OPTIMIZING PERFORMANCE OF A DRILLING ASSEMBLY

• US 20180245446A1
• Filed: 02/23/2018
• Published: 08/30/2018
• Est. Priority Date: 10/03/2012
• Status: Active Grant

• Current Assignee: Shell USA Incorporated (Shell Plc)
• Original Assignee: Shell Oil Company (Shell Plc)
• Inventors: ASTRID, Patricia, SINGH, Abhay Kumar, HUHMAN, John Edward, STOEVER, Matthew Alan, DYKSTRA, Mark William, GRAUWMANS, Rob Hendrikus Gerardus Marinus, BLANGE, Jan-Jette
• Granted Patent: US 10,577,914 B2
• Time in Patent Office: Days
• CPC Class Codes: E21B 21/08 Controlling or monitoring pressure or flow of drilling fluid, e.g. automatic filling of boreholes, automatic control of bottom pressure valve arrangements therefor E21B21/10
• CPC Class Codes: E21B 44/04 in response to the torque of the drive ; Measuring drilling torque E21B44/06 takes precedence; measuring stresses in a well bore pipe E21B47/007
• CPC Class Codes: G05B 13/021 in which a variable is automatically adjusted to optimise the performance
• CPC Class Codes: G05B 13/04 involving the use of models or simulators

Abstract

A system and method for optimized control of an assembly for drilling a borehole comprises a self-tuning, multivariable controller and an optimization engine that manipulates the setpoints of the controller such that drilling performance may be continuously optimized. The method includes evaluation of a characteristic system time constant, using this constant to compute bit ROP, using computed ROP to compute process gains, which are used to tune the multivariable controller, automatically refining controller setpoints based on controller performance, and using an optimization engine to systematically adjust controller setpoints such that drilling parameters are optimized based on any of several performance indicators, or a weighted combination of performance indicators. The method further comprises using at least one performance indicators which may be computed using estimated bit ROP: bit wear parameter; gradient of cost per foot; gradient of bit ROP versus WOB; simplified mechanical specific energy; and hydraulic specific energy.

Claims

1. A system for controlling a drilling assembly comprising a self-tuning, multivariable controller wherein said multivariable controller detects a plurality of drilling variables and adjusts the performance of said drilling assembly based on said plurality of drilling variables.

2. The system of claim 1 wherein said performance adjustment of said self-tuning, multivariable controller uses at least one manipulated variable wherein said manipulated variable is at least one of a proportional variable, integral variable, and differential variable.

3. The system of claim 2 wherein said at least one manipulated variable comprises one of block descent velocity, drillstring rotation speed, and strokes per minute for each pump.

4. The system of claim 1 wherein said system automatically adjusts said setpoints using a system of equations:

5. A system for optimizing performance of a drilling assembly comprising:

selecting means for selecting a setpoint value of each of at least one manipulated variable and each of at least one controlled variable;

operating means for operating the drilling assembly so as to drill a borehole such that one of said selected manipulated and said controlled variables are at the setpoint values;

varying means for varying the drilling variables setpoint values within a respective range;

determining means for determining the values of at least one performance indicator for a given combination of setpoints;

optimizing means for optimizing setpoint selection based on the magnitude of the at least one performance indicator;

wherein said operating means comprises the system of claim 4, and operates the drilling assembly based on the optimized setpoint selection the operating means.

6. The system of claim 5 wherein the at least one performance indicator includes a gradient of a bit rate of penetration versus weight on bit response.

7. The system of claim 5 where in the at least one performance indicator includes a deviation of a bit (rate of penetration):

(weight on bit) data pair from a linear best fit of bit (rate of penetration);

(weight on bit) data pairs.

8. The system of claim 5 wherein the at least one performance indicator includes testing the bit rate of penetration versus weight on a bit response for bit flounder using the following criterion:

9. The system of claim 5 wherein the at least one performance indicator includes a second order gradient of bit rate of penetration versus weight on bit.

10. The system of claim 5 wherein the at least one performance indicator includes a bit wear parameter as defined by:

11. The system of claim 5 wherein the at least one performance indicator includes a gradient of a cumulative cost per foot defined with respect to at least one of one of time drilled and distance drilled as illustrated by a formula:

12. The system of claim 5 wherein the at least one performance indicator includes a simplified mechanical specific energy defined in an equation:

13. The system of claim 5 wherein the at least one performance indicator includes a hydraulic specific energy defined in an equation:

14. A method for optimizing drilling performance of a drilling assembly for drilling a borehole in an earth formation using the system of claim 5, said method comprising the steps of:

selecting a setpoint value of at least one variable drilling parameter;

operating the drilling assembly to drill the borehole, wherein said at least one variable drilling parameter is set at said setpoint value;

determining the value of at least one performance indicator;

varying the variable drilling parameter from the setpoint value within a predetermined range;

determining a second value of said at least one performance indicator;

varying the setpoint value of said at least one variable drilling parameter to a second setpoint value based on the change in value of the at least one performance indicator.

15. The method of claim 14 wherein a third setpoint value of said at least one variable drilling parameter is used for determination of performance indicators before selecting the next setpoint of said at least one variable drilling parameter.

16. A method of optimizing drilling performance of a drilling assembly for drilling a borehole in an earth formation using the system of claim 5, said method comprising the steps of:

selecting a setpoint value of at least one variable drilling parameter;

operating the drilling assembly to drill the borehole, wherein the at least one variable drilling parameter is set at said setpoint value;

determining the value of at least one performance indicator;

selecting zero as the next setpoint for the block descent velocity;

determining at least one of a second and third value of at least one performance indicator using the formula;

17. The method of claim 16 wherein a change of drilling condition is identified by comparing said measured at least one performance indicator with at least one standard deviation of said at least one performance indicator.

18. The method of claim 16 wherein said determined at least one performance indicator includes process gain, K_P defined as:

20. A method of optimizing drilling performance of a drilling assembly for drilling a borehole in an earth formation using the system of claim 4, comprising the steps of:

selecting a setpoint value of at least one variable drilling parameter;

operating the drilling assembly to drill the borehole, wherein the at least one variable drilling parameter is set at the setpoint value;

determining the value of mechanical power input to the bit;

determining the value of hydraulic power input to the bit;

varying the setpoint value of said at least one variable drilling parameter such that mechanical power and hydraulic power are related as per the equation;

MP_max=K₈ HP

wherein MP_max is defined as maximum mechanical power input, HP is defined as hydraulic power input, and K₈ is a user-controlled constant.

19. The method of 16 claim wherein the determined at least one performance indicator includes bit aggressiveness, μ

, defined as;