Pump-off control responsive to time changes between rod string load

Claim 2

In a prime mover subjected to a cyclic load normally varying between substantially repeated maximum and minimum values on successive cycles of operation and wherein the time intervals of a maximum and minimum load value changes appreciably upon loss of load, the combination with said prime mover of a pumpoff control device for de-energizing said prime mover upon significant reduction in load thereon; said device having means generating a signal related to the time interval of said maximum and minimum load value; a first pacing timer means having switch contacts associated therewith which are actuated following a first time delay interval upon pacing timer being actuated; a second pacing timer means having switch contacts associated therewith which are actuated following a second time delay interval upon said second pacing timer being actuated; said first and second time delay interval being greater in time duration respective to the time interval of the minimum load, said first time delay interval being greater than said second time delay interval; circuit means by which said signal actuates said second pacing timer means coincident with occurrence of a minimum load time interval; means, including circuitry, by which the contacts of said first pacing timer are connected to de-energize the prime mover when the contacts are actuated; means, including circuitry, by which actuation of the contacts of said second pacing timer are connected to establish a current flow path to said first pacing timer; circuit means by which said signal actuates said first pacing timer means coincident with the occurrence of a maximum load signal; said prime mover being an electric motor; means, including a current transformer, connected to measure the current flow to the electric motor to provide said means generating a signal; whereby said second pacing timer is reset by said signal each cycle of operation only when the duration of the signal is of a smaller time duration than said second time delay interval, and said first pacing timer continues energization of the prime mover only when said time interval of said maximum load value is greater than said first time delay interval.

Claim 3

The combination of claim 1, and further including a third pacing timer means having switch contacts which are actuated after a third time delay upon said third pacing timer being energized; the last said switch contacts being actuated in response to actuation of the switch contacts of said first pacing timer means; means including circuitry by which the contacts of said third pacing timer delays the de-energization of the prime mover until a plurality of successive reduced load time intervals have transpired; a rest timer means and circuitry, by which the prime mover is again energized after a rest period of sufficient time duration to enable the cause of the reduced load to be obviated.

Claim 4

The combination of claim 1 and further including a third pacing timer means having switch contacts which are actuated after a third time delay upon said third pacing timer being energized; the last said switch contacts being actuated in response to actuation of the switch contacts of said first pacing timer means; means including circuitry by which the contacts of said third pacing timer delays the de-energization of the prime mover until a plurality of successive reduced load time intervals have transpired.

Claim 5

The combination of claim 3 and further including a rest timer means and circuitry, by which the prime mover is again energized after a rest period of sufficient time duration to enable the cause of the reduced load to be obviated.

Claim 6

In a pumpjack apparatus having an electric motor connected to reciprocate a string of sucker rods which drive a downhole production pump, with the motor current cyclically varying between a maximum and minimum value each stroke of the rod string until a pump-off condition is encountered, whereupon the time interval of the one minimum current value increases, while the time interval of one maximum current value decreases; the combination with said motor of a pump-off controller device for de-energizing the motor when the production pump encounters said pump-off condition; said controller having means by which a signal is generated which is proportional to the time interval of said minimum and maximum current value; a first, second, and third pacing timer means; said first pacing timer means having switch means which are actuated after a time delay interval which exceeds the time interval of the second pacing timer means and which is less than the time interval of the third pacing timer means; means, including circuitry, by which said minimum current value signal causes said second pacing timer means to commence timing out; means, including circuitry, by which actuation of the switch of the second pacing timer causes said first pacing timer to become responsive to said maximum current value, and to commence timing out concurrently with the time interval of said maximum current value; means, including circuitry, by which actuation of the switch means of said first pacing timer means actuates said third pacing timer means; circuit means by which said third pacing timer shuts in the well after a plurality of strokes; and means by which said first pacing timer prevents said third pacing timer from shutting in the well should said maximum signal indicate that the pump-off condition has been obviated.

Claim 7

In a pumpjack apparatus having an electric motor connected to reciprocate a string of sucker rods which drive a downhole production pump, with the motor current cyclically varying between a maximum and minimum value each stroke of the rod string until a pump-off condition is encountered, whereupon the time interval of the one minimum current value increases, while the time interval of one maximum current value decreases; the combination with said motor of a pump-off controller device for de-energizing the motor when the production pump encounters said pump-off condition; said controller having means by which a signal is generated which is proportional to the time interval of said minimum and maximum current value; a first, second, and third pacing timer means; said first pacing timer means having switch means which are actuated after a time delay interval which exceeds the time interval of the second pacing timer means and which is less than the time interval of the third pacing timer means; means, including circuitry, by which said minimum current value signal causes said second pacing timer means to commence timing out; means, including circuitry, by which actuation of the switch of the second pacing timer causes said first pacing timer to become responsive to said maximum current value, and to commence timing out concurrently with the time interval of said maximum current value; means, including circuitry, by which actuation of the switch means of said first pacing timer means actuates said third pacing timer means; circuit means by which said third pacing timer shuts in the well after a plurality of strokes; and means by which said first pacing timer prevents said third pacing timer from shutting in the well should said maximum signal indicate that the pump-off condition has been obviated.

Claim 8

The pump-off controller of claim 5, and further including a rest timer, including circuitry, by which the well is shut in for a time interval of several minutes to enable the pump-off condition to be obviated; means responsive to rest timer for energizing said motor after said rest timer has timed out.

Claim 9

The combination of claim 6 wherein said prime mover is an electric motor; a current transformer connected to said motor, means by which said signal is generated in response to current flow through said transformer.

Claim 10

Method of controlling a pumpjack apparatus wherein the pumpjack has a string of sucker rods manipulated to reciprocate a downhole pump comprising: 1. measuring the tension of the sucker rod string while the pumpjack apparatus is producing the well to determine the time intervals of the increased and decreased rod loads each pumping cycle; 2. generating a signal having a time duration proportional to the time intervals of the increased and decreased rod loads; 3. actuating a time delay control means in response to the time interval of the decreased rod load increasing in time duration; 4. actuating another time delay control means in response to actuation of the first said control means and measuring the time interval of the increased rod load tension; 5. shutting in the well if the time interval of the increased rod load fails to increase from a small value indicative of a pump-off condition to a larger value indicative of the absence of a pump-off condition; 6. continuing the well production if the time interval of the increased rod tension increases from a value indicative of a pump-off condition to a value indicative of the absence of a pump-off condition; 7. restarting the well after a rest period which enables the fluid reservoir within the borehole to recover sufficiently to avoid a pump-off condition.

Claim 11

Method of controlling a pumpjack apparatus wherein the pumpjack has a string of sucker rods manipulated to reciprocate a downhole pump comprising: 1. measuring the tension of the sucker rod string while the pumpjack apparatus is producing the well to determine the time intervals of the increased and decreased rod loads each pumping cycle; 2. generating a signal having a time duration proportional to the time intervals of the increased and decreased rod loads; 3. actuating a time delay control means in response to the time interval of the decreased rod load increasing in time duration; 4. actuating another time delay control means in response to actuation of the first said control means and measuring the time interval of the increased rod load tension; 5. shutting in the well if the time interval of the increased rod load fails to increase from a small value indicative of a pump-off condition to a larger value indicative of the absence of a pump-off condition; 6. continuing the well production if the time interval of the increased rod tension increases from a value indicative of a pump-off condition to a value indicative of the absence of a pump-off condition; 7. restarting the well after a rest period which enables the fluid reservoir within the borehole to recover sufficiently to avoid a pump-off condition.

Claim 12

The method of claim 8 and further including the step of 8. measuring the tension of the sucker rod in step (1) by measuring the load on the prime mover each pump cycle and generating a signal proportional to the load; 9. using the last signal to actuate a solenoid-actuated switch whereby the switch contacts are actuated only during high current flow; and, 10. using the last named switch for producing said signal.

Claim 13

The method of claim 9 wherein said solenoid has a normal open and a normal closed switch, said normal closed switch being used for the low tension signal and said normal open switch being used for the high tension signal.

Claim 14

In a prime mover subjected to a cyclic load normally varying between substantially repeated maximum and minimum values on successive cycles of operation and wherein the time intervals of a maximum and minimum load value changes appreciably upon loss of load, the combination with said prime mover of a pumpoff control device for de-energizing said prime mover upon significant reduction in load thereon; said device having means generating a signal related to the time interval of said maximum and minimum load value; a first pacing timer means having switch contacts associated therewith which are actuated following a first time delay interval upon said pacing timer being actuated; a second pacing timer means having switch contacts associated therewith which are actuated following a second time delay interval upon said second pacing timer being actuated; said first and second time delay interval being greater in time duration respective to the time interval of the minimum load, said first time delay interval being greater than said second time delay interval; circuit means by which said signal actuates said second pacing timer means coincident with occurrence of a minimum load time interval; means, including circuitry, by which the contacts of said first pacing timer are connected to de-energize the prime mover when the contacts are actuated; means, including circuitry, by which actuation of the contacts of said second pacing timer are connected to establish a current flow path to said first pacing timer; circuit means by which said signal actuates said first pacing timer means coincident with the occurrence of a maximum load signal; whereby said second pacing timer is reset by said signal each cycle of operation only when the duration of the signal is of a smaller time duration than said second time delay interval, and said first pacing timer continues energization of the prime mover only when said time interval of said maximum load value is greater than said first time delay interval; and further including a third pacing timer means having switch contacts which are actuated after a third time delay upon said third pacing timer being energized; the last said switch contacts being actuated in response to actuation of the switch contacts of said first pacing timer means; means including circuitry by which the contacts of said third pacing timer delays the de-energization of the prime mover until a plurality of successive reduced load time intervals have transpired; a rest timer means and circuitry, by which the prime mover is again energized after a rest period of sufficient time duration to enable the cause of the reduced load to be obviated.

Claim 15

In a prime mover subjected to a cyclic load normally varying between substantially repeated maximum and minimum values on successive cycles of operation and wherein the time intervals of a maximum and minimum load value changes appreciably upon loss of load, the combination with said prime mover of a pumpoff control device for de-energizing said prime mover upon significant reduction in load thereon; said device having means generating a signal related to the time interval of said maximum and minimum load value; a first pacing timer means having switch contacts associated therewith which are actuated following a first time delay interval upon said pacing timer being actuated; a second pacing timer means having switch contacts associated therewith which are actuated following a second time delay interval upon said second pacing timer being actuated; said first and second time delay interval being greater in time duration respective to the time interval of the minimum load, said first time delay interval being greater than said second time delay interval; circuit means by which said signal actuates said second pacing timer means coincident with occurrence of a minimum load time interval; means, including circuitry, by which the contacts of said first pacing timer are connected to de-energize the prime mover when the contacts are actuated; means, including circuitry, by which actuation of the contacts of said second pacing timer are connected to establish a current flow path to said first pacing timer; circuit means by which said signal actuates said first pacing timer means coincident with the occurrence of a maximum load signal; whereby said second pacing timer is reset by said signal each cycle of operation only when the duration of the signal is of a smaller time duration than said second time delay interval, and said first pacing timer continues energization of the prime mover only when said time interval of said maximum load value is greater than said first time delay interval; and further including a third pacing timer means having switch contacts which are actuated after a third time delay upon said third pacing timer being energized; the last said switch contacts being actuated in response to actuation of the switch contacts of said first pacing timer means; means including circuitry by which the contacts of said third pacing timer delays the de-energization of the prime mover until a plurality of successive reduced load time intervals have transpired; a rest timer means and circuitry, by which the prime mover is again energized after a rest period of sufficient time duration to enable the cause of the reduced load to be obviated.