Methods and systems for control of wellbore trajectories

Patent metadata

Field	Value
Publication number	US-2016341027-A1
Application number	US-201515114703-A
Country	US
Kind code	A1
Filing date	Jan 27, 2015
Priority date	Jan 27, 2014
Publication date	Nov 24, 2016
Grant date	—

Abstract

There are described methods for controlling the direction of a wellbore trajectory during directional sliding drilling by means of a drill string having a drill bit rotatable, by means of a mud motor, around a drill bit rotation axis at its lower end, the direction of the drill bit rotation axis defining a tool face, wherein one of the methods comprises the following steps:
a2) obtaining data indicative of the torque of the mud motor; and b2) calculating a reactive twist angle of the drill string by multiplying the obtained torque from step a2) by the torsional drill string compliance, wherein the method further comprises the step of: c2) rotating the drill string, by means of a drill string rotation means, an angle substantially equal to but in the opposite direction of the calculated reactive twist angle.

There are also described systems for executing the methods as well as computer program products comprising instructions for causing a processor to perform the methods as described herein.

First claim

1 . A method for controlling the direction of a wellbore trajectory during directional sliding drilling by means of a drill string having a drill bit rotatable, by means of a mud motor, around a drill bit rotation axis at its lower end, the direction of the drill bit rotation axis defining a tool face, the method comprising:
a1) estimating a pressure drop across the mud motor by measuring a drilling fluid pressure, wherein the estimating includes consideration of any transient drilling fluid pressure; b1) utilizing the estimated pressure drop from step a1) to calculate the torque of the mud motor; c1) calculating a reactive twist angle of the drill string by multiplying the calculated torque from step b1) by the torsional drill string compliance, and d1) rotating the drill string., by means of a drill string rotation means, an angle substantially equal to but in the opposite direction of the calculated reactive twist angle and forward feeding the calculated reactive twist angle to a control loop of the drill string rotation means for instantly regulating the tool face.

2 . The method according to claim 1 , wherein step a1) further comprises the step of including a drilling fluid pressure response time in the estimate.

3 . The method according to claim 2 , wherein step a1) further includes determining the drilling fluid pressure response time theoretically.

4 . The method according to claim 2 , wherein step a 1) further includes determining the drilling fluid pressure response time experimentally.

5 . The method according to claim 2 , wherein step a1) further includes using an assumed linear coupling between drill bit torque and drill bit load for estimating the drilling fluid pressure response time.

6 . The method according to any of the claim 2 , wherein step a1) further includes utilizing a low-pass filter to filter out high-frequency components of a derivative of the drilling fluid pressure.

7 . The method according to a claim 2 , wherein step c1) further includes estimating the torsional drill string compliance by means of the shear modulus of elasticity and the geometric dimensions of the drill string.

8 . The method according to claim 1 , further comprising measuring a downhole drill string torque and a surface drill string torque, and using any difference between the measured string torques as an additional feed-forward input to the control loop of the drill string rotation means.

9 . The method of to claim 1 , further comprising:
measuring the actual tool face and transmitting the measured actual tool face to the surface; comparing the measured tool face to a desired tool face; and using said measured tool face in the closed loop feedback to the drill string rotation means so as to reduce the error between the desired and the measured tool face.

10 . The method according to claim 1 , further comprising reducing the magnitude of the curvature of the wellbore by varying the tool face around a set direction

11 . The method according to claim 10 , further comprising magnitude of the curvature of the well bore by cyclic variation of the tool face.

12 . The method according to claim 10 , further comprising the step of controlling the magnitude of the wellbore curvature by rotating the tool face substantially monotonically in one direction while varying the rotation rate as a function of a measured tool face.

13 . The method according to claim 12 , further comprising keeping the tool face constant for a certain period of time and subsequently rotating the tool face an integer number of turns at a constant rotation rate

14 . The method according to claim 10 , further comprising controlling the magnitude of the wellbore curvature by rotating the tool face continuously at a modulated rate.

15 . A system for controlling the direction of a wellbore trajectory during directional drilling comprising a drill string having a drill bit rotatable, by means of a mud motor, around a drill bit rotation axis at its lower end, the direction of the drill bit rotation axis defining a tool face; and a control unit adapted to execute the method of claim 1 .

16 .- 64 . (canceled)

Assignees

• Nat Oilwell Varco Norway As

Inventors

• Kyllingstad Åge

Classifications

• G06F30/17

  Mechanical parametric or variational design · CPC title

• E21B7/10

  Correction of deflected boreholes · CPC title

• E21B44/04 Primary

  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

• E21B7/06

  Deflecting the direction of boreholes · CPC title

• E21B7/04 Primary

  Directional drilling · CPC title