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BACKGROUND 
     The present disclosure is directed to an apparatus and method for extracting and communicating natural gas from gas wells, for example those operating under vacuum conditions, to a natural gas-fired piece of oil field equipment. 
     A pump jack (also known as a nodding donkey, pump unit, horsehead pump, beam pump, sucker rod pump, grasshopper pump, thirsty bird and jack pump) is often used to assist in the production of natural gas from low pressure wells by pumping liquid from the wellbore so that natural gas is able to flow from the well. Pump jacks are commonly driven by motors, or engines, which are commonly referred to as prime movers and may run on electricity, diesel, propane or natural gas. Due to their proximity to the well and the inherent difficulty in servicing many well sites, a large number of prime movers operate on natural gas supplied directly from the well. Unfortunately, natural gas-fired prime movers cease to operate when the pressure in a well, or gas supply line, develops a negative pressure or drops to such a low pressure level that it cannot supply natural gas to the prime mover. 
     As reservoir pressure drops, natural gas production from wells accessing the reservoir decreases. Liquid build up in natural gas wells also causes gas production to drop. When there is not a sufficient level of natural gas provided to a natural gas-fired prime mover due to low pressure in the well, the prime mover and pump jack cease to operate. This situation requires a manual restart of the prime mover, if possible, which may take days or weeks. The resulting fluid build up in the well frequently kills all production of natural gas from the well. 
     In a large field of natural gas wells, many wells are put under a vacuum to assist in the extraction of gas to be supplied to a gas supply line. When a well, or a field of wells, cease to produce gas without assistance, a compressor may be used to create a vacuum on the well to supply gas to a gas supply line. Whenever a vacuum is drawn on the well, there is usually an insufficient level of gas pressure available to provide fuel for the natural gas-fired prime mover. The vacuum on the well makes the use of a natural gas prime mover impractical or impossible without providing another fuel source. 
     The foregoing issues show there is a need for an apparatus to provide a consistent supply of natural gas to a prime mover for uninterrupted operations. 
     SUMMARY OF THE INVENTION 
     The current disclosure is directed to a device and method to supply natural gas to a prime mover which drives a pump jack. An adjustable bracket is also disclosed. The disclosure also provides for a method to install the adjustable bracket for connecting the device to the pump jack. 
     In a first aspect, the apparatus comprises a volume tank and a natural gas-fired prime mover. The volume tank receives natural gas from a natural gas well. The volume tank provides the natural gas to the prime mover which is used to drive a pump jack. 
     In another aspect, the apparatus comprises a pump, a volume tank and a natural gas-fired prime mover. The pump is used for extracting the natural gas from a natural gas well. The volume tank is adapted to receive the natural gas from the pump. The prime mover is positioned to receive and operate on natural gas communicated from the volume tank and is adapted to drive the pump jack. 
     In yet another aspect, the apparatus comprises a pump jack, a pump, a volume tank and a prime mover. The pump is used for extracting the natural gas from the natural gas well. The pump has a piston adapted to provide compression of the extracted natural gas. The piston is movably attached to the pump jack. The volume tank receives the natural gas communicated from the pump, and the volume tank communicates natural gas to the prime mover, which drives the pump jack. 
     In still another aspect, an adjustable bracket comprises an anchor channel, a clamping channel, a plurality of thread rods, and a set of securing devices. The adjustable bracket connects the pump to a beam. The anchor channel has a mounting flange with a plurality of holes disposed in an interior edge. The clamping channel has a securing block with a plurality of holes disposed therethrough. The plurality of holes disposed through the clamping channel are equal in number to the plurality of holes disposed in the mounting flange. The plurality of threaded rods are adapted to be disposed in the plurality of holes in the anchor channel, and adapted to be disposed through the plurality of holes in the securing block. The set of securing devices are for securing the anchor channel, clamping channel and plurality of threaded rods to each other. 
     In another aspect, a method to install an adjustable bracket for connecting a pump to a pump jack is disclosed and comprises the following steps:
         (a) placing the adjustable bracket on the walking beam of the pump jack;   (b) connecting a first end of the pump to the adjustable bracket;   (c) sliding the adjustable bracket along the walking beam until the pump is positioned to be able to complete a full stroke of a piston operably associated with the pump; and   (d) securing the adjustable bracket to the walking beam.       

     In another aspect, a method for operating a pump jack is disclosed and comprises the following steps: 
     (a) extracting natural gas from a well; 
     (b) communicating the natural gas to a tank; 
     (c) communicating the natural gas from the tank to a prime mover; and 
     (d) driving the pump jack with the prime mover. 
     The objects, features and advantages of the present invention will be readily apparent to those skilled in the art upon reading the description of the preferred embodiments which follow when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic of two pump jacks with pumps connected thereon and incorporated as part of a producing natural gas field. 
         FIG. 2  is a perspective view of a pump jack positioned on a well, with the pump jack being driven by a prime mover, and having the pump and volume tank installed thereon. 
         FIG. 3  is a bottom perspective view of an adjustable bracket installed on a pump jack. 
         FIG. 4  is a top perspective view of the adjustable bracket. 
         FIG. 5  is a bottom perspective view of the adjustable bracket. 
         FIG. 6  is an exploded perspective view of the adjustable bracket. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to the drawings and more particularly to  FIGS. 1 and 2 , the natural gas supply apparatus of the current disclosure is illustrated and generally designated by the numeral  10 . As shown by the drawings and understood by those skilled in the art, natural gas supply apparatus  10  and components thereof are particularly well adapted to extract natural gas from well  12 .  FIGS. 1 and 2  have been greatly simplified to eliminate much of the piping and wiring associated with natural gas supply apparatus  10 . The omitted items are known in the art, and are not necessary for an understanding of the invention. 
     Natural gas supply apparatus  10  is shown in  FIGS. 1 and 2  connected to pump jack  14 , which is driven by prime mover  16 . A representative example of pump jack  14  is depicted in  FIGS. 1 and 2 , and is used to describe the natural gas supply apparatus  10 . Other variations of pump jacks known to those skilled in the art will also work with natural gas supply apparatus  10 . 
       FIG. 2  shows pump jack  14  positioned so that the reciprocal pivoting motion of walking beam  18  moves polish rod  20  in and out of well  12 . Walking beam  18  is positioned on top of Samson post  22 . Typically, prime mover  16  provides input to turn crank  24  which is connected to counter weight  26 . Counter weight  26  is connected to walking beam  18  by pitman arm  28 . The reciprocal pivoting motion of walking beam  18  is driven by the input from prime mover  16 . 
     In one embodiment, natural gas supply apparatus  10  comprises pump  30  and volume tank  46 . Pump  30  is shown in  FIGS. 1 and 2  as being positioned between walking beam  18  and Samson post  22 . Pump  30  is a piston driven pump that creates a vacuum on well  12  to extract gas therefrom. Pump  30  shown in  FIG. 3  has one lug mount  32  positioned on piston  36 , and another lug mount  32  positioned on opposite end  37 . Lug mount  32  provides a mount point for pump  30  for attachment to pump jack  14 . Lug mount  32  is a representative example of the variety of mounting devices available for mounting pump  30 . 
     Continuing to refer to  FIG. 3 , adjustable bracket  34  is shown positioned on walking beam  18 , and sliding bracket  38  is shown positioned on Samson post  22 . Adjustable bracket  34  provides a mounting point for lug mount  32  on piston  36 , and sliding bracket  38  provides a mounting point for lug mount  32  on opposite end  37 . Both adjustable bracket  34  and sliding bracket  38  are adapted for moving during installation of pump  30 . Additionally, pump  30  may be easily inverted to have piston  36  attached to sliding bracket  38 . 
     Pump  30  has gas inlet  40  for receiving gas from well  12 , and gas outlet  42  for directing gas to volume tank  46 . As shown in  FIGS. 2 and 3 , gas input line  44  provides a fluid connection and communication between gas inlet  40  and well  12 , while gas outlet line  48  provides fluid connection and communication between gas outlet  42  and volume tank  46 . 
     Pump  30  may be any pump capable of creating a lower pressure on well  12  such that natural gas is extracted and communicated to pump  30 . A preferred double acting pump is shown in  FIGS. 2 and 3 . Both gas inlet  40  and gas outlet  42  perform the inlet and outlet function when they are used with the preferred double acting pump air cylinder. As shown in  FIGS. 2 and 3 , gas inlet  40  and gas outlet  42  both apply suction on gas inlet feed  40   a , which connects to upper and lower quick exhaust valves  41   a  and  41   b . The preferred double acting pump also exhausts gas through gas inlet  40  and gas outlet  42 , thereby pressurizing gas into gas outlet feed  42   a  via a second set of upper and lower quick exhaust valves  41   c  and  41   d . Quick exhaust valves  41   a - d  are commercially available shuttle valves. Using a double acting pump allows pump  30  to apply suction and exhaust gas on both the up and down strokes of piston  36 . As shown in  FIGS. 2 and 3 , gas inlet feed  40   a  receives gas from gas input line  44  and gas outlet feed  42   a  provides gas to outlet line  48 . 
     An example of the preferred pump  30  presented in  FIGS. 2 and 3  may be an ENS.Series air cylinder having either a five (5) or six (6) inch bore. The ENS.Series air cylinder is available from www.aircylindersdirect.com. Additionally, the example quick exhaust valves  41   a - d  that may be used are Humphrey® QE3 or QE4 Super Quick Exhaust Valves. Other models of pump  30  by different manufacturers are also used, and may have larger or smaller bores. The Humphrey® Super Quick Exhaust Valves in the example are replaceable by other manufacturers&#39; check valves. 
     Volume tank  46  has tank gas input  50 , primary gas output  52 , and overflow gas output  54 . Tank gas input  50  is adapted to receive gas from gas output line  48 . Alternatively, volume tank  46  is adapted to receive natural gas directly from well  12 , or from gas supply line  58 . Primary gas output  52  is in fluid communication with prime mover  16 . Referring to  FIG. 2 , primary gas line  56  connects primary gas output  52  with prime mover  16 . Other gas-fired equipment may be attached to volume tank  46  as long as positive pressure is maintained in volume tank  46 . 
     Tank gas input  50  is preferably a one-way valve allowing gas to enter volume tank  46 . Primary gas output  52  is preferably a one-way valve allowing gas to exit volume tank  46 . Overflow gas output  54  is preferably a pressure relief valve set to release gas from volume tank  46  when the gas reaches a pre-determined pressure level as described below. Overflow gas output  54  is in fluid communication with a gas supply line  58 , which is ultimately communicated to a gas sales line. 
     In a normal operations cycle, it is common for prime mover  16  to start, warm-up and operate pump jack  14  for a period of time. This period of time may be intermittent, or it may be until there is no more gas to extract from well  12 . For intermittent operations, prime mover  16  drives pump jack  14  until the liquid level is lowered to a desired level, whereby prime mover  16  is turned off and/or on stand-by for the next operations cycle. Thus, volume tank  46  is sized to have enough gas in a sufficient volume such that prime mover  16  is able to at least start, and in some cases, warm-up and begin operating pump jack  14 , while always maintaining a positive pressure within volume tank  46 . Once pump jack  14  begins operating, pump  30  begins to replenish volume tank  46 , so that the supply of gas from volume tank  46  being communicated to to prime mover  16  is sufficient to continue operating pump jack  14  for the desired time, whether that time is a defined period or a continuous operation. The sizing of volume tank  46  and the pre-determined pressure level of overflow gas output  54  is dependent upon the particular prime mover utilized. The volume of gas in volume tank  46  is always maintained at a positive pressure. For a larger prime mover  16 , volume tank  46  will need to be larger, or contain a larger pressure volume of gas. 
     For a continuously operating prime mover  16 , prime mover  16  drives pump jack  14  until there is insufficient gas in well  12  to extract, or until prime mover  16  is manually stopped. Excess gas in volume tank  46  is removed through overflow gas output  54 . In the embodiment described, once prime mover  16  starts, it will begin operating pump jack  14 , which will operate pump  30  so that natural gas is extracted from well  12  and delivered to prime mover  16  through volume tank  46 . In some cases, the prime movers may employ a system (not shown) to engage/disengage a drive mechanism providing input to crank  24 . In this situation, volume tank  46  is sized to have sufficient gas to provide for the startup, warm-up and cyclical engagement/disengagement of the drive mechanism providing input to crank  24 : 
     A typical oil field worker can easily calculate what is a sufficient volume of gas in volume tank  46  by knowing the total volume of gas, the pressure of the gas at startup, the fuel gas requirements of prime mover  16 , and the time period required to produce a sufficient flow of gas from well  12  to replenish the gas being consumed by prime mover  16 . For intermittent operations of prime mover  16 , the fuel gas requirements of prime mover  16  include startup, warm-up in some systems, and the time to operate pump jack  14  until enough gas is communicated to volume tank  46  to replenish volume tank  46  so that any necessary startup, warm-up and operation can be repeated. The foregoing information provides sufficient information for the oil field worker to properly size volume tank  46  and to calculate the pre-determined pressure of overflow gas output  54 . 
     One element in determining the period of time required to replenish the natural gas in volume tank  46  requires knowing how much gas a prime mover  16  burns. Prime mover  16  burns a volume of natural gas, measured in cubic feet of natural gas per hour. For example, a small prime mover  16  may burn about 0.1 mcf of natural gas per hour, and a larger prime mover  16  may burn about 0.2 mcf of natural gas per hour. Thus, for repeated intermittent operations, volume tank  46  must have enough natural gas so that prime mover  16  is able to operate through startup, warm-up, and if necessary, operate for an additional period of time to replenish the volume of gas in volume tank  46 . An example of a desired period of time may be as little as about five (5) minutes, or as much as 30 minutes. If prime mover  16  is not a continuously operating prime mover  16 , prime mover  16  can be shutoff once volume tank  46  has a sufficient volume of gas to repeat the startup procedure. 
     By way of an example, natural gas supply apparatus  10  uses a 13 horsepower prime mover  16  and has a volume tank  46  with a starting volume of about 1.5 cubic feet of natural gas at a pressure level of about 40 pounds per square inch prior to startup. Preferably, prior to the first use of volume tank  46  with pump  30 , volume tank  46  is filled from another source of natural gas. The natural gas pressure is at least equal to or less than the pre-determined level of pressure that is set for overflow gas output  54 . Once prime mover  16  is started, natural gas in volume tank  46  rapidly burns, thus decreasing the volume and pressure within volume tank  46 . The input to pump jack  14  causes pump  30  to start pumping and extracting natural gas from well  12 . Pump  30  communicates natural gas to volume tank  46 , increasing the pressure to a level equal to pressure of overflow gas output  54 . 
     As discussed herein, pump  30  is attached to walking beam  18  with adjustable bracket  34 . Adjustable bracket  34  is adapted to allow movement of pump  30  during setup to maximize the stroke length of piston  36 . As shown in  FIG. 3 , adjustable bracket  34  is designed to be mounted on a beam with two parallel flanges, such as an I-beam or parallel flange  96  of walking beam  18 . 
     Adjustable bracket  34  includes anchor channel  60  and clamping bracket  62 . Anchor channel  60  comprises mounting flange  64 , anchor flange  66  and spacer block  68 . Mounting flange  64  and anchor flange  66  are separated by spacer block  68 . Mounting flange  64  has mounting side  70  and beam side  72 . Mounting side  70  has mounting fixture  74  affixed. As shown in  FIG. 3 , mounting fixture  74  is adapted to receive lug mount  32  on piston  36 . However, any mounting fixture used on pump  30  and piston  36  will have a compatible mounting fixture  74  on mounting side  70 . 
     Mounting flange  64  has interior edge  76  with a plurality of threaded holes  78  drilled and tapped therein. As shown in  FIGS. 4-6 , threaded rods  80  are disposed within threaded holes  78 . 
     Mounting flange  64  and anchor flange  66  have threaded adjusting pins  82  and  84  disposed therethrough. As seen in  FIGS. 5 and 6 , threaded adjusting pins  82  are disposed through mounting flange  64  from mounting side  70  to beam side  72 . Threaded adjusting pins  84  are disposed through anchor flange  66  from exterior side  86  to support side  88 . Threaded adjusting pins  82  and  84  are adapted to provide leveling for anchor channel  60 . Adjusting pins  82  and  84  are preferably adjustable set screws. 
     Clamping bracket  62  includes support flange  90  and securing block  92 . Support flange  90  is adapted to support clamping bracket  62  on one of the parallel flanges  96  of beam  18 , as shown in  FIG. 3 . Securing block  92  has holes  94  disposed therethrough. Holes  94  are compatible with threaded holes  78 , and are adapted to receive threaded rods  80  therethrough. Securing devices  98  are used to secure clamping bracket  62 , anchor channel  60  and threaded rods  80  to each other. 
     A method for extracting natural gas from well  12  under a low or negative pressure condition uses pump  30  to extract natural gas from well  12  by drawing a vacuum on well  12 . Pump  30  is able to create a vacuum on well  12  by harnessing the motion of walking beam  18  pivoting about Samson post  22 , which drives piston  36  of pump  30 . The up and down motion of walking beam  18  provides for the stroke of piston  36  in and out of pump  30 . 
     Pump  30  directs the extracted natural gas to volume tank  46  via gas output line  48 . The natural gas in volume tank  46  is made available to prime mover  16 . 
     In another embodiment, the invention provides for the method of installing adjustable bracket  34  on walking beam  18  of pump jack  14 . In a first step, adjustable bracket  34  is in an open position, and is placed on walking beam  18  with mounting fixture  74  oriented in a downward direction. A second step connects one of lug mounts  32  of pump  30  to mounting fixture  74 , and the other lug mount  32  of pump  30  to sliding bracket  38 . Adjustable bracket  34  and sliding bracket  38  are each moved, together or independently, to position pump  30  for a full stroke of piston  36 . One step to position pump  30  is for walking beam  18  to be positioned in a raised position thereby allowing piston  36  to be fully extended during the placement of adjustable bracket  34  on walking beam  18 . Another step is to secure adjustable bracket  34  to walking beam  18 , and to secure sliding bracket  38  to Samson Post  22  when piston  36  is in a compressed state with walking beam  18  in a down position. 
     Other embodiments of the current invention will be apparent to those skilled in the art from a consideration of this specification or practice of the invention disclosed herein. Thus, the foregoing specification is considered merely exemplary of the current invention with the true scope thereof being defined by the following claims.

Summary:
An apparatus and method for supplying natural gas from a well operating under vacuum conditions by extracting, storing and communicating it to a natural gas-fired piece of oil field equipment is provided. The apparatus has a pump associated with a pump jack for extracting natural gas. The apparatus communicates natural gas to a volume tank and stores it until it needed by a natural gas-fired piece of oil field equipment.