Abstract: Apparatus for continuously recovering oil-only from mature wells with typically low production. The apparatus includes a continuous chain which is suspended in the oil-containing portion of the well. By continuously moving the chain, oil is drawn out of the well and deposited in a collection box.

Abstract: An automatic pumping system for removal of floating contaminants and oil and gasoline seepage from water wells. A vertically reciprocating cone-shaped member, like an inverted funnel, is moved between positions above and below the water surface. As it submerges, the inverted funnel collects the floating product within its circumference and transfers it to a collection space surrounding the cone. In the upper position, this collection space is sealed so that air may be blown into it while the collected product is driven out through a pickup tube to a collection sump for ultimate disposal. A second embodiment incorporates a hydraulic pumping system which operates in synchronism with the contamination collection and disposal system to create a cone of depression which draws the floating product into the space covered by the circumference of the reciprocating cone.

Abstract: An apparatus injects sealing balls into a well in response to closed loop control. The apparatus measures the fluid flow into the well, computes a total amount of fluid which has been introduced into the well, and actuates the release of a sealing ball upon a predetermined amount of fluid being reached. A related method is also disclosed.

Abstract: In an oilfield production system, a water driven jet pump is used to evacuate vapors from storage tanks to thereby recover the vapors and prevent emissions from passing to the atmosphere. The jet pump entrains the vapors in process water which is passed to a process separator already in the system. The gas is separated for recovery.

Abstract: A method for introducing a surfactant into an oil bearing formation includes plurality of a micro-slug injections of surfactant. Each micro-slug injection comprises an "on time" in which the surfactant is introduced into the formation and which is based upon the time needed for the surfactant to generate foam in the formation and a "off time" in which surfactant flow is stopped and is based upon the time period for the generated foam to degrade to a predetermined degree in the formation.

Abstract: In a subterranean well for producing a production fluid flow through a flow line having a main control valve, a flow control system including means to remotely actuate the main flow valve to open position in response to a radio signal subsequent to the main valve being closed under elective or emergency conditions. Initial fluid flow from the well is commenced by provisionally opening the main flow regulating valve for a predetermined time interval. During said timed interval, if the pressure in the well flow line is not stabilized to an acceptable operating range, the main flow valve will be automatically closed in response to a pressure sensing means which communicates said main flow line with the main valve actuator.

Abstract: A system for monitoring and controlling the injection rate of fluid by an injection well of an in-situ remediation system for treating a contaminated groundwater plume. The well is fitted with a gated insert, substantially coaxial with the injection well. A plurality of openings, some or all of which are equipped with fluid flow sensors and gates, are spaced along the insert. The gates and sensors are connected to a surface controller. The insert may extend throughout part of, or substantially the entire length of the injection well. Alternatively, the insert may comprise one or more movable modules which can be positioned wherever desired along the well. The gates are opened part-way at the start of treatment. The sensors monitor and display the flow rate of fluid passing through each opening on a controller.

Abstract: In a preferred method, a spilled fluid, lighter than and immiscible with water, is removed by, first, penetrating through the fluid zone and at least partially through the groundwater zone to provide a bore in communication therewith. Then, at suitable intervals, an amount of fluid is extracted from the fluid zone through the bore at a rate selected to maintain contact between at least a portion of the fluid being extracted through the bore and at least a portion of the fluid remaining in the fluid zone. In addition, at suitable intervals, an amount of water from the groundwater zone is extracted through the bore to produce a head of fluid above the fluid/water interface adjacent the bore sufficient to cause gravity drainage of the fluid from the fluid zone in a direction generally toward the bore.

Abstract: A system for providing filtered well water to a building includes a filter, an accumulator downstream of the filter, and an automatic backwash valve between the filter and the well. When the well pump is deactivated, the accumulator discharges its contents back through the filter, towards the valve, which contains a shuttle that automatically diverts the backwash water to a drain line. The valve also prevents contaminants from being siphoned into the system through the drain line.

Abstract: A method for removing floating immiscible liquids from a well containing both the floating immiscible liquids and water, where the floating immiscible liquids and water meet at a water interface, by controlling a cone of depression within the well. A removal system for removing said floating immiscible liquids is used including a microprocessor, a discharge water line and an upper water interface sensor where at least a portion of the discharge water line is located within the well. The upper water interface sensor is located within the well at a sensor location.

Abstract: A method for producing a plunger lift well which optimizes production through the evaluation of the speed at which a plunger arrives at the wellhead within a fixed on-cycle interval. Time interval windows representing fast, good, and slow plunger performance are established and, based upon plunger performance with respect to these windows, afterflow time and off-cycle intervals are varied toward an achievement of plunger arrivals within the good window. A minimum off-time is established as a limit. The method may be employed with two motor valves, one performing in conjunction with a sales and the other to low pressure such as the atmospheric pressure of a tank or a low pressure sales line. In the event of failure of the plunger to arrive within the on-cycle interval, resort is made to the tank cycle. Additionally, an afterlow delay cycle is provided as well as a delay cycle intended for response to high sales line pressure conditions.

Abstract: A gas and oil well controller includes a microcomputer control circuit which can control well production by monitoring well pressure levels, by time limitations, or any combination of the two. The controller includes a casing pressure sensor, a tubing pressure sensor for sensing casing/tubing differential pressure and tubing/line differential (flow) pressure, a line pressure sensor for sensing pressure in the sales line, and a plunger position sensor for sensing the position of a plunger adjacent a top position in the well tubing. The microcomputer control circuit is in operative communication with the production valve, the casing pressure sensor, the tubing pressure sensor, the line pressure sensor, and the plunger to open and close the production valve for gas flow to the sales line when the casing, tubing, and line pressures bear a predetermined relationship to preselected pressure limits or when the plunger is sensed by the plunger sensor.

Abstract: An apparatus for recovering liquids from a wellbore includes a primary pump for pumping a primary fluid through a primary fluid conduit positioned in the wellbore, and a secondary, displacement-type pump. The displacement pump includes a recovery section and a drive section, the volume of the recovery section being adapted to vary in inverse proportion with the volume of the drive section. The secondary or displacement pump also includes an inlet arrangement with a suitable one-way valve for allowing wellbore liquid to flow into the recovery section, and an outlet arrangement adapted to carry liquid expelled from the recovery section to the surface. A venturi body is connected in the primary fluid conduit and is adapted to produce a reduced pressure at a venturi outlet as the primary pump pumps the primary fluid through the conduit and venturi body at a first flow rate and with a first pressure differential across the venturi body.

Abstract: A groundwater pollutant recovery system using the cone of depression approach, in which a sensing probe having liquid level sensors responsive to both water and pollutant levels and having attached to it the pollutant intake is deployed in a recovery well above the submerged water and pollutant pumps. The pollutant intake on the sensing probe is attached to the pollutant pump by an extendable hose so that the sensing probe may be raised and lowered in response to changing hydraulic conditions in the well, without the necessity of changing the water or pollutant pump positions. The recovery sequence is controlled by a microprocessor under the control of a program responsive to the liquid levels indicated by the sensors in the sensing probe.

Abstract: An improved mobile pumping apparaus for producing fluids from, for instance, shallow and/or slow-flowing marginal oil wells. The invention comprises a boom assembly which is adapted for mounting on a tractor, truck, or other vehicle having a standpipe mounted on the front thereof which is lowered into engagement with a wellhead and a winch having a cable attached at one end thereto, the other end of the cable extending down into the standpipe and having a swab bar attached thereto. The swab bar is provided with a heavy lead weight, so that the swab bar will sink down into the fluid as the cable is wound off of the winch, and a plurality of cups for lifting the fluid up out of the well when the direction of the winch is reversed. The oil is lifted up out of the well into the standpipe and on into a hose for collection in a storage tank.

Abstract: A well fluid sampling apparatus provides a time delay after actuation of the tool and before a sample is taken. The tool is operated by well pressure acting on a piston. The piston is initially hydraulically blocked so that it cannot move. The time delay is provided after the piston begins moving. Additional time delay devices can optionally be included.

Abstract: A control system and method utilizing a race between two responses to a changing stimulus are disclosed. An example of a changing stimulus is pressure which increases at a decreasing rate of change during a closed-in period of a drill stem test in an oil or gas well. In a preferred embodiment two components are moved in different directions, but in a net first direction, until the rate of change of the pressure is sufficiently low (e.g., near steady state), at which time the rates of movement of the two components produce net movement in a second direction. In a preferred embodiment, the change in direction of the net movement moves a control valve which communicates a pressure control signal for opening a bypass valve to commence a flow period of the drill stem test.

Abstract: A control system for an in-well pump for recovery of hydrocarbons which are lighter than water. Two electrical probes and a float switch are used to control the automatic raising and lowering of the pump within the well to always maintain its input within the hydrocarbon layer. The pump is also controlled so that it only operates when its input is within the hydrocarbons to assure that it does not pump water and that it is not operated in air.

Abstract: A sequential remote control plug release system allows actuation of plug release plungers and manifold valves associated with a cementing plug container only in a predetermined sequence. With regard to a plug container having two plugs, and thus two plug release plungers, and three manifold valves, the middle and upper manifold valves and the upper plug release plunger can be opened and retracted only in a predetermined sequence. This is implemented through interconnected actuation valves and sequencing valves contained in a housing which can be located remotely from the plug container. An improvement in plug release plungers is also disclosed.

Abstract: A method of startup of oil production in a gas-lift well in which inlet flow (22) of gas is controlled (46, 42) while means (34, 28) controlling fluid flow from the well is progressively opened. Preferably, fluid flow rate from the well is monitored and valve means (28) opening rate reduced on detection of a greater than predetermined increase in flow rate. A method of controlling the oil production is also provided wherein flow rate from the well is monitored and a flow regulating device (28) in the flow path from the well controlled in accordance with that monitored flow rate which is indicative of the onset of slugging.

Abstract: A floating layer recovery apparatus is disclosed for selectively pumping a liquid floating on groundwater. The apparatus preferably includes a first float which is buoyant in the floating layer attached by a guide to a bottom float which has neutral buoyancy in the groundwater. A middle float is slidably attached to the guide for upward and downward movement between the first and bottom floats. The middle float being an inlet is constructed to have an effective density in the assembly such that it rests at a point where its inlet is near the bottom of the floating layer. Coiled conduits disposed above and below the bottom float carry the floating layer liquid received by the inlet to a pump disposed below. The pump then pumps the floating layer liquid from the conduit to the ground surface. In a preferred embodiment, more precise control over the level of the inlet port is achieved by means of an adjustable inlet port means.

Abstract: A gas and oil well controller includes a microcomputer control circuit which can control well production by monitoring well pressure levels, by time limitations, or any combination of the two. The controller includes a casing pressure sensor, a tubing pressure sensor, and a line pressure sensor for sensing pressure in the sales line, and a plunger position sensor for sensing the position of a plunger adjacent a top position in the well tubing. The microcomputer control circuit is in operative communication with the production valve, the casing pressure sensor, tubing pressure sensor, the line pressure sensor and the plunger sensor to open and close the production valve for gas flow to the sales line when the casing, tubing, and line pressures bear a predetermined relationship to preselected pressure limits or when the plunger is sensed by the plunger sensor. The controller includes a device for preselecting limit delays to suspend valve operations during pressure surges to avoid premature opening or closing.

Abstract: A mud saver valve for automatically closing to prevent loss and spilling of drilling mud. The valve contains a diaphragm, rigid backup means and diaphragm support means so that the valve can be used in high pressure wells.

Abstract: An injection manifold for use in injecting fluid into a well and method of use. Several embodiments of the apparatus are shown. In each embodiment, a bypass valve is used to control the discharge pressure of a pump, and a throttling valve is used to control the fluid injection flow rate to the well in response to a flow rate measured by a flow meter. In a first embodiment, the throttling is carried out manually. In a second embodiment, the throttling is carried out automatically by a controller which compares a flow rate signal from the meter with a predetermined flow rate set point and sends a corresponding output signal to an actuator of the throttling valve. A third embodiment is a combination manifold which may also be used for flowback tests from the well. In this third embodiment, the electronic controller may also be used to control the flow rate during the flowback test in response to a flow rate signal from the flow meter. A method of injecting fluid into a well using the apparatus is also disclosed.

Abstract: A method and system for removing and recovering fuel oil, and other liquid hydrocarbons, from ground water. A well is drilled and the ground water and any other liquid floating thereon are allowed to enter the well. An enclosed tank is filled with water, and essentially sealed to prevent ingress of air. An outlet tube is connected to the tank at one end, and its other end is placed in the well, below water level. Another tube is connected at one end to the tank and fixedly attached at the other end to a float device at a position above the hydrocarbon/water interface. As water drains from the tank into the well it is replaced by the liquid hydrocarbon which is thus forced to travel up the tube into the tank. Thus, this system is operated entirely by gravity due to the difference in specific gravities of water and the liquid hydrocarbon, and no pump or other external power source is required.

Abstract: A groundwater pollutant recovery system using the cone of depression approach, in which a sensing probe having liquid level sensors responsive to both water and pollutant levels and having attached to it the pollutant intake is deployed in a recovery well above the submerged water and pollutant pumps. The pollutant intake on the sensing probe is attached to the pollutant pump by an extendable hose so that the sensing probe may be raised and lowered in response to changing hydraulic conditions in the well without the necessity of changing the water or pollutant pump positions. The recovery sequence is controlled by a microprocessor under the control of a program responsive to the liquid levels indicated by the sensors in the sensing probe.

Abstract: A method for minimizing the production of sand in submersible-pump well applications is disclosed, in which control of fluid production rates is used to maintain a low rate of change of formation pressure. Simulation of well drawdown conditions in advance of startup allow the prediction of well performance and the selection of a drawdown profile to be implemented in control systems.

Abstract: A hydraulic system and method are provided for supplying high pressure hydraulic fluid to a cylinder for operating a ram, e.g. a shearing and/or shut-off ram for a blowout preventer. It comprises means for supplying high pressure hydraulic fluid to the cylinder, said hydraulic fluid supply means comprising first and second storage means for storing hydraulic fluid under pressure, first conduit means for supplying hydraulic fluid under pressure from said first storage means to the cylinder, a pressure sensing device for determining the back pressure in said first conduit means, second conduit means for supplying hydraulic fluid under pressure from said second storage means to the cylinder and valve means for automatically opening said second conduit means when the back pressure in the first conduit means reaches a predetermined amount.

Abstract: A programmable system for controlling the operation of a plunger completion oil or gas production well to optimize production from the well. The controller operates one or more motor valves controlling the well in accordance with programmable values of off-time, on-time and exhaust-time. The controller monitors whether or not a plunger arrival signal is received on each cycle of intermitting the well and changes either the off-time or the exhaust-time for the next cycle in response thereto. In oil well mode, the off-time is decreased slightly for each cycle following a cycle in which plunger arrival occurred and increased slightly for each cycle following one in which it did not. In gas well mode, the exhaust-time is increased slightly for each cycle following a cycle in which plunger arrival occurred before on-time expired and decreased slightly for each cycle following one in which it did not.

Abstract: A controller for gas-oil well installations which is microprocessor driven and compiles a datalog which is accessible locally for operator use. Customized microprocessor control for a given well installation is available on a practical basis by resort to the employment of a program approach utilizing bit-string patterns selected from a relatively large sequence of predefined well installation operational parameters or variables which have been identified. The masking and pattern recognition approach permits the handling of relatively large amounts of data and greatly simplifies the customization of well programming. This programming facility permits remote alteration of programs either by telephonic communication or by networking of a plurality of controllers within a given oil field. The programming feature is complemented by the utilization of a variable opening control over a motor valve.

Abstract: A well testing tool includes a plurality of valves, a plurality of well tool control systems connected, respectively, to the plurality of valves, and an electronics section connected to the plurality of well tool control systems for energizing one of the control systems thereby opening or closing a valve associated with the one control system when the electronics section of the tool detects the existance of an input stimulus transmitted downhole by an operator at the well surface. The operator need only know the particular input stimulus to transmit for a particular valve and need not know how many well tools are disposed downhole or in which tool a particular valve is disposed. The opening or closing of a particular valve is accomplished independantly of any other valves disposed in the tool.

Abstract: A method and apparatus are disclosed to detect periodic well loading by produced accumulated secondary fluids, and accordingly to remove the undesired secondary fluid from the tubing of a hydrocarbon producing well. The method according to the present invention employs a surface control system that controls the operation of the fluid removal cycle, and the production cycle of the hydrocarbon producing well. Periodically, the well is "shut-in" and upper and lower flow control valves, connected at a predetermined depth to the well tubing, are actuated to a closed position to form an accumulation chamber within the tubing. The closed flow control valves block off the fluid in the accumulation chamber formed in the lower portion of the tubing string, which contains the undesired accumulated secondary fluids.

Abstract: A multi-valve well testing system adapted to be disposed downhole in a borehole, includes a plurality of valves and a plurality of well tool control systems connected, respectively, to the plurality of valves and further includes an automatic control mode feature. The well testing system includes a controller board which comprises a microprocessor and a read only memory (ROM). The ROM has encoded therein a set of microcode which, when executed by the microprocessor, causes the various plurality of valves in the well testing system to be opened and closed automatically, without intervention from the operator at the well surface. A kickoff stimulus is required in order to begin execution of the microcode by the microprocessor. This kickoff stimulus could include a sensing, by a pressure transducer, of a predetermined bottom hole pressure, or a sensing, by a strain gauge, of a predetermined set down weight of the well testing system.

Abstract: A method of controlling the recovery of landfill gas from a sanitary landfill and apparatus for performing the method. Landfill gas, which mainly consists of methane and carbon dioxide, is formed by anaerobic decomposition of the organic content of the refuse. This process develops a very small amount of heat. If more gas is drawn from the sanitary landfill than is formed by the anaerobic decomposition, air is drawn into the landfill. The decomposition thereby becomes aerobic, developing large quantities of heat and increasing the content of carbon dioxide and nitrogen in the gas. According to the disclosed method, the temperature of the gas from each gas well is measured, thereby providing information for controlling the flow of gas from the corresponding wells. The apparatus disclosed by the invention comprises a control chamber connected to one or more gas wells on the one hand and to a gas furnace over a gas fan on the other hand.

Abstract: In accordance with illustrative embodiments disclosed herein, a formation testing tool suspended in a well on a pipe string includes a valve actuator control system which responds to a command signal having a certain signature. The command signal is applied at the surface to the well annulus, and includes a series of two or more low level pressure pulses which are detected at the downhole tool, each pressure pulse having, for example, a certain peak value which lasts for a certain time. On detection of the command signal, a control system within the testing tool permits selective application of hydrostatic pressure which forces the valve actuator to shift from one position to another, thereby to open or close an associated valve element.

Abstract: An apparatus for measuring the quantity and flow rate of liquids in a flowing fluid stream containing liquids and gases such as found in oil well production, with an optional controller for oil well pumps to control the pumping period or speed based on pump displacement. Total number of tank fill events provide a precise measurement of total volume. Volumes are accumulated on a time base to determine flow rate and on the basis of strokes to determine pump displacement. Liquid measurement is accomplished without restriction to the flowing stream, even in the event of a valve failure. The filling of each tank with oil of low or high viscosity can be measured by level, hydrostatic pressure, or weight sensors. Measurement of total produced volumes are accumulated with the accuracy and repeatability needed when correlating producing wells with injection wells, and when diagnosing well problems.

Abstract: A method and apparatus of chemically inhibiting corrosion of a borehole and connected flowlines. A mixing tank receives flow from the chemical pump. The mixing device is connected to the borehole. A timer device operates to allow sequential flow to the mixing tank. The treatment fluid admixes with the formation fluid downhole.

Abstract: A method for continuous analysis of mixtures for determining selective properties of components in the mixture flowing along a flow path includes the steps of, firstly, directly measuring and/or calculating the pressure, temperature, density and mass flow rate of the mixture at a first point upstream of a characteristic change zone in the flow path. A change in the characteristics of the mixture flow is caused in the characteristic change zone, and thereafter, the pressure, temperature, density and mass flow rate are measured directly and/or calculated at a second point downstream of a characteristic change zone. Selected properties of the mixture are determined on the basis of the information collected together with known parameters using algorithms.

Abstract: Method and installation for the production of hydrocarbons from a mixture of said hydrocarbons with an aqueous phase by use of a reinjection unit (7), and a separation unit (8) and with regulating the reinjection rate as a function of the content of hydrocarbons (16,15) in the aqueous phase.

Abstract: In accordance with illustrative embodiments disclosed herein, a formation testing tool suspended in a well on a pipe string includes a valve actuator control system which responds to a command signal having a certain signature. The command signal is applied at the surface to the well annulus, and includes a series of two or more low level pressure pulses which are detected at the downhole tool, each pressure pulse having, for example, a certain peak value which lasts for a certain time. On detection of the command signal, a control system within the testing tool permits selective application of hydrostatic pressure which forces the valve actuator to shift from one position to another, thereby to open or close an associated valve element.

Abstract: In a device for separating and extracting components having different densities from an effluent as applicable in particular to the separation of oil and water in crude oil, a single pump has the function of sucking the effluent into a separator and maintaining a pressure of higher value than the highest pressure which is necessary for extraction of one of the components. At least one regulator is provided for regulating the delivery of the lower-density component and at least one regulator is provided for regulating the delivery of the other component.

Abstract: A method and apparatus are disclosed to detect periodic well loading by produced accumulated secondary fluids, and accordingly to remove the undesired secondary fluid from the tubing of a hydrocarbon producing well. The method according to the present invention employs a surface control system that controls the operation of the fluid removal cycle and the production cycle of the hydrocarbon producing well. Periodically, the well is "shut-in" and a flow control valve, connected to the well tubing, is actuated to block fluid flow from the lower portion of the tubing string, which contains the undesired accumulated secondary fluids.

Abstract: An apparatus for automatically dispensing chemicals into the well bore of a hydrocarbon producing well utilizes a double acting cylinder and piston to sequentially operate a plurality of valves associated with the well. The handles of each valve have a spring steel tine secured thereto which engages with a portion of the piston shaft which actuates the operation of each valve.

Abstract: Production of pertroleum deposits in which water is mixed with the hydrocarbons. The quality of separation is controlled by incorporating within a packer (200) a regulated valve (100) which receives the flow of reinjection water after its separation in a unit (7), the water passing into a fluorescence analyzer (4). The results of the measurement are transmitted to a microprocessor unit (12) which produces a signal which actuates a hydraulic pump (9), which in its turn, actuates the valve (100). Separation of water from the hydrocarbons at the bottom of the well and control of the quality of the separation are effected before the reinjection of the water in a subterranean deposit zone (3).

Abstract: A method and apparatus for effecting the gravitational separation of hydrocarbons and water discharged from a production formation of a subterranean well. The well casing is extended downwardly beyond the production zone to a water absorbing zone of the subterranean well. A mixture of hydrocarbons and water flows into the interior of the casing through perforations disposed adjacent the production zone. A fluid collection chamber is provided either exteriorly or interiorly of the casing perforations permitting the hydrocarbons to rise to the top of any water. The water flows downwardly, or is forcibly pumped downwardly to the water absorbing formation and is absorbed in such formation. If the fluid pressure of the formation is not sufficient to force the hydrocarbons to the surface of the well, any conventional pump may be mounted in the well casing to effect the pumping of the separated hydrocarbons to the well surface.

Abstract: An apparatus for controlling and monitoring an electrical motor used to pump petroleum from beneath the surface of the earth. A computerized metering apparatus is used to monitor overload power, underload power, as well as other conditions. When the demand power consumption of the electric motor exceeds or falls below preprogrammed limits, the computer provides an indication of the detected condition. A display panel with a particular combination of display lights is thus controlled by the computer to provide oil well service personnel with an indication of a detected problem, even from a distance. This allows service personnel to monitor the condition of a well without getting out of their service vehicle. Additionally, capability is provided to respond to signals provided from the company supplying electric power in order to control the pumping unit.

Abstract: Apparatus and method for removing fluid from a well. The apparatus is mobile, and includes a power winch mounted on a mobile support means with a cable attached to the winch. A constant tension maintaining unit is connected to the winch to maintain relatively constant tension on the cable while the cable is wound off the power winch into the well, and a swab is mounted on the free end of the cable. The swab is operable to lift the fluid out of the well when the cable is wound back onto the power winch. Also included is a means in fluid connection with the well operable to receive the fluid lifted out of the well by the swab. Also provided is a swab bar for use in removing fluid from a well and a device for effecting a seal with the well head.

Abstract: A system for controlling production in an oil well comprises a first level sensor mounted upon the outer surface of the tubing near the lower end of the tubing and a second level sensor mounted upon the outer surface of the tubing above the first level sensor. The first level sensor is tuned to a first electrical signal frequency. The second level sensor is tuned to a second electrical signal frequency. A control device at spaced intervals transmits electrical signals of the first and second frequencies down the oil well and senses the liquid level by detecting impedance.

Abstract: A system for controlling production in an oil well comprises a first level sensor mounted upon the outer surface of the tubing near the lower end of the tubing and a second level sensor mounted upon the outer surface of the tubing above the first level sensor. The first level sensor is tuned to a first electrical signal frequency. The second level sensor is tuned to a second electrical signal frequency. A control device at spaced intervals transmits electrical signals of the first and second frequencies down the oil well and senses the liquid level by detecting impedance.

Abstract: Apparatus is disclosed for automatically operating a gas and oil producing well of the plunger lift type, including a comparator for comparing casing and tubing pressures, a device for opening the gas delivery valve when the difference between casing and tubing pressure is less than a selected minimum value, a device for closing the gas discharge valve when casing pressure falls below a selected casing bleed value, an arrival sensor switch for initially closing the fluid discharge valve when the plunger reaches the upper end of the tubing, and a device for reopening the fluid discharge valve at the end of a given downtime period in the event that the level of oil in the tubing produces a pressure difference greater than the given minimum differential value, and the casing pressure is greater than lift pressure. The gas discharge valve is closed if the pressure difference exceeds a selected maximum value, or if the casing pressure falls below a selected casing bleed value.