Optimized rotation of a drill string during sliding mode of directional drilling

Patent metadata

Field	Value
Publication number	US-2016168973-A1
Application number	US-201314907765-A
Country	US
Kind code	A1
Filing date	Aug 30, 2013
Priority date	Aug 30, 2013
Publication date	Jun 16, 2016
Grant date	—

Abstract

An example method for optimized rotation of a drill string coupled to a drill bit and disposed within a borehole may comprise determining an angular velocity of at least part of the drill string. An angular velocity threshold to avoid static friction may also be determined. Additionally, a minimum input torque to apply to the drill string to maintain the angular velocity at or above the angular velocity threshold may be determined. The method may further include generating a control signal to a top drive motor based, at least in part, on the minimum input torque.

First claim

What is claimed is:

1 . A method for controlling rotation of a drill string coupled to a drill bit within a borehole, comprising:
determining an angular velocity of at least part of the drill string; determining an angular velocity threshold to avoid static friction; determining a minimum input torque to apply to the drill string to maintain the angular velocity at or above the angular velocity threshold; and generating a control signal to a top drive motor based, at least in part, on the minimum input torque.

2 . The method of claim 1 , wherein determining the angular velocity of the portion of the drill string comprises one of receiving an angular velocity measurement from within the borehole and estimating the angular velocity using a mathematical model of the drill string.

3 . The method of claim 2 , wherein
determining the angular velocity of at least part of the drill string comprises determining the angular velocity of a first segment of the drill string adjacent to the drill bit; and the first segment is one of a plurality of segments of a lumped mass model corresponding to the drill string.

4 . The method of claim 3 , wherein determining the minimum input torque comprises utilizing a model predictive control scheme with a cost function.

5 . The method of claim 3 , wherein determining the minimum input torque comprises utilizing a model predictive control scheme with the following cost function:

min

τ

i



n



∫
0
T



[

W
1

·

I

n
,
s



(
t
)

+

W
2

·

(



τ

i



n


t

)

2

]




t

where I n,s (t) corresponds to a static friction state of the first segment at a given time t; 0 to T represents the time horizon for the calculation; dτ in /dt corresponds to the rate of change of the input torque; and W 1 and W 2 are weighting factors penalizing static friction on the first segment and non-smooth torque signals, respectively.

6 . The method of claim 5 , wherein the cost function is subject to the following model equations:
J i θ •• i −k i−1 (θ i −θ i−1 )+ k i (θ i+1 −θ i )− c i J i =0  (M1)
c i =c i,s *I i,s +c i,k *I i,k with I i,s +I i,k =1  (M2)
I i,k *θ • safe ≦θ • i   (M3)
I i,s ,I i,k =0 or 1;  (M4)

and the following constraint equations:

τ

m



i



n

≤

τ

i



n

≤

τ

m



ax

(
C1
)

∫
o
T



θ
n
·




t

=
0

(
C2
)

where θ i corresponds to an angular orientation of a segment of the lumped mass model; θ • i corresponds to an angular velocity of a segment of the lumped mass model; θ •• i corresponds to an angular acceleration of a segment of the lumped mass model; J i corresponds to an inertia of a segment of the lumped mass model; c i corresponds to a friction coefficient of a segment of the lumped mass model; c i,s corresponds to a static friction coefficient of a segment of the lumped mass model; c i,k corresponds to a kinetic friction coefficient of a segment of the lumped mass model; k i corresponds to a sp

Assignees

• Halliburton Energy Services Inc

Inventors

• Dykstra Jason D
• Sun Zhijie

Classifications

• 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

• E21B7/068 Primary

  drilled by a down-hole drilling motor (down-hole drives per se E21B4/00, E21B7/067 takes precedence) · CPC title

• E21B7/10

  Correction of deflected boreholes · CPC title

• G05B13/041

  in which a variable is automatically adjusted to optimise the performance · CPC title

• G05D13/62

  characterised by the use of electric means, e.g. use of a tachometric dynamo, use of a transducer converting an electric value into a displacement {(electric motor control H02P)} · CPC title