Method for detecting the rotation of a rod-string in a wellbore

Abstract

An apparatus for monitoring rod rotation in a rod lift system. The apparatus comprises one or more sensors that reside on the rod string of the rod lift system. The sensor is configured via a processor to generate a signal indicative of radial position of the sensor relative to an external frame of reference. The signal may be sent to a wireless I/O module, with the signals being indicative of at least partial rotation or, alternatively, a lack of rotation, of the rod-string. The processor is configured to generate an alarm if an absence of rod rotation is detected while the rod lift system is running and transmit this signal to the nearby wireless I/O module. A method for monitoring a reciprocating rod lift system is also provided.

I claim: 
     
         1 . A method for monitoring a rod lift system, comprising:
 placing a sensing device onto a rod lift system of a well, wherein the sensing device comprises at least one sensor; the sensing device is further associated with a processor and is configured to;   receive signals from the at least one sensor at the processor wherein the processor interprets the signal to determine whether the rod lift system is operationally stroking in a linear direction;   receive signals from the at least one sensor at the processor wherein the processor interprets the signal to determine a rotational status of a rod-string extending down into the well;   using the processor, generating a status signal indicating the rotational state of the rod-string determined during periods when the rod lift system is operational.   
     
     
         2 . The method of  claim 1 , wherein:
 the processor is in electrical communication with an I/O module; and   the I/O module is located remote from a wellhead associated with the rod lift system; and   the processor is in electrical communication with the I/O module by means of (i) a wired connection, or (ii) a wireless communication link.   
     
     
         3 . The method of  claim 2 , wherein:
 the I/O module is located proximate a pump-off controller associated with the well; and   the processor is configured to determine a change in rotational orientation of the rod-string over a period of time, and send a signal via the I/O module to the pump-off controller located proximate the well;   as an alarm if the rotational state of the rod-string is determined to be in a failed or sub-optimal state; or   as an indicative status if the rotational state is as expected; or   as an indicative status if the rotational state is indeterminate, and for periods where the status is indeterminate, provide a status or alarm corresponding to the last determined rotational state; wherein   the expected rotation is determined during periods where the rod lift system is operationally moving.   
     
     
         4 . The method of  claim 2  wherein
 the sensing device is in electrical communication with the I/O module by means of a wireless communication link; and 
 is configured to monitor a signal strength of the wireless communication link at the stationary I/O module; and 
 identify rotation of the rod-string by virtue of signal strength being periodically reduced as a wireless transmitter associated with the sensing device rotates around a distal side of the attached rod-string. 
 
     
     
         5 . The method of  claim 1 , wherein sensing device enters a low power mode; and
 periodically resumes sensing of linear stroking motion and rotational status for the purpose of generating the signal indicating the rotational state of the rod-string.   
     
     
         6 . The method of  claim 1 , wherein:
 the sensing device is positioned (i) on a polished rod of the rod lift system, (ii) a bridle assembly of the rod lift system, or (iii) a fixed location on or near a wellhead associated with the rod lift system; and   the sensor comprises a magnetometer; wherein   the magnetometer is configured to provide signals to the processor indicative of linear position of the rod-string, or   the magnetometer is configured to provide signals to the processor indicative of rotational status of the rod-string, or   the magnetometer is configured to provide signals to the processor indicative of both linear position and rotational status of the rod-string.   
     
     
         7 . The method of  claim 1 , wherein:
 the sensing device is positioned (i) on a polished rod of the rod lift system, or (ii) a bridle assembly of the rod lift system; and   the sensing device further comprises a processor and one or more sensor selected from the group consisting of a magnetometer sensor, an accelerometer sensor, a barometric pressure sensor, a gyroscope sensor; wherein   the magnetometer, the accelerometer, or the barometer is configured to send signals to the processor indicative of linear position of the rod-string,   the magnetometer, the accelerometer, or the gyroscope is configured to send signals to the processor indicative of a change in rotational orientation of the rod-string.   
     
     
         8 . The method of  claim 6 , wherein:
 the magnetometer is calibrated during periods of active rotation and linear motion in which the sensor experiences a full range of magnetic field variations through the motion of the rod lift system.   
     
     
         9 . The method of  claim 6 , wherein:
 a hard iron distortion is positioned on a member separate from the magnetometer, and which is moving relative to the magnetometer;   in a linear direction, or   in a rotational direction, or   in a combination of linear and rotational directions; to   provide a localized magnetic field distortion which may be sensed by the magnetometer.   
     
     
         10 . A method for monitoring a rod lift system, comprising:
 placing one or more sensors on a rod lift system with an associated rod rotation mechanism; wherein   the one or more sensors are selected from the group consisting of a magnetometer sensor, an accelerometer sensor, a gyroscope sensor, a barometric pressure sensor; and   the one or more sensor is positioned (i) on a polished rod of the rod lift system, or (ii) a bridle assembly of the rod lift system; and   the one or more sensor is operationally connected to a processor with an associated remote I/O module; and   using the processor, determine a rotational deflection of the sensor and an attached member of the rod lift system during a stroke of the rod lift system; and   by observing the rotational deflection through an individual stroke, compare the rotational change in deflection over multiple strokes to determine at least one of;   a rotational restriction resisting the free rotation of a rod-string, at a point distant from the sensor, or   an increase in imparted torque present in the rod-string caused by a distant rotational restriction, or   a release of a torque imparted on the rod-string by the overcoming of distant rotational restriction, or   a free rotating rod-string, or   a failed or inactive rotator mechanism; wherein   the determined state of rotation is provided as an indication to an operator to adjust the operation of the rod lift system.   
     
     
         11 . The method of  claim 10 , wherein the deflection of the polished rod or bridle assembly is determined by observing the sensor values during a distinct stroke; wherein
 the distinct stroke is determined from linear motion sensed by one or more of the selected sensors.   
     
     
         12 . The method of  claim 10 , wherein the processor is further configured to:
 generate an alarm if a change in radial orientation of the rod-string is not achieved in a given period of time, wherein the time period is active only while the rod lift system is stroking.   
     
     
         13 . The method of  claim 10 , wherein the processor is further configured to:
 generate an alarm if ineffective rotation of the rod-string is determined by a periodic increase and release of imparted torque on the rod-string.   
     
     
         14 . The method of  claim 10 , wherein;
 a hard iron distortion is positioned on a member separate from the magnetometer, and which is moving relative to the magnetometer;   in a linear direction,   in a rotational direction,   or a in a combination of linear and rotational directions; to provide a localized field distortion which may be sensed by the magnetometer.   
     
     
         15 . A method for monitoring a rod lift system at a well, comprising one or more sensors selected from the group consisting of:
 a magnetometer,   barometric pressure sensor,   a combination of an accelerometer and a magnetometer,   a combination of an accelerometer and a barometric pressure sensor,   a combination of an accelerometer, a magnetometer, and a barometric pressure sensor,   a combination of a gyroscope and a magnetometer,   a combination of a gyroscope, a magnetometer, and an accelerometer,   a combination of a gyroscope, a magnetometer, an accelerometer, and a barometric pressure sensor,   wherein the selected sensor, or combination of sensors, is placed on the rod lift system and is configured to generate a signal indicative of a relative or an absolute linear displacement of a rod-string extending down into the well from a polished rod; and   a processor configured to:   receive electrical signals from the sensor indicative of a linear positional status of the rod-string; and   provide a positional signal;   for the purpose of controlling the rod lift system; or   for the purpose of analyzing the operation of the rod lift system.   
     
     
         16 . The method of  claim 15 , wherein:
 the linear position signal is used to determine points within the stroke for identifying periods of expected rotation.   
     
     
         17 . The method of  claim 15 , wherein:
 the linear position signal is used to determine points within the stroke for identifying a period of a stroke cycle; to   determine an immediate rotational deflection during a stroke; or   to determine the bounds of a stroke for comparing subsequent stroke dynamics.   
     
     
         18 . The method of  claim 15 , wherein:
 the signal provided by the magnetometer determines a location or orientation within a distorted magnetic field from historical observations.   
     
     
         19 . The method of  claim 18 , wherein:
 the historical signal provided by the magnetometer observations is used to determine;   a change in the magnetic field, indicating linear stroking motion,   a change in sensed field direction, indicating rotational motion.   
     
     
         20 . The method of  claim 15 , wherein:
 a hard iron distortion is positioned on a member separate from the magnetometer, and which is moving relative to the magnetometer;   in a linear direction, or   in a rotational direction, or   in a combination of linear and rotational directions; to   provide a localized magnetic field distortion which may be sensed by the magnetometer.