Abstract: It is an object of the invention to provide a pump jack pump-off control method and a pump jack control apparatus in which, even when the speed of a pump jack is reduced due to generation of a pump-off condition, the pump jack is not caused to stop due to the motor overload abnormality or the coagulated crude oil and, even when the pump-off condition is generated, the reduction of the production capacity of the pump jack can be prevented as much as possible. On detecting the pump-off condition, while the pump jack is in operation with the speed thereof being reduced, or while the pump jack is in operation at the lowest speed, according to the overload warning signal of an ac electric motor, the pump jack is switched over to its intermittent operation.

Abstract: An oil extraction system is provided. The oil extraction system includes a sucker rod pump (10) provided for a production well (2) so as to pump up crude oil; a signal detecting section (12) for detecting a pump-off signal sent from the sucker rod pump (10); and an injection pump (20) provided for an injection well (3) so as to pressure-inject fluid which is used for secondary extraction or tertiary extraction. The pressure injection pump (20) is operated based on the pump-off signal detected by the signal detecting section (12).

Abstract: It is an object of the invention to provide a pump jack pump-off control method and a pump jack control apparatus in which, even when the speed of a pump jack is reduced due to generation of a pump-off condition, the pump jack is not caused to stop due to the motor overload abnormality or the coagulated crude oil and, even when the pump-off condition is generated, the reduction of the production capacity of the pump jack can be prevented as much as possible. On detecting the pump-off condition, while the pump jack is in operation with the speed thereof being reduced, or while the pump jack is in operation at the lowest speed, according to the overload warning signal of an ac electric motor, the pump jack is switched over to its intermittent operation.