US2326442A - Gas-lift control - Google Patents

Description

' Patented Aug. 10, 1943 GAS -IJF1 CONTROL Hendrik Pieter de Wit, Casigua, Venezuela, as-

signor to Shell Development Company, San Francisco, Calif., a corporation 01' Delaware Application August 5, 1941, Serial No. 405,563

8 Claims. (01. 103-240) This invention relates to an automatic timing device for controlling the flow of oil from a well and pertains more particularly to a device for automatically controlling the intermittent supply of compressed gas to gas-lift pumps.

In most gas-lift devices the duration of the working period, that is, of the time during which gas is supplied to the gas-lift pump, is independent of fluctuations in the pressure of the gas supply and of variations in the quantity of well liquid being raised. Thus, the working period is generally longer than necessary, and the gas conswnption is higher than the optimum.

Also, in many gas-lift systems, central gas distributors have been used, which cause the valves controlling the flow of pressure gas to individual wells to open and close in succession, so that the working periods do not coincide, thereby avoiding overlapping working periods which may cause violent pressure fluctuations throughout the system. However, such central control devices are not easily subject to fine control so asto obtain the optimum gas consumption. The working periods for the various wells are generally longer than necessary, and consequently there is some waste of gas.

It is therefore an object of this invention to provide a gas-lift system having a central gas supply intermitter or regulator capable of serially spacing the working periods of individual wells, and means associated with each well and responsive to the liquid discharged therefrom for terminating the working period of said well independently of the central intermitter, whereby an economical consumption of pressure gas is insured.

It is another object to provide an intermittent gas-lift system having automatic means for controlling the supply of pressure gas to each well, whereby the need for fine manual adjustment of the working periods of the individual wells is eliminated.

It is another object to provide a gas-lift system attaining the above objects, which system is mechanically simple and advantageously flexible for application to varying field conditions.

Briefly, these and other objects are attained by the present gas-lift control system wherein a central timing device serially spaces the closure or completion of electrical circuits energizing electrically-actuated valves which control the supply of pressure gas to the individual wells, and interrupter means associated with each well adapted to break the electrical circuit and thereby to stop the input of pressure gas for said well in response to flow of oil therefrom.

header The present invention will be more clearly un derstood from the following description oil a preferred embodiment taken with reference to the drawings, wherein:

Figure I is a diagrammatic view of the present,

ferred embodiment of the interrupter switch mechanism.

The gas-lift control system of the present invention is described in relation to a pump having a displacement chamber and an eduction tube, although the present device may b applied equally well to other intermittent gas-lift pumps. Referring to well A shown in vertical section in Figure 1, a casing 2 having a perforated liner 3 attached to the lower end thereofis placed in a borehole l. Depending within the casing 2 is a tubing string 4 having at the bottom thereof an enlarged portion forming a displacement chamber 5. An inwardly-opening check valve 6 is provided in the lower portion of chamber 5 to permit well liquid to accumulate therein. Extending downwards through the tubing string 4 and into the displacement chamber is an eduction tube 1. In operation, liquid from the producing formations surrounding the borehole is allowed to flow through the perforations oi the liner 3 into the chamber 5 through the check valve 6 when the pressure in chamber 5 is sufllciently reduced: the accumulated liquid is then lifted through the eduction tube 7 by compressed gas supplied from a gas supply pipe Hi to the annular space 9 between the tubing string 4 and eduction tube 1; the check valve 6 in the lower portion 01' the chamber 5 closes to avoid applying high pressures to the producingformations, which may cause production losses; the well liquid and the gas raising said liquid are discharged from the eduction tube 1 through discharge or oil flow line to attached thereto at the well head.

To effect this operation of the elements described or their equivalents which, in combination, may be referred to as a gas-lift pump, the pressure gas or working fluid in the pipe or line It, which communicates with the gas supply I5, is alternately admitted into the annular space 9 and shut oi! therefrom by means of an electrically-operated control valve 24. In the general arrangement of the present gas-lift control system. as shown in Figure I, the operation of the control valve 24 for each well is controlled by the combination comprising an electricallyoperated central timing device or regulator 2|, which also governs the operation of the control valves 24 in a plurality of wells .8. C, D, etc.. an electrical current source 22 and, for each well, a current interrupter 21 actuated by or responsive to the liquid flow or discharge in line II and adapted to break the electrical current actuating the control valve 24 in response to a flow or oil from the discharge line l9.

Referring to Figures II and DI showing the various parts in more detail, a preferred embodiment of the central intermitter or regulator 2i comprises a housing 30, an electric motor 3| connected to the electrical source 22 which may comprise a cell, storage battery, or the terminals of any suitable power supply system, and clockwork or escapement means 32 or the like adapted to regulate the rotation of the motor shaft 33. Attached to the shaft 33 and rotatable therewith is a disk 34, or other suitable means, provided with an insulated ring 35 in its outer circumferential portion. An electrical contact 35 attached to the insulated ring 35 is carried in a circular path by the rotation of the disk 34 and makes contact with a stationary ring 40 having suitably spaced sector contacts 4| between insulating sectors 4la, as shown more clearly in Figure I11. To each contact 41 is connected an electrical conduit 42 leading to a gas-injection control valve 24. By means of a stationary contact 43 attached to the wall of the housing 30 and held against .the rotating ring 35, electrical current may pass from the electrical current source 22 through the stationary contact 43, the rotating ring 35, the rotating contact 36, and one of the insulated contacts 4| in the stationary ring 40 through the electrical conductors 42 comprising contacts 90-9i to an electrically-operated valve 24. Suitable connections may also be provided between the electrical current source 22 and each control valve 24 through the ground. For example, when the distance from the central regulator 2| to the valve 24 is greater than about 400 feet, the conductor 45 may be eliminated by grounding the lower terminal of the source 22 and the left-hand terminal of valve 24. If desired, the upper end of the motor shaft 33 may be terminated outside the housing 30 and fitted with a pointer 31 to indicate which well is bein produced at the moment by the position of the pointer in relation to a dial r markings (not shown) formed on the adjacent upper surface of the housing. Instead, signal lights (not shown) may be provided in series with the various cir-.

cuits to the wells for the same purpose. It is to be noted that the length of the contact sectors 4| may be varied to roughly set the length of the gas admission periods for the different wells and that, further, the various contacts 4i may be combined, if desired, into groups or combinations for timing the gas injection periods to suit individual well requirements.

The gas control valve 24 may be any suitable electro-magnetic valve or the like. For example, in a preferred mechanism a solenoid-operated pilot valve 48 controls a diaphragm-motor valve 49 which, in turn, controls the passage of gas supply through the gas injection line ii. The pilot valve 48 may comprise a valve 50, a valve casing 5|. a valve' stem 52 entending through the ends of the casing 5|, a spring-restraining plate 53 attached to one end of the valve stem 52. a spring 54 compressed between the end of the casing 5i and the plate 53, an armature 56 attached to the other end of the valve stem 52, and

a solenoid 51 surrounding the armature 58. The

solenoid 51 and armature 56 may be encased in a protective housing 59., if desired. The valve casing Si is provided with a centrally spaced port 64 and two oflset ports 62 and 53. Attached to offset port 62 is a vent pipe 54 and to port 93 is a 80 and leads to the diaphragm chamber I0 of the diaphragm-motor valve 49. When current is applied to the solenoid 51, the armature and the valve stem 52 and valve 50 attached theretoare moved against the action of spring 54 to a position with the valve 59 between the vent port 62 and the diaphragm port 60, whereby fluid communication between the gas supply port 53 and diaphragm port 50 is provided. When the solenoid 51 is not energized, the valve is moved to the other side of the diaphragm port 60 by the action of the spring 54 whereby the pressure in the diaphragm chamber 10 is released through port 62 and vent line 64.

The diaphragm-motor valve 49 may be of any suitable type adapted to open when pressure is applied to one side of its diaphragm and may, in

a preferred form, comprise diaphragm chamber diaphragm H and tending to close the valve 12.

'In the electrical circuit, such as in conductor 42, from the central regulator 2i to the control valve 24 is a normally closed circuit interrupter 21 adapted to break the electrical circuit in response to a certain condition (pressure, impact, rate of flow, etc.) in the discharge line l0 due to flow of liquid or oil therethrough. For example, a suitable arrangement comprises 9. diaphragm exposed to the pressure in the flow line l0 near the well head, a stem 8i attached at one end to the diaphragm 80, a normally closed switch operatively connected to the other end of the stem 8|, and a spring 83 acting against the low pressure side of the diaphragm 80 and tending to close the switch. The switch is preferably adapted, for example, by means of a toggle arrangement, to open at a predetermined high pressure and to return .to closed position at a predetermined lower pressure. In a preferred form, as shown in Figure IV, the switch may comprise a pair of stationary contacts terminating the break in the electrical conductor 42, a movable contact 9i adapted to bridge said pair of stationary contacts 90 and carried at one end of an arm 92 pivoted at the other end on a shaft 91 carried by the housing 95, and a toggle spring 93 linking the center of the arm 92 to the stem 8i. The contacts 90 are supported on a bracket 94 extending from the inner wall of the switch housing 95. The swing of the pivoted arm 92 is limited in one direction by the contacts 90 and bracket 94 and in the other direction by a stop 95. By suitably adjusting or selecting the springs 83 .and 93, the opening and closing pressures of the switch can be controlled.

, the discharge line In.

tion of the contact 36 pressing against the spaced contacts 4| of the ring 40 causes the completion of the electrical circuits to the various control valves 24 in a predetermined sequence, whereby only one well at a time draws on the supply of pressure gas and violent fluctuations in the pressure of the gas supply are avoided. On completing the electrical circuit from the electrical current source 22 through stationary contact 43, rotating ring 35 and contact 36, one of the individual contacts 4| in the ring 40, electrical conductor 42 and the closed interrupter switch 90-93 to the solenoid 51, the armature 56 with the valve stem 52 and valve 50 attached thereto are caused to be moved into diaphragm-actuating position by the energization of the solenoid 51. With the valve 50 in this position, pressure gas passes from the gas supply line l6 through the small pipe 55, the valve casing 5|, the diaphragm port 60 and the conduit 61 into the diaphragm chamber 1|], wherein the pressure acts upon and depresses the diaphragm H and thereby causes the valve 12 attached to the diaphragm 1| by means of stem I3 to be opened against the action of the spring 14.

Pressure gas then flows through the thusopened valve 12 down the annular space 9 to the displacement chamber 5 and forces the accumulated liquid up the education tube 1 and out The flow of oil through the discharge line causes an increase in the pressure on the diaphragm 80 of the circuit interrupter 21. The pressure-responsive upward movement of the diaphragm 80 movesthe switch arm 92 attached thereto by stem 8| into open position at a predetermined pressure against the action of the spring 83, whereby the electrical circuit through line 42 from the central regulator 2| to the solenoid 51 of the control valve 24 is broken. The armature 55 is then no longer pulled upward by the magnetic field of the solenoid and the valve 50 is moved to the opposite side of the diaphragm port 60 by the action of the spring 54, whereby the ports 62 and 60 are in communication and the pressure in the diaphragm chamber i is vented to the atmosphere through vent conduit 64. With the release of pressure in the chamber ill, the diaphragm II is moved upward and the valve 12 is closed by the action of spring 14. lift pump is shut off at the optimum time, that is, when the oil flows from the dischargeor flow line H].

The gas then remaining in the annular space 9 expands, thereby further lifting the liquid in the eduction tube 1, and finally escapes through the discharge line Ill. During the expansion of the remaining pressure gas in the annular space 9 and its exhaustion from the gas-lift pump, the continued rotation of the ring 35 causes the electrical circuit to the the control valve 24 of the well concerned to be broken-.. Thereafter, the pressure against the diaphragm 80 of the circuit interrupter 21 drops to a predetermined low pressure, at which the spring 8.3 re-closes the switch after overcoming the pressure in the line H! and, with the preferred form, also the. delayed action of the toggle-type switch 9|l93. It is preferable that the diiference between opening and closing pressures of the circuit interrupter 21 should be substantial in order to avoid accidental closing of the circuit due to pressure pulsations. Then this well again passes through the stage of accumulation of well liquids in the chamber while a similar series of actions are automatically ef- Thus, the supply of pressure gas to the gasfected in series on the other wells connected to the central regulator 2| By means of the present gas-lift control system the most economical gas consumption is obtained. The present control system likewise eliminates the necessity of frequent attendance of an oper-- ator to adjust the length of the contacts 4| in the central regulator 2|. Rather, the gas supply is automatically shut 0113 at the optimum time, either by the central regulator 2| .or, if the lifting operation is effected in a time shorter than that for which the central regulator had been adjusted, by the circuit interrupter 21 in response to a flow of oil out through the discharge line l0. In other words, the working period is roughly adjusted in the central regulator 2| by the length of the contact 4| and the fine adjustment to the optimum is obtained by the action of the circuit interrupter 2|. In addition to efiecting a decrease in gas consumption, the present control system increases crude oil production by increasing the liquid accumulation time and thereby increasing the volume of oil raised in each operation of the gas-lift pump.

I claim as my invention:

1. In an intermittent gas-lift system comprising a plurality of Wells, a source of supply of pressure gas, and for each well a displacement chamber for liquid to be lifted, pressure conduit means communicating with said pressure gas source for admitting said gas to said chamber, an electrically operated valve in said pressure con.- duit means for controlling the flow of said gas, and conduit means from said chamber for discharging from said well the liquid raised by said gas, a control system comprising a source of electric current, a circuit for each well connecting said electric source to the electrically operated valve for said well, a time-responsive intermitter common to said circuits for cyclically making and breaking said circuits in a predetermined.

sequence, and a normally closed interrupter at each well operated by the liquid discharged therefrom for breaking the circuit for each well.

2. In an intermittent gas-lift system comprising a plurality of wells, a supply of pressure gas,

valve-controlled conduit means for each well for admitting said gas to said wells, and conduit means for discharging from each well the liquid raised by said gas, a control system comprising an intermitter for controlling the cyclical opening and closing of the valves admitting the gas to the several wells, and an interrupter at each well operated by the liquid discharged therefrom for controlling the closing of the valve admitting the pressure gas to said well.

3. In an intermittent gas-lift system comprising a plurality of wells, a supply of pressure gas, valve-controlled conduit means for each well for admitting said gas to said wells, and conduit means for discharging from each well the liquid raised by said gas, a control system comprising a time-responsive intermitter for controlling the cyclical opening and closing of the valves admitting the gas to the several wells in a predetermined sequence, and an interrupter at each well operated by the liquid discharged therefrom for controlling the closing of thevalve admitting the pressure gas to said well.

4. In an intermittent gas-lift system comprising a plurality of wells, a supply of pressure gas, conduit means between said pressure gas supply and each of said wells for admitting said gas thereinto, an electrically operated valve in each of said pressure conduit means for controlling the flow of said gas, and conduit means for discharging from each well the liquid raised by said gas, a control system comprising a source electric current, a circuit for each well connecting said source to the electrically operated valve for said well, an intermitter for cyclically making and breaking said circuits, thereby controlling the cyclical opening and closing of said valves, a normally closed interrupter in each circuit adapted to break said circuit, thereby controlling the closing of said valve independently of the intermitter, and means actuated by the liquid discharged from the well controlled by said circuit for opening said interrupter.

5. In an intermittent gas-lift system comprising a plurality of wells, a supply of pressure gas, conduit means between said pressure gas supply and each of said wells for admitting said gas thereinto, an electrically operated valve in each of said means for controlling the flow of said gas, and conduit means for discharging from each well the liquid raised by said gas, a control system comprising a source of electric current, a circuit for each well connecting said source to the electrically operated valve for said ,well, a time-responsive intermitter for cyclically making and breaking said circuits in a predetermined sequence, thereby controlling the cyclical opening and closing of said valves, a normally closed interrupter in each circuit adapted to break said circuit, thereby controlling the closing of said valve independently of the intermit ter, and means actuated by the liquid discharged from the well controlled by said circuit for opening said interrupter.

6. In an intermittent gas-lift system comprising a plurality of wells, a supply of pressure gas, conduit means between said pressure gas supply and each of said wells for admitting said gas thereinto, an electrically operated valve in each of said means for controlling the flow of said gas, and conduit means for discharging from each well the liquid raised by said gas, a control system comprising a source of electric current, a circuit for each well connecting said source to the electrically operated valve for said well, a time-responsive intermitter for cyclically making and breaking said circuits in a predetermined sequence, thereby controlling the cyclical opening and closing of said valves, a normally closed interrupter in each circuit adapted to break said circuit, thereby controlling the closing of said valve independently of the intermitter, and

7. In an intermittent gas-lift system comprising a plurality of wells, a supply of pressure gas, conduit means between said pressure gas supply and each of said wells for admitting said gas thereinto, an electrically operated valve in each of said means for controlling the flow of said gas, and conduit means for discharging from each well the liquid raised by said gas, a control system comprising a source or electric current, a circuit for each well connecting said source to the electrically operated valve for said well, a time-responsive intermitter common to said circuits for cyclically making and breaking said circuits in a predetermined sequence, thereby controlling the cyclical opening and closing of said valves, a normally closed interrupter in each circuit adapted to break said circuit, thereby controlling the closing of said valve independently of the intermitter, and means responsive to the pressure in the liquid discharge conduit of the .well controlled by said circuit for opening said interrupter, and resilient means adapted to overcome a predetermined lower pressure in said conduit for closing said interrupter.

8. In an intermittent gas-lift system comprising a plurality of wells, a source of supply of pressure gas, and for each well a displacement chamber for liquid to be lifted, pressure conduit means communicating with said pressure gas source for admitting said gas to said chamber,

an electrically operated valve in said pressureconduit means for controlling the flow of said gas, and conduit means from said chamber for discharging from said well the liquid raised by said gas, a control system comprising a source rupter in open position when liquid is discharged from the well.

I-IENDRK PIETER DE WIT.

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