Method and apparatus for breaking gas lock in an electrical submersible pump
A software implemented method that facilities operational processes through control of a variable speed drive (VSD) that electrically drives a motor of an Electrical Submersible Pump (ESP). The control system utilizes a human interface displaying drive and pump parameters that permits adjustments. Detection of a drop in motor amps indicates gas lock wherein pump stages nearest the intake are affected by gas entering the pump. Motor speed is increased for increasing head generated by stages unaffected by gas. The motor speed increase generates total head in excess of pump depth. Feet of head generated may be calculated for each of stage of the pump at a given motor speed. The feet of head per stage is multiplied by a number of stages to determine total head generated. The total head generated is compared to the pump depth, and motor speed is increased until the total head exceeds pump depth.
1 . A method of operating an electrical submersible pump installation comprising:
monitoring a drive output current load of a drive of an electrical submersible pump;
determining when said drive output current load is below a current setpoint for establishing an undercurrent condition;
executing a fault routine that includes changing a drive frequency of said drive to a reaction speed parameter for a reaction time period; wherein
said current setpoint is below an operating current setpoint corresponding to a normal operating speed;
said reaction speed parameter is a reaction speed that is greater than said normal operating speed;
said electrical submersible pump comprises a pump having multiple stages;
said reaction speed increases head generated by each stage of said multiple stages of said pump that is not affected by gas;
said stages not affected by gas and being driven at said reaction speed generate a total amount of head in excess of a depth of said electrical submersible pump.
2 . The method according to claim 1 , further comprising:
after said step of determining, ignoring said undercurrent condition for a period of time equal to a trip delay time; then
initiating the fault routine.
3 . The method according to claim 2 , wherein:
said fault routine includes shutting down said drive; and further comprising determining if a number of restart attempts is less than or equal to a number of permissible restart attempts; and, if so,
automatically executing a restart attempt.
4 . The method according to claim 3 , further comprising:
determining a reset delay reflecting an amount of time that there has been no subsequent fault condition after said restart attempt; and
resetting said number of permissible restart attempts.
5 . The method according to claim 1 , further comprising:
starting said drive; and
after said step of determining, ignoring said undercurrent condition for a period of time equal to a bypass time from the step of starting said drive.
6 . A method of eliminating gas lock in an electrical submersible pump having a pump with multiple stages and a pump intake, the pump driven by a motor, said method comprising the steps of:
detecting a drop in amps of the motor for determining a gas lock condition of the pump wherein a stage of said pump nearest the pump intake are affected by a gas;
increasing a speed of said motor of the electrical submersible pump for increasing head generated by each of the multiple stages of said pump that are not affected by the gas;
wherein said step of increasing the speed of said motor is sufficient to generate a total amount of head in excess of a depth of said pump.
7 . The method according to claim 6 , further comprising:
calculating feet of head generated for each of said multiple stages of said pump at a given speed of said motor;
multiplying said feet of head per stage by a number of said stages in said pump to determine total head generated;
comparing said total head generated with said depth of said pump;
increasing said speed of said motor until said total head generated exceeds said depth of said pump.