Abstract:
An axial assembly of pistons is axially disposed in the depending end of tubing in a gas well and packer set above the formation. Gas and fluid from the production zone enters the casing through an orifice below the piston assembly. Fluid in the annulus between the tubing and the casing creates a static head of back pressure against the orifice resulting in decreasing the gas pressure at the well head or flow line, which is sensed by pressure sensors to energize a compressor generating gas under pressure forced down the tubing to move piston rods and close the orifice. The gas pressure lifts the fluid in the annulus to the well head and flow line connected therewith. This cycle is repeated each time gas pressure falls below a predetermined pressure at the well head or flow line.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     Not applicable. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the oil and gas industry and more particularly to a compressor operated piston system for removing fluid build up in a gas well hampering the production of the gas from the well. As is well known in the industry, some gas wells produce fluids. Fluid build up in the casing of a gas well results in a static head hampering or shutting off production of gas from earth formations or perforations in the casing. Therefore many different apparatuses have been employed to remove such fluid, such as a gas lift system or as by pumping, neither being entirely satisfactory. 
     This invention on the other hand provides an automatic operating system responding to gas pressure sensors and an axial piston assembly which removes fluid from the well bore casing permitting commercial production of gas to the fullest extent possible of a particular gas well. 
     2. Description of the Prior Art 
     I do not know of any patents or publications disclosing the apparatus of this invention. 
     BRIEF SUMMARY OF THE INVENTION 
     An axial assembly of pistons is axially attached to the depending end of tubing in a gas well and set above the formation or casing perforations. Fluid from the production zone enters the casing through an orifice at the depending end of the piston assembly. The piston assembly in an open position allows fluid from the production formation, after passing through the orifice, to enter the annulus between the tubing and the casing. Fluids in the flow stream separate and settle to the depending limit of the casing and create a static head of back pressure against the orifice which results in decreasing the gas pressure at the well head. This decrease in gas pressure is detected by pressure sensors which releases compressed gas from a recycling tank on the surface of the earth which enters the tubing and forces pistons in the piston assembly downward. The several pistons in the piston assembly multiplies the force of the recycling tank gas pressure so that the injected gas passes outwardly of the piston assembly through exit ports in the depending end thereof and enters the annulus under the trapped liquid in the annulus around the tubing to lift it to the surface of the earth while simultaneously closing the orifice and preventing any loss of injected gas into the earth formation. When the accumulated liquid in the casing annulus has been removed a pressure sensor opens a closed valve in the gas injection line and gas pressure generated by a compressor is directed to the recycling tank while the gas production enters the flow line connected with the gas well head, thus completing one cycle of operation which is automatically repeated when fluid build up in the casing annulus subsequently occurs. 
     The principal object of this invention is to provide a compressor lift system employing a series of axially connected pistons periodically removing fluid build up in a gas well casing annulus in response to gas well pressure sensors controlling the operation of a compressor and gas recycling tank. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     FIG. 1 is a fragmentary diagrammatic view of a producing gas well; 
     FIG. 2 is a fragmentary vertical cross-section view  1 ; of a piston assembly in open position taken substantially along line  2 — 2  of FIG. 1; 
     FIG. 3 is a similar cross section view in piston closed position; 
     FIG. 4 is a top view of a spacer looking in the direction of the arrows  4 — 4  of FIG. 2; and, 
     FIG. 5 is a diagram of system components. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Description of preferred embodiment. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Like characters of reference designate like parts in those figures of the drawings in which they occur. 
     In the drawings: 
     The reference numeral  10  indicates a producing gas well having a bore hole  12  terminating in or passing through a gas producing zone  14  and containing a length of casing  16  having a well head  18  at its upper end projecting above the surface of the earth  20 . Gas, not shown, from the earth formation  14  enters the casing through its depending end or through perforations  22  in the casing wall. The well head  18  is normally connected with a tank or other apparatus receiving gas produced by the well  10  by a flow line  50 . 
     As mentioned hereinabove, such a gas well produces fluid, not shown, which also enters the depending end portion of the casing  16  with the gas and results in a static head of water accumulating in the depending end of the casing which at least hampers or stops the gas from entering the tubing. It is such a gas well that the apparatus of this system is intended to alleviate the fluid problem. 
     This is accomplished by installing a string of tubing  26  in the casing  16  with a packer  28  at its depending end which is set in the casing  16  at a point above the gas production zone  14 . A series of axially connected superposed pistons, indicated at  30  (FIG.  2 ), are installed in the tubing  26  above perforations  32  in the tubing wall spaced above the packer  28  and below the lowermost limit of the series of pistons  30 . 
     Operation of the several pistons  30  is accomplished by control apparatus  34  (FIG.  5 ). The control apparatus includes a compressor unit  36 , a recycling gas tank  38 , a pressure supply gas tank or reservoir  40  and an electrical control system  42  and several interconnected components such as valves, pressure sensors and air lines for opening and closing various valves in sequence for operation of the system as will now be described. 
     A pipe line  44  is connected at one end with the gas well tubing  26  through an air valve  46  and a check valve  48  to the pressure supply tank  40 . The well casing  16  is connected with the air compressor unit  36  by a tubular line  50  through a pressure sensor  52 , an air valve  54 , a regulator  56 , a separator  58 , a pressure regulator  60  and an air valve  62  and a compressor  66 . The compressor unit  36  includes a scrubber  64  communicating with the air valve  62  and the gas compressor  66  by a tubing line  68  having a normally closed valve  69  connected with the tubing line  68 . Compressed gas from the compressor  66  is connected to the recycling tank by a tubular line  70  through a three-way valve  72  and a discharge valve  74 . An outlet of the three-way valve is also connected to the gas sales or discharge line  76  through a check valve  78 . The discharge line  76  is also connected with a pressure sensor  80  upstream from the check valve  78 . The compressor discharge line  70  is provided with a lateral line open to the atmosphere through a normally closed valve  82  and a normally closed manually opened valve  84 . A pressure sensor recycling tank pressure switch  86  is connected with the compressor discharge line  70  adjacent the three-way valve  72 . Gas line  70  is provided with a branch line  25  connecting the separator  58  with the gas sales line  76  downstream with respect to the three-way valve  72  and upstream with respect to the check valve  78 . 
     The electrical control system  42  includes solenoids  90 ,  92  and  94  connected in parallel with the pressure supply tank  40  by other tubing  96 . A bank of batteries  98  includes necessary wiring connecting the electrical energy with the respective solenoid. Solenoid  90  is connected by an air line  100  with the valves  46  and  54 , and solenoid  92  is connected by an air line  102  with the three-way valve  72 , while the solenoid  94  is connected by a line  104  with the air valves  62 ,  69 ,  82 , and  74  for opening or closing these valves as presently explained. 
     OPERATION 
     In operation the compressor  66  is started by utilizing gas from the well head  18  via a bypass line  65  or a propane starter tank supply, not shown. The electrical control panel  42  controls all functions of the compressor as dictated by well head and discharge gas pressure in the well gas line  76  by responding to changes in preset parameters for operating the gas well  10 . Assuming the pressure in line  50  is not above the discharge set point, as controlled by pressure switch  80  or the low pressure set point of pressure switch  81 , the normally closed pneumatic valves  62  and  74  will open while the normally closed valves  69  and  82  will close. This is accomplished by the pressure supplied by the gas well  10  through the line  44  into the air pressure supply tank  40 . The pneumatic pressure supply tank  40  allows the gas to pass from normally open solenoid  94  through tubing line  104  to open valves  62  and  74  and close valves  69  and  82 . When the well pressure in line  50  is above the set point of pressure switch  52 , the solenoid  90  is excited and opens valve  54  and simultaneously closes valve  46 . Gas flows through pneumatic valve  54  and regulator  56  through the compressor scrubber  58 , regulator  60  and valve  62  into the compressor unit  36 . Compressed gas flows through the sales line  70 , normally open valve  74  and the three-way valve  72 , to the recycling tank  38 . When the recycling tank  38  is at preset pressure point, pressure switch  86  excites solenoid  92  and diverts gas flow through the three-way valve  72  to the sales line  76 . The compressor  66  will continue pumping gas until there are pressure changes in the system. In the event pressure in the sales pipe line  76  exceeds set pressure point, the pressure switch  80  excites the solenoid  94  to close valves  62  and  74 . Simultaneously, pressure release opens the valves  69  and  82  to atmosphere, allowing the compressor  66  to run in idle mode by circulating air and keeping the compressor running. Pressure switch  80  or  81  activates solenoid  94 . The delay relay  51  allows the compressor  66  to shift to the idle position and recycle to atmosphere for a predetermined time. After the time interval elapses, solenoid  94  will return to its normally open position. However, if the suction pressure or the discharge of the compressor  66  remains out of set point range, solenoid  94  will automatically be reversed again by pressure switch  80  or  81  before the pneumatic valves have time to change their position. This action will be repeated until the intake or discharge pressure falls to the acceptable pressure range. Should the well have a sudden slug or surge while the compressor  66  is in the idle mode the gas may pass through the bypass line  25  and into the sales line  76 . When the well head pressure decreases as the result of liquid in the bore hole, and the result of this liquid in line  50 , the pressure drops below the set point of pressure switch  52 , and excites solenoid  90  to close valve  54  and open valve  46  allowing the pressurized gas in the recycling tank  38  to enter the well tubing  26  through line  44 , putting pressure on the piston assembly  30 . 
     The piston assembly  30  consists of a series of independent axially connected piston housings, as mentioned hereinabove, separated from each other by apertured partitions  33  which are cylindrical with apertures adjacent its periphery and containing a central threaded bore to axially attach the piston housings  31  to each other and the piston stem guide  35 . The spacers also align each piston guide  35  and pistons  39  with each other, allowing each piston stem  37  to extend axially as the depending piston  39  is moved downwardly by the gas being injected into the well tubing  26 . The injected gas enters the top of each piston housing  31  through port holes  41 . As the injected gas enters in the piston assembly  30 , it places pressure on the top of each piston  39 . This pressure causes the piston  39  enclosed in each piston housing  31  to move downward against its return spring  29  placing axial pressure on its stem  37  and axial pressure of the stem  37  on the depending piston in the attached piston housing. Each piston  39  is sealed by an O-ring  43 . This action multiplies the force of the gas being injected from the recycling tank  38  by the surface area of the combined pistons  39 , thus enabling the force being injected into the piston housing to oppose a much larger force, and close the lowermost piston stem  45  on the packer seat  47  preventing gas and liquid from the producing formation  14  entering the piston assembly  30 . By closing the orifice  47  to the production formation of the well, the gas being injected will exit the well tubing port holes  32  and enter the annulus  32 ′ between the tubing  26  and the well casing  16 . 
     The apparatus control valve  54  is closed during gas injection from the recycling tank  38 . The injection period is closed by the preset time delay relay  91  in the electric control system  42 . At the end of time delay, the valve  54  is opened and injected gas and liquid exit the well head  18 . 
     The injected gas is restricted from returning to the piston assembly by check valve  49  during the cycling process. One-way bleed valves  67  in the bottom of each piston housing  31  allows each piston to move downward. The one-way bleed valves  67  allow any air or gas trapped in the lower chamber of the piston housing to bleed off. The remaining downward pressure on the piston assembly  31  is dissipated by the time delay of relay  91 , holding open the valve  46  which allows the injected pressure to dissipate back into the recycling tank  38 . This cycle is repeated each time the static head of the liquid is sufficient to lower the well head pressure. 
     Obviously the invention is susceptible to changes or alterations without defeating its practicability. Therefore, I do not wish to be confined to the preferred embodiments shown in the drawings and described herein.