U.S. patent application number 11/381171 was filed with the patent office on 2006-11-09 for steerable drilling system.
This patent application is currently assigned to SCHLUMBERGER TECHNOLOGY CORPORATION. Invention is credited to GEOFFREY C. DOWNTON, NIGEL HALE.
Application Number | 20060249287 11/381171 |
Document ID | / |
Family ID | 34685107 |
Filed Date | 2006-11-09 |
United States Patent
Application |
20060249287 |
Kind Code |
A1 |
DOWNTON; GEOFFREY C. ; et
al. |
November 9, 2006 |
STEERABLE DRILLING SYSTEM
Abstract
A steerable drilling system comprises a bias unit 14 operable by
means of a control valve arrangement 22, the control valve
arrangement 22 comprising a rotary valve 24 having a control shaft
28 the angular position of which is controlled by a motor 30.
Inventors: |
DOWNTON; GEOFFREY C.;
(GLOUCESTERSHIRE, GB) ; HALE; NIGEL; (BRISTOL,
GB) |
Correspondence
Address: |
SCHLUMBERGER OILFIELD SERVICES
200 GILLINGHAM LANE
MD 200-9
SUGAR LAND
TX
77478
US
|
Assignee: |
SCHLUMBERGER TECHNOLOGY
CORPORATION
SUGAR LAND
TX
|
Family ID: |
34685107 |
Appl. No.: |
11/381171 |
Filed: |
May 2, 2006 |
Current U.S.
Class: |
166/250.1 |
Current CPC
Class: |
E21B 7/06 20130101; E21B
17/1014 20130101 |
Class at
Publication: |
166/250.1 |
International
Class: |
E21B 49/00 20060101
E21B049/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 5, 2005 |
GB |
0509153.3 |
Claims
1. A steerable drilling system comprising a bias unit operable by
means of a control valve arrangement, the control valve arrangement
comprising a rotary valve having a control shaft the angular
position of which is controlled by a motor.
2. A system according to claim 1, wherein the motor is an
electrically operated motor.
3. A system according to claim 2, wherein the operation of the
motor is controlled by a control unit.
4. A system according to claim 3, wherein the control unit controls
the motor using information relating to the orientation of the bias
unit and the angular position of the control shaft relative to the
bias unit.
5. A system according to claim 4, wherein the control unit further
uses information relating to the rotational speed of the bias
unit.
6. A system according to claim 4, wherein the information relating
to the orientation of the bias unit is derived from the outputs of
accelerometers and/or magnetometers mounted upon, carried by or
associated with the bias unit.
7. A system according to claim 5, wherein rotational speed
information is derived from a rotational rate sensor.
8. A system according to claim 7, wherein the rotational rate
sensor comprises a gyroscope.
9. A system according to claim 4, wherein the information relating
to the angular position of the control shaft relative to the bias
unit is derived from the output of an angle transducer arranged to
monitor the control shaft.
10. A control valve arrangement for use in a drilling system as
claimed in claim 1, the control valve arrangement comprising a
rotary valve having a control shaft the angular position of which
is controlled by a motor.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to UK Application No.
0509153 3 filed on May 5th 2005.
BACKGROUND OF INVENTION
[0002] 1. FIELD OF THE INVENTION
[0003] This invention related to a steerable drilling system for
use in the formation of boreholes, for example for use in
hydrocarbon extraction.
[0004] 2. DESCRIPTION OF THE RELATED ART
[0005] One known form of steerable drilling system includes a bias
unit having several bias pads mounted thereon. Each bias pad is
moveable from a retracted position to an extended position by means
of an associated piston to which drilling fluid under pressure is
supplied through a control valve arrangement. The bias pads are
arranged such that, when in their extended positions, they engage
the adjacent part of the wall of the borehole and apply a sideways
acting load to the bias unit. It will be appreciated that if the
drill bit is connected to the bias unit, the application of such a
load to the bias unit will apply a similar load to the drill bit
thereby urging the bit to form a desired deviation in the
borehole.
[0006] The control valve arrangement typically comprises a rotary
valve arranged to supply drilling fluid to the pistons in turn. A
control shaft of the rotary valve is connected to a suitably
controlled roll stabilised platform so that the control shaft and
associated part of the valve are held in a substantially
geostationary manner.
[0007] The provision of a roll stabilised platform results in the
control valve arrangement being of fairly complex form and also
being of fairly large dimensions.
SUMMARY OF INVENTION
[0008] According to the present invention there is provided a
steerable drilling system comprising a bias unit operable by means
of a control valve arrangement, the control valve arrangement
comprising a rotary valve having a control shaft the angular
position of which is controlled by a motor.
[0009] The motor is conveniently an electrically operated motor.
Preferably the operation of the motor is controlled by a control
unit, conveniently using information relating to the orientation of
the bias unit and the angular position of the control shaft
relative to the bias unit.
[0010] The information relating to the orientation of the bias unit
may be derived from the outputs of accelerometers and/or
magnetometers mounted upon, carried by or associated with the bias
unit. The information relating to the angular position of the
control shaft relative to the bias unit may be derived from the
output of an angle transducer arranged to monitor the control
shaft.
[0011] The invention also relates to a control valve arrangement
suitable for use in such a drilling system, the control valve
arrangement comprising a rotary valve having a control shaft the
angular position of which is controlled by a motor.
BRIEF DESCRIPTION OF DRAWINGS
[0012] The invention will further be described, by way of example,
with reference to the accompanying drawings to which:
[0013] FIG. 1 is a diagrammatic view of a drilling system in
accordance with one embodiment of the invention, and
[0014] FIG. 2 is a diagram illustrating part of the drilling system
of FIG. 1.
DETAILED DESCRIPTION
[0015] The drilling system illustrated diagrammatically in FIG. 1
comprises a drill bit 10 connected to a drilling collar 12 forming
the housing of a bias unit 14. A plurality of bias pads 16 are
pivotally connected to the collar 12, each bias pad 16 including a
piston region 18 slidable within a respective bore 20 provided in
the collar 12 so as to be moveable between a retracted position and
an extended position. In the retracted position, the bias pad 16
lies adjacent the periphery of the collar 12. When in its extended
position, the pad 16 projects from the circumference of the collar
12 and, in use, will engage an adjacent part of the wall of the
borehole being formed so as to apply a sideways acting load to the
collar 12, and hence to the bit 10.
[0016] A control valve arrangement 22 is provided to control the
supply of drilling fluid or mud under pressure to the bores 20
within which the piston regions 18 are moveable. The control valve
arrangement 22 comprises a rotary valve 24 having an inlet to which
fluid under pressure is supplied and a series of outlets, each
outlet being connected through appropriate lines 26 to the bores
20. A valve member is rotatably moveable, the valve member being
shaped to define a flow path which communicates with the inlet and
which communicates with the outlets, in turn, as the valve member
is rotated so as to supply fluid under pressure to the bores 20 in
turn as the valve member rotates. Depending upon the valve design,
there may be times at which fluid is supplied to more than one of
the lines. It will be appreciated, therefore, that the bias pads 16
are each moved from their respective retracted positions to their
respective extended positions, in turn, as the valve member
rotates. The valve member is connected to a control shaft 28, and
it will be appreciated that the angular position of the control
shaft 28 determine which one or ones of the lines 26, and hence the
bores 20 are supplied with fluid under pressure at any given
time.
[0017] The bias unit 14 and drill bit 10 are connected to an output
of a downhole motor so as to be driven for rotation. A load is
applied to the bias unit 14 and bit 10 and it will be appreciated
that the combination of the application of the load and the rotary
motion of the bit causes the bit to gouge, scrape or abrade
material from the formation in which the borehole is being formed.
Drilling fluid is used to carry away material removed in this
manner.
[0018] As the bias unit 14 is arranged to rotate, in use, in order
to apply a sideways acting load to the bias unit 14 and bit 10
acting in a desired direction so as to cause a desired deviation in
the direction of the borehole being formed it will be appreciated
that the bias pads 16 need to be removed from their retracted
positions to their extended position in a manner synchronised with
the rotation of the bias unit 14, and this is achieved by holding
the control shaft 28 against rotation relative to the
formation.
[0019] In accordance with the invention, the control shaft 20 is
connected to or forms an extension of the output shaft of a motor
30 the operation of which is controlled by a motor controller 32.
As illustrated in FIG. 2, the motor controller is driven from a DC
power source generated downhole by means of a turbine 34 and
alternator 36. Although it is convenient to use a downhole
generated electrical supply to control the operation of the motor
controller 32 and motor 30, it will be appreciated that other forms
of power source could be used if desired. For example, suitable
batteries could be used.
[0020] The motor controller 32 is arranged to receive, in real
time, tool face measurement signals representative of the
orientation of the collar 12. These signals are generated by
sensors in the form of an accelerometer 38 and a magnetometer 40,
in the illustrated arrangement. However, it will be appreciated
that rather than use signals from a plurality of different types of
sensor, a single type of sensor could be used if desired. In
addition to the signals representative of the orientation of the
drilling collar 12, the motor controller 32 is further supplied
with signals representative of the angular position of the control
shaft 28 relative to the drilling collar 12. These signals are
derived from the output of an angle transducer 42.
[0021] The information representative of the absolute orientation
of the drilling collar 12 is used, in combination with the
information representative of the angle of the shaft 28 relative to
the drilling collar 12 to determine, substantially in real time,
the absolute orientation of the control shaft 28. Using a downhole
computer 44, the calculated angular position of the shaft 28 is
compared with a desired angular position thereof, and a signal is
generated to cause the motor 30 to be driven to cause rotation of
the drive shaft 28 to the desired position at any given time. It
will be appreciated, therefore, that the bias pads 16 can be driven
to their extended positions, in turn, at the desired time to
achieve drilling in the desired direction.
[0022] It will be appreciated that a range of modifications and
alterations to the arrangement described herein may be made within
the scope of the invention. It will further be appreciated that the
provision of a roll stabilised platform, and the associated
disadvantages, are avoided.
* * * * *