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TECHNICAL FIELD  
       [0001]     This invention relates generally to a plunger lift apparatus and method that includes one or more sensors.  
       BACKGROUND  
       [0002]     To produce hydrocarbons from a subterranean reservoir, one or more wellbores are drilled through the earth formation to the reservoir. Each wellbore is then completed by installing casing or liner sections and by installing production tubing, packers, and other downhole components. For certain types of wells, artificial lift systems are installed to enhance the production of hydrocarbons. One such artificial lift system includes an electrical submersible pump that pumps fluids from a downhole location in a wellbore to the well surface. Another type of artificial lift system is a gas lift system, where pressurized gas (pumped from the surface of the well or from an adjacent wellbore) is used to lift well fluids from a downhole location in the wellbore.  
         [0003]     Yet another type of artificial lift mechanism is a plunger lift production mechanism often used to remove oil or other liquids from gas wells. Gas wells that require swabbing, soaping, blowing down, or stop cocking are candidates for plunger lift production mechanisms. A plunger lift production mechanism typically includes a relatively small cylindrical plunger that travels through tubing extending from a downhole location adjacent a producing reservoir to surface equipment located at the open end of the wellbore. In general, liquids that collect in the wellbore and inhibit the flow of gas out of the reservoir and into the wellbore are collected in the tubing. Periodically, the end of the tubing is opened at the surface and the accumulated reservoir pressure is sufficient to force the plunger up the tubing. The plunger carries with it to the surface a load of accumulated fluids that are ejected out of the top of the well to allow gas to flow more freely from the reservoir into the wellbore and to a distribution system at the well surface. After the flow of gas has again become restricted due to further accumulation of fluids downhole, a valve in the tubing at the well surface is closed so that the plunger falls back down the tubing for lifting another load of fluids to the well surface upon reopening of the valve.  
         [0004]     In plunger lift production mechanisms, there is a requirement for the periodic operation of a motor valve at the wellhead to control the flow of fluids from the well to assist in the production of gas and liquids from the well. Conventionally, a motor valve is controlled by a timing mechanism that is programmed in accordance with principles of reservoir engineering to determine the length of time that the well should either be “shut in” (and restricted from flowing) and a time the well should be “opened” to freely produce. Generally, the criterion used for operation of the motor valve is strictly based on a pre-selected time period. In most cases, parameters such as well pressure, temperature, and so forth, are not available in conventional plunger lift production mechanisms because of the costs associated with intervention to obtain well pressure, temperature, and other information.  
         [0005]     Operation of a motor valve based only on time is often not adequate to control outflow from the well to enhance well production. Proper setting of logic to control the plunger lift production mechanisms usually is based on trial and error, with continued evaluation needed for changing well performance that necessitates well site trips to adjust timing for the control of motor valves.  
       SUMMARY  
       [0006]     In general, according to the invention, a plunger lift production mechanism includes a plunger having one or more sensors to measure well parameters to enable operation of the plunger lift production mechanism based on the measured well parameters. For example, a plunger lift apparatus includes wellhead equipment containing a receiver, a conduit extending from the wellhead equipment into a wellbore, and a plunger adapted to be run through the conduit to a downhole location in the wellbore. The plunger includes at least a sensor to measure a downhole parameter, where the plunger is adapted to communicate the measured downhole parameter to the receiver.  
         [0007]     Other or alternative features will become apparent from the following description, from the drawings, and from the claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]      FIG. 1  illustrates well equipment that includes a plunger lift production mechanism according to an embodiment.  
         [0009]      FIGS. 2A-2E  illustrate an example operation of the plunger lift production mechanism according to an embodiment.  
         [0010]      FIG. 3  is a block diagram of components of a plunger and a receiver in the plunger lift production mechanism of  FIG. 1 . 
     
    
     DETAILED DESCRIPTION  
       [0011]     In the following description, numerous details are set forth to provide an understanding of the present invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these details and that numerous variations or modifications from the described embodiments are possible.  
         [0012]     As used here, the terms “up” and “down”; “upper” and “lower”; “upwardly” and “downwardly”; “upstream” and “downstream”; “above” and “below” and other like terms indicating relative positions above or below a given point or element are used in this description to more clearly describe some embodiments of the invention. However, when applied to equipment and methods for use in wells that are deviated or horizontal, such terms may refer to a left to right, right to left, or other relationship as appropriate.  
         [0013]      FIG. 1  illustrates equipment associated with a well that includes a plunger lift production mechanism  100 , wellhead equipment  102 , an electronic controller  104 , and a motor valve  106 . A wellbore  108  is lined with casing or liner  110 , with perforations  112  formed at a wellbore interval to enable the communication of wellbore fluids with surrounding formation. A tubing  114  extends from the wellhead equipment  102  to the wellbore interval adjacent the perforated region of the casing and formation. A tubing stop  116  is located at the bottom portion of the tubing  114 , with the tubing stop  116  including a bleed valve. Above the tubing stop  116  is a bumper spring  118  that is used for receiving a traveling plunger  120  (a plunger that travels between a downhole location and the well surface). The bumper spring  118  includes a spring that absorbs shock when the plunger  120  is dropped onto the bumper spring  118 .  
         [0014]     The wellhead equipment  102  includes a lubricator  122 , and a master valve  124  for shutting in the wellbore during insertion of intervention equipment through the lubricator  122 . Also, a catch  126  is provided between the master valve  124  and the lubricator  122 . The catch  126  includes a receiver  128  to receive the plunger  120 . The receiver in the catch  126  provides both a physical (mechanical) and electrical connection to the plunger  120 . The electrical connection enables electrical communication (of power and signaling) over a cable  129  with the electronic controller  104 . In addition, the receiver  128  in the catch  126  has a telemetry element to enable wired or wireless communication with the plunger  120 . Wireless communications may include electromagnetic, radio frequency (RF), infrared, inductive coupler, pressure pulse, or other forms of wireless communications. RF and inductive coupler communications between the receiver  128  and plunger  120  may be most efficient.  
         [0015]     The electronic controller  104  is connected over a link  130  to the motor valve  106 . The electronic controller  104  controls the motor valve  106  to determine when the motor valve  106  is to be opened or closed. When opened, the motor valve  106  enables flow of well fluids, such as gas, out of the wellbore through pipe  136 . Although referred to as a “motor valve,” other types of valves or flow control devices can be used in other embodiments.  
         [0016]     In accordance with some embodiments of the invention, the plunger  120  includes one or more sensors  132 ,  134  that are used for measuring characteristics associated with the wellbore and surrounding formation. As used here, the term “plunger” refers to any moveable element that is capable of traveling through at least a portion of the wellbore. The sensors  132 ,  134  communicate through a telemetry element  236  with the corresponding telemetry element in the receiver  128  of the catch  126 . As noted above, such communication includes wireless or wired communications. The measured characteristics are communicated from the sensors  132 ,  134  through the receiver  128  to the electronic controller  104 .  
         [0017]     Examples of measured characteristics include pressure, temperature, other well characteristics such as fluid flow rate, fluid density, formation characteristics such as formation pressure, formation resistivity, and other downhole characteristics. More generally, the sensors measure downhole parameters. The provision of sensors  132 ,  134  allows the electronic controller  104  to determine when the motor valve  106  should be opened or closed. In addition to timing criterion programmed into the electronic controller  104 , the electronic controller  104  takes into account data from the sensors  132 ,  134  to control opening and closing of the motor valve  106 . The sensors  132 ,  134  are powered by a power source, such as a battery.  
         [0018]     By being able to monitor downhole environment information (information pertaining to well characteristics, formation or reservoir characteristics, and/or other downhole parameters) using the sensors  132 ,  134 , the electronic controller  104  is able to automatically adjust the operation of the plunger lift production mechanism, thus eliminating manual intervention by the well operator for determining when the motor valve  106  needs to be opened or closed. Consequently, trial-and-error approaches to plunger lift control can be avoided or reduced. For example, motor valve  106  can be controlled to lift the plunger  120  or allow the plunger  120  to drop back into the wellbore in response to preset pressure thresholds as measured by the sensor  132  or  134  in the plunger  120 .  
         [0019]     Additionally, the electronic controller  104  is configured to communicate measurement data (from the sensors  132 ,  134 ) over a network  140  (wired and/or wireless network) to a remote node  142 . The electronic controller  104  is also able to communicate operational information regarding operation of the plunger lift production mechanism  100  to the remote node  140 .  
         [0020]     Measured downhole parameters can also be communicated to the remote node  142 , or processed locally at the wellsite, to evaluate the reservoir and field associated with the wellbore. For example, the measured downhole parameters can be compared to historical information of the reservoir or surrounding reservoirs. The sensors provided in the traveling plunger  120  enable acquisition of the downhole parameters without the use of an expensive or highly sophisticated telemetry system. Integrating the sensors  132 ,  134  into the plunger lift production mechanism allows well monitoring to be provided as an integral part of the relatively low cost plunger lift production mechanism without additional wellbore infrastructure. Consequently, administrative and production costs related to well production supervision can be reduced.  
         [0021]     Alternatively, the telemetry element  236  can communicate wirelessly with the receiver  128  (as the wellhead) from a remote location, such as a remote location in the wellbore. To enable long distance wireless communication, the plunger  120  can be fitted with a larger capacity power source, such as a high-capacity battery.  
         [0022]     In an alternative embodiment, instead of providing a sensor in the plunger, a sensor (or sensors)  135  can be positioned in a stationary location downhole in the wellbore (such as proximate the bumper string  118 ). In this alternative embodiment, the traveling plunger acts as a telemetry device to communicate the information from the downhole stationary sensor  135  to the surface receiver  128 . The traveling plunger can download information from the downhole stationary sensor  135  to a storage  133  ( FIG. 3 ) in the plunger when the plunger is positioned downhole proximate this sensor  135 . The communication between the plunger and the sensor can be wired communication or wireless communication (e.g., electromagnetic, inductive coupler, etc.). The stored information (in the storage  133  of the sensor) is carried by the plunger to the surface, where the stored information is communicated through the receiver  128  to the controller  104 .  
         [0023]      FIGS. 2A-2E  illustrate an example operation of the plunger lift production mechanism under control of the electronic controller  104 . Initially, as illustrated in  FIG. 2A , the well is closed (the motor valve  106  is closed). Pressure in the wellbore builds (as a result of gas from the surrounding reservoir entering the wellbore through perforations  112  of  FIG. 1 ), with a liquid column  202  building above the plunger  120  that is located at the bottom of the tubing  114 . Note that the plunger  120  is sitting on the bumper spring  118  ( FIG. 1 ).  
         [0024]     Next, as depicted in  FIG. 2B , the motor valve  106  is opened by the electronic controller  104 , which allows the built-up pressure in the wellbore to move the plunger  120  (and the liquid column  202 ) upwardly towards the wellhead equipment. The decision to open the motor valve  106  can be based on a timing criterion and/or measured downhole parameters (either parameters measured previously or in real time). As depicted in  FIG. 2B , gas flow  204  is provided underneath the plunger  120  to move the plunger  120  upwardly. When the plunger  120  is received in the catch  126  ( FIG. 1 ), as depicted in  FIG. 2C , the gas flow is allowed to pass by the plunger  120  and through the conduit  136  (with the motor valve  106  still open). As depicted in  FIG. 2D , as liquids accumulate in the wellbore, the velocity of gas flow drops. Upon detection of the reduced gas flow, the electronic controller  104  shuts the motor valve  106 . Once the motor valve  106  is shut, the plunger  120  is allowed to drop toward the accumulated liquid column  206  at the bottom of the tubing  114 , as depicted in  FIG. 2E . The plunger  120  drops to the bottom of the tubing  114  to the position depicted in  FIG. 2A . The process of  FIGS. 2A-2E  is then repeated.  
         [0025]     As depicted in  FIG. 3 , the components of the plunger  120  and the receiver  128  are depicted in greater detail. The plunger  120  includes the sensors  132 ,  134 . Note that the plunger  120  can include less than or more than the two sensors  132 ,  134  depicted in  FIG. 3 . The sensors  132 ,  134  are powered by a power source  202 , which can be a battery, a capacitor, or a combination of a battery and capacitor. Other power sources can also be used in other embodiments. The sensors  132 ,  134  are coupled to the telemetry element  236 . Also, at the upper end of the plunger  120  is a connector  204  for connection to a mating connector  206  in the receiver  128 . The connectors  204 ,  206  enable electrical connection between the plunger  120  and the receiver  128  to allow wired electrical communication. Also, the electrical connection enables the receiver  128  to charge the power source  202  in the plunger  120 .  
         [0026]     Alternatively, instead of a wired connection between connectors  204  and  206 , the telemetry element  236  is capable of wireless communications, such as electromagnetic communications, RF communications, inductively-coupled communications, infrared communications, pressure pulse communications, and so forth. The telemetry element  236  can, for example, communicate wirelessly with a telemetry element  208  in the receiver  128 . Thus, the telemetry elements  236 ,  208  can be electromagnetic telemetry units (for communicating electromagnetic signals), radio frequency telemetry units (for communicating radio frequency signals), inductively coupled telemetry units, infrared telemetry units (for communicating infrared signals), or pressure pulse telemetry units (to communicate pressure pulse signals).  
         [0027]     The telemetry element  208  is connected to an interface  210  in the receiver  128 . The interface  210  communicates over the cable  129  with the electronic controller  104 . The electronic controller  104  includes a central processing unit (CPU)  212  and an associated storage  214 . Software modules in the electronic controller  104  are executable on the CPU  212 . Such software modules  216  include software modules to receive and process measurement information from the sensors  132 ,  134 . The software modules  216  also are capable of communicating with the remote node  142  ( FIG. 1 ) to communicate measurement information, as well as other operational information associated with the plunger lift production mechanism. The software modules  216  can also include software to process information gathered from the sensors  132 ,  134  to monitor the performance of the wellbore as well as to control operation of the plunger lift production mechanism. For example, one such software module can be programmed with timing intervals at which the plunger mechanism should be cycled between its well surface position and downhole position, taking into account the downhole parameters measured from the sensors  132 ,  134 .  
         [0028]     The software modules  216  can also evaluate performance of the plunger lift production mechanism based on the measured downhole parameters associated with the wellbore, field, and reservoir. The cycling of the plunger  120  can be adjusted based on the evaluated performance.  
         [0029]     The plunger  120  can also be configured to include pressurized gas that is bled off by a low power relief valve while at the well surface lubricator. When the monitored wellbore pressure crosses a predetermined threshold, the pressurized gas can be bled off to cause the plunger  120  to be able to drop back into the wellbore.  
         [0030]     Also, maintenance of the plunger lift production mechanism can be optimized and better scheduled by enabling remote monitoring at the remote node  142 .  
         [0031]     Instructions of such software routines or modules are stored on one or more storage devices in the corresponding systems and loaded for execution on corresponding processors. The processors include microprocessors, microcontrollers, processor modules or subsystems (including one or more microprocessors or microcontrollers), or other control or computing devices. As used here, a “controller” refers to hardware, software, or a combination thereof. A “controller” can refer to a single component or to plural components (whether software or hardware).  
         [0032]     Data and instructions (of the software) are stored in respective storage devices, which are implemented as one or more machine-readable storage media. The storage media include different forms of memory including semiconductor memory devices such as dynamic or static random access memories (DRAMs or SRAMs), erasable and programmable read-only memories (EPROMs), electrically erasable and programmable read-only memories (EEPROMs) and flash memories; magnetic disks such as fixed, floppy and removable disks; other magnetic media including tape; and optical media such as compact disks (CDs) or digital video disks (DVDs).  
         [0033]     While the invention has been disclosed with respect to a limited number of embodiments, those skilled in the art will appreciate numerous modifications and variations there from. It is intended that the appended claims cover such modifications and variations as fall within the true spirit and scope of the invention.

Summary:
A plunger lift apparatus includes wellhead equipment containing a receiver, a conduit extending from the wellhead equipment into a wellbore, and a plunger to be run through the conduit to a downhole location in the wellbore. The plunger includes at least a sensor to measure a downhole parameter, and a plunger is adapted to communicate the measured downhole parameter to the receiver.