Jet pump controller with downhole prediction

1. An artificial lift system for producing production fluid from a well having tubing disposed therein, the system comprising:

a surface unit disposed at surface, the surface unit having a suction line in communication with a source of power fluid and having a discharge line in communication with the well, the surface unit comprising a variable speed drive operable to pressurize the power fluid from the suction line to the discharge line;

a jet pump disposed downhole in the tubing and receiving the pressurized power fluid, the jet pump mixing the power fluid and the production fluid and outputting a product of the mixed fluid for delivery to the surface;

a first pressure transducer disposed to measure discharge pressure in the discharge line of the surface pump;

a flowmeter disposed to measure discharge flowrate in the discharge line of the surface pump; and

a controller disposed in communication with the surface unit, the first pressure transducer, and the flowmeter, the controller being configured to:

calculate a production rate of product from the well,

calculate an intake pressure at the downhole jet pump,

determine that an operating condition of the jet pump based on the intake pressure at the downhole jet pump as a function of the production rate of the product from the well lies within one of at least two areas predicted to produce cavitation in the product and in the power fluid,

adjust the variable speed drive of the surface unit based on the determination.

2. The system of claim 1 , wherein the controller is configured to:

adjust the artificial lift system relative to a set value based on a first of the measured discharge pressure or flowrate,

trend a change in a second of the measured discharge flowrate or pressure over time, and

initiate an operation in the artificial lift system based on the trended change.

3. The system of claim 1 , wherein the surface unit comprises:

a prime mover powered by the variable speed drive; and

a surface pump connected to the prime mover and operable by the prime mover to pressurize the power fluid from the suction line to the discharge line.

4. The system of claim 3 , further comprising at least one of:

a second pressure transducer disposed to measure suction pressure in the suction line of the surface pump;

a vibration sensor disposed at the surface pump, the controller being configured to monitor vibration of the surface pump and compare the monitored vibration to a vibration threshold;

an oil level sensor disposed at the surface pump, the controller being configured to monitor oil level of the surface pump and compare the monitored oil level to an oil level threshold; and

a temperature sensor disposed at the prime mover, the controller being configured to monitor temperature of the prime mover and compare the monitored temperature to a temperature threshold.

5. The system of claim 4 , wherein the prime mover comprises an electric motor coupled to the variable speed drive.

6. The system of claim 4 , wherein the surface pump comprises a positive displacement pump coupled to the prime mover with a gear box.

7. The system of claim 4 , wherein the surface pump comprises a centrifugal pump coupled to the prime mover with a thrust chamber.

8. The system of claim 1 , wherein the discharge line is disposed in communication with the tubing or an annulus between the tubing and the well; and wherein the jet pump is disposed downhole in the tubing and receives the power fluid from the tubing or the annulus, the jet pump outputting the product of the mixed fluid to the other of the annulus or the tubing for delivery to the surface.

9. The system of claim 8 , wherein the jet pump comprises a nozzle, a throat, a diffuser, and an outlet, the nozzle disposed in communication with the power fluid in the tubing, the throat disposed in communication with the production fluid and the nozzle, the diffuser receiving a mix of the power fluid and the production fluid from the throat, the outlet disposed in communication between the diffuser and the annulus.

10. The system of claim 9 , wherein to adjust the artificial lift system relative to the set value, the controller is configured to compare the measured discharge pressure to the set value for discharge pressure and adjust the variable speed drive of the surface unit based on the comparison.

11. The system of claim 10 , wherein to trend the change, the controller is configured to periodically trend the discharge flowrate over time and compare a rate of change of the trended flowrate relative to a threshold.

12. The system of claim 11 , wherein to initiate the operation, the controller is configured, based on the comparison of the rate to the threshold, to at least one of: adjust the variable speed drive, shutdown a prime mover of the surface unit, adjust the discharge flowrate, adjust the discharge pressure, initiate an alarm condition, request a repair, and request a replacement.

13. The system of claim 9 , wherein to adjust the artificial lift system relative to the set value, the controller is configured to compare the measured flowrate to the set value for the discharge flowrate and adjust the variable speed drive of the surface unit based on the comparison.

14. The system of claim 13 , wherein to trend the change, the controller is configured to periodically trend the discharge pressure over time and compare a rate of change of the trended discharge pressure relative to a threshold.

15. The system of claim 14 , wherein to initiate the operation, the controller is configured, based on the comparison of the rate to the threshold, to at least one of: adjust the variable speed drive, shutdown a prime mover of the surface unit, adjust the discharge flowrate, adjust the discharge pressure, initiate an alarm condition, request a repair, and request a replacement.

16. The system of claim 1 , wherein to adjust the artificial lift system, the controller is configured to:

calculate a first of the at least two areas of the intake pressure at the jet pump as the function of the production rate predicted to produce the cavitation in the product,

determine that the operating condition lies within the first area, and

adjust the variable speed drive of the surface unit based on the determination.

17. The system of claim 1 , wherein to adjust the artificial lift system, the controller is configured to:

calculate a second of the at least two areas of the intake pressure at the jet pump as the function of the production rate predicted to produce the cavitation in the power fluid,

determine that the operating condition lies within the second area, and

adjust the variable speed drive of the surface unit based on the determination.

18. An artificial lift method of producing fluid from a well having tubing disposed therein, the method comprising:

pressurizing, with a surface unit of an artificial lift system disposed at surface having a variable speed drive, a power fluid from a suction line to a discharge line;

injecting the pressurized power fluid of the discharge line into the well;

receiving the power fluid at a jet pump of the artificial lift system disposed downhole, mixing the power fluid and the production fluid in the jet pump, and outputting a product of the mixed fluid from the jet pump for delivery to the surface;

monitoring, with a controller disposed at surface and disposed in operable control of the variable speed drive, a discharge pressure of the surface unit with a pressure transducer and a discharge flowrate of the surface unit with a flowmeter;

calculating a production rate of product from the well;

calculating an intake pressure at the downhole jet pump;

determining that an operating condition of the jet pump based on the intake pressure at the downhole jet pump as a function of the production rate of the product from the well lies within one of at least two areas predicted to produce cavitation in the product and in the power fluid;

adjusting the variable speed drive of the surface unit based on the determination.