CPC E21B 43/128 (2013.01) [F04D 13/06 (2013.01); F04D 15/0066 (2013.01); H02P 6/06 (2013.01); H02P 27/04 (2013.01)] | 20 Claims |
1. A method of restarting a downhole pump for pumping downhole fluid and located in a wellbore after operation of the downhole pump in a forward rotation has ceased, the method comprising:
determining a pump reverse rotational frequency of a downhole pump caused by downhole fluid flowing in a downhole direction to cause the downhole pump to rotate in a reverse rotational direction using a phase locked loop;
driving a pump motor at a motor reverse rotational frequency matching the pump reverse rotational frequency;
driving the pump motor to accelerate the pump reverse rotational frequency in the reverse rotation direction and thereby pump the downhole fluid in an uphole direction;
driving the pump motor to decrease the pump reverse rotational frequency while continuing to pump the downhole fluid in the uphole direction; and
driving the pump motor to change the rotation of the downhole pump to the forward rotation at a pump forward rotational frequency to pump the downhole fluid in the uphole direction.
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