, hydrogen sulphide, crude oil, and natural gas liquids (often referred to as condensate).

[0003] The presence of natural gas within the well can have negative impacts on the functioning of an oil and gas producing well system. It can for example create a back pressure on the reservoir at the bottom of the well shaft that inhibits or restricts the flow of oil to the well pump from the reservoir. Accordingly, it is often desirable to remove the natural gas from the well shaft to reduce the pressure at the bottom of the well shaft particularly in the vicinity of the well pump. Natural gas that migrates into the casing of the well shaft may be drawn upwards - such as by venting to atmosphere or connecting the casing annulus to a pipe that allows for gas to flow out of the casing annulus. To further improve the flow of gas out of the casing annulus and reduce the pressure of the gas at the bottom of the well shaft, the natural gas flowing from the casing annulus may be compressed by a gas compressor and then may be utilized at the site of the well and/or transported for use elsewhere.
The use of a gas compressor will further tend to create a lower pressure at the top of the well shaft compared to the bottom of the well shaft, assisting in the flow of natural gas upwards within the well bore and casing.

[0004] There are concerns in using hydraulic gas compressors in oil and gas field environments, relating to the potential contamination of the hydraulic fluid in the hydraulic cylinder of a gas compressor from components of the natural gas that is being compressed.

[0005] Improved gas compressors are desirable, including gas compressors employed in connection with oil and gas field operations including in connection with oil and gas producing wells.
SUMMARY

[0006] In one embodiment, the present disclosure relates to a gas compressor system that comprises a driving fluid cylinder having a driving fluid chamber adapted for containing a driving fluid therein, and a driving fluid piston movable within the driving fluid chamber. A gas compression cylinder having a gas compression chamber adapted for holding a gas therein and a gas piston movable within the gas compression chamber. A buffer chamber located between the driving fluid chamber and the gas compression chamber, the buffer chamber adapted to inhibit movement of at least one non-driving fluid component, when gas is located within the gas compression chamber, from the gas compression chamber into the driving fluid chamber.

[0007] In another embodiment, the present disclosure relates to a gas compressor system that comprises a first driving fluid cylinder having a first driving fluid chamber adapted for containing a first driving fluid therein, and a first driving fluid piston movable within the first driving fluid chamber. A gas compression chamber adapted for holding a gas therein and a gas piston movable within the gas compression chamber. A first buffer chamber located between the first driving fluid chamber and a first section of the gas compression chamber. A second driving fluid cylinder having a second driving fluid chamber adapted for containing a second driving fluid therein, and a second driving fluid piston movable within the second driving fluid chamber. A second buffer chamber located between the first driving fluid chamber and a second section of the gas compression chamber. The first buffer chamber is adapted to inhibit movement of at least one non-driving fluid component, when gas is located within a first section of the gas compression chamber, from the first section gas compression chamber section into the first driving fluid chamber. The second buffer chamber is adapted to inhibit movement of at least one non-driving fluid component, when gas is located within a second section of the gas compression chamber, from the second section of the gas compression chamber into the second driving fluid chamber.

[0008] In another embodiment, the present disclosure relates to a gas compressor that comprises a driving fluid cylinder having a driving fluid chamber operable for containing a driving fluid therein and a driving fluid piston movable within the driving fluid chamber. A gas compression cylinder having a gas compression chamber operable for holding a gas therein and a gas piston movable within the gas compression chamber. A buffer chamber located between the driving fluid chamber and the gas compression chamber, the buffer chamber configured and operable to inhibit movement of at least one non-driving fluid component from the gas compression chamber to substantially avoid contamination of the driving fluid, when gas is located within the gas compression chamber.

[0009] In another embodiment, the present disclosure relates to a gas compressor that comprises a driving fluid cylinder having a driving fluid chamber operable for containing a driving fluid therein and a driving fluid piston movable within the driving fluid chamber. A gas compression cylinder having a gas compression chamber operable for holding natural gas therein and a gas piston movable within the gas compression chamber. A buffer chamber located between the driving fluid chamber and the gas compression chamber, the buffer chamber containing a non-natural gas component so as to substantially avoid contamination of the driving fluid in the driving fluid chamber, when gas is located within the gas compression chamber.
BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In the figures, which illustrate example embodiments:

[0011] FIG. 1. is a schematic view of an oil and gas producing well system;

[0012] FIG. 1A. is an enlarged schematic view of a portion of the system of FIG. 1;

[0013] FIG. 1B is an enlarged view of part of the system of FIG. 1;

[0014] FIG. 1C is an enlarged view of another part of the system of FIG.
1;

[0015] FIG. 1D is a schematic view of an oil and gas well producing system like the system of FIG. 1 but with an alternate lift system;

[0016] FIG. 2 is a side view of a gas compressor forming part of the system of FIG. 1;

[0017] FIG. 3 (i) to (iv) are side views of the gas compressor or FIG. 2 showing a cycle of operation;

[0018] FIG. 4 is a schematic side view of the gas compressor of FIG. 2;

[0019] FIG. 5 is a perspective view a gas compressor system including the gas compressor of FIG. 2 forming part of an oil and gas producing well systems of FIG. 1 or 1D;

[0020] FIG. 6 is a perspective view of a potion of the gas compressor system of FIG. 5 with some parts thereof exploded;

[0021] FIG. 7 is a schematic diagram of the gas compressor system of FIG.
8;

[0022] FIG. 8 is a perspective exploded view of a gas compressor substantially like the gas compressor of FIG. 2;

[0023] FIG. 8A is enlarged view of the portion marked FIG. 8A in FIG. 8;

[0024] FIG. 8B is enlarged view of the portion marked FIG. 8B in FIG. 8;

[0025] FIG. 9A is a perspective view of the gas compressor of FIG. 2;

[0026] FIG. 9B is a top view of the gas compressor of FIG. 2;

[0027] FIG. 9C is a side view of the gas compressor of FIG. 2.
DETAILED DESCRIPTION

[0028] With reference to FIGS. 1, 1A, 1B and 1C, an example oil and gas producing well system 100 is illustrated schematically that may be installed at, and in, a well shaft (also referred to as a well bore) 108 and may be used for extracting liquid and/or gases (e.g. oil and/or natural gas) from an oil and gas bearing reservoir 104.

[0029] Extraction of liquids including oil as well as other liquids such as water from reservoir 104 may be achieved by operation of a down-well pump 106 positioned at the bottom of well shaft 108. For extracting oil from reservoir 104, down-well pump 106 may be operated by the up-and-down reciprocating motion of a sucker rod 110 that extends through the well shaft 108 to and out of a well head 102.
It should be noted that in some applications, well shaft 108 may not be oriented entirely vertically, but may have horizontal components and/or portions to its path.

[0030] Well shaft 108 may have along its length, one or more generally hollow cylindrical tubular, concentrically positioned, well casings 120a, 120b, 120c, including an inner-most production casing 120a that may extend for substantially the entire length of the well shaft 108. Intermediate casing 120b may extend concentrically outside of production casing 120a for a substantial length of the well shaft 108, but not to the same depth as production casing 120a. Surface casing 120c may extend concentrically around both production casing 120a and intermediate casing 120b, but may only extend from proximate the surface of the ground level, down a relatively short distance of the well shaft 108. The casings 120a, 120b, 120c may be made from one or more suitable materials such as for example steel. Casings 120a, 120b, 120c may function to hold back the surrounding earth / other material in the sub-surface to maintain a generally cylindrical tubular channel through the sub-surface into the oil / natural gas bearing formation 104. Casings 120a, 120b, 120c may each be secured and sealed by a respective outer cylindrical layer of material such as layers of cement 111a, 111b, 111c which may be formed to surround casings 120a-120c in concentric tubes that extend substantially along the length of the respective casing 120a-120c.
Production tubing 113 may be received inside production casing 120a and may be generally of a constant diameter along its length and have an inner tubing passageway / annulus to facilitate the communication of liquids (eg. oil) from the bottom region of well shaft 108 to the surface region. Casings 120a-120c generally, and casing 120a in particular, can protect production tubing 120 from corrosion, wear/damage from use. Along with other components that constitute a production string, a continuous passageway (a tubing annulus) 107 from the region of pump 106 within the reservoir 104 to well head 102 is provided by production tubing 113.
Tubing annulus 107 provides a passageway for sucker rod 110 to extend and within which to move and provides a channel for the flow of liquid (oil) from the bottom region of the well shaft 108 to the region of the surface.

[0031] An annular casing passageway or gap 121 (referred to herein as a casing annulus) is typically provided between the inward facing generally cylindrical surface of the production casing 120a and the outward facing generally cylindrical surface of production tubing 113. Casing annulus 121 typically extends along the co-extensive length of inner casing 120a and production tubing 113 and thus provides a passageway / channel that extends from the bottom region of well shaft 108 proximate the oil! gas bearing formation 104 to the ground surface region proximate the top of the well shaft 108. Natural gas (that may be in liquid form in the reservoir 104) may flow from reservoir 104 into the well shaft 108 and may be, or transform into, a gaseous state and then flow upwards through casing annulus 121 towards well head 102. In some situations, such as with a newly formed well shaft 108, the level of the liquid (mainly oil and natural gas in solution) may actually extend a significant way from the bottom/end of the well shaft 108 to close to the surface in both the tubing annulus 107 and the casing annulus 121, due to relatively high downhole pressures.

[0032] Down-well pump 106 may have a plunger 103 that is attached to the bottom end region of sucker rod 110 and plunger 103 may be moved downwardly and upwardly within a pump chamber by sucker rod 110. Down well pump 106 may include a one way travelling valve 112 which is a mobile check valve which is interconnected with plunger 103 and which moves in up and down reciprocating motion with the movement of sucker rod 110. Down well pump 106 may also include a one way standing intake valve 114 that is stationary and attached to the bottom of the barrel of pump 106/ production tubing 113. Travelling valve 112 keeps the liquid (oil) in the channel 107 of production tubing 113 during the upstroke of the sucker rod 110. Standing valve 114 keeps the fluid (oil) in the channel 107 of the production tubing 113 during the downstroke of sucker rod 110. During a downstroke of sucker rod 110 and plunger 103, travelling valve 112 opens, admitting liquid (oil) from reservoir 104 into the annulus of production tubing 113 of down-well pump 106. During this downstroke, one-way standing valve 114 at the bottom of well shaft 108 is closed, preventing liquid (oil) from escaping.

[0033] During each upstroke of sucker rod 110, plunger 103 of down-well pump 106 is drawn upwardly and travelling valve 112 is closed. Thus, liquid (oil) drawn in through one-way valve 112 during the prior downstroke can be raised. And as standing valve 114 opens during the upstroke, liquid (oil) can enter production tubing 113 below plunger 103 through perforations 116 in production casing 120a and cement layer illa, and past standing valve 114. Successive upstrokes of down-well pump 106 form a column of liquid/oil in well shaft 108 above down-well pump 106. Once this column of liquid/oil is formed, each upstroke pushes a volume of oil toward the surface and well head 102. The liquid/oil, eventually reaches a T-junction device 140 which has connected thereto an oil flow line 133. Oil flow line 133 may contain a valve device 138 that is configured to permit oil to flow only towards a T-junction interconnection 134 to be mixed with compressed natural gas from piping 130 that is delivered from a gas compressor system 126 and then together both flow way in a main oil/gas output flow line 132.

[0034] Sucker rod 110 may be actuated by a suitable lift system 118 that may for example as illustrated schematically in FIG. 1, be a pump jack system 119 that may include a walking beam mechanism 117 driven by a pump jack drive mechanism 120 (often referred to as a prime mover). Prime mover 120 may include a motor 123 that is powered for example by electricity or a supply of natural gas, such as for example, natural gas produced by oil and gas producing well system 100. Prime move 120 may be interconnected to and drive a rotating counter weigh device that may cause the pivoting movement of the walking beam mechanism 120 that causes the reciprocating upward and downward movement of sucker rod 110.

[0035] As shown in FIG. 1 D, lift mechanism 118 may in other embodiments be a hydraulic lift system 1119 that includes a hydraulic fluid based power unit 1120 that supplies hydraulic fluid through a fluid supply circuit to a master cylinder apparatus 1117 to controllably raise and lower the sucker rod 110. The power unit 1120 may include a suitable controller to control the operation of the hydraulic lift system 1119.

[0036] With reference to FIGS. 1 to 1C, natural gas exiting from annulus 121 of casing 120 may be fed by suitable piping 124 through valve device 128 to inter-connected gas compressor system 126. Piping 124 may be made of any suitable material(s) such as steel pipe or flexible hose such as Aeroquip FC 300 AOP
elastomer tubing made by Eaton Aeroquip LLC. In normal operation of system 100, the flow of natural gas communicated through piping 124 to gas compressor system 126 is not restricted by valve device 128 and the natural gas will flow there through.
Valve 128 may be closed (eg. manually) if for some reason it is desired to shut off the flow of natural gas from annulus 121.

[0037] Compressed natural gas that has been compressed by gas compressor system 126 may be communicated via piping 130 through a one way check valve device 131 to interconnect with oil flow line 133 to form a combined oil and gas flow line 132 which can deliver the oil and gas therein to a destination for processing and/or use. Piping 130 may be made of any suitable material(s) such as steel pipe or flexible hose such as Aeroquip FC 300 AOP elastomer tubing made by Eaton Aeroquip LLC.

[0038] Gas compressor system 126 may include a gas compressor 150 that is driven by a driving fluid. As indicated above, natural gas from casing annulus of well shaft 108 may be supplied by piping 124 to gas compressor system 126.
Natural gas may be compressed by gas compressor 150 and then communicated via piping 130 through a one way check valve device 131 to interconnect with oil flow line 133 to form combined oil and gas flow line 132.

[0039] The driving fluid for driving gas compressor 150 may be any suitable fluid such as a fluid that is substantially incompressible, and may contain anti-wear additives or constituents. The driving fluid may, for example, be a suitable hydraulic fluid. For example, the hydraulic fluid may be SKYDROL TM aviation fluid manufactured by Solutia Inc. The hydraulic fluid may for example be a fluid suitable as an automatic transmission fluid, a mineral oil, a bio-degradable hydraulic oil, or other suitable synthetic or semi-synthetic hydraulic fluid.

[0040] Hydraulic gas compressor 150 may be in hydraulic fluid communication with a hydraulic fluid supply system which may provide an open loop or closed loop hydraulic fluid supply circuit. For example gas compressor 150 may in hydraulic fluid communication with a hydraulic fluid supply system 1160 as depicted in FIG.
10.

[0041] Turning now to FIGS. 2 and 7, hydraulic gas compressor 150 may have first and second, one-way acting, hydraulic cylinders 152a, 152b positioned at opposite ends of hydraulic gas compressor 150. Cylinders 152a, 152b are each configured to provide a driving force that acts in an opposite direction to each other, both acting inwardly towards each other and towards a gas compression cylinder 180. Thus, positioned generally inwardly between hydraulic cylinders 152a, 152b is gas compression cylinder 180. Gas compression cylinder 180 may be divided into two gas compression chamber sections 181a, 181b by a gas piston 182. In this way, gas such as natural gas in each of the gas chamber sections 181a, 181b, may be alternately compressed by alternating, inwardly directed driving forces of the hydraulic cylinders 152a, 152b driving the reciprocal movement of gas piston and piston rod 194

[0042] Gas compression cylinder 180 and hydraulic cylinders 152a, 152b may have generally circular cross-sections although alternately shaped cross sections are possible in some embodiments.

[0043] Hydraulic cylinder 152a may have a hydraulic cylinder base 183a at an outer end thereof. A first hydraulic fluid chamber 186a may thus be formed between a cylinder barrel / tubular wall 187a, hydraulic cylinder base 183a and hydraulic piston 154a. Hydraulic cylinder base 183a may have a hydraulic input/output fluid connector 1184a that is adapted for connection to hydraulic fluid communication line 1166a. Thus hydraulic fluid can be communicated into and out of first hydraulic fluid chamber 186a.

[0044] At the opposite end of gas compressor 150, is a similar arrangement.
Hydraulic cylinder 152b has a hydraulic cylinder base 183b at an outer end thereof.
A second hydraulic fluid chamber 186b may thus be formed between a cylinder barrel / tubular wall 187b, hydraulic cylinder base 183b and hydraulic piston 154b.
Hydraulic cylinder base 183b may have an input /output fluid connector 1184b that is adapted for connection to a hydraulic fluid communication line 1166b. Thus hydraulic fluid can be communicated into and out of second hydraulic fluid chamber 186b.

[0045] In embodiments such as is illustrated in FIG. 7, the driving fluid connectors 1184a, 1184b may each connect to a single hydraulic line 1166a, 1166b that may, depending upon the operational configuration of the system, either be communicating hydraulic fluid to, or communicating hydraulic fluid away from, each of hydraulic fluid chamber 186a and hydraulic fluid chamber 186b, respectively.
However, other configurations for communicating hydraulic fluid to and from hydraulic fluid chambers 186a, 186b are possible.

[0046] As indicated above, gas compression cylinder 180 is located generally between the two hydraulic cylinders 152a, 152b. Gas compression cylinder 180 may be divided into the two adjacent gas chamber sections 181a, 181b by gas piston 182. First gas chamber section 181a may thus be defined by the cylinder barrel /
tubular wall 190, gas piston 182 and first gas cylinder head 192a. The second gas chamber section 181b may thus be defined by the cylinder barrel/tubular wall 190, gas piston 182 and second gas cylinder head 192b and formed on the opposite side of gas piston 182 to first gas chamber section 181a.

[0047] The components forming hydraulic cylinders 154a, 154b and gas compression cylinder 180 may be made from any one or more suitable materials.
By way of example, barrel 190 of gas compression cylinder 180 may be formed from chrome plated steel; the barrel of hydraulic cylinders 152a, 152b, may be made from a suitable steel; gas piston 182 may be made from T6061aluminum; the hydraulic pistons 154a, 154b may be made generally from ductile iron; and piston rod 194 may be made from induction hardened chrome plated steel.

[0048] The diameter of hydraulic pistons 154a, 154b may be selected dependent upon the required output gas pressure to be produced by gas compressor 150 and a diameter (for example about 3 inches) that is suitable to maintain a desired pressure of hydraulic fluid in the hydraulic fluid chambers 186a, 186b (for example ¨ a maximum pressure of about 2800 psi).

[0049] Hydraulic pistons 154a, 154b may also include seal devices 196a, 196b respectively at their outer circumferential surface areas to provide fluid /
gas seals with the inner wall surfaces of respective hydraulic cylinder barrels 187a, 187b respectively. Seal devices 196a, 196b, may substantially prevent or inhibit movement of hydraulic fluid out of hydraulic fluid chambers 186a, 186b during operation of hydraulic gas compressor 150 and may prevent or at least inhibit the migration of any gas/liquid that may be in respective adjacent buffer chambers 195a, 195b (as described further hereafter) into hydraulic fluid chambers 186a, 186b.

[0050] Also with reference now to FIGS. 8, 8A and 8B, hydraulic piston seal devices 196a, 196b may include a plurality of olytetrafluoroethylene (PTFE) (eg.Tef Ion (TM) seal rings and may also include Hydrogenated nitrile butadiene rubber (HNBR) energizers / energizing rings for the seal rings. A mounting nut 188a 188b may be threadably secured to the opposite ends of piston rod 194 and may function to secure the respective hydraulic pistons 154a, 154b onto the end of piston rod 194.

[0051] The diameter of the gas piston 182 and corresponding inner surface of gas cylinder barrel 190 will vary depending upon the required volume of gas and may vary widely (eg. from about 6 inches to 12 inches or more). In one example embodiment, hydraulic pistons 154a, 154b have a diameter of 3 inches; piston rod 194 has a diameter or 2.5 inches and gas piston 182 has a diameter of 8 inches.

[0052] Gas piston 182 may also include a conventional gas compression piston seal device at its outer circumferential surfaces to provide a seal with the inner wall surface of gas cylinder barrel 190 to substantially prevent or inhibit movement of natural gas and any additional components associated with the natural gas, between gas compression cylinder sections 181a, 181b. Gas piston seal device may also assist in maintaining the gas pressure differences between the adjacent gas compression cylinder sections 181a, 181b, during operation of hydraulic gas compressor 150.

[0053] As noted above, hydraulic pistons 154a, 154b may be formed at opposite ends of a piston rod 194. Piston rod 194 may pass through gas compression cylinder sections 181a, 181b and pass through a sealed (eg. by welding) central axial opening 191 through gas piston 182 and be configured and adapted so that gas piston 182 is fixedly and sealably mounted to piston rod 194.

[0054] Piston rod 194 may also pass through axially oriented openings in head assemblies 200a, 200b that may be located at opposite ends of gas cylinder barrel 190. Thus, reciprocating axial / longitudinal movement of piston rod 194 will result in reciprocating synchronous axial / longitudinal movement of each of hydraulic pistons 154a, 154b in respective hydraulic fluid chambers 186a, 186b, and of gas piston 182 within gas compression chamber sections 181a, 181b of gas compression cylinder 180.

[0055] Located on the inward side of hydraulic piston 154a, within hydraulic cylinder 154a, between hydraulic fluid chamber 186a and gas compression cylinder section 181a, may be located first buffer chamber 195a. Buffer chamber 195a may be defined by an inner surface of hydraulic piston 154a, the cylindrical inner wall surface of hydraulic cylinder barrel 187a, and hydraulic cylinder head 189a.

[0056] Similarly, located on the inward side of hydraulic piston 154b , within hydraulic cylinder 154b, between hydraulic fluid chamber 186b and gas compression cylinder section 181b, may be located second buffer chamber 195b.
Buffer chamber 195b may be defined by an inner surface of hydraulic piston 154b, the cylindrical inner wall surface of cylinder barrel 187b, and hydraulic cylinder head 189b.

[0057] As hydraulic pistons 154a, 154b are mounted at opposite ends of piston rod 194, piston rod 194 also passes through buffer chambers 195a, 195b.

[0058] With particular reference now to FIGS. 2, 6, 8, 8A-C, and 9A-C and C, head assembly 200a may include hydraulic cylinder head 189a and gas cylinder head 192a and a hollow tubular casing 201a. Hydraulic cylinder head 189a may have a generally circular hydraulic cylinder head plate 206a formed or mounted within casing 201a (FIG. 8B).

[0059] A barrel flange plate 290a (FIG. 9A), hydraulic cylinder head plate 206a (FIG. 8B) and a gas cylinder head plate 212a may have casing 201a disposed there between. Gas cylinder head plate 212a may be interconnected to an inward end of hollow tubular casing 201a for example by welds or the two parts may be integrally to formed together. In other embodiments, hollow tubular casing 201a may be integrally formed with both hydraulic cylinder head plate 206a and gas cylinder head plate 212a.

[0060] Hydraulic cylinder barrel 187a may have an inward end 179a, interconnected such as by welding to the outward facing edge surface of a barrel flange plate 290a. Barrel flange plate 290a may be configured as shown in FIGS. 2, 8,8A-C, and 9A-C.

[0061] Barrel flange plate 290a may be connected to the hydraulic cylinder head plate 206a by bolts 217 (FIG. 8) received in threaded openings 218 of outward facing surface 213a of hydraulic head plate 206a (FIGS. 8 and 8B). A gas and liquid seal may be created between the mating surfaces of hydraulic head plate 206a and barrel flange plate 290a. A sealing device may be provided between these plate surfaces such as TEFLON hydraulic seals and buffers.

[0062] Gas cylinder barrel 190 may have an end 155a (FIG. 8B) interconnected to the inward facing surface of gas cylinder head plate 212a such as by passing first threaded ends of each of the plurality of tie rods 193 through openings in head plate 212a and securing them with nuts 168.

[0063] Piston rod 194 may have a portion that moves longitudinally within the inner cavity formed through openings within barrel flange plate 290a, hydraulic cylinder head plate 206a and gas cylinder head plate 212a and within tubular casing 210a.

[0064] A structure and functionality corresponding to the structure and functionality just described in relation to hydraulic cylinder 152a, buffer chamber __ 195a, and gas compression cylinder section 181a, may be provided on the opposite side of hydraulic gas compression cylinder 150 in relation to hydraulic cylinder 152b, buffer chamber 195b, and gas compression cylinder section 181b.

[0065] Thus with particular reference to FIGS. 8, 8A and 8B, head assembly 200b may include hydraulic cylinder head 189b, gas cylinder head 192b and a __ hollow tubular casing 201b. Hydraulic cylinder head 189b may have a hydraulic cylinder head plate 206b formed or mounted within casing 201b (FIG. 8A)

[0066] A barrel flange plate 290b /hydraulic cylinder head plate 206b and a gas cylinder head plate 212b (FIGS. 8 and 8A) may have casing 201b generally disposed there between. Gas cylinder head plate 212b may be interconnected to __ hollow tubular casing 201b for example by welds or the two parts may be integrally formed together. In other embodiments, hollow tubular casing 201b may be integrally formed with hydraulic cylinder head plate 206b and gas cylinder head plate 212b.

[0067] Hydraulic cylinder barrel 187b (FIG. 9A) may have an inward end 179b, __ interconnected such as by welding to the outward facing edge surface of a barrel flange plate 290b. Barrel flange plate 290b may also be configured as shown in FIGS. 2, 8, 8A-C, and FIGS. 9A-C.

[0068] Barrel flange plate 290b may be connected to the hydraulic cylinder head plate 206b by bolts 217 received in threaded openings 218b of outward facing __ surface 213b of hydraulic head plate 206b (FIG. 9B). A gas and liquid seal may be created between the mating surfaces of hydraulic head plate 206b and barrel flange plate 290b. A sealing device may be provided between these plate surfaces such as TEFLON hydraulic seals and buffers.

[0069] Gas cylinder barrel 190 may have an end 155b (FIG. 9A) interconnected to the inward facing surface of gas cylinder head plate 212b such as by passing first threaded ends of each of the plurality of tie rods 193 through openings in head plate 212b and securing them with nuts 168.

[0070] Piston rod 194 may have a portion that moves longitudinally within the inner cavity formed through openings within hydraulic cylinder head plate 206b and gas cylinder head plate 212b and within tubular casing 210b.

[0071] With particular reference now to FIGS. 8, 8A and 8B, two head sealing 0-rings 308a, 308b may be provided and which may be made from highly saturated nitrile-butadiene rubber (HNBR). One 0-ring 308a may be located between a first circular edge groove 216a at end 155a of gas cylinder barrel 190 and the inward facing surface of gas cylinder head plate 212a. 0-ring 308a may be retained in a groove in the inward facing surface of gas cylinder head plate 212a. 0-ring 308b may be located between a second opposite circular edge groove 216b of at the opposite end of gas cylinder barrel 190 and the inward facing surface of gas cylinder head plate 212b. 0-ring 308b may be retained in a groove in the inward facing surface of gas cylinder head plate 212b. In this way gas seals are provided between gas compression chamber sections181a, 181b and their respective gas cylinder head plates 212a, 212b.

[0072] By securing threaded both opposite ends of each of the plurality of tie rods 193 through openings in gas cylinder head plates 212a, 212b and securing them with nuts 168, tie rods 193 will function to tie together the head plates 212a and 212b with gas cylinder barrel 190 and 0-rings 308a, 308b securely held there between and providing a sealed connection between cylinder barrel 190 and head plates 212a, 212b.

[0073] Seal / wear devices 198a, 198b may be provided within casing 201a to provide a seal around piston rod 194 and with an inner surface of casing 201a to prevent or limit the movement of natural gas out of gas compression cylinder section 181a, into buffer chamber 195a. Corresponding seal / wear devices may be provided within casing 201b to provide a seal around piston rod 194 and with an inner surface of casing 201b to prevent or limit the movement of natural gas out of gas compression cylinder section 181b, into buffer chamber 195b. These seal devices198a, 198b may also prevent or at least limit/inhibit the movement of other components (such as contaminants) that have been transported with the natural gas from well shaft 108 into gas compression cylinder sections 181a, 181b, from migrating into respective buffer chambers 195a, 195b.

[0074] While in some embodiments, the gas pressure in gas compression chamber sections 181a, 181b will remain generally, if not always, above the pressure in the adjacent respective buffer chambers 195a, 195b, the seal /
wear devices 198a, 198b may in some situations prevent migration of gas and/or liquid that may be in buffer chambers 195a, 195b from migrating into respective gas compression chamber sections 181a 181b. The seal / wear devices 198a, 198b may also assist to guide piston rod 194 and keep piston rod 194 centred in the casings 201a, 201b and absorb transverse forces exerted upon piston rod 194.

[0075] Also, with particular reference to FIGS. 8, 8A and 8B, each seal device 198a, 198b may be mounted in a respective casing 201a, 201b. Associated with each head assembly 200a, 200b may also be a rod seal retaining nut 151 which may be made from any suitable material, such as for example aluminium bronze.
A
rod seal retaining nut 151 may be axially mounted around piston rod 194. Rod seal retaining nut 151 may be provided with inwardly directed threads 156. The threads 156 of rod sealing nut 151 may engage with internal mating threads in opening of the respective casing 201a, 201b. By tightening rod sealing nut 151, components of sealing devices 198a, 198b may be axially compressed within casing 201a, 201b.
The compression causes components of the sealing devices 198a, 1987b to be pushed radially outwards to engage an inner cylindrical surface of the respective casings 201a, 201b and radially inwards to engage the piston rod 194. Thus seal devices 198a, 198b are provided to function as described above in providing a sealing mechanism.

[0076] As each rod seal retaining nut 151 can be relatively easily unthreaded from engagement with its respective casing 201a, 201b, maintenance and/or replacement of one or more components of seal devices 198a, 198b is made easier.
Additionally, by turning a rod seal retaining nut 151 may be engaged to thread the rod seal retaining nut further into opening 153 of the casing, adjustments can be made to increase the compressive load on the components of the sealing devices 198a, 198b to cause them to be being pushed radially further outwards into further and stronger engagement with an inner cylindrical surface of the respective casings 201a, 201b and further inwards to engage with the piston rod 194. Thus the level of sealing action /force provided by each seal device 198a, 198b may be adjusted.

[0077] However, even with an effective seal provided by the sealing devices 198a, 198b, it is possible that small amounts of natural gas, and/or other components such as hydrogen sulphide, water, oil may still at least in some circumstances be able to travel past the sealing devices 198a, 198b into respective buffer chambers 195a, 195b For example, oil may be adhered to the surface of piston rod 194 and during reciprocating movement of piston rod 194, it may carry such other components from the gas compression cylinder section 181a, 181b past sealing devices 198a, 198b, into an area of respective cylinder barrels 187a, 187b that provide respective buffer chambers 195a, 195b. High temperatures that typically occur within gas compression chamber sections 181a, 181b may increase the risk of contaminants being able to pass seal devices 198a, 198b. However buffer chambers 195a, 195b each provide an area that may tend to hold any contaminants that move from respective gas compression chamber sections 181a, 181b and restrict the movement of such contaminants into the areas of cylinder barrels that provide hydraulic cylinder fluid chambers 186a, 186b.

[0078] Mounted on and extending within cylinder barrel 187a close to hydraulic cylinder head 189a, is a proximity sensor 157a. Proximity sensor 157a is operable such that during operation of gas compressor 150, as piston 154a is moving from left to right, just before piston 154a reaches the position shown in FIG. 3(i), proximity sensor 157a will detect the presence of hydraulic piston 154a within hydraulic cylinder 152a at a longitudinal position that is shortly before the end of the stroke.
Sensor 157a will then send a signal to controller 200, in response to which controller 200 can take steps to change the operational mode of hydraulic fluid supply system 1160 (FIG. 7).

[0079] Similarly, mounted on and extending within cylinder barrel 187b close to hydraulic cylinder head 189b, is another proximity sensor 157b. Proximity sensor 157b is operable such that during operation of gas compressor 150, as piston 154b is moving from right to left, just before piston 154b reaches the position shown in FIG. 5(iii), proximity sensor 157b will detect the presence of hydraulic piston 154b within hydraulic cylinder 152b at a longitudinal position that is shortly before the end of the stroke. Proximity sensor 157b will then send a signal to controller 200, in response to which controller 200 can take steps to change the operational mode of hydraulic fluid supply system 1160.

[0080] Proximity sensors 157a, 157b may be in communication with controller 200. In some embodiments, proximity sensors 157a, 157b may be implemented using inductive proximity sensors, such as model BI 2--M12-Y1X-H1141 sensors manufactured by Turck, Inc. These inductive sensors are operable to generate proximity signals responsive to the proximity of a metal portion of piston rod proximate to each of hydraulic piston 154a, 154b. For example sensor rings may be attached around piston rod 194 at suitable positions towards, but spaced from, hydraulic pistons 154a, 154b respectively such as annular collar 199b in relation to hydraulic piston 154b - FIGS. 6 and 8. Proximity sensors 157a, 157b may detect when collars 199a, 199b on piston rod 194 pass by. Steel annular collars 199a, 199b may be mounted to piston rod 194 and may be held on piston rod 194 with set screws and a LOCTITE TM adhesive made by Henkel Corporation.

[0081] It is possible for controller 200 (FIG. 7) to be programmed in such manner to control the hydraulic fluid supply system 1160 in such a manner as to provide for a relatively smooth slowing down, a stop, reversal in direction and speeding up of piston rod 194 along with the hydraulic pistons 154a, 154b and gas piston 182 as the piston rod 194, hydraulic pistons 154a, 154b and gas piston 182 transition between a drive stroke providing movement to the right to a drive stroke providing the stroke to the left and back to a stroke providing movement to the right.

[0082] An example hydraulic fluid supply system 1160 for driving hydraulic pistons 154a, 154b of hydraulic cylinders 152a, 152b of hydraulic gas compressor 150 in reciprocating movement is illustrated in FIG. 7. Hydraulic fluid supply subsystem 1160 may be a closed loop system and may include a pump unit 1174, hydraulic fluid communication lines 1163a, 1163b, 1166a, 1166b, and a hot oil shuttle valve device 1168. Shuttle valve device 1168 may be for example a hot oil shuttle valve device made by Sun Hydraulics Corporation under model XRDCLNN-AL.

[0083] Fluid communication line 1163a fluidly connects a port S of pump unit 1174 to a port 0 of shuttle valve 1168. Fluid communication line 1163b fluidly connects a port P of pump 1174 to a port R of shuttle valve 1168. Fluid communication line 1166a fluidly connects a port V of shuttle valve 1168 to a port 1184a of hydraulic cylinder 152a. Fluid communication line 1166b fluidly connects a port W of shuttle valve 1168 to a port 1184b of hydraulic cylinder 152b.

[0084] An output port M of shuttle valve 1168 may be connected to an upstream end of a bypass fluid communication line 1169 having a first portion 1169a, a second portion 1169b and a third portion 1169c that are arranged in series A filter may be interposed in bypass line 1169 between portions 1169a and 1169b. Filter 1171 may be operable to remove contaminants from hydraulic fluid flowing from shuttle valve device 1168 before it is returned to reservoir 1172. Filter 1171 may for example include a type HMK05/25 5 micro-m filter device made by Donaldson Company, Inc. The downstream end of line portion 1169b joins with the upstream end of line portion 1169c at a T-junction where a downstream end of a pump case drain line 1161 is also fluidly connected. Case drain line 1161 may drain hydraulic fluid leaking within pump unit 1174. Fluid communication line portion 1169c is connected at an opposite end to an input port of a thermal valve device 1142.
Depending upon the temperature of the hydraulic fluid flowing into thermal valve device 1142 from communication line portion 1169c of bypass line 1169, thermal valve device 1142 directs the hydraulic fluid to either fluid communication line 1141a or 1141b. If the temperature of the hydraulic fluid flowing into thermal valve device 1142 is greater than a set threshold level, valve device 1142 will direct the hydraulic fluid through fluid communication line 1141a to a cooling device 1143 where hydraulic fluid can be cooled before being passed through fluid communication line 1141c to reservoir 1172. If the hydraulic fluid entering fluid valve device 1142 does not require cooling, then thermal valve 1142 will direct the hydraulic fluid received therein from communication line portion 1169c to communication line 1141b which leads directly to reservoir 1172. An example of a suitable thermal valve device 1142 is a model 67365-110F made by TTP (formerly Thermal Transfer Products). An example of a suitable cooler 1143 is a a model BOL-16-216943 also made by TTP.

[0085] Drain line 1161 connects output case drain ports U and T of pump unit 1174 to a T-connection in communication line 1169b at a location after filter 1171.
Thus any hydraulic fluid directed out of case drain ports U / T of pump unit 1174 can pass through drain line 1161 to the T-connection of communication line portions 1169b, 1169c, (without going through the filter device 1171) where it can mix with any hydraulic fluid flowing from filter 1171 and then flow to thermal valve device 1142 where it can either be directed to cooler 1143 before flowing to reservoir 1172 or be directed directly to reservoir 1172. By not passing hydraulic fluid from case drain 1161 through relatively fine filter 1171, the risk of filter 1171 being clogged can be reduced. It will be noted that filter 1182 provides a secondary filter for fluid that is re-charging pump unit 1174 from reservoir 1172.

[0086] Hydraulic fluid supply system 1160 may include a reservoir 1172 may utilize any suitable driving fluid, which may be any suitable hydraulic fluid that is suitable for driving the hydraulic cylinders 152a, 152b.

[0087] Cooler 1143 may be operable to maintain the hydraulic fluid within a desired temperature range, thus maintaining a desired viscosity. For example, in some embodiments, cooler 1143 may be operable to cool the hydraulic fluid when the temperature goes above about 50 C and to stop cooling when the temperature falls below about 45 C. In some applications such as where the ambient temperature of the environment can become very cold, cooler 1143 may be a combined heater and cooler and may further be operable to heat the hydraulic fluid when the temperature reduces below for example about -10 C. The hydraulic fluid may be selected to maintain a viscosity generally in hydraulic fluid supply system 1160 of between about 20 and about 40 MM2S-1 over this temperature range.

[0088] Hydraulic pump unit 1174 is generally part of a closed loop hydraulic fluid supply system 1160. Pump unit 1174 includes outlet ports S and P for selectively and alternately delivering a pressurized flow of hydraulic fluid to fluid communication lines 1163a and 1163b respectively, and for allowing hydraulic fluid to be returned to pump unit 1174 at ports Sand P. Thus hydraulic fluid supply system 1160 may be part of a closed loop hydraulic circuit, except to the extent described hereinafter.
Pump unit 1174 may be implemented using a variable-displacement hydraulic pump capable of producing a controlled flow hydraulic fluid alternately at the outlets S and P. In one embodiment, pump unit 1174 may be an axial piston pump having a swashplate that is configurable at a varying angle a. For example pump unit may be a HPV-02 variable pump manufactured by Linde Hydraulics GmBH & Co.
KG of Germany, a model that is operable to deliver displacement of hydraulic fluid of up to about 55 cubic centimeters per revolution at pressures in the range of psi. In other embodiments, the pump unit 1174 may be other suitable variable displacement pump, such as a variable piston pump or a rotary vane pump, for example. For the Linde HPV-02 variable pump, the angle a of the swashplate may be adjusted from a maximum negative angle of about -21 , which may correspond to a maximum flow rate condition at the outlet S, to about 00, corresponding to a substantially no flow condition from either port S or P, and a maximum positive angle of about +21 , which corresponds to a maximum flow rate condition at the outlet P.

[0089] In this embodiment the pump unit 1174 may include an electrical input for receiving a displacement control signal from controller 200. The displacement control signal at the input is operable to drive a coil of a solenoid (not shown) for controlling the displacement of the pump unit 1174 and thus a hydraulic fluid flow rate produced alternately at the outlets P and S. The electrical input is connected to a 24VDC coil within the hydraulic pump 1174, which is actuated in response to a controlled pulse width modulated (PWM) excitation current of between about 232 mA (ion) for a no flow condition and about 425 mA (iu) for a maximum flow condition.

[0090] For the Linde HPV-02 variable pump unit 1174, the swashplate is actuated to move to an angle a either +21 or -21 , only when a signal is received from controller 200. Controller 200 will provide such a signal to pump unit 1174 based on the position of the hydraulic pistons 154a, 154b as detected by proximity sensors 157a, 157b as described above, which provide a signal to the controller 200 when the gas compressor 150 is approaching the end of a drive stroke in one direction, and commencement of a drive stroke in the opposite direction is required.

[0091] Pump unit 1174 may also have be part of a fluid charge system 1180.
Fluid charge system 1180 is operable to maintain sufficient hydraulic fluid within pump unit 1174 and may maintain/hold fluid pressure of for example at least 300 psi at both ports S and P so as to be able to control and maintain the operation of the main pump so it can function to supply a flow of hydraulic fluid under pressure alternately at ports S and P.

[0092] Fluid charge system 1180 may include a charge pump that may be a 16cc charge pump supplying for example 6-7 gpm and it may be incorporated as part of pump unit 1174. Charge system 1180 functions to supply hydraulic fluid as may be required by pump unit 1174, to replace any hydraulic fluid that may be directed from port M of shuttle valve device 1168 through a relief valve associated with shuttle valve device 1168 to reservoir 1172 and to address any internal hydraulic fluid leakage associated with pump unit 1174. The shuttle valve device 1168 may for example redirect in the range of 3-4 gpm from the hydraulic fluid circuit. The charge pump will then replace the redirected hydraulic fluid 1:1 by maintain a low side loop pressure.

[0093] The relief valve associated with shuttle valve device 1168 will typically only divert to port M a very small proportion of the total amount of hydraulic fluid circulating in the fluid circuit and which passes through shuttle valve device into and out of hydraulic cylinders 152a, 152b. For example, the relief valve associated with shuttle valve device may only divert approximately 3 to 4 gallons per minute of hydraulic fluid at 200 psi, accounting for example only about 1% of the hydraulic fluid in the substantially closed loop the hydraulic fluid circuit.
This allows at least a portion of the hydraulic fluid being circulated to gas compressor 150 on each cycle to be cooled and filtered.

[0094] The charge pump may draw hydraulic fluid from reservoir 1172 on a fluid communication line 1185 that connects reservoir 1172 with an input port B of pump unit 1174. The charge pump of pump unit 1174 then directs and forces that fluid to port A where it is then communicated on fluid communication line 1181 to a filter device 1182 (which may for example be a 10 micro-m filter made by Linde.

[0095] Upon passing through filter device 1182 the hydraulic fluid may then enter port F of pump unit 1174 where it will be directed to the fluid circuit that supplies hydraulic fluid at ports S and P. In this way a minimum of 300 psi of pressure of the hydraulic fluid may be maintained during operation at ports S and P. The charge pressure gear pump may mounted on the rear of the main pump and driven through a common internal shaft.

[0096] In a swashplate pump, rotation of the swashplate drives a set of axially oriented pistons (not shown) to generate fluid flow. In an embodiment of Figure 10, the swashplate of the pump unit 1174 is driven by a rotating shaft 1173 that is coupled to a prime mover 1175 for receiving a drive torque. In some embodiments, prime mover 1175 is an electric motor but in other embodiments, the prime mover may be implemented in other ways such as for example by using a diesel engine, gasoline engine, or a gas driven turbine.

[0097] Prime mover 1175 is responsive to a control signal received from controller 200 at a control input to deliver a controlled substantially constant 1() rotational speed and torque at the shaft 1173. While there may be some minor variations in rotational speed, the shaft 1173 may be driven at a speed that is substantially constant and can for a period of time required, produce a substantially constant flow of fluid alternately at the outlet ports S and P. In one embodiment the prime mover 256 is selected and configured to deliver a rotational speed of about 1750 rpm which is controlled to be substantially constant within about 1%.

[0098] To alternately drive the hydraulic cylinders 152a, 152b to provide the reciprocating axial motion of the hydraulic pistons 154a, 154b and thus reciprocating motion of gas piston 182, a displacement control signal is sent from controller 200 to pump unit 1174 and a signal is also provided by controller to prime mover 1175. In response, prime mover 1175 drives rotating shaft 1173, to drive the swashplate in rotation. The displacement control signal at the input of pump unit 1174 drives a coil of a solenoid (not shown) to cause the angle a of the swashplate to be adjusted to desired angle such as a maximum negative angle of about -21 , which may correspond to a maximum flow rate condition at the outlet S and no flow at outlet P.
The result is that pressurized hydraulic fluid is driven from port S of pump unit 1174 along fluid communication line 1163a to input port Q of shuttle valve device 1168.
The shuttle valve device 1168 with the lower pressure hydraulic fluid at port R will be configured such that the pressurized hydraulic fluid flows into port Q will flow out port V of shuttle valve device 1168 and into and along fluid communication line 1166a and then will enter hydraulic fluid chamber 186a of hydraulic cylinder 152a.
The flow of hydraulic fluid into hydraulic fluid chamber 186a will cause hydraulic piston 154a to be driven axially in a manner which expands hydraulic fluid chamber 186a, thus resulting in movement in one direction of piston rod 194, hydraulic pistons 154a, 154b and gas piston 182.

[0099] During the expansion of hydraulic fluid chamber 186a as piston 154a moves within cylinder barrel 187a, there will be a corresponding contraction in size of hydraulic fluid chamber 186b of hydraulic cylinder 152b within cylinder barrel 187b. This results in hydraulic fluid being driven out of hydraulic fluid chamber 186b through port 1184b and into and along fluid communication line 1166b. The configuration of shuttle valve device 1168 will be such that on this relatively low pressure side, hydraulic fluid can flow into port W and out of port R of shuttle valve device 1168, then along fluid communication line 1163b to port P of pump unit 1174.
However, the relief valve associated with shuttle valve device 1168 may in this operational configuration, direct a small portion of the hydraulic fluid flowing along line 1166b to port M for communication to reservoir 1172, as discussed above.
However, most (eg. about 99%) of the hydraulic fluid flowing in communication line 1166b will be directed to communication line 1163b for return to pump unit 1174 and enter at port P.

[00100] When the hydraulic piston 154a approaches the end of its drive stroke, a signal is sent by proximity sensor 157a to controller 200 which causes controller 200 to send a displacement control signal to pump unit 1174. In response to receiving the displacement control signal at the input of pump unit 1174, a coil of the solenoid (not shown) is driven to cause the angle a of the swashplate of pump unit 1174 to be altered such as to be set at a maximum negative angle of about +210 , which may correspond to a maximum flow rate condition at the outlet P and no flow at outlet S. The result is that pressurized hydraulic fluid is driven from port P of pump unit 1174 along fluid communication line 1163b to port R of shuttle valve device 1168. The configuration of shuttle valve device 1168 will have been adjusted due lathe change in relative pressures of hydraulic fluid in lines 1163a and 1163b, such that on this relatively high pressure side, hydraulic fluid can flow into port R and out of port W of shuttle valve device 1168, then along fluid communication line 1166b to port 1184b. Pressurized hydraulic fluid will then enter hydraulic fluid chamber 186b of hydraulic cylinder 152b. This will cause hydraulic piston 154b to be driven in an opposite axial direction in a manner which expands hydraulic fluid chamber 186b, thus resulting in synchronized movement in an opposite direction of hydraulic cylinders 154a, 154b and gas piston 182.

[00101] During the expansion of hydraulic fluid chamber 186b, there will be a corresponding contraction of hydraulic fluid chamber 186a of hydraulic cylinder 152a. This results in hydraulic fluid being driven out of hydraulic fluid chamber 186a through port 1184a and into and along fluid communication line 1166a. The configuration of shuttle valve device 1168 will be such that on what is now now a relatively low pressure side, hydraulic fluid can now flow into port V and out of port Q
of shuttle valve device 1168, then along fluid communication line 1163a to port S of pump unit 1174. However, the relief valve associated with shuttle valve device 1168 may in this operational configuration, direct as small portion of the hydraulic fluid flowing along line 1166a to port M for communication to reservoir 1172, as discussed above. Again most of the hydraulic fluid flowing in communication line 1166a will be directed to communication line 1163a for return to pump unit 1174 at port S but a small portion (eg. 1%) may be directed by shuttle valve device 1168 to port M for communication to reservoir 1172, as discussed above. However, most (eg. about 99%) of the hydraulic fluid flowing in communication line 1166a will be directed to communication line 1163a for return to pump unit 1174 and enter at port S.

[00102] The foregoing describes one cycle which can be repeated continuously for multiple cycles, as may be required during operation of gas compressor system 126. If a change in flow rate! fluid pressure is required in hydraulic fluid supply system 1160, to change the speed of movement and increase the frequency of the cycles, controller 200 may send an appropriate signal to prime mover 1175 to vary the output to vary the rotational speed of shaft 1173. Alternately and/or additionally, controller 200 may send a displacement control signal to the input of pump unit 1174 to drives the solenoid (not shown) to cause a different angle a of the swashplate to provide different flow rate conditions at the port P and no flow at outlet S
or to provide different flow rate conditions at the port S and no flow at outlet P.
If zero flow is required, the swash plate may be moved to an angle of zero degrees.

[00103] Controller 200 may also include an input for receiving a start signal operable to cause the controller 200 to start operation of gas compressor system lo 126 and outputs for producing a control signal for controlling operation of the prime mover 1175 and pump unit 1174. The start signal may be provided by a start button within an enclosure that is depressed by an operator on site to commence operation.
Alternatively, the start signal may be received from a remotely located controller, which may be communication with the controller via a wireless or wired connection.
The controller 200 may be implemented using a microcontroller circuit although in other embodiments, the controller may be implemented as an application specific integrated circuit (ASIC) or other integrated circuit, a digital signal processor, an analog controller, a hardwired electronic or logic circuit, or using a programmable logic device or gate array, for example.

[00104] With reference now to Figure 4, it may be appreciated that hydraulic cylinder barrel 187a may be divided into three zones: (i) a zone ZH dedicated exclusively to holding hydraulic fluid; (ii) a zone ZB dedicated exclusively for the buffer area and (iii) a overlap zone that which, depending upon where the hydraulic piston 154a is in the stroke cycle, will vary between an area holding hydraulic fluid and an area providing part of the buffer chamber. Hydraulic cylinder barrel 187b may be divided into a corresponding set of three zones in the same manner with reference to the movement of hydraulic piston 154b.

[00105] If the length XBa (which is the length of the cylinder barrel from gas cylinder head 192a to the inward facing surface of hydraulic cylinder 154a at its full right position) is greater than the stroke length Xs, then any point 131a on piston rod 194 on the piston rod 194 that is at least for part of the stroke within gas compression chamber section 181a, will not move beyond the distance XBa when the gas piston 182 and the hydraulic cylinder 154a move from the farthermost right positions of the stroke position (1) to the farthermost left positions of the stroke position (2). Thus, any materials/contaminants carried on piston rod 194 starting at P1 a will not move beyond the area of the hydraulic cylinder barrel 187a that is dedicated to providing buffer chamber 195a. Thus, any such contaminants travelling on piston rod 194 will be prevented, or at least inhibited, from moving into the zones ZH and Zo of hydraulic cylinder barrel 187a that hold hydraulic fluid. Thus any point 131 a on piston rod 194 that passes into the gas compression chamber will not pass into an area of the hydraulic cylinder barrel 187a that will encounter hydraulic fluid (ie. It will not pass into Zh or Zo). Thus, all portions of piston rod 194 that encounter gas, will not be exposed to an area that is directly exposed to hydraulic fluid. Thus cross contamination of contaminants that may be present with the natural gas in the gas compression cylinder 180 may be prevented or inhibited from migrating into the hydraulic fluid that is in that areas of hydraulic cylinder barrel 187a adapted for holding hydraulic fluid. It may be appreciated, that since there is an overlap zone, the hydraulic pistons do move from a zone where there should be never anything but hydraulic fluid to a zone which transitions between hydraulic fluid and the contents (eg. air) of the buffer zone. Therefore, contaminants on the inner surface wall of the cylinder barrel 187a, 187b in the overlap zone could theoretically get transferred to the edge surface of the piston. However, the presence of buffer zone significantly reduces the level of risk of cross contamination of contaminants into the hydraulic fluid.

[00106] With reference continuing to Figure 4, it may be appreciated that hydraulic cylinder barrel 187b may also be divided into three zones - like hydraulic cylinder barrel 187a, namely: (i) a zone ZH dedicated exclusively to holding hydraulic fluid; (ii) a zone ZB dedicated exclusively for the buffer area and (iii) a overlap zone that which, depending upon where the device is in the stroke cycle, will vary between an area holding hydraulic fluid and an area providing part of the buffer chamber.

[00107] If the length XBb (which is the length of the cylinder barrel from gas cylinder head 192b to the inward facing surface of hydraulic cylinder 152b at its full right position) is greater than the stroke length Xs, then any point P1b on piston rod 194 will not move beyond the distance XBb when the gas piston 182 and the hydraulic cylinder 154b move from the farthermost right positions of the stroke (1) to the farthermost left positions of the stroke (2). Thus any materials/contaminants on piston rod 194 starting at P1b will be prevented or at least inhibited from moving beyond the area of the hydraulic cylinder barrel 187b that provides buffer chamber 195b. Thus, any such contaminants travelling on piston rod 194 will be prevented, or at least inhibited, from moving into the zones ZH and Zo of hydraulic cylinder barrel 187b that hold hydraulic fluid. Thus any point P2b on piston rod 194 that passes into the gas compression chamber will not pass into an area of the hydraulic cylinder barrel 187b that will encounter hydraulic fluid (ie. It will not pass into Zh or Zo). Thus, all portions of piston rod 194 that encounter gas, will not be exposed to an area that is directly exposed to hydraulic fluid. Thus cross contamination of contaminants that may be present with the natural gas in the gas compression cylinder 180 may be prevented or inhibited from migrating into the hydraulic fluid that is in that areas of hydraulic cylinder barrel 187b adapted for holding hydraulic fluid.
Thus, any such contaminants travelling on piston rod 194 will be prevented or a least inhibited from moving into the area of hydraulic cylinder barrel 187b that in operation, holds hydraulic fluid. Thus cross contamination of contaminants that may be present with the natural gas in the gas compression cylinder 180 may be prevented or at least inhibited from migrating into the hydraulic fluid that is in that area of hydraulic cylinder barrel 187b that is used to hold hydraulic fluid.

[00108] In some embodiments, during operation of hydraulic gas compressor 150, buffer chambers 195a, 195b may each be separately open to ambient air, such that air within buffer chamber may be exchanged with the external environment (eg.

air at ambient pressure and temperature). However, it may not desirable for the air in buffer chambers 195a, 195b to be discharged into the environment and possibly other components to be discharged directly into the environment, due to the potential for other components that are not environmentally friendly also being present with the air. Thus a closed system may be highly undesirable such that for example buffer chambers 195a, 195b may be in communication with each such that a substantially constant amount of gas (eg. such as air) can be shuttled back and forth through communication lines ¨ such as communication lines 215a, 215b in FIG. 7.

[00109] Buffer chambers 195a and/or 195b may in some embodiments be adapted to function as a purge region. For example, buffer chambers 195a, 195b may be fluidly interconnected to each other, and may also in some embodiments, be in fluid communication with a common pressurized gas regulator system 214 (Figure 7), through gas lines 215a, 215b respectively. Pressurized gas regulator system 214 may for example maintain a gas at a desired gas pressure within buffer chambers 195a, 195b that is always above the pressure of the compressed natural gas and/or other gases that are communicated into and compressed in gas compression cylinder chamber sections 181a, 181b respectively. For example, pressurized gas regulator system 214 may provide a buffer gas such as purified natural gas, air, or purified nitrogen gas, or another inert gas, within buffer chambers 195a, 195b. This may then prevent or substantially restrict natural gas and any contaminants contained in gas compression cylinder sections 181a, 181b migrating into buffer chambers 195a, 195b. The high pressure buffer gas in buffer chambers 195a, 195b may prevent movement of natural gas and possibly contaminants into the buffer chambers 195a, 195b. Furthermore if the buffer gas is inert, any gas that seeps into the gas compression cylinder chamber sections 181a, 181b will not react with the natural gas and/or contaminants. This can be particularly beneficial if for example the contaminants include hydrogen sulphide gas which may be present in one or both of gas compression cylinder chamber sections 181a, 181b.

[00110] In some embodiments, gas lines 215a, 215b (FIG. 7) may not be in fluid communication with a pressurized gas regulator system 214 ¨ but instead may be interconnected directly with each other to provide a substantially unobstructed communication channel for whatever gas is in buffer chambers 195a, 195b. Thus during operation of gas compressor 150, as hydraulic pistons 154a, 154b move right and then left (and/or upwards downwards) in unison, as one buffer chamber (eg.

buffer chamber 195a) increases in size, the other buffer chamber (eg. buffer chamber 195b) will decrease in size. So instead of gas in in each buffer chamber 195a, 195b being alternately compressed and then de-compressed, a fixed total volume of gas at a substantially constant pressure may permit gas thereof to shuttle between the buffer chambers 195a, 195b in a buffer chamber circuit.

[00111] Also, instead of being directly connected with each other, buffer chambers 195a, 195b may be both in communication with a common holding tank 1214 (FIG. 7) that may provide a source of gas that may be communicated between buffer chambers 195a, 195b. The gas in the buffer chamber gas circuit may be at ambient pressure in some embodiments and pressurized in other embodiments.
The holding tank 1214 may in some embodiments also serve as a separation tank whereby any liquids being transferred with the gas in the buffer chamber system can be drained off.

[00112] In the embodiment of FIGS. 2, and 9A-9C, a drainage port 207a for buffer chamber 195a may be provided on an underside surface of hydraulic cylinder barrel 187a. A corresponding drainage port 207b may be provided for buffer chamber 195b. Drainage ports 207a, 207b may allow drainage of any liquids that may have accumulated in each of buffer chambers 195a, 195b respectively.
Alternately or additionally such liquids may be able to be drained from an outlet in a holding tank 1214.

[00113] As illustrated in FIGS. 5 and 6, gas compressor system 126 may include a cabinet enclosure 1290 for holding components of hydraulic fluid supply system 1160 including pump unit 1174, prime mover 1175, reservoir 1172, shuttle device 1168, filters 1182 and 1171, thermal valve device 1142 and cooler 1143.

Controller 200 may also be held in cabinet enclosure 1290. One or more electrical cables 1291 may be provided to provide power and communication pathways with the components of gas compressor system 126 that are mounted on a support frame 1292. Additionally, piping 124 (FIG. 1) carrying natural gas to compressor 150 may be connected to connector 250 when gas compressor 150 is mounted on support frame 1292 to provide a supply of natural gas to gas compressor 150.

[00114] Gas compressor system 126 may thus also include a support frame 1292. Support frame 1292 may be generally configured to support gas compressor 150 in a generally horizontal orientation. Support frame 1292 may include a longitudinally extending hollow tubular beam member 1295 which may be made from any suitable material such as steel or aluminium. Beam member 1295 may be supported proximate each longitudinal end by pairs of support legs 1293a, 1293b which may be attached to beam member 1295 such as by welding. Pairs of support legs 1293a, 1293b may be transversely braced by transversely braced support members 1294a, 1294b respectively that are attached thereto such as by welding.
Support legs 1293a, 1293b and brace members 1294a, 1294b may be made also be made from any suitable material such as steel or aluminium.

[00115] Mounted to an upper surface of beam member 1295 may be L-shaped, transversely oriented support brackets 1298a, 1298b that may be appropriately longitudinally spaced from each other (see also FIGS. 8 to 9C). Support brackets 1298a, 1298b may be secured to beam member 1295 by U-members 1299a, 1299b respectively that are secured around the outer surface of beam member 1295 and then secured to support brackets 1298a, 1298b by passing threaded ends through openings 1300a, 1300b and securing the ends with pairs of nuts 1303a, 1303b (FIG.
6). Support bracket 1298a may be secured to gas cylinder head plate 212a by bolts 1302 received through aligned openings in support bracket 1298a and gas cylinder head plate 212a, secured by nuts 1301. Similarly, support bracket 1298b may be secured to gas cylinder head plate 212b by bolts 1302 received through aligned openings in support bracket 1298b and gas cylinder head plate 212, secured by nuts 1301. In this way, gas compressor 150 may be securely mounted to and supported by support frame 1292.

[00116] Hydraulic fluid communication lines 1166a, 1166b extend from ports 184a, 184b respectively to opposite ends of support frame 1294 and may extend under a lower surface of beam member 1295 to a common central location where they may then extend together to enclosure cabinet 1290 housing shuttle valve device 1168.

[00117] Tubular beam member 1295 maybe hollow and may be configured to act as, or to hold a separate tank such as, holding tank 1214. Thus beam member 1285 may serve to act as a gas / liquid separation and holding tank and may serve to provide a gas reservoir for gas for buffer chamber system of buffer chambers 195a, 195b. Lines 215a, 215b may lead from ports of buffer chambers 195a, 195b into ports 1305a, 1305b into holding tank 1214 within tubular member 1295.

[00118] Holding tank 1214 within beam member 1295 may also have an externally accessible tank vent 1296 that allow for gas in holding tank 1214 to be vented out. Also, holding tank 1214 may have a manual drain device 1297 that is also externally accessible and may be manually operable by an operator to permit liquids that may accumulate in holding tank 1214 to be removed.

[00119] In operation of gas compressor system 126 including hydraulic gas compressor 150, the reciprocal movement of the hydraulic pistons 152a, 152b, can be driven by a hydraulic fluid supply system such as for example hydraulic fluid supply system 1160 as described above. The reciprocal movement of hydraulic pistons 154a, 154b will cause the size of the buffer chambers 195a, 195b to grow smaller and larger, with the change in size of the two buffer chambers 195a, 195b being for example 180 degrees out of phase with each other. Thus, as hydraulic piston 154b moves from position 1 to position 2 in FIG. 6 driven by hydraulic fluid forced into hydraulic fluid chamber 186b, some of the gas (eg. air) in buffer chamber 195b will be forced into gas line(s) 215a, 215b (FIG. 7) that interconnect chambers 195a, 195b, and flow through holding tank 1214 towards and into buffer chamber 195a. In the reverse direction, as hydraulic piston 154a moves from position 2 to position 1 in FIG. 4 driven by hydraulic fluid forced into hydraulic fluid chamber 186a, some of the gas (eg air) in buffer chamber 195a will be forced into gas lines 215a, 215b and flow through holding tank 1214 towards and into buffer chamber 195b.
In this way, the gas in the system of buffer chambers 195a, 195b can be part of a closed loop system, and gas may simply shuttle between the two buffer chambers 195a, 195b, (and optionally through holding tank 1214) thus preventing 1() contaminants that may move into buffer chambers 195a, 195b from gas cylinder sections 181a, 181b respectively, from contaminating the outside environment.
Additionally, such a closed loop system can prevent any contaminants in the outside environment from entering the buffer chambers 195a, 195b and thus potentially migrating into the hydraulic fluid chambers 186a, 186b respectively.

[00120] Gas compressor system 126 may also include a natural gas communication system to allow natural gas to be delivered from piping 124 (FIG. 1) to the two gas compression chamber sections 181a, 181b of gas compression cylinder 180 of gas compressor 150, and then communicate the compressed natural gas from the sections 181a, 181b to piping 130 for delivery to oil and gas flow line 133.

[00121] With reference to FIG. 2 in particular, the natural gas communication system may include a first input valve and connector device 250, a second input valve and connector device 260, a first output valve and connector device 261 and a second output valve and connector device 251. A gas input suction distribution line 204 fluidly interconnects input valve and connector device 250 with input valve and connector device 260. A gas output pressure distribution line 209 fluidly interconnects output valve and connector device 261with valve and connector device 251.

[00122] With reference also to FIGS. 8, 8A and 8B, input valve and connector device 250 may include a gas compression chamber section valve and connector, a gas pipe input connector, and a gas suction distribution line connector. In an embodiment as shown in FIGS. 2 and 3(i) to (iv) an excess pressure valve and bypass connector is also provided. In an alternate embodiment as shown in FIGS. 8 to 9C, there is no bypass connector. However, in this latter embodiment there is a lubrication connector 1255 to which is attached in series to an input port of a lubrication device 1256 comprising suitable fittings and valves. Lubrication device 1256 allows a lubricant such as a lubricating oil (like WD-40 oil) to be injected into the passageway where the natural gas passes though connector device 250. The WD40 can be used to dissolve hydrocarbon sludges and soots to keep seals functional.

[00123] An electronic gas pressure sensing / transducer device 1257 may also be provided which may for example be a model AST46HAP00300PGT1L000 made by American Sensor technologies. This sensor reads the casing gas pressure.

[00124] Gas pressure sensing device! transducer 1257 may be in electronic communication with controller 200 and may provide signals to controller 200 indicative of the pressure of the gas in the casing / gas distribution line 204. In response to such signal, controller 200 may modify the operation of system 100 and in particular the operation of hydraulic fluid supply system 1160. For example, if the pressure in gas suction distribution line 204 descends to a first threshold level (eg. 8 psi), controller 200 can control the operation of hydraulic fluid supply system 170 to slow down the reciprocating motion of gas compressor 150, which should allow the pressure of the gas that is being fed to connector device 250 and gas suction distribution line 204 to increase. If the pressure measured by sensing device reaches a second lower threshold ¨ such that it may be getting close to zero or negative pressure (eg. 3 psi) controller 200 may cause hydraulic fluid supply system 1160 to cease the operation of gas compressor 150.

[00125] Hydraulic fluid supply system 1160 may then be re-started by controller 200, if and when the pressure measured by gas pressure sensing device /
transducer 1257 again rises to an acceptable threshold level as detected by a signal received by controller 200.

[00126] The output port of gas pressure sensing device 1257 may be connected to an input connector of gas suction distribution line 204.

[00127] With reference to FIGS. 8A and 8B, output valve and connector device 251 may include a gas compression chamber section valve, gas pipe output connector 205 and a gas pressure distribution line connector 263. In an embodiment as shown in FIG. 2, an excess pressure valve and bypass connector is also provided. In an alternate embodiment as shown in FIGS. 8 to 9C, there is no bypass connector.

[00128] With reference to the embodiment of FIGS. 2 and 3(i) to 3(iv), a pressure relief valve 265 is provided limit the gas discharge pressure. In some embodiments, relief valve 265 may discharge pressurized gas to the environment.
However, in this illustrated embodiment, the relieved gas can be sent back through a bypass hose 266 to the suction side of the gas compressor 150 to limit environmental discharge. One end of a bypass hose 266 may be connected for communication of natural gas from a port of an excess gas pressure bypass valve 265 (FIG. 2). The opposite end of bypass port may be connected to an input port of connector 250. The output port from bypass valve 265 may provide one way fluid communication through bypass hose 266 of excessively pressured gas in for example gas output distribution line 209, to connector 250 and back to the gas input side of gas compressor 150. Thus, once the pressure is reduced the pressure to a level that is suitable for transmission in piping 120 (FIG. 2A) gas pressure relief valve will close.

[00129] With reference to FIGS. 8 and 8B, installed within connector 250 is a one way check valve device 1250. When connector 250 is received in an opening 1270 on the inward seal side of casing 201a, gas may flow through connector and its check valve device 1250, through casing 201a into gas compression chamber section 181a. Similarly within connector 251 is a one way check valve device 1251. When connector 262 is received in an opening 1271 on the inward seal side of casing 201b, gas may flow out of gas compression chamber section 181a through casing 201a, and then through one-way valve device 1251 of connector 251 where gas can then flow through output connector 205 (FIG. 2) into piping 130 (FIG. 1).

[00130] The check valve device 1250 associated with connector 250 is operable to allow gas to flow into casing 201a and gas compression chamber section 181a, if the gas pressure at connector 250 is higher than the gas pressure on the inward side of the check valve device 1250. This will occur for example when gas compression chamber section 181a is undergoing expansion in size as gas piston 182 moves away from head assembly 200a resulting in a drop in pressure within compression chamber section 181a. Check valve device 1251 is operable to allow gas to flow out of casing 201a and gas compression chamber section 181a, if the gas pressure in gas compression chamber section 181a and casing 201a is higher than the gas pressure on the outward side of check valve device 1251 of connector 251, and when the gas pressure reaches a certain minimum threshold pressure that allows it to open. The check valve device 1251 may be operable to be adjusted to set the threshold opening pressure difference that causes/allows the one way valve to open. The increase in pressure gas compression chamber section 181a and casing 201a will occur for example when gas compression chamber section 181a is undergoing reduction in size as gas piston 182 moves towards from head assembly 200a resulting in an increase in pressure within compression chamber section 181a.

[00131] With reference to FIG. 8, at the opposite end of gas suction distribution line 204 to the end connected to gas pressure sensing device 1257, is a second input connector 260. Installed within connector 260 is a one way check valve device 1260. When connector 260 is received in an opening on the inward seal side of casing 201b, gas may flow from gas distribution line 204 through connector 260 and valve device 1260, through casing 201b into gas compression chamber section 181b.

[00132] Similarly at the opposite end of gas pressure distribution line 209 to the end connected to connector 210, is an output connector 261. Installed within connector 261 is a one way check valve device 1261. When connector 261 is received in an opening on the inward seal side of casing 201 b, gas may flow out of gas compression chamber section 181b through casing 201b and then through valve device 1261 and connector 261 where pressurized gas can then flow through gas pressure distribution line 209 to output connector 205 and into piping 130 (FIG.
1).

[00133] One way check valve device 1260 is operable to allow gas to flow into casing 201b and gas compression chamber section 181b, if the gas pressure at connector 260 is higher than the gas pressure on the inward side of check valve device 1260. This will occur for example when gas compression chamber section 181b is undergoing expansion in size as gas piston 182 moves away from head assembly 200b resulting in a drop in pressure within compression chamber section 181 b. One way check valve device 1261 is operable to allow gas to flow out of casing 201b and gas compression chamber section 181b, if the gas pressure in gas compression chamber section 181b and casing 201b is higher than the gas pressure on the outward side of check valve device 1261 of connector 261, and when the gas pressure reaches a certain minimum threshold pressure that allows it to open. The check valve device 1261 may be operable to be adjusted to set the threshold opening pressure difference that causes/allows the one way valve to open.
The increase in pressure gas compression chamber section 181b and casing 201b will occur for example when gas compression chamber section 181b is undergoing reduction in size as gas piston 182 moves towards from head assembly 200b resulting in an increase in pressure within compression chamber section 181b.

[00134] With particular reference to FIG. 8B, interposed between an output end of gas pressure distribution line 209 and valve and connector 251 may be a bypass valve 1265. If the gas pressure in gas pressure distribution line 209 and/or in connector 250, reaches or exceeds a pre-determined upper pressure threshold level, excess pressure valve 1265 will open to relieve the pressure and reduce the pressure to a level that is suitable for transmission into piping 130 (FIG.
1).

[00135] In operation of gas compressor 150, hydraulic pistons 154a, 154b may be driven in reciprocating longitudinal movement for example by hydraulic fluid supply system 1160 as described above, thus driving gas piston 182 as well.
The following describes the operation of the gas flow and gas compression in gas compressor system 126.

[00136] With hydraulic pistons 154a, 154b and gas piston 182 in the positions shown in FIG. 3(i) natural gas will be already located in gas cylinder compression section 181a, having been previously drawn into gas cylinder compression section 181a during the previous stroke due to pressure the differential that develops between the outer side of one way valve device 1250 and the inner side of valve device 1250 as piston 182 moved from left to right. During that previous stroke, natural gas will have been drawn from pipe 124 through connector 202 and connector device 250 and its check valve device 1250 into gas compression chamber section 181a, with check valve 1251 of connector device 251 being closed due to the pressure differential between the inner side of check valve device and the outer side of check valve device 1251 thus allowing gas compression cylinder section 181a to be filled with natural gas at a lower pressure than the gas on the outside of connector device 251.

[00137] Thus, with the pistons in the positions shown in FIG. 3(i), hydraulic cylinder chamber 186b is supplied with pressurized hydraulic fluid in a manner such as is described above, thus driving hydraulic piston 154b, along with piston rod 194, gas piston 182 and hydraulic piston 154a attached to piston rod 194, from the position shown in FIG. 3(i) to the position shown in FIG. 3(ii). As this is occurring, hydraulic fluid in hydraulic cylinder chamber 186a will be forced out of chamber 186a, and flow as described above.

[00138] As hydraulic piston 154b, along with piston rod 194, gas piston 182 and hydraulic piston 154a attached to piston rod 194, move from the position shown in FIG. 3(i) to the position shown in FIG. 3(11), natural gas will be drawn from supply line 124, through connector device 250 into gas suction distribution line 204, and then pass through input valve connector 260 and one way valve device 1260 and into gas compression section 181b. Natural gas will flow in such a manner because as gas piston 182 moves to the left as shown in FIGS. 3(i) to (ii), the pressure in gas compression chamber 181b will drop, which will create a suction that will cause the natural gas in pipe 124 to flow.

[00139] Simultaneously, the movement of gas piston 182 to the left, will compress the natural gas that is already present in gas compression chamber section 181a. As the pressure rises in gas chamber section 181a, gas flowing into connector 250 from pipe 124 will not enter chamber section 181a. Additionally, gas being compressed in gas compression chamber section 181a will stay in gas compression chamber section 181a until the pressure therein reaches the threshold level of gas pressure that is provided by one way check valve device 1251. Gas being compressed in chamber section 181a can't flow out of chamber section 181a into connector 250 because of the orientation of check valve device 1250.

[00140] The foregoing movement and compression of natural gas and movement of hydraulic fluid will continue as the pistons continue to move from the positions shown in FIG. 3(11) to the position shown in FIG. 3(111). During that time, dependent upon the pressure in gas compression chamber section 181a, gas will be allowed to pass out of gas compression chamber section 181a through connector 251 and will pass into piping 130 once the pressure is high enough to activate one way valve device 1251.

[00141] Just before hydraulic piston 154b reaches the position shown in FIG.
3(iii), proximity sensor 157b will detect the presence of hydraulic piston 154b within hydraulic cylinder 152b at a longitudinal position that is a short distance before the end of the stroke within hydraulic cylinder 152b. Proximity sensor 157b will then send a signal to controller 200, in response to which controller 200 will change the operational configuration of hydraulic fluid supply system 1160, as described above.
This will result in hydraulic piston 154b not being driven any further to the left in hydraulic cylinder 152b than the position shown in FIG. 3(iii).

[00142] Once hydraulic piston 154b, along with piston rod 194, gas piston 182 and hydraulic piston 154a attached to piston rod 194, are in the position shown in FIG. 3(iii), natural gas will have been drawn through connector 260 and one way valve device 1260 again due to the pressure differential that is developed between gas compression chamber section 181b and gas suction distribution pipe 204, so that gas compression chamber section 181b is filled with natural gas. Much of the gas in gas compression chamber 181a that has been compressed by the movement of gas piston 182 from the position shown in FIG. 3(i) to the position shown in FIG.
3(iii), will, once compressed sufficiently to exceed the threshold level of valve device 1251, have exited gas compression chamber 181a and pass from gas pipeline output connector 205 into piping 130 (FIG. 1) for delivery to oil and gas pipeline 133.
If the gas pressure is too high to be received in piping 130, excess valve and bypass connector 265/1265 will be opened to allow excess gas to exit to reduce the pressure.

[00143] Next, gas compressor system 126, including hydraulic fluid supply system 1160 is reconfigured for the return drive stroke. As natural gas has been drawn into gas compression cylinder section 181b it is ready to be compressed by gas piston 182. With hydraulic pistons 154a, 154b and gas piston 182 in the positions shown in FIG. 3(iii), hydraulic cylinder chamber 186a is supplied with pressurized hydraulic fluid by hydraulic fluid supply system 1160 for example as described above. This movement drives hydraulic piston 154a, along with piston rod 194, gas piston 182 and hydraulic piston 154a attached to piston rod 194, from the position shown in FIG. 3(iii) to the position shown in FIG. 3(iv). As this is occurring, hydraulic fluid in hydraulic cylinder chamber 186b will be forced out of the hydraulic fluid chamber 186a and may be handled by hydraulic fluid supply system 1160 as described above.

[00144] As hydraulic piston 154a, along with piston rod 194, gas piston 182 and hydraulic piston 154b attached to piston rod 194, move from the position shown in FIG. 5(iii) to the position shown in FIG. 3(iv), natural gas will be drawn from supply line 124, through connector 253 of valve and connector device 250 into gas compression section 181a due the drop in pressure of gas in gas compression section 181a, relative to the gas pressure in supply line 124 and the outside of connector 250. Simultaneously, the movement of gas piston 182 will compress the natural gas that is already present in gas compression section 181b. As the gas in gas compression chamber 181b is being compressed by the movement of gas piston 182, once the gas pressure reaches the threshold level of valve device to be activated, gas will be able to exit gas compression chamber 181b and pass through connector 261, into gas pressure distribution line 209 and then pass through output connector 205 into piping 130 (FIG. 3) for delivery to oil and gas pipeline 133.
Again, if the gas pressure is too high to be received in piping 130, excess valve and bypass connector 265/1265 will be opened to allow excess gas to exit to reduce the gas pressure in gas pressure distribution line 209 and piping 130.

[00145] The foregoing movement and compression of natural gas and hydraulic fluid will continue as the pistons continue to move from the positions shown in FIG. 3(iv) to return to the position shown in FIG. 3(i). Just before piston 154a reaches the position shown in FIG. 3(i), proximity sensor 157a will detect the presence of hydraulic piston 154a within hydraulic cylinder 152a at a longitudinal position that is shortly before the end of the stroke within hydraulic cylinder 152a.
Proximity sensor 157a will then send a signal to controller 200, in response to which controller 200 will reconfigure the operational mode of hydraulic fluid supply system 1160 as described above. This will result in hydraulic piston 154a not be driven any further to the right than the position shown in FIG. 3(i).

[00146] Once hydraulic piston 154a, along with piston rod 194, gas piston 182 and hydraulic piston 154b attached to piston rod 194, are in the position shown in FIG. 3(i), natural gas will have been drawn through valve and connector 253 so that gas compression chamber section 181a is once again filled and controller 200 will send a signal to the hydraulic fluid supply system 1160 so that gas compressor system 126 is ready to commence another cycle of operation.

[00147] During the operation of the gas compressor 150 as described above, any contaminants that may be carried with the natural gas from supply pipe 124 will enter into gas compression chamber sections 181a, 181b. However, the components of seal devices 198a, 198b associated with casings 201a, 201b, as described above, will provide a barrier preventing, or at least significantly limiting, the migration of any contaminants out of gas compression chamber sections 181a, 181b. However, any contaminants that do pass seal devices 198a, 198b are likely to be held in respective buffer chambers 195a, 195b and in combination with seal devices 196a, 196b of hydraulic pistons 154a, 154b respectively, may prevent contaminants from entering into the respective hydraulic cylinder chambers 186a, 186b Particularly if buffer chambers 195a, 195b are pressurized, such as with pressurized air or a pressurized inert gas, then this should greatly restrict or inhibit the movement of contaminants in the natural gas in gas compression chamber sections 181a, 181b from migrating into buffer chambers 195a, 195b, thus further protecting the hydraulic fluid in hydraulic cylinder chambers 186a, 186b.

[00148] It should be noted that in use, hydraulic gas compressor 150 may be oriented generally horizontally, generally vertically, or at an angle to both vertical and horizontal directions.

[00149] While the gas compressor system 126 that is illustrated in FIGS. 1 to 9C discloses a single buffer chamber 195a, 195b on each side of the gas compressor 150 between the gas compression cylinder 180 and the hydraulic fluid chambers 186a, 186b, in other embodiments more than one buffer chamber may be configured on one or both sides of gas compression cylinder 180. Also, the buffer cavities may be pressurized with an inert gas to a pressure that is always greater than the pressure of the gas in the gas compression chambers so that if there is any gas leakage through the gas piston rod seals, that leakage is directed from the buffer chamber(s) toward the gas compression chamber(s) and not in the opposite direction. This may ensure that no dangerous gases such as H2S are leaked from the gas compressor system.

[00150] Various other variations to the foregoing are possible. By way of example only - instead of having two opposed hydraulic cylinders each being single acting but in opposite directions to provide a combined double acting hydraulic cylinder powered gas compressor:
- a single but double acting hydraulic cylinder with two adjacent hydraulic fluid chambers may be provided with a single buffer chamber located between the innermost hydraulic fluid chamber and the gas compression cylinder;
- a single, one way acting hydraulic cylinder with one hydraulic fluid chamber may be provided with a single buffer chamber located between the hydraulic fluid chamber and the gas compression cylinder, in which gas in only compressed in one gas compression chamber when the hydraulic piston of the hydraulic cylinder is moving on a drive stroke.

[00151] In various other variations a buffer chamber may be provided adjacent to a gas compression chamber but a driving fluid chamber may be not immediately adjacent to the buffer chamber; one or more other chambers may be interposed between the driving fluid chamber and the buffer chamber ¨ but the buffer chamber still functions to inhibit movement of contaminants out of the gas compression chamber and in some embodiments may also protect a driving fluid chamber.

[00152] In other embodiments, more than one separate buffer chamber may be located in series to inhibit gas and contaminants migrating from the gas compression chamber.

[00153] One or more buffer chambers may also be used to ensure that a common piston rod through a gas compression chamber and hydraulic fluid chamber, which may contain adhered contamination from the gas compressor, is not transported into any hydraulic fluid chamber where the hydraulic oil may clean the rod. Accumulation of contamination over time into the hydraulic system is detrimental and thus employment of one or more buffer chambers may assist in reducing or substantially eliminating such accumulation.

[00154] When introducing elements of the present invention or the embodiments thereof, the articles "a," "an," "the," and "said" are intended to mean that there are one or more of the elements. The terms "comprising,"
"including," and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements.

[00155] Of course, the above described embodiments are intended to be illustrative only and in no way limiting. The described embodiments of carrying out the invention are susceptible to many modifications of form, arrangement of parts, details, and order of operation. The invention, therefore, is intended to encompass all such modifications within its scope.

Claims (101)

CLAIMS:

1. A gas compressor system comprising:
- a driving fluid cylinder having a driving fluid chamber adapted for containing a driving fluid therein, and a driving fluid piston movable within said driving fluid chamber;
- a gas compression cylinder having a gas compression chamber adapted for holding a gas therein and a gas piston movable within said gas compression chamber;
- a buffer chamber located between said driving fluid chamber and said gas compression chamber;
said buffer chamber adapted to inhibit movement of at least one non-driving fluid component, when gas is located within said gas compression chamber, from said gas compression chamber into said driving fluid chamber.

2. A gas compressor systems as claimed in claim 1 wherein said buffer chamber is adapted such that during operation when said when gas is compressed in said gas compression chamber, said buffer chamber is operable to inhibit movement of at least one non-driving fluid component, when gas is located within said gas compression chamber, from said gas compression chamber into said driving fluid chamber.

3. A gas compressor system as claimed in claims 1 or 2 further comprising a piston rod that is fixedly connected to said driving fluid piston and said gas piston, such that in operation when said driving fluid flows into said driving fluid chamber said driving fluid piston drives said driving fluid piston such that said driving piston and said gas piston move together within said respective driving fluid chamber and said gas compression chamber.

4. A gas compressor as claimed in claim 3 wherein a volume of said driving fluid chamber and a volume of said buffer chamber overlap within said driving fluid cylinder.

5. A gas compressor as claimed in claims 3 or 4 wherein said piston rod extends from said driving fluid piston through said buffer chamber into said gas compression chamber to said gas piston.

6. A gas compressor as claimed in any one of claims 1 to 5 wherein during operation, said buffer chamber varies in length dependent upon the position of said driving fluid piston in said driving fluid cylinder.

7. A gas compressor as claimed in claim 5 wherein during operation, said buffer chamber varies in length dependent upon the position of said driving fluid piston in said driving fluid cylinder and the minimum length of said buffer chamber is greater than the stroke length of said gas piston, said piston rod and said hydraulic fluid piston.

8. A gas compressor as claimed in claim 5 wherein said buffer chamber is configured such that in operation, no portion of said piston rod that is received within said gas compression chamber will be received in a portion of said hydraulic cylinder that receives hydraulic fluid.

9. A gas compressor system as claimed in any one of claims 1 to 8 wherein said at least one non-driving fluid component comprises natural gas.

10. A gas compressor system as claimed in any one of claims 1 to 8 wherein said at least one non-driving fluid component comprises a contaminant.

11. A gas compressor system as claimed in any one of claims 1 to 10, wherein said at least one non-driving fluid component comprises hydrogen sulphide.

12. A gas compressor system as claimed in any one of claims 1 to 11 wherein said driving fluid is a hydraulic fluid.

13. A gas compressor system as claimed in any one of claims 1 to 12 wherein said buffer chamber is located immediately adjacent to said gas compression chamber.

14. A gas compressor system as claimed in claim 13 wherein said buffer chamber is located immediately adjacent to said driving fluid chamber.

15. A gas compressor system as claimed in any one of claims 1 to 14 wherein said driving fluid chamber and said buffer chamber are both located within said driving fluid cylinder.

16. A gas compressor system as claimed in any one of claims 1 to 15 wherein said buffer chamber is located on an opposite side of said driving fluid piston to said driving fluid chamber.

17. A gas compressor as claimed in any one of claims 1 to 16 wherein a volume of said driving fluid chamber and a volume of said buffer chamber overlap within said driving fluid cylinder.

18. A gas compressor system as claimed in any one of claims 1 to 17 further comprising a casing assembly located between said buffer chamber and said gas compression chamber.

19. A gas compressor system as claimed in claim 18 further comprising a seal device located at least partially within said casing, said seal device operable to inhibit gas from migrating from said gas compression chamber into said buffer chamber.

20. A gas compressor system as claimed in claim 18 further comprising a seal device located at least partially within said casing, said seal device operable to inhibit a non-gas component in said gas compression chamber from migrating from said gas compression chamber into said buffer chamber.

21. A gas compressor system as claimed in claim 19 wherein said seal device is also operable to inhibit a non-gas component from migrating from said gas compression chamber into said buffer chamber.

22. A gas compressor system as claimed in claim 18 further comprising a seal device located at least partially within a casing located between said gas compression chamber and said buffer chamber, said seal device operable to inhibit gas from migrating from said gas compression chamber into said buffer chamber;

and wherein said seal device comprises a plurality of sealing rings mounted in said casing and engaging with an outer surface of said piston rod and an inner surface of said casing to provide a gas seal between said casing and said piston rod.

23. A gas compressor system as claimed in any one of claims 1 to 22 further comprising:
- a controller;
- a proximity sensor associated with said driving fluid cylinder, said proximity sensor operable to detect a position of said driving fluid piston within said driving fluid cylinder and send a signal to said controller;

- said controller operable in response to receiving said signal received from said proximity sensor, to control the flow of driving fluid into and out of said driving fluid chamber.

24. A gas compressor system as claimed in claim 23 wherein said proximity sensor is operable to detect a position of said piston rod within said driving fluid chamber at a position proximate an end point of a drive stroke of said driving fluid piston.

25. A gas compressor system as claimed in any one of claims 1 to 24 wherein in operation, said buffer chamber is filled with an inert gas maintained at a pressure that exceeds the pressure at any time within the gas compression chamber.

26. A gas compressor system as claimed in claim 25 wherein said inert gas comprises nitrogen.

27. A gas compressor as claimed in claims 25 or 26 further comprising a gas pressure regulator system in communication with said buffer chamber, said gas pressure regulator system operable to maintain the inert gas in said buffer chamber at a pressure that exceeds the pressure within the gas compression chamber during compression of the gas in the gas compression chamber.

28. A gas compressor system as claimed in any one of claims 1 to 24 wherein said buffer chamber is filled with air.

29. A gas compressor system as claimed in claim 28 wherein said air in said buffer chamber is in communication with a holding tank.

30. A gas compressor system as claimed in any one of claims 1 to 29 wherein said gas compression cylinder and said driving fluid cylinder are mounted on a support frame.

31. A gas compressor system as claimed in claim 30 wherein said gas compression cylinder, said driving fluid cylinder and said holding tank are mounted on a support frame.

32. A gas compressor system as claimed in claim 31 wherein said holding tank is integrated within said support frame.

33. A gas compressor system as claimed in any one of claims 1 to 32, said system further comprising a driving fluid supply system operable to supply driving fluid to said driving fluid chamber to drive said driving fluid piston.

34. A gas compressor system as claimed in claim 33 wherein said driving fluid supply system comprises a pump unit and at least one fluid communication line operable for supplying pressurized driving fluid to said driving fluid chamber.

35. A gas compressor system as claimed in claims 33 or 34 wherein said driving fluid supply system is a closed loop system.

36. A gas compressor system as claimed in any one of claims 33 to 35 further comprising a controller for controlling said driving fluid supply system for controlling the flow of driving fluid to said driving fluid chamber.

37. A gas compressor system as claimed in claim 36 further comprising:
- a proximity sensor associated with said driving fluid cylinder, said proximity sensor operable to detect a position of said driving fluid piston within said driving fluid cylinder and send a signal to said controller;

- said controller operable in response to receiving said signal received from said proximity sensor, and send a signal to said driving fluid supply system to control the flow of driving fluid into and out of said driving fluid chamber.

38. A gas compressor system as claimed in any one of claims 1 to 37 further comprising a gas communication system operable to supply gas to said gas compression chamber and operable to remove gas compressed by said gas piston in gas compression chamber, from said gas compression chamber.

39. A gas compressor as claimed in any one of claims 1 to 38 wherein:
- said driving fluid chamber is a first driving fluid cylinder having a first driving fluid chamber and a first driving fluid piston movable within said first driving chamber;
- said buffer chamber is a first buffer chamber located between a first driving fluid chamber and a first section of said gas compression chamber, - said gas compressor further comprises:
- a second driving fluid cylinder having a second driving fluid chamber operable in use for containing a driving fluid and a second driving fluid piston movable within said second driving fluid chamber, and wherein said second driving fluid cylinder is located on an opposite side of said gas compression cylinder as said first driving fluid cylinder;
- a second buffer chamber located between said second driving fluid chamber and a second section of said gas compression chamber, said second section of said gas compression chamber being on an opposite side of said gas piston to said first section of said gas compression chamber in said gas compression cylinder, - said first buffer chamber is adapted to inhibit movement of a gas located within said first gas compression chamber section into said first driving fluid chamber;
and - said second buffer chamber is adapted to inhibit movement of a gas located within said second gas compression chamber section, from said second gas compression chamber section into said second driving fluid chamber.

40. A gas compressor system as claimed in claim 39 further comprising a driving fluid supply system operable to supply driving fluid to said first driving fluid chamber to drive said first driving fluid piston and operable to supply driving fluid to said second driving fluid chamber to drive said second driving fluid piston.

41. A gas compressor system as claimed in claim 40 wherein said driving fluid supply system comprises a pump unit and at least one fluid communication line operable for supplying pressurized driving fluid to said driving fluid chambers.

42. A gas compressor system as claimed in claims 40 or 41 wherein said driving fluid supply system is a closed loop system.

43. A gas compressor system as claimed in any one of claims 40 to 42 further comprising a controller for controlling said driving fluid supply system for controlling the flow of driving fluid to said first and second driving fluid chambers.

44. A gas compressor system as claimed in any one of claims 39 to 43 wherein said piston rod that is fixedly connected to said first driving fluid piston, said gas piston and said second driving fluid piston, such that in operation when said driving fluid flows into said first driving fluid chamber said first driving fluid piston drives said first driving fluid piston such that said first driving fluid piston, said second driving fluid piston and said gas piston move together within said respective first driving fluid chamber, said second driving fluid chamber and said gas compression chamber, and such that in operation when said driving fluid flows into said second driving fluid chamber, said second driving fluid piston drives said second driving fluid piston such that said first driving fluid piston, said second driving fluid piston and said gas piston move together in an opposite direction within said respective first driving fluid chamber, said second driving fluid chamber and said gas compression chamber.

45. A gas compressor as claimed in claim 44 wherein a volume of said first driving fluid chamber and a volume of said first buffer chamber overlaps within said first driving fluid cylinder and a volume of said second driving fluid chamber and a volume of said second buffer chamber overlap within said second driving fluid cylinder.

46. A gas compressor as claimed in claims 44 or 45 wherein said piston rod extends from said first driving fluid piston through said first buffer chamber into said gas compression chamber to said gas piston and extends further through said second buffer chamber to said second driving fluid piston.

47. A gas compressor as claimed in any one of claims 39 to 46 wherein during operation, said first buffer chamber varies in length dependent upon the position of said first driving fluid piston in said first driving fluid cylinder and said second buffer chamber varies in length dependent upon the position of said second driving fluid piston in said second driving fluid cylinder.

48. A gas compressor as claimed in claim 47 wherein during operation, said first buffer chamber varies in length dependent upon the position of said first driving fluid piston in said first driving fluid cylinder and the minimum length of said first buffer chamber is greater than the stroke length of said gas piston, said piston rod and said first and second hydraulic fluid pistons.

49. A gas compressor as claimed in claim 48 wherein during operation, said second buffer chamber varies in length dependent upon the position of said second driving fluid piston in said second driving fluid cylinder and the minimum length of said second buffer chamber is greater than the stroke length of said gas piston, said piston rod and said first and second hydraulic fluid pistons.

50. A gas compressor as claimed in any one of claims 44 to 49 wherein said first buffer chamber is configured such that in operation, no portion of said piston rod that is received within said gas compression chamber will be received in a portion of said first hydraulic cylinder that receives hydraulic fluid and wherein said second buffer chamber is configured such that in operation, no portion of said piston rod that is received within said gas compression chamber will be received in a portion of said second hydraulic cylinder that receives hydraulic fluid.

51. A gas compressor as claimed in any one of claims 39 to 50 wherein said first driving fluid piston is operable to drive said gas piston in an opposite direction to said second driving fluid piston.

52. A gas compressor system comprising:
- a first driving fluid cylinder having a first driving fluid chamber adapted for containing a first driving fluid therein, and a first driving fluid piston movable within said first driving fluid chamber;
- a gas compression chamber adapted for holding a gas therein and a gas piston movable within said gas compression chamber;
- a first buffer chamber located between said first driving fluid chamber and a first section of said gas compression chamber;
- a second driving fluid cylinder having a second driving fluid chamber adapted for containing a second driving fluid therein, and a second driving fluid piston movable within said second driving fluid chamber;
- a second buffer chamber located between said first driving fluid chamber and a second section of said gas compression chamber;
- wherein said first buffer chamber is adapted to inhibit movement of at least one non-driving fluid component, when gas is located within a first section of said gas compression chamber, from said first section gas compression chamber section into said first driving fluid chamber;

- wherein said second buffer chamber adapted to inhibit movement of at least one non-driving fluid component, when gas is located within a second section of said gas compression chamber, from said second section of said gas compression chamber into said second driving fluid chamber.

53. A gas compressor systems as claimed in claim 52 wherein said first buffer chamber is adapted such that during operation when gas is compressed in said first gas compression chamber section, said first buffer chamber is operable to inhibit movement of at least one non-driving fluid component, when gas is located within said first gas compression chamber section, from said first gas compression chamber into said first driving fluid chamber; and wherein said second buffer chamber is adapted such that during operation when gas is compressed in said second gas compression chamber section, said second buffer chamber is operable to inhibit movement of at least one non-driving fluid component, when gas is located within said second gas compression chamber section, from said second gas compression chamber section into said second driving fluid chamber.

54. A gas compressor system as claimed in claims 52 or 53 wherein said at least one non-driving fluid component in both of said first and second gas compression chamber sections comprises natural gas.

55. A gas compressor system as claimed in claims 52, 53 or 54 wherein said at least one non-driving fluid component in both of said first and second gas compression chamber sections comprises a contaminant.

56. A gas compressor system as claimed in any one of claims 52 to 55, wherein said at least one non-driving fluid component in both of said first and second gas compression chamber sections comprises hydrogen sulphide.

57. A gas compressor system as claimed in any one of claims 52 to 56 wherein said first buffer chamber is located adjacent to said first gas compression chamber section and said second buffer chamber is located adjacent to said second gas chamber section.

58. A gas compressor system as claimed in any one of claims 52 to 57 wherein said first driving fluid chamber and said first buffer chamber are both located within said first driving fluid cylinder.

59. A gas compressor system as claimed in claim 58 further comprising a first seal device operable to inhibit gas in said first gas compression chamber section from migrating from said first gas compression chamber section into said first buffer chamber.

60. A gas compressor system as claimed in claim 59 further comprising a second seal device operable to inhibit gas in said second gas compression chamber section from migrating from said second gas compression chamber section into said second buffer chamber.

61. A gas compressor system as claimed in claims 58, 59 or 60 wherein said second driving fluid chamber and said second buffer chamber are both located within said second driving fluid cylinder.

62. A gas compressor system as claimed in any one of claims 52 to 61 wherein said first buffer chamber is located on an opposite side of said first driving fluid piston to said first driving fluid chamber.

63. A gas compressor system as claimed in claim 62 wherein said second buffer chamber is located on an opposite side of said second driving fluid piston to said second driving fluid chamber.

64. A gas compressor system as claimed in any one of claims 52 to 63 wherein said gas compression chamber is formed in a gas compression cylinder located between said first driving fluid cylinder and said second driving fluid cylinder.

65. A gas compressor system as claimed in claim 64 wherein first driving fluid cylinder, said gas compression cylinder and said second driving fluid cylinder are interconnected to each other.

66. A gas compressor system as claimed in any one of claims 52 to 65 further comprising a piston rod that is fixedly connected to said first driving fluid piston, said gas piston, and said second driving fluid piston such that in operation, said driving fluid flowing into said first driving fluid chamber drives said first driving fluid piston in a first direction, and said driving fluid entering said second driving fluid chamber drives said second driving fluid piston in a second direction opposite to said first direction, and said first fluid driving piston, said gas piston and said second fluid driving piston are operable to move together within said respective first driving fluid cylinder, said gas compression cylinder and said second driving fluid cylinder, in reciprocating movement.

67. A gas compressor as claimed in claim 66 wherein a volume of said first driving fluid chamber and a volume of said first buffer chamber overlap within said first driving fluid cylinder and a volume of said second driving fluid chamber and a volume of said second buffer chamber overlap within said second driving fluid cylinder.

68. A gas compressor as claimed in claims 66 or 67 wherein said piston rod extends from said first driving fluid piston through said first buffer chamber into said gas compression chamber to said gas piston and extends further through said second buffer chamber to said second driving fluid piston.

69. A gas compressor as claimed in any one of claims 66 to 68 wherein during operation, said first buffer chamber varies in length dependent upon the position of said first driving fluid piston in said first driving fluid cylinder and said second buffer chamber varies in length dependent upon the position of said second driving fluid piston in said second driving fluid cylinder.

70. A gas compressor as claimed in claim 69 wherein during operation, said first buffer chamber varies in length dependent upon the position of said first driving fluid piston in said first driving fluid cylinder and the minimum length of said first buffer chamber is greater than the stroke length of said gas piston, said piston rod and said first and second hydraulic fluid pistons.

71. A gas compressor as claimed in claim 70 wherein during operation, said second buffer chamber varies in length dependent upon the position of said second driving fluid piston in said second driving fluid cylinder and the minimum length of said second buffer chamber is greater than the stroke length of said gas piston, said piston rod and said first and second hydraulic fluid pistons.

72. A gas compressor as claimed in any one of claims 66 to 71 wherein said first buffer chamber is configured such that in operation, no portion of said piston rod that is received within said gas compression chamber will be received in a portion of said first hydraulic cylinder that receives hydraulic fluid and wherein said second buffer chamber is configured such that in operation, no portion of said piston rod that is received within said gas compression chamber will be received in a portion of said second hydraulic cylinder that receives hydraulic fluid.

73. A gas compressor system as claimed in any one of claims 52 to 72, further comprising a first casing located between said first buffer chamber and said first gas compression chamber section and further comprising a second casing located between said second buffer chamber and said second gas compression chamber section.

74. A gas compressor system as claimed in claim 73 further comprising a first seal device located at least partially within said first casing, said first seal device operable to inhibit gas from migrating from said gas compression chamber into said first buffer chamber; and further comprising a second seal device located at least partially within said second casing, said second seal device operable to inhibit gas from migrating from said gas compression chamber into said second buffer chamber.

75. A gas compressor system as claimed in claim 74 further comprising a first seal device located at least partially within said first casing, said first seal device operable to inhibit a non-gas component in said first gas compression chamber section from migrating from said first gas compression chamber section into said first buffer chamber.

76. A gas compressor system as claimed in claim 75 further comprising a second seal device located at least partially within said second casing, said second seal device operable to inhibit a non-gas component in said second gas compression chamber section from migrating from said second gas compression chamber section into said second buffer chamber.

77. A gas compressor system as claimed in claim 76 wherein said first and second seal devices each further comprise a rod wiper operable to remove contaminants that may deposited onto said piston rod, from a portion of said piston rod as said portion of said piston rod moves from within respective said first and second gas compression chamber seconds into respective said first and second casings.

78. A gas compressor system as claimed in any one of claims 52 to 77 further comprising:
- a controller;
- a first proximity sensor associated with said first driving fluid cylinder, said first proximity sensor operable to detect a position of said first driving fluid piston within said first driving fluid cylinder and send a signal to said controller;
- a second proximity sensor associated with said second driving fluid cylinder, said first second proximity sensor operable to detect a position of said second driving fluid piston within said second driving fluid cylinder and send a signal to said controller;
- said controller operable in response to receiving said signal received from said first proximity sensor, to control the flow of driving fluid into and out of said first driving fluid chamber and operable in response to receiving said signal received from said seond proximity sensor, to control the flow of driving fluid into and out of said second driving fluid chamber.

79. A gas compressor system as claimed in claim 78 wherein said first proximity sensor is operable to detect a position of said first driving fluid piston within said first driving fluid chamber at a position proximate an end point of a drive stroke of said first driving fluid piston and said second proximity sensor is operable to detect a position of said second driving fluid piston within said second driving fluid chamber at a position proximate an end point of a drive stroke of said first driving fluid piston.

80. A gas compressor system as claimed in any one of claims 52 to 79 wherein in operation, said first and second buffer chamber each contain an inert gas maintained at a pressure that exceeds the pressure within the respective first and second gas compression chambers sections during compression of gas in said first and second gas compression chamber sections.

81. A gas compressor system as claimed in claim 80 wherein said inert gas comprises nitrogen.

82. A gas compressor as claimed in claims 80 or 81 further comprising a gas pressure regulator system in communication with said first and second buffer chambers, said gas pressure regulator system operable to maintain the inert gas in said first and second buffer chambers at pressures that exceeds the respective pressure within the first and second gas compression chamber sections during compression of gas in said first and second gas compression chamber sections.

83. A gas compressor system as claimed in any one of claims 52 to 82 wherein each of said first and second buffer chambers contains air.

84. A gas compressor as claimed in claim 83 wherein said air is pressurized to a pressure that exceeds the respective pressure within the first and second gas compression chamber sections during compression of gas in said first and second gas compression chamber sections.

85. A gas compressor system as claimed in claims 83 or 84 wherein said air in said buffer chamber is in communication with a holding tank.

86. A gas compressor system as claimed in claims 83, 84 or 85 wherein said holding tank and said first and second buffer chambers are in a closed system.

87. A gas compressor system as claimed in any one of claims 52 to 85 wherein said first and second buffer chambers are in a closed system.

88. A gas compressor system as claimed in any one of claims 52 to 87 wherein said gas compression cylinder and said first and second driving fluid cylinder are supported on a support frame with said gas compression cylinder positioned between said first and second driving fluid cylinders.

89. A gas compressor system as claimed in claim 85 wherein said holding tank, said gas compression cylinder and said first and second driving fluid cylinder are supported on a support frame with said gas compression cylinder positioned between said first and second driving fluid cylinders and wherein said gas compression cylinder, said driving fluid cylinder and said holding tank are mounted on a support frame.

90. A gas compressor system as claimed in claim 89 wherein said holding tank is integrated within said support frame.

91. A gas compressor system as claimed in any one of claims 52 to 90 further comprising a driving fluid supply system operable to supply driving fluid to said first driving fluid chamber to drive said first driving fluid piston and operable to supply driving fluid to said second driving fluid chamber to drive said second driving fluid piston.

92. A gas compressor system as claimed in claim 91 wherein said driving fluid supplied to said first fluid driving chamber and the driving fluid supplied to said second fluid driving chamber are part of driving fluid supply circuit.

93. A gas compressor system as claimed in claims 91 or 92 wherein said driving fluid supply system comprises a pump unit and at least two fluid communication lines, operable for supplying pressurized driving fluid to each of said first and second driving fluid chambers.

94. A gas compressor system as claimed in claims 91, 92 or 93 wherein said driving fluid supply system is a closed loop system.

95. A gas compressor system as claimed in any one of claims 91 to 94 further comprising a controller for controlling said driving fluid supply system for controlling the flow of driving fluid to and from said first and second driving fluid chambers.

96. A gas compressor system as claimed in claim 95 further comprising:
- a proximity sensor associated with said driving fluid cylinder, said proximity sensor operable to detect a position of said driving fluid piston within said driving fluid cylinder and send a signal to a controller;
- a controller operable in response to receiving said signal received from said proximity sensor, and send a signal to said driving fluid supply system to selectively control the flow of driving fluid into and out of said first and second driving fluid chamber to provide reciprocating movement of said first and second driving fluid pistons and said gas piston.

97. A gas compressor system as claimed in any one of claims 52 to 96 further comprising a gas supply system operable to supply gas to said gas compression chamber and operable to remove gas compressed by said gas piston in gas compression chamber, from said gas compression chamber.

98. An oil well producing system comprising:
- a production tubing having a length extending along a well shaft that extends to an oil bearing formation;
- a passageway extending along at least the well shaft , said passageway operable to supply natural gas to a gas supply line, said gas supply line in communication with a gas compression chamber of a gas compressor system, said gas compressor system comprising any of the gas compressor systems of claims 1 to 97.

99. A system as claimed in claim 98 further comprising a casing surrounding the production tubing and extending along at least part of the length of the production tubing and wherein the passageway extends between an outer surface of said production tubing and an inner surface of said casing.

100. A gas compressor comprising:
- a driving fluid cylinder having a driving fluid chamber operable for containing a driving fluid therein and a driving fluid piston movable within said driving fluid chamber;
- a gas compression cylinder having a gas compression chamber operable for holding a gas therein and a gas piston movable within said gas compression chamber;
- a buffer chamber located between said driving fluid chamber and said gas compression chamber, said buffer chamber configured and operable to inhibit movement of at least one non-driving fluid component from said gas compression chamber to substantially avoid contamination of said driving fluid, when gas is located within said gas compression chamber.

101. A gas compressor comprising:
- a driving fluid cylinder having a driving fluid chamber operable for containing a driving fluid therein and a driving fluid piston movable within said driving fluid chamber;
- a gas compression cylinder having a gas compression chamber operable for holding natural gas therein and a gas piston movable within said gas compression chamber;
- a buffer chamber located between said driving fluid chamber and said gas compression chamber, said buffer chamber containing a buffer gas component so as to substantially avoid contamination of said driving fluid in said driving fluid chamber, when natural gas is located within said gas compression chamber.