Anti-stick-slip systems and methods

Patent metadata

Field	Value
Publication number	US-2019106979-A1
Application number	US-201715730367-A
Country	US
Kind code	A1
Filing date	Oct 11, 2017
Priority date	Oct 11, 2017
Publication date	Apr 11, 2019
Grant date	—

Abstract

Systems and methods for reducing or eliminating stick-slip are described. The system includes a controller and a drawworks. The controller is configured to collect downhole information, detect one or more stick-slip conditions, determine correlative relationships, model a stick-slip region, generate a control algorithm for top drive RPM and WOB that avoids a stick-slip region, determine a WOB autodriller set point for a particular top drive RPM using the control algorithm and provide one or more operational control signals that limit the WOB to the WOB autodriller set point for the particular top drive RPM. The drawworks is configured to receive the one or more operational control signals from the controller, and limit the WOB so that the WOB does not exceed the WOB autodriller set point for the particular top drive RPM.

First claim

What is claimed is:

1 . A system, comprising:
a controller configured to:
collect downhole bit rotary speed (RPM), weight on bit (WOB), torque on bit (TOB), annular pressure, and differential pressure (DP) data,
detect one or more stick-slip conditions,
determine a correlative relationship between:
(1) WOB and the difference between static friction TOB and dynamic friction TOB, and
(2) downhole viscous damping and DP or annular pressure,

model a stick-slip region using the determined relationships for (1) and (2),
generate a control algorithm for top drive RPM and WOB that avoids the stick-slip region,
determine a WOB autodriller set point for a particular top drive RPM using the control algorithm, and
provide one or more operational control signals that limit the WOB to the WOB autodriller set point for the particular top drive RPM; and
a drawworks configured to:
receive the one or more operational control signals from the controller, and
limit the WOB so that the WOB does not exceed the WOB autodriller set point for the particular top drive RPM.

2 . The system of claim 1 , wherein the controller is further configured to use at least one of the collected downhole RPM, DP, annular pressure, WOB, and TOB data to detect the one or more stick-slip conditions.

3 . The system of claim 1 , wherein the controller is further configured to calculate the static friction TOB and the dynamic TOB based on the collected TOB and bit RPM data.

4 . The system of claim 1 , wherein the controller is further configured to calculate downhole viscous damping data based on the collected bit RPM data.

5 . The system of claim 1 , wherein determining the relationships for (1) and (2) comprises running linear regression algorithms, non-linear regression algorithms, or both.

6 . The system of claim 1 , wherein the controller is further configured to calculate drill string stiffness (k) and inertia of a bottom hole assembly based on operator input.

7 . The system of claim 1 , wherein modeling the stick-slip region using the determined relationships for (1) and (2) comprises substituting the determined relationships for (1) and (2) in an inequality:
wherein:
c is the downhole viscous damping in Nms,
k is the drill string stiffness in N/m,
J BHA is the inertia of the BHA, in kgm 2 ,
Ω is the RPM at the surface, in rad/sec,
T s is the static friction TOB, in Nm, and
T d is the dynamic friction TOB, in Nm.

8 . The system of claim 7 , wherein the controller is further configured to generate a graph of the inequality to show the stick-slip region and display the graph to a user.

9 . The system of claim 1 , wherein the control algorithm corresponds to a line or curve that is below the stick-slip region.

10 . A method of reducing stick-slip in a drill bit, which comprises:
determining, by a controller, relationships for:
(1) weight on bit (WOB) and the difference between static friction torque on bit (TOB) and dynamic friction TOB, and
(2) downhole viscous damping and differential pressure (DP) or annular pressure,
generating, by the controller, a graph of a stick-slip region using an inequality:
wherein:
c is the downhole viscous damping in Nms,
k is the drill string stiffness in N/m,
J BHA is the inertia of the BHA, in kgm 2 ,
Ω is the rotary speed (RPM) at the surface, in rad/sec,
T s is the static friction TOB, in Nm, and
T d is the dynamic friction TOB, in Nm

and the determined relationships for (1) and (2),
generating, by the controller, a control algorithm that avoids the stick-slip region;
determining, by the controller, a WOB autodriller set point for a particular top drive RPM using the control algorithm; and
instructing a drawworks to limit a WOB to the WOB autodriller set point for the particular top drive RPM.

11 . The method of claim 10 , further comprising detecting one or more stick-slip conditions based on at least one of received downhole RPM, DP, WOB and dynamic friction and static friction TOB data.

12 . The method of claim 10 , wherein determining the relationships for (1) and (2) comprises running linear regression algorithms, non-linear regression algorithms, or both.

13 . The method of claim 10 , further comprising calculating the static TOB and the dynamic TOB based on measured TOB and bit RPM data.

14 . The method of claim 10 , further comprising calculating the downhole viscous damping based on measured bit RPM data.

15 . The method of claim 10 , wherein the graph comprises a two-dimensional plot of WOB versus top drive RPM.

16 . A non-transitory machine-readable medium having stored thereon machine-readable instructions executable to cause a machine to perform operations that, when executed, comprise:
determining, using regression analysis, relationships for:
(1) weight on bit (WOB) and the difference between static friction torque on bit (TOB) and dynamic friction TOB, and
(2) downhole viscous damping and differential pressure (DP) or annular pressure,
modeling a stick-slip region using the determined relationships for (1) and (2) and an inequality:
wherein:
c is the downhole viscous damping in Nms,
k is the drill string stiffness in N/m,
J BHA is the inertia of the BHA, in kgm 2 ,
Ω is the rotary speed (RPM) at the surface, in rad/sec,
T s is the static friction TOB, in Nm, and
T d is the dynamic friction TOB, in Nm
generating a control algorithm that avoids the stick-slip region;
limiting a WOB autodriller set point for a particular top drive RPM using the control algorithm,
detecting that a WOB at the particular top drive RPM is less than or greater than the WOB autodriller set point, and
instructing a drawworks to increase or decrease the WOB at the particular top drive RPM.

17 . The non-transitory machine-readable medium of claim 16 , wherein the operations further comprise calculating the static TOB and the dynamic TOB based on measured values for TOB and bit RPM.

18 . The non-transitory machine-readable medium of claim 16 , wherein the operations further comprise calculating the downhole viscous damping based on measured values of bit RPM.

19 . The non-transitory machine-readable medium of claim 16 , wherein the operations further comprise generating a plot of the inequality to show the stick-slip region and displaying the plot to a user.

20 . The non-transitory machine-readable medium of claim 19 , wherein the plot comprises a two-dimensional plot of WOB versus top drive RPM.

Assignees

• Nabors Drilling Tech Usa Inc

Inventors

• Hadi Mahmoud
• Ellis Brian

Classifications

• G05D19/02

  characterised by the use of electric means · CPC title

• E21B44/02 Primary

  Automatic control of the tool feed ({E21B44/005,} E21B44/10 take precedence) · CPC title

• E21B44/08 Primary

  in response to the amplitude of the movement of the percussion tool, e.g. jump or recoil · CPC title

• E21B44/04

  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 title

• G06F30/00

  Computer-aided design [CAD] · CPC title