Patent Publication Number: US-7219723-B2

Title: Integrated control system for beam pump systems

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application is a continuation of U.S. patent application Ser. No. 10/350,157, filed on Jan. 23, 2003 now U.S Pat. No. 7,032,569, which application is herein incorporated by reference in its entirety. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   Aspects of the present invention generally relate to apparatus and methods of operating a rod-pumped well. Particularly, aspects of the present invention relate to an apparatus for controlling the operation of a rod-pumped well where the apparatus is mounted on a walking beam (or structural member) of a pumping system. More particularly, aspects of the present invention relates to an integrated control apparatus for operating a pumping system and measuring strain on the polished rod. 
   2. Description of the Related Art 
   Oil well rod pumping systems sometimes require a method to accurately determine the weight of the fluid in the production tubing during operation. This information is primarily required on wells that “pump-off”, that is wells that do not produce enough fluid to permit them to be pumped continuously. When a well has been pumped off and there is insufficient fluid present in the wellbore at the pump intake, the pump is said to be undergoing “partial filling.” Partial filling is an undesirable condition because it lessons the overall efficiency of the pumping system and may cause system failures over the operating life of the producing well. 
   Generally, partial filling causes fluid pounding, which can be damaging to various components of the pumping system. Fluid pound is typically caused by the pump not completely filling with fluid on the upstroke. As the downstroke begins, the entire fluid and rod string load moves down through a void until the plunger hits the fluid level in the pump barrel. When the traveling valve opens, the load is suddenly transferred to the tubing, thereby causing a sharp decrease in load. As a result, a shock wave transmits through the pumping system. The shock wave produced may damage the components of the pumping system. 
   To reduce the occurrence of partial filling, and to produce a well at or near maximum efficiency, a pump off control system is typically used on these wells. A pump-off control system generally includes a controller, a sensor for detecting the weight of the fluid in the production tubing during operation of the pumping system, and a device for measuring the position of the pumping system over each cycle of stroke. Examples of the load measurement devices employed for pump off control include use of load cell based technology installed on the pumping rod or mounted on the walking beam. Generally, these devices interface with the controller to produce information for well analysis. Analysis of this information will provide data relating to the amount of fluid in the wellbore and the accurate detection of fluid pound. The control system will shut the pump down when it determines that the wellbore is partially full or empty, thereby avoiding excess wear on the pumping equipment and also saving energy. The pump-off control system also protects the pumping system in the event of a critical malfunction in the sucker rod string or drive train. The system is turned off when such malfunctions are detected. 
   A device for measuring strain in the polished rod of a rod-pumped well unit is disclosed in U.S. Pat. No. 3,965,736 issued to Welten, et al. Welten discloses a system utilizing a strain-gage transducer welded to the top flange of the walking beam of an oil well pumping unit. The sensor is welded to the walking beam in order to achieve maximum sensitivity. A cable is used to connect the system to a controller. 
   More recently, a strain measuring device utilizing an integral clamp-on mechanism is attached to the load-bearing surface of the walking beam or any convenient location as disclosed in U.S. Pat. No. 5,423,224 issued to Paine, which is herein incorporated by reference. This device eliminates the requirement for welding of the load measurement device to the walking beam, thereby allowing for easier installation and maintenance of the device. However, this device, as with the Welten system, requires a cable to connect the transducer to the controller. In  FIG. 1 , a pump off control system, according to Paine, includes a strain measuring device  1  attached to the walking beam  2  of the pumping system  3 . Information from the device  1  is relayed via cable  4  to the controller  6 . After processing the information, the controller  6  sends signals to the motor control panel  5  to operate the pumping system  3 . 
   Although the pump off control system shown in  FIG. 1  is widely utilized, the pump off control system is difficult to install and maintain. For instance, to install the pump-off control system on an existing pumping system, a controller must be installed near the pumping unit, which, in most cases requires trenching, a pole to mount the controller, and cement to hold this structure in place. In addition, cables must be used to connect the various components of the system to relay information. To accommodate the landscape, the installation of the pump-off control system may be different each time, thereby requiring modification of the installation materials and procedure. Typical installation times per system may exceed several hours and require personnel of varied skill levels. Also, several key areas of this pump off control system require on-going maintenance, such as the cable interconnecting system. Further, the pump off control system may be susceptible to failure due to wear of the cables and the normal maintenance process for the pumping system. 
   There is a need, therefore, for a pump off control system that offers less complexity to install and that can be easily maintained. There is a further need for a pump-off control unit having an integrated controller and a pump rod load measuring device. Further still, there is a need for a pump-off control unit having an integrated controller and a pump rod load measuring device that transmits a control signal using a cable-less communications system. 
   SUMMARY OF THE INVENTION 
   The present invention generally provides apparatus and methods of controlling the operation of a well pumping system. The pump control apparatus includes a first sensor for measuring strain on a structure of the well pumping system and a second sensor for measuring a position of the structure. The apparatus also has a controller configured to control the well unit by receiving output signals from the first and second sensors and generating control signals according to a motor control sequence. The control signals may be transmitted to a motor control panel using a cable-less communications system. 
   In another aspect, the load measurement sensor, position measurement sensor, and the controller unit of the pump control apparatus may be integrated into a single unit. The pump control apparatus may further includes clamp members for selective attachment to a structure of the pumping system. In one embodiment, the pump control apparatus has a self-sustaining power supply. 
   In another aspect still, a method of operating a pumping system includes measuring a strain on a structure of the pumping system. The measured strain may used to generate a control signal to operate the pumping system. The control signal is transmitted to a motor control apparatus using a cable-less communications system. In one embodiment, the method may further include measuring a position of the structure of the pumping system. The measured position of the structure may be correlated with the measured strain to generate a control signal. 
   In yet another aspect, a method of operating a pumping system includes installing an integrated control unit on a structure of the pumping system. The integrated control unit is equipped with a controller and a first sensor for measuring strain. A strain measured on the structure is used to generate a control signal. The control signal may be transmitted to a motor control apparatus to operate the pumping system. 
   In yet another aspect, a cable-less communications system is mounted to a structure of a pumping system for transmitting control and diagnostic data. 
   In yet another aspect, an energy storage cell having a solar voltaic panel is mounted to a structure of a pumping system. 
   In yet another aspect, a pump control apparatus for operating a pumping system includes a sensor for measuring strain on a structure of a well unit, the sensor having a cable-less communications system. The pump control apparatus also has a controller configured to control the well unit by receiving an output signal from the sensor and generating one or more control signals according to a motor control sequence. In one embodiment, the output signal from the sensor is transmitted to the controller using a cable-less communications system. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
       FIG. 1  shows a prior art pump off control unit. 
       FIG. 2  shows one embodiment of a pump-off control system mounted on a pumping system according to aspects of the present invention. 
       FIG. 3  is shows a strain-measuring apparatus usable with the aspects of the present invention. 
       FIG. 4  is an exploded view of a portion of the strain-measuring apparatus shown in  FIG. 3 . 
       FIG. 5  is a diagrammatic view illustrating the manner of interconnection of the strain gauges. 
       FIG. 6  is a block diagram of the various components of an embodiment of the control unit of the present invention. 
       FIG. 7  is a flow chart of a method of operating of the pump off control system according to aspects of the present invention. 
       FIG. 8  illustrates another embodiment of a pump-off control system mounted on a pumping system according to aspects of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 2  shows an embodiment of the pump-off control unit  200  of the present invention installed on a rod pumped well unit  100 . The rod pumped well unit  100  is one that is commonly used to produce oil from a subterranean formation. The well unit  100  includes a walking beam  110  operatively connected to one or more posts  120 . Attached to one end of the walking beam  110  is a horse head  125  operatively connected to a polished rod  130 . A rod string (not shown) is connected below the polished rod  130  and is connected to a down-hole pump (not shown). The pumping system  135  is operated by a motor control panel  140  and powered by a motor  145 . 
   In one aspect, the pump off control unit  200  is an integrated control unit capable of measuring the strain on the polished rod  130  and controlling the pumping system  135  based on the strain measured. The integrated control unit  200  may include a strain-measuring apparatus  210  integrated with electronic components for monitoring and controlling the pumping system  135 . Preferably, the strain measuring apparatus  210  and the electronic components are at least partially housed together in an enclosure  202 . The control unit  200  may further include means for attaching the control unit  200  to the well unit  100 . The strain-measuring apparatus  210  may be selected from a variety of strain-measuring apparatus known to a person of ordinary skill in the art. 
   In one embodiment, the strain-measuring apparatus  210  comprises two main components, one being a deflection collector base assembly generally designated in  FIG. 3  by the numeral  12  and a sensor member  40  for sensing deflection in a flexure area  16  of a base member  14  which forms a part of the deflection collector base assembly  12 . Base member  14  defines an elongated, bar-like member having first and second ends  14   a ,  14   b  and an intermediate portion  14   c . Forming a part of intermediate portion  14   c  of the base member  14  is a first flexure area  16 . The first flexure area  16  is located between two longitudinally, spaced-apart slots  18 ,  20 . Slot  18  extends downwardly from the top surface  14   d  of the base member  14  while slot  20  extends upwardly from lower surface  14   e  of the base member  14 . 
   Proximate the first and second ends  14   a ,  14   b  of the base member  14  are clamping means for clamping the deflection collector base  12  to a structural beam of the dynamic load-bearing structure such as the walking beam  110  of a rod pumped well unit  100 . In one embodiment, the clamping means includes first and second clamping members  21 ,  22 . The clamping members  21 ,  22  are interconnected with ends  14   a ,  14   b , respectively. Each of the clamping members  21 ,  22  includes first and second spaced apart jaws  24 ,  26 . Each jaw  24 ,  26  is provided with a multiplicity of gripping protuberances or teeth  28 . Each of the jaws  24 ,  26 , is further provided with a threaded aperture  30  which is adapted to threadably receive a threaded bolt  32  for urging the structural beam  110  into clamping engagement with teeth  28  of the jaws  24 ,  26 . 
   As illustrated in  FIG. 3 , the intermediate portion  14   c  of the base member  14  is also provided with a second flexure area  34 , which comprises a thin wall  36  that is disposed between first and second cutout portions  38 ,  39  formed in side walls  14   f ,  14   g  of the base member  14 . The thin wall  36  preferably moves approximately 0.005 inches per pound across the wall  36 . This permits bending of base member  14  in the second flexure area  34  instead of the first flexure area  16 . This feature helps to prevent the sensor member  40  from mechanical overload and makes the first bending flexure area  16  primarily sensitive to tension and compression forces rather than to bending forces. 
   Turning now to  FIG. 4 , the sensing member  40 , in one embodiment, may include a sensor base  41 , which is preferably formed from a section of stainless steel plate. The sensor base  41  is provided with a plurality of cutout portions that define a plurality of thin wall areas on which foil strain gauges are affixed in a manner now to be described. 
   As shown in  FIG. 4 , the sensor base  41  is provided with a central aperture  42  and a pair of apertures  44 ,  46  that are located on either side of central aperture  42 . Provided in the top and bottom walls  41   a ,  41   b  of the base  41  are semi-circular, cutout portions  48 ,  50 . These cutout portions  48 ,  50  form in conjunction with the central aperture  42  first and second thin-wall portions  52 ,  54 . Formed between apertures  44 ,  46  and central aperture  42  are third and fourth thin-wall portions  56 ,  58 . The strain gauge sensors  60 ,  62 ,  64 ,  66 , as will be described below, may be interconnected with the sensor base  41  in these thin-wall areas  52 ,  54 ,  56 ,  58 . 
   In one embodiment, a first sensor  60  is affixed proximate the first thin-wall portion  52 , and a second sensor  62  is affixed proximate the second thin-wall portion  54 . Similarly, a third sensor  64  is affixed proximate the third thin-wall portion  56 , and a fourth sensor  66  is affixed proximate the fourth thin-wall  58 . The sensors  60 ,  62 ,  64 ,  66  are bonded to the respective thin-wall portions  52 ,  54 ,  56 ,  58  of the sensor base  41  with an appropriate adhesive, such as an epoxy glue, and are heat cured in position. Each of the sensors  60 ,  62 ,  64 ,  66  may include a foil strain gauge of a character readily commercially available and known to a person of ordinary skill in the art. In one example, the foil strain gauges may be made of platinum, tungsten/nickel, or chromium, as is readily commercially available from Muse Measurements of San Dimas, Calif. Preferably, the sensors  60 ,  62 ,  64 ,  68  are wired in a typical Wheatstone bridge configuration  71  as shown in  FIG. 5 . Thin-wall portions  52 ,  54 ,  56 ,  58  respond to tension and compression loading across their length. The load varies depending upon the deflection transmitted from the structure  110  through base member  14  to the sensors  60 ,  62 ,  64 ,  66 . The range of force needed to deflect the sensor for a typical application is between zero and approximately fifty (50) pounds. Signal output and deflection is approximately 0.00025 inches of deflection equaling 0.10 MV/V. It is to be understood that for certain applications, semi-conductor gauges may be used in place of the foil strain gauges. Additionally, the sensor itself may be affixed by any suitable means such as welding or by the use of mechanical fasteners if clamping is for any reason undesirable. 
   The control unit  200  may include a position measurement device  250  for measuring the position of the walking beam  110  relative to the top or bottom of the stroke, as schematically shown in  FIG. 2 . In this respect, the output from the strain measuring apparatus  210  may be correlated to the position of the polished rod  130  and used to determine strain experienced by the polished rod  130  during the stroke cycle. In one embodiment, the position measurement device  250  is a dual position sensor, which is a dual axis accelerator based position sensor. The dual position sensor combines a means of producing a continuous position measurement and a discrete switch output, which closes and opens at preset positions of the polished rod  130 , into one device. The position measurement device  250  also provides means of filtering data in order to increase accuracy of the position measurement, thereby contributing to the overall accuracy of the control unit  200 . 
   Referring to  FIG. 6 , outputs from the strain measuring apparatus  210  and the position measurement device  250  are ultimately processed by a controller  220  programmed to perform a motor control sequence. Initially, the outputs are transmitted to a signal conditioning circuit  230  to condition the signals into a signal suitable for processing by an analog-to-digital (A/D) converter  240 . For example, low-level signal from the sensors  210 ,  250  may be conditioned into a higher-level analog signal before being transmitted to the A/D converter  240 . Thereafter, the converted signals are transmitted to the controller  220 . 
   The controller  220  may include internal or external memory, which may be any suitable type. For example, the memory may be a battery-backed volatile memory or a non-volatile memory, such as a one-time programmable memory or a flash memory. Further, the memory may be any combination of suitable external and internal memories. 
   In one embodiment, the control unit  200  may include a program memory  260  and a data memory  270 . The program memory  260  may store a motor control sequence and the data memory  270  may store a data log. The data log may store data read from the strain sensors  210  and the position sensor  250 . The motor control sequence may be stored in any data format suitable for execution by the controller  220 . For example, the motor control sequence may be stored as executable program instructions. Although  FIG. 6  shows these components as being separate, it must be noted that any or all of these components may be integrated or embedded into one component as is known to a person of ordinary skill in the art. 
   The control unit  200  may also include a power system for operating the control unit  200  itself. The power system may include a power controller  281 , power supply  282 , and a power transducer  283 , as is known to a person of ordinary skill in the art. Power may be supplied through a battery  284  or a battery charger. In one embodiment, the control unit  200  has a battery charger  205  for collecting power from a solar panel attached to the walking beam  110  as illustrated in  FIG. 2 . For example, the battery charger  205  may comprise an energy storage cell having a solar voltaic panel and any other energy cell known to a person of ordinary skill in the art. 
   In another aspect, the control unit  200  may further include a serial data communications port  290  and any suitable communications subsystem and transducer  295  for communicating with other control elements. In one embodiment as shown in  FIG. 2 , a radio unit  311  having an antenna  321  is provided for remote communication with a control element such as the motor control panel  140 . In another embodiment, the antenna  321  may be embedded into the controller  220  when a non-conductive enclosure  202 , such as a fiberglass enclosure, is used. It is contemplated that these components include any suitable communication ports, antenna, and radio unit known to a person of ordinary skill in the art. 
   Outputs generated from the controller  220  in accordance with the motor control sequence are transmitted to the motor control panel  140 , using a cable-less communications system, for controlling the operations of the pump unit  135 . In one embodiment, the motor control panel  140  may include a radio unit  312  having an antenna  322  for receiving signals from the radio unit  311  of the control unit  200 . Preferably, the radio units  311 ,  312  are configured to operate with spread spectrum technology. In another embodiment, the signal from the control unit  200  may be transmitted to the motor control panel  140  using a cable. The motor control panel  140  may be equipped with one or more motor control relay assemblies to facilitate transmission of the control signals to operate the pumping system  135 . By integrating the strain sensors  210  and the position device  250  with the controller  220  for control and optimization of the pump system  135 , aspects of the present invention provide a control unit  200  that significantly eliminates the cabling between the major control elements, thereby minimizing the maintenance requirements of the control unit  200  and vastly simplifying the installation of the control system. 
     FIG. 7  is a flow diagram illustrating exemplary operations of a method according to an embodiment of the present invention.  FIG. 7  may be described with reference to the exemplary embodiment of  FIG. 6 . However, it will be appreciated that the exemplary operations of  FIG. 7  may be performed by embodiments other than that illustrated in  FIG. 6 . Similarly, the exemplary embodiment of  FIG. 6  is capable of performing operations other than those illustrated in  FIG. 7 . 
   The method begins with installing the integrated control unit on the walking beam of the rod pumped well unit, as indicated by step  7 - 1 . During operations, strain on the walking beam is measured using the strain-measuring apparatus, step  7 - 2 . The strain is measured with respect to the position of the walking beam as determined by the position measurement device, step  7 - 3 . The two outputs are transmitted to the controller, which generates one or more control signals in response to the measured outputs, step  7 - 4 . The control signals are then transmitted to the motor control panel for controlling the well pumping system  7 - 5 . Preferably, the control signals are transmitted using a cable-less communications system equipped with an antenna. In this manner, the pumping system may be controlled without the need of cables to relay signals between the control unit and the motor control panel. Further, integration of the components of the control system streamlines the installation procedure by eliminating the separate installation of the control system components as required by a conventional method. 
   In another aspect, the strain measuring apparatus  210  may be separate from the control unit  200  as illustrated in  FIG. 8 . In this embodiment, the strain measuring apparatus  210  may include strain gauges  211  and a cable-less communication unit  212   a  for communicating with the control unit  200 . The strain gauges  211  may be attached to the polishing rod  130  to measure the strain experienced by the polishing rod  130 . The measured strain may be transmitted to the communication unit  212   a  to relay the information to the control unit  200  for processing. The control unit  200  may include a receiver unit  212   b  to receive the information from the strain measuring apparatus  210 . Accordingly, it is not necessary to attach the control unit  200  to the walking beam  110 . Instead, the control unit  200  may be attached to or integrated with the motor control panel  140  and still receive outputs from the strain measuring apparatus  210 . It must be noted that the cable-less communication units  212   a ,  212   b  may include any suitable communication ports, antenna, and radio unit, as is known to a person of ordinary skill in the art. 
   In another aspect still, the position measuring device  250  may also be separate from the control unit  200 . As shown in  FIG. 8 , the position measuring device  250  is attached to the walking beam  110  and may include position sensors and a cable-less communication unit. The position sensors measure the position of the walking beam  110  and relay the information to the control unit  200  via the cable-less communication unit. 
   While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.