U.S. patent application number 11/383524 was filed with the patent office on 2008-01-31 for tri stable actuator apparatus and method.
This patent application is currently assigned to SCHLUMBERGER TECHNOLOGY CORPORATION. Invention is credited to EUGENE JANSSEN, EDWARD RICHARDS, DAVID L. SMITH.
Application Number | 20080023229 11/383524 |
Document ID | / |
Family ID | 38171044 |
Filed Date | 2008-01-31 |
United States Patent
Application |
20080023229 |
Kind Code |
A1 |
RICHARDS; EDWARD ; et
al. |
January 31, 2008 |
TRI STABLE ACTUATOR APPARATUS AND METHOD
Abstract
An actuator to direct a downhole drilling tool includes a stator
and an armature configured to be electromagnetically displaced into
one of three stable positions. A cavity within the stator is in
communication with a high-pressure fluid and hydraulic ports in the
stator allow the high-pressure fluid to communicate with
low-pressure regions. Plungers on the armature selectively block
either or none of the hydraulic ports, allowing for three control
options from the actuator to the downhole drilling tool.
Inventors: |
RICHARDS; EDWARD; (WITNEY,
GB) ; SMITH; DAVID L.; (SUGAR LAND, TX) ;
JANSSEN; EUGENE; (SAINT CLOUD, FR) |
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: |
38171044 |
Appl. No.: |
11/383524 |
Filed: |
May 16, 2006 |
Current U.S.
Class: |
175/74 |
Current CPC
Class: |
E21B 7/06 20130101; E21B
41/00 20130101 |
Class at
Publication: |
175/74 |
International
Class: |
E21B 7/08 20060101
E21B007/08; E21B 7/10 20060101 E21B007/10 |
Claims
1. An actuator to direct a rotary steerable tool, the actuator
comprising: a stator having an internal cavity in communication
with a high-pressure zone, a first hydraulic port and a second
hydraulic port; an armature housed within said internal cavity,
said armature including a first valve plunger and a second valve
plunger; said first valve plunger configured to block said first
hydraulic port from said high-pressure zone when said armature is
in a first position; said second valve plunger configured to block
said second hydraulic port from said high-pressure zone when said
armature is in a second position; said first and said second
hydraulic ports in communication with said high-pressure zone when
said armature is in a third position; and said actuator configured
to be electromagnetically displaced into said first and said second
positions.
2. The actuator of claim 1 wherein said armature includes an
electromagnetic coil to generate electromagnetic force when
energized by a power source.
3. The actuator of claim 1 wherein said stator comprises a
ferromagnetic material.
4. The actuator of claim 1 wherein said stator comprises an
electromagnetic coil to generate electromagnetic force when
energized by a power source.
5. The actuator of claim 1 wherein said armature comprises a
ferromagnetic material.
6. The actuator of claim 1 further comprising a first spring to
bias said first valve plunger away from said first hydraulic port
and a second spring to bias said second valve plunger away from
said second hydraulic port.
7. The actuator of claim 6 wherein said first and said second
springs act as electrical leads in communication with an
electromagnetic coil of said armature.
8. The actuator of claim 1 wherein said armature is held into said
first position by the force of fluids flowing from said
high-pressure zone through said second port.
9. The actuator of claim 1 wherein said armature is held into said
second position by the force of fluids flowing from said
high-pressure zone through said first port.
10. The actuator of claim 1 wherein said armature is held into said
third position through electromagnetic force.
11. The actuator of claim 1 wherein said armature is held into said
third position by the force of fluids flowing from said
high-pressure zone simultaneously through said first and said
second ports.
12. A method to operate a rotary steerable tool with a tri-stable
actuator, the method comprising: installing an armature within an
internal cavity of a stator, the stator having a first hydraulic
port and a second hydraulic port; hydraulically communicating
between a high-pressure zone and the internal cavity; blocking the
first hydraulic port and communicating between the high-pressure
zone and the second hydraulic port when the stator is in a first
position; blocking the second hydraulic port and communicating
between the high-pressure zone and the first hydraulic port when
the stator is in a first position; communicating between the
high-pressure zone and both first and second hydraulic ports when
the stator is in a third position; and displacing the stator into
the first and the second positions with electromagnetic force.
13. The method of claim 12 further comprising biasing the armature
away from the first position with a first spring.
14. The method of claim 12 further comprising biasing the armature
away from the second position with a second spring.
15. The method of claim 12 further comprising retaining the
armature in the first position with the force of fluid flowing from
the high-pressure zone through the second hydraulic port.
16. The method of claim 12 further comprising retaining the
armature in the second position with the force of fluid flowing
from the high-pressure zone through the third hydraulic port.
17. The method of claim 12 further comprising retaining the
armature in the third position with electromagnetic force.
18. A tri-stable actuator comprising: a stator having an internal
cavity in communication with a high-pressure zone, a first
hydraulic port and a second hydraulic port; an armature housed
within said internal cavity, said armature including a first valve
plunger and a second valve plunger; said first valve plunger
configured to block said first hydraulic port from said
high-pressure zone when said armature is in a first stable
position; said second valve plunger configured to block said second
hydraulic port from said high-pressure zone when said armature is
in a second stable position; said first and second hydraulic ports
in communication with said high-pressure zone when said armature is
in a third stable position; said actuator configured to be
electromagnetically displaced into said first and said second
stable positions; and said armature is configured to be held into
said first stable position by a force of fluids flowing from said
high-pressure zone through said second port and held into said
second stable position by said force of fluids flowing from said
high-pressure zone through said first port.
19. The tri-stable actuator of claim 18 further comprising a first
spring to bias said first valve plunger away from said first
hydraulic port and a second spring to bias said second valve
plunger away from said second hydraulic port.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention generally relates to apparatuses and
methods to actuate downhole drilling tools. More particularly, the
present invention relates to downhole actuators to position a drill
bit assembly in a desired trajectory by a rotary steerable
assembly. More particularly still, the present invention relates to
a tri-stable actuator to be used in a rotary steerable system to
accommodate more precise positioning of a drill bit assembly.
[0002] Boreholes are frequently drilled into the Earth's formation
to recover deposits of hydrocarbons and other desirable materials
trapped beneath the Earth's crust. Traditionally, a well is drilled
using a drill bit attached to the lower end of what is known in the
art as a drillstring. The drillstring is a long string of sections
of drill pipe that are connected together end-to-end through rotary
threaded pipe connections. The drillstring is rotated by a drilling
rig at the surface thereby rotating the attached drill bit. The
weight of the drillstring typically provides all the force
necessary to drive the drill bit deeper, but weight may be added
(or taken up) at the surface, if necessary. Drilling fluid, or mud,
is typically pumped down through the bore of the drillstring and
exits through ports at the drill bit. The drilling fluid acts both
lubricate and cool the drill bit as well as to carry cuttings back
to the surface. Typically, drilling mud is pumped from the surface
to the drill bit through the bore of the drillstring, and is
allowed to return with the cuttings through the annulus formed
between the drillstring and the drilled borehole wall. At the
surface, the drilling fluid is filtered to remove the cuttings and
is often used recycled.
[0003] In typical drilling operations, a drilling rig and rotary
table are used to rotate a drillstring to drill a borehole through
the subterranean formations that may contain oil and gas deposits.
At downhole end of the drillstring is a collection of drilling
tools and measurement devices commonly known as a Bottom Hole
Assembly (BHA). Typically, the BHA includes the drill bit, any
directional or formation measurement tools, deviated drilling
mechanisms, mud motors, and weight collars that are used in the
drilling operation. A measurement while drilling (MWD) or logging
while drilling (LWD) collar is often positioned just above the
drill bit to take measurements relating to the properties of the
formation as borehole is being drilled. Measurements recorded from
MWD and LWD systems may be transmitted to the surface in real-time
using a variety of methods known to those skilled in the art. Once
received, these measurements will enable those at the surface to
make decisions concerning the drilling operation. For the purposes
of this application, the term MWD is used to refer either to an MWD
(sometimes called a directional) system or an LWD (sometimes called
a formation evaluation) system. Those having ordinary skill in the
art will realize that there are differences between these two types
of systems, but the differences are not germane to the embodiments
of the invention.
[0004] A popular form of drilling is called "directional drilling."
Directional drilling is the intentional deviation of the wellbore
from the path it would naturally take. In other words, directional
drilling is the steering of the drill string so that it travels in
a desired direction. Directional drilling is advantageous offshore
because it enables several wells to be drilled from a single
platform. Directional drilling also enables horizontal drilling
through a reservoir. Horizontal drilling enables a longer length of
the wellbore to traverse the reservoir, which increases the
production rate from the well. A directional drilling system may
also be beneficial in situations where a vertical wellbore is
desired. Often the drill bit will veer off of a planned drilling
trajectory because of the unpredictable nature of the formations
being penetrated on the varying forces that the drill bit
experiences. When such a deviation occurs, a directional drilling
system may be used to put the drill bit back on course.
[0005] A traditional method of directional drilling uses a bottom
hole assembly that includes a bent housing and a mud motor. The
bent housing includes an upper section and a lower section that are
formed on the same section of drill pipe, but are separated by a
permanent bend in the pipe. Instead of rotating the drillstring
from the surface, the drill bit in a bent housing drilling
apparatus is pointed in the desired drilling direction, and the
drill bit is rotated by a mud motor located in the BHA. A mud motor
converts some of the energy of the mud flowing down through the
drill pipe into a rotational motion that drives the drill bit.
Thus, by maintaining the bent housing at the same azimuth relative
to the borehole, the drill bit will drill in a desired direction.
When straight drilling is desired, the entire drill string,
including the bent housing, is rotated from the surface. The drill
bit angulates with the bent housing and drills a slightly overbore,
but straight, borehole.
[0006] A more modern approach to directional drilling involves the
use of a rotary steerable system (RSS). In an RSS, the drill string
is rotated from the surface and downhole devices force the drill
bit to drill in the desired direction. Rotating the drill string is
preferable because it greatly reduces the potential for getting the
drillstring stuck in the borehole. Generally, there are two types
of RSS, "point the bit" systems and "push the bit" systems. In a
point system, the drill bit is pointed in the desired position of
the borehole deviation in a similar manner to that of a bent
housing system. In a push system, devices on the BHA push the drill
bit laterally in the direction of the desired borehole deviation by
pressing on the borehole wall.
[0007] A point the bit system works in a similar manner to a bent
housing because a point system typically includes a mechanism to
provide a drill bit alignment that is different from the drill
string axis. The primary differences are that a bent housing has a
permanent bend at a fixed angle and a point the bit RSS typically
has an adjustable bend angle that is controlled independent of the
rotation from the surface. A point RSS typically has a drill collar
and a drill bit shaft. The drill collar typically includes an
internal orienting and control mechanism that counter rotates
relative to the rotation of the drillstring. This internal
mechanism controls the angular orientation of the drill bit shaft
relative to the borehole. The angle between the drill bit shaft and
the drill collar may be selectively controlled, but a typical angle
is less than 2 degrees. The counter rotating mechanism rotates in
the opposite direction of the drill string rotation. Typically, the
counter rotation occurs at the same speed as the drill string
rotation so that the counter-rotating section maintains the same
angular position relative to the inside of the borehole. Because
the counter rotating section does not rotate with respect to the
borehole, it is often called "geo-stationary" by those skilled in
the art.
[0008] Most rotary steerable systems involve the conversion of
energy in the drilling fluids into mechanical energy. Drilling
fluids are typically delivered to the drill bit through a bore of
the drillstring and return through the annulus formed between the
borehole and the outer diameter of the drillstring. Therefore,
because the cross-sectional area of the bore of the drillstring is
smaller than the cross-sectional area of the annulus, the
drillstring bore fluid pressures are significantly higher than
those in the annulus. This pressure differential is of great
importance to drilling operations as it allows various devices to
use the pressure differential to generate work and power downhole.
The rotary steerable system is such a device, often employing the
pressure differential between delivered and returning drilling
fluids to activate thrust pads and bend angle actuators to achieve
the rotary steerable effect of the downhole drilling apparatus.
[0009] Former downhole actuators used with rotary steerable systems
acted to divert the high-pressure drilling fluids from the bore of
the drillstring to various devices to produce mechanical work and
push against the drilled formation in various directions. These
actuators were typically electromagnetically activated and are
constructed as bi-stable actuators having only "on" and "off"
positions. Typically, to maintain a bi-stable electromagnetic
actuator into one of its positions, powerful permanent magnets were
used to retain an armature in the designated position. To overcome
the retaining force of the permanent magnets, higher currents were
necessary to break the armature free of the permanent magnets that
would have otherwise been necessary to displace the armature. As
such, former bi-stable actuators consumed more energy in switching
positions than necessary. An actuator requiring less energy to
switch between two or more stable positions would be highly
desirable in the oilfield today.
SUMMARY OF THE INVENTION
[0010] The deficiencies of the prior art are addressed by an
actuator to direct a rotary steerable tool. The actuator preferably
includes a stator having an internal cavity in communication with a
high-pressure zone, a first hydraulic port and a second hydraulic
port. The actuator preferably includes an armature housed within
the internal cavity, wherein the armature includes a first valve
plunger and a second valve plunger. Preferably, the first valve
plunger is configured to block the first hydraulic port from the
high-pressure zone when the armature is in a first position and the
second valve plunger is configured to block the second hydraulic
port from the high-pressure zone when the armature is in a second
position. Preferably, the first and second hydraulic ports are in
communication with the high-pressure zone when the armature is in a
third position and the actuator is configured to be
electromagnetically displaced into the first and second
positions.
[0011] The deficiencies of the prior art are also addressed by a
method to operate a rotary steerable tool with a tri-stable
actuator. The method preferable includes installing an armature
within an internal cavity of a stator, wherein the stator has a
first hydraulic port and a second hydraulic port. The method
preferably includes hydraulically communicating between a
high-pressure zone and the internal cavity. The method preferably
includes blocking the first hydraulic port and communicating
between the high-pressure zone and the second hydraulic port when
the stator is in a first position. The method preferably includes
blocking the second hydraulic port and communicating between the
high-pressure zone and the first hydraulic port when the stator is
in a first position. The method preferably includes communicating
between the high-pressure zone and both first and second hydraulic
ports when the stator is in a third position. The method preferably
includes displacing the stator into the first and the second
positions with electromagnetic force.
[0012] The deficiencies of the prior art are also addressed by a
tri-stable actuator. The tri-stable actuator preferably includes a
stator having an internal cavity in communication with a
high-pressure zone, a first hydraulic port and a second hydraulic
port. The tri-stable actuator preferably includes an armature
housed within the internal cavity, wherein the armature includes a
first valve plunger and a second valve plunger. Preferably, the
first valve plunger is configured to block the first hydraulic port
from the high-pressure zone when the armature is in a first stable
position. Preferably, the second valve plunger is configured to
block the second hydraulic port from the high-pressure zone when
the armature is in a second stable position. Preferably, the first
and second hydraulic ports are in communication with the
high-pressure zone when the armature is in a third stable position
and the actuator is configured to be electromagnetically displaced
into the first and second stable positions. Preferably, the
armature is configured to be held into the first stable position by
the force of fluids flowing from the high-pressure zone through the
second port and held into the second stable position by the force
of fluids flowing from the high-pressure zone through the first
port.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a schematic representation of a tri-stable
actuator in accordance with an embodiment of the present
invention.
[0014] FIG. 2 is a schematic representation of the tri-stable
actuator of FIG. 1 engaged in a first position.
[0015] FIG. 3 is a schematic representation of the tri-stable
actuator of FIG. 1 engaged in a second position.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0016] Referring initially to FIG. 1, a tri-stable actuator
assembly 100 in accordance with an embodiment of the present
invention is shown schematically. Tri-stable actuator assembly 100
is shown having a stator 102 and an armature 104. Stator 102
preferably is in communication with high-pressure fluids and has
two ports 106, 108 in communication with lower pressure zones.
Actuator 100 selectively diverts high-pressure flow (e.g. drilling
fluids) from internal cavity 110 to low-pressure ports 106, 108.
Biasing springs 112, 114 between stator 102 and armature 104
centralize armature 104 along its axis 116 within stator 102 when
no other forces are present. Armature 102 is shown in FIG. 1 in a
neutral position, one where both port 106 and 108 are unobstructed
and in communication with high-pressure fluids inside cavity 110.
Because ports 106 and 108 are of substantially the same size and
geometry and because armature 104 is symmetrical, high-pressure
fluid flowing from cavity 110 through ports 106,108 will not
displace armature 104 with respect to stator 102 along axis 116. As
such, with armature 102 in position shown in FIG. 1, high-pressure
fluid flows through both ports 106 and 108 at substantially the
same rate to drive any equipment attached thereto with equal
amounts of energy.
[0017] Furthermore, stator 102 and armature 104 are preferably
components of an electromagnetic system whereby armature is thrust
along its axis 116 to close ports 106 and 108. Typically, an
electromagnetic system comprises a magnetic field and an electric
coil. The field is preferably a permanent magnet but can be
constructed as an electromagnet, one that requires electric current
to be magnetized, if desired. The electric coil is preferably
constructed as a coil of electrically conductive wire. The number
of coils, the gauge of the wire, and the amount and potential of
current applied thereto designate the amount of electromagnetic
force. Depending on the polarity of the electrical charge applied
to the coil, the coil will create a magnetic force that interacts
with the magnetic properties of the field. If the poles of the
field and the coil are reversed, they are attracted to one another.
If the poles are aligned, then they are repelled.
[0018] In FIG. 1, stator 102 is shown constructed as field and
armature 104 is constructed as a coil. While this configuration is
preferred, it should be understood that alternate configurations
could be accomplished by one of ordinary skill without departing
from the spirit of the present invention. When constructed as a
coil, Armature 104 is able to conserve mass. The operation of
armature 104 is more efficient and exhibits greater responsiveness
when the mass thereof is minimized. Stator 102 is shown constructed
from a ferromagnetic material having a positive pole (+) and a
negative pole (-). Alternatively, stator 102 can be constructed as
an electromagnetic device also having a coil so that the magnitude
and polarity of the magnetic field generated thereby can be varied
or reversed. With no current applied to coil of armature 104,
springs 112 and 114 center armature upon axis 116 and allow
hydraulic communication between both ports 106 and 108 and
high-pressure fluids within cavity 110. When either port 106 or 108
is intended to be closed, an electrical current is applied to the
coil of armature 104 and one of two plungers 118, 120 is driven
into port 106 and 108, depending on the polarity of armature 104
with respect to the polarity of stator 102.
[0019] If the forces from springs 112, 114 are not strong enough to
maintain armature 104 in a centralized position between ports 106
and 108, an electromagnetic device 122 of stator 102 can be used in
conjunction with a corresponding electromagnetic device 124 of
armature 104 to retain armature 104. Using electromagnetic devices
122, 124, armature 104 can be kept clear of ports 106, 108 in
circumstances where high turbulent flow from high-pressure cavity
110 through ports 106, 108 might otherwise cause movement of
armature 104 along axis 116. Furthermore, since it can be difficult
to extend electrical leads to armature 104 from inside cavity 110
of stator 102, springs 112, 114 can optionally be constructed as
electrical conductors to activate coils within armature 104.
Alternatively, armature 104 can be constructed as a permanent
magnetic field and stator 102 can contain the electrical coil.
[0020] Referring briefly now to FIG. 2, actuator assembly 100 is
shown with armature 102 displaced such that plunger 118 is in
engaged within port 106 allowing high-pressure fluids to flow from
cavity 110 only through port 108. The particularities of the seal
between plunger 118 and port 106 (or plunger 120 and port 108) are
not shown, but as long as engagement of plunger 118 into or against
port 106 acts to seal off port 106 with sufficient integrity, the
actuator assembly 100 functions as desired. Therefore, port 106 can
include a socket configured to seal with plunger 118 or the face of
plunger 118 can alternatively be configured to seal access to port
106 without engagement therein.
[0021] Furthermore, once plunger 118 of actuator assembly 100
engages port 106, electromagnetic force is no longer required to
retain armature 104 in its displaced position so long as pressure
of fluids flowing from cavity 110 through port 108 is maintained.
High-pressure fluids flowing from cavity 110 through port 108 act
upon face 126 and thrust plunger 118 further into engagement with
port 106. As such, considerable electrical energy is conserved in
that actuator assembly 100 is considered "stable" in the position
shown in FIG. 2. To disengage plunger 118 from port 106, only
enough current is needed to activate to coil within armature 104 to
overcome the pressure forces thrusting against face 126. Former
systems either required continuous current to flow through coil of
armature 104 or permanent magnets to retain a plunger within a
port. The former systems necessitated that current to be consumed
throughout the engagement period and the latter system required
elevated current to disengage the armature from the permanent
magnet holding the plunger in place. The actuator assembly 100 of
the present invention only consumes electrical energy when the
position of armature 104 is changed and requires less current than
prior art systems in changing that position.
[0022] Referring briefly to FIG. 3, actuator assembly 100 is shown
with armature 104 displaced such that plunger 120 is engaged with
port 108. Like the position of armature 104 in FIG. 2, the position
of armature 104 shown in FIG. 3 is also "stable" when no current
flows through armature 104 or stator 102 as high-pressure fluids
flowing from cavity 110 through port 106 act upon face 128 to keep
plunger 120 engaged. Similarly, as there is no magnetic force
holding plunger 120 in engagement with port 108, electrical current
in coil of armature 102 is only required to overcome the force of
the flow against face 128.
[0023] Actuator assembly 100 has three "stable" positions, shown in
FIGS. 1, 2, and 3 respectively, enabling various modes of
communication between high-pressure fluids in cavity 110 and ports
106 an 108. Particularly, Actuator 100 has three selectable modes:
1) port 106 in communication with cavity 110; 2) port 108 in
communication with cavity 110; and 3) both ports 106 and 108 in
simultaneous communication with cavity 110. With these three modes,
a rotary steerable system (or any other downhole tool) using
tri-stable actuator 100 in accordance with the present invention
can divert drilling fluids in one of three ways to enable the tool
to be more precisely controlled and much more efficiently.
[0024] Former systems consumed more electrical energy than the
tri-stable actuator 100 of the present invention and only provided
for two positions, on and off. Therefore, former systems required
the installation and control of several actuators to completely
control a downhole tool. Using actuators in accordance with the
present invention, the tool designer has the option of either using
fewer actuators (thereby conserving valuable space) or using the
same number of actuators, but with much more precise control than
previously possible. Most downhole systems operate on limited power
supplies that are either generated downhole or delivered and stored
downhole in lithium battery packs. Because the power output of
these devices is always finite, a reduction in electrical power
consumption of downhole equipment is highly desirable.
[0025] Numerous embodiments and alternatives thereof have been
disclosed. While the above disclosure includes the best mode belief
in carrying out the invention as contemplated by the inventors, not
all possible alternatives have been disclosed. For that reason, the
scope and limitation of the present invention is not to be
restricted to the above disclosure, but is instead to be defined
and construed by the appended claims.
* * * * *