Pumpjack dynamometer and method

Details Pumpjack dynamometer and method Pumpjack dynamometer and method

2000-12-22

2002-06-25

Walberg, Teresa (Department: 3742)

Pumps

Condition responsive control of pump drive motor

Single motor control element responsive to means sensing...

C417S012000

Reexamination Certificate

active

06409476

ABSTRACT:

1. FIELD OF THE INVENTION
The present invention generally relates to pumpjack dynamometers and, more particularly, to apparatus and methods for producing and transmitting dynamometer card information.
2. BACKGROUND OF THE INVENTION
Dynamometers are commonly utilized in the oil field to monitor the operation of pumpjacks used to pump oil to the surface. The dynamometer card provides information related to pumping conditions as described in detail in subsequently listed patents. For instance, a typical use of such information involves determining when a well has reached what is known as a “pump-off” condition wherein the wellbore does not receive enough oil to fill the downhole pump during the entire pump stroke. Changes in the dynamometer card readings over time may be used to provide this information. It may be desirable to temporarily stop operating the pump until the pump off condition has been obviated by continued flow from the formation into the wellbore while the pump is shut down. Pump-off control techniques are known to improve field development efficiency and reduce maintenance costs.
Changes in the dynamometer card readings over time is one of the more important uses of dynamometer card information. Consistency over time in the way measurements are taken is important for this use of dynamometer card information. Consistency requires that calibrations remain constant and do not change over time, as has been a problem with many prior art devices. It would be desirable to have a sensor that does not require time consuming initial calibration procedures, that automatically calibrates itself, and that continuously re-calibrates itself so that one can be assured that changes in dynamometer card information over time are due to changes in the well rather than changes in the calibrations.
Various sensors are provided in the prior art for determining the position of the walking beam of the pumpjack. Potentiometers, reed switches, and other types of switches have been used in the past in order to supply signals indicative of the position of the walking beam. The problem with such position sensing devices is that they are usually subject to wear, require careful initial calibration, require maintenance including regular re-calibrations, and may not always provide accurate or reliable information. Hydrogen sulfide gas is often present in the vicinity of the pump jack, and that gas adversely affects the reliability of much of this sensing equipment. Well personnel working on the pumpjack may inadvertently loosen or change components in such a way that calibrations are affected. Prior art equipment for sensing the position of a walking beam is frequently mounted on the walking beam at a location where it is highly susceptible to weather conditions such as variable temperature, and may have reduced reliability due to temperature drift errors. Minor irregularities or mechanical jitters in movement of the walking beam may also cause spurious or repeatable errors.
As the dynamometer data is produced, various means are used to collect and use the data, some of which require expensive sensors, some of which may be less reliable over time, and some of which may require significant maintenance for calibration requirements. It would be desirable to provide methods for sampling dynamometer card information that may be used to monitor well conditions over time at less cost with improved reliability.
Once data is collected, radio transmitters have been used in the past to transmit the data to another location. However in some areas, use of radio transmitters is not allowed. Where radio transmitters are allowed, it is often difficult to obtain additional channels for transmission. As well, FCC rules must be followed and may require radio transmitters to be installed according to certain specifications that may limit their usefulness for some purposes. Infrared transmitters have limited usefulness in sunlight due to ambient infrared noise that results in a short transmission distance if operation is possible at all. As well, infrared transmitters have limited selectivity and would have problems for use with closely spaced wells where multiple transmissions may occur.
The following patents discuss the aforementioned background and problems in some depth along with previous solutions to the many problems encountered in this area:
U.S. Pat. No. 4,363,605, issued Dec. 14, 1982, to Manuel D. Mills, discloses an apparatus for generating an electrical signal which is proportional to the tension in a bridle that supports a string of sucker rod associated with a pumpjack unit.
U.S. Pat. No. 5,458,466, issued Oct. 17, 1995, to Manuel D. Mills, discloses an apparatus and method for minimizing fluid pounding in a pumpjack by dictating the length of the run cycles of the pumpjack.
U.S. Pat. No. 4,631,954, issued Dec. 30, 1986, to Manuel D. Mills, discloses an improved pump control having a device for measuring relative movement between structural components of a pumpjack, and converting the movement into a signal which varies according to the magnitude of the movement.
U.S. Pat. No. 4,873,635, issued Oct. 10, 1989, to Manuel D. Mills, discloses a pump off control device for controlling a pumpjack unit. The device measures the length of time required for the pump to down-stroke successive numbers of times. When the time differential reaches a predetermined value, the well is shut in for a time interval.
U.S. Pat. No. 4,492,029, issued Jan. 8, 1985, to Tanaka et al., discloses an inclinometer comprising a sector weight pivotally supported on a main body, which may become inclined. The weight is relatively rotatable with respect to the main body and constantly hanging vertically due to gravity regardless of an inclination of the main body. A code part and a detecting part produces a detection output based on the predetermined code according to the inclination of the angle of the body.
U.S. Pat. No. 4,584,778, issued Apr. 19, 1986, to Komasaku et al., discloses an angle change indicator comprising a pair of opposing magnets, a sector-shaped pendulum made of an electro-conductive non-magnetic material and pivotal past a spacing between the opposing magnets, and a pair of photo sensors disposed on both side edges of the pendulum.
U.S. Pat. No. 4,467,527, issued Aug. 28, 1984, to North et al. discloses a digital level that includes a digital display for displaying the angle of inclination between a straight edge of a digital level and a desired reference plane. An alarm is also included to indicate whenever the digital level is held parallel to a desired reference plane.
U.S. Pat. No. 4,716,534, issued Dec. 29, 1987, to Baucom et al., discloses an angle finder with a rotatably mounted disc on which is mounted a weight. The disc has markings that represent two degrees of arc. Three photo detectors sense the movement of the markings and a microprocessor determines angular alignment of the reference surface.
U.S. Pat. No. 4,798,087, issued Jan. 17, 1989, to Takeda et al., discloses an inclination detector of a generally fan shaped detector having a plurality of slits formed therein concentrically at intervals, and a light emitting element and a light sensitive element constituting a photo coupler disposed on opposite sides of the displacement detection plate.
U.S. Pat. No. 4,811,492, issued Mar. 14, 1989, to Kakuta et al., discloses a cant angle sensor assembly that includes a pendulum pivoted on a supporting system adapted to be mounted on an object whose cant angle is to be sensed for swinging movement in a direction of the tilt of the object. A moveable electrode is provided on the pendulum and has a first and second movable electrode plate, and a first stationary electrode plate is fixedly mounted on the supporting system in an opposed relation.
U.S. Pat. No. 4,922,620, issued May 8, 1990, to E. Terragni, discloses a device for determining the inclination of a plane with respect to a theoretical horizontal plane wherein an inclination detector element is rotatably associated with a box like body. Light detectors

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