Oil and gas production well control system and method

A control system for an oil and gas production well including:

• a subsurface borehole;
• casing lining the borehole;
• a liner within the casing;
• tubing with lower and upper ends;
• said tubing located within the casing;
• an annular casing-tubing backside between the casing and the tubing;
• a downhole pump connected to said tubing lower end;
• a prime mover connected to said downhole pump;
• and a surface wellhead connected to said tubing upper end, said surface wellhead receiving at a production flow rate primarily oil production through said tubing and primarily gas production through said casing-tubing backside, said control system including:
• a control valve connected to said casing-tubing backside and said surface wellhead;
• a programmable controller connected to said pump prime mover, said casing-tubing backside and said surface wellhead, said controller configured for adjustably controlling the production flow rate to said wellhead;
• said controller programmed with a control algorithm:
• equating the gas flow rate at the pump to the backside gas flow rate as computed from measurements taken at the surface wellhead;
• computing a predicted instantaneous gas velocity at the downhole pump based on operating parameters specific to said well;
• correlating gas velocity at said pump with gas volume intake to said pump;
• analyzing surface backside pressure data including computation of the time-dependent rate of change based on said downhole pump prime mover;
• transforming surface backside pressure from time domain to frequency domain;
• monitoring changes in frequency attenuation and harmonic distribution of said surface backside pressure as a function of control valve position and said pump prime mover operation;
• detecting transient changes in the state of gas flow in the well and operational changes in the pumping system components;
• and
• commanding a state change of the control valve position and the pump prime mover operation in response to said transient changes in the state of gas flow and said operational changes in the pumping system components.