Method and apparatus to automate pump-down operation

1. A system, comprising:

a winch controller configured to control a line speed of a support cable for conveying a wireline tool string down a section of a wellbore;

a pump controller configured to control a pumprate of a hydraulic pump; and

a control module configured to communicate with the winch controller and the hydraulic pump, the control module further configured to:

generate a line speed signal for controlling a line speed of the support cable and a pumprate signal to control a pumprate of a hydraulic fluid in the wellbore;

determine a first error between a target value for downhole tension of the support cable and a measured value of the downhole tension;

determine a second error between a recommended job speed and an actual line speed; and

maintain the target value for the downhole tension by simultaneously controlling the line speed of the support cable and the pumprate of the hydraulic fluid using a value for the line speed signal and a value for the pumprate signal generated based on the first and second errors.

2. The system of claim 1 , wherein the control module is further configured to:

maintain the recommended job speed when measured downhole tension is within a range of a minimum downhole tension target and a maximum downhole tension target.

3. The system of claim 1 , wherein the control module is further configured to:

simultaneously control the line speed of the support cable and the pumprate of the hydraulic fluid automatically with a control algorithm using the generated value for the line speed signal and the generated value for the pumprate signal.

4. The system of claim 1 , wherein the section of the wellbore is a vertical section, an inclined section, or a horizontal section.

5. The system of claim 1 , wherein the control module is further configured to:

determine the target value for downhole tension based on at least one of weight of the wireline tool string, inclination of the wellbore or a target value of downhole tension in a horizontal section.

6. The system of claim 1 , wherein the control module is further configured to:

determine the target value for downhole tension from a look-up table correlating the target value for downhole tension with an inclination of the wellbore.

7. The system of claim 1 , wherein the control module is further configured to:

adjust the target value for downhole tension based on at least one of the recommended job speed, measured line speed, minimum downhole tension target, or measured pump rate, or maximum available pumprate.

8. A method for controlling a pump-down operation in a wellbore, the method comprising:

selecting a target value for downhole tension of a support cable and a recommended job speed to convey a wireline tool string down a section of the wellbore;

generating a line speed signal for controlling a line speed of the support cable and a pumprate signal to control a pumprate of a hydraulic fluid in the wellbore;

determining a first error between the target value for downhole tension and a measured value of the downhole tension;

determining a second error between the recommended job speed and an actual line speed; and

maintaining the target value for the downhole tension by simultaneously controlling the line speed of the support cable and the pumprate of the hydraulic fluid using a value for the line speed signal and a value for the pumprate signal generated based on the first and second errors.

9. The method of claim 8 , further comprising:

maintaining the recommended job speed when measured downhole tension is within a range of a minimum downhole tension target and a maximum downhole tension target.

10. The method of claim 8 , further comprising:

simultaneously controlling the line speed of the support cable and the pumprate of the hydraulic fluid automatically with a control algorithm using the generated value for the line speed signal and the generated value for the pumprate signal.

11. The method of claim 8 , further comprising:

displaying the generated value for the line speed signal and the generated value for the pumprate signal on a user interface; and

manually controlling the line speed and the pumprate based on the generated value for the pumprate signal.

12. The method of claim 8 , wherein the recommended job speed is selected by an operator.

13. The method of claim 8 , wherein the recommended job speed is determined based on geometries of the wireline tool string and the wellbore, fluid properties, inclination of the wellbore, or a maximum pumprate available.

14. The method of claim 8 , wherein the recommended job speed is determined using a prediction model based on one or more of the target value for downhole tension, maximum available pumprate, maximum outer diameter of the wireline tool string, weight of the wireline tool string, length of the wireline tool string, casing inner diameter, density of hydraulic fluid used, or maximum safe line speed of a winch.

15. The method of claim 8 , wherein the target value for downhole tension is determined based on at least one of weight of the wireline tool string, inclination of the wellbore or a target value of downhole tension in a horizontal section.

16. The method of claim 8 , wherein the target value for downhole tension is determined from a look-up table correlating the target value for downhole tension with an inclination of the wellbore.

17. The method of claim 8 , wherein the target value for downhole tension is adjusted based on at least one of the recommended job speed, measured line speed, minimum downhole tension target, or measured pump rate, or maximum available pumprate.

18. A non-transitory computer-readable medium having stored therein instructions for making a processor execute a method for controlling a pump-down operation in a wellbore, the processor-executable instructions comprising instructions for performing operations including:

selecting a target value for downhole tension of a support cable and a recommended job speed to convey a wireline tool string down a section of the wellbore;

generating a line speed signal for controlling a line speed of the support cable and a pumprate signal to control a pumprate of a hydraulic fluid in the wellbore;

determining a first error between the target value for downhole tension and a measured value of the downhole tension;

determining a second error between the recommended job speed and an actual line speed; and

maintaining the target value for the downhole tension and the recommended job speed by simultaneously controlling the line speed of the support cable and the pumprate of the hydraulic fluid using a value for the line speed signal and a value for the pumprate signal generated based on the first and second errors,

wherein the recommended job speed is maintained when measured downhole tension is within a range of a minimum downhole tension target and a maximum downhole tension target.

19. The non-transitory computer-readable medium of claim 18 , wherein the instructions for selecting the recommended job speed include instructions for:

determining the recommended job speed using a prediction model based on one or more of the target value for downhole tension, maximum available pumprate, maximum outer diameter of the wireline tool string, weight of the wireline tool string, length of the wireline tool string, casing inner diameter, density of hydraulic fluid used, or maximum safe line speed of a winch.

20. The non-transitory computer-readable medium of claim 18 , wherein the instructions for controlling a pump-down operation include:

adjusting the target value for downhole tension based on at least one of the recommended job speed, measured line speed, minimum downhole tension target, or measured pump rate, or maximum available pumprate.