Oil well pumpoff control system

Abstract

Abstract A sensor associated with the production of an oil well generates a signal indicative of pumpable fluid available in the wellbore. The signal activates a first oscillator whose count is compared with a variable frequency oscillator having a frequency of approximately one-half that of the first oscillator. The comparison is made over a given period of time to ascertain the percentage of time the well has produced fluid. The integrated timer is adjusted to shut down the system when the percentage of time the valve is open drops to the preselected amount. In response to the integration timer producing a signal, a shutdown timer is turned on which restarts the cycle after a preselected amount of time. The length of shutdown time for the pumping unit is preset according to the well fill-in rate. When the system is restarted by the shutdown timer, a pump-up timer is turned on which is adjusted to allow for a desired pump-up time. As the pump-up timer is allowing the system to recycle, the integration timer is reset and the recycling is completed if the requirements of the integration timer are met. Otherwise, the unit is shut down again and the system recycled. A variable electronic scaler is connected to the output of the integration timer which monitors the output signals from this timer. A reset circuit between the integrator and the scaler resets the scaler to zero after a successful recycle of the system. A successful recycle occurs when fluid is pumped at a flow rate equal to or greater than the present minimum when the pump has been restarted after a shutdown period. If the pumped fluid flow rate achieves the minimum preset flow value during or at the end of the pump-up period, a reset signal is conveyed to the scaler to reset it to zero and continue pump operation and system recycling indefinitely, or until malfunctions interfere with the pumping operation or production drops below a level economically feasible for pumping operations. When malfunctions do occur, such as parting of the sucker rod, the pumped fluid flow rate will remain below the desired preset value and no reset signal will be conveyed to the scaler. At the end of the pump-up cycle the pump will not be pumping fluids and will be shut down in response to the signal from the integrator assembly. Since there will be no reset signal to the scaler, it will begin to accumulate the shutdown signals. After the preset number of times the integration timer produces a shutdown signal, the scaler turns off the whole system. It can then be restarted manually. This provides a safety device for equipment failure such as breaking of the sucker rod. Means are also provided for recording the various timed cycles and also for monitoring the number of signals transmitted to the scaler, thus being indicative of the number of times the system has automatically shut down and successfully recycled. Also a circuit is provided to determine the exact percentage of time that the pump is producing fluid flow, whether above or below the preset minimum percentage. A continuous recorder may be used with this circuit to maintain a constant record of the percentage of time the pump is flowing well fluids to allow the operator to determine if the preset minimum percentage should be lowered, and how much it should be lowered to obtain successful recycling of the pumping system.

Inventors

• 👤 Bobby L. Douglas

Bibliographic Details