U.S. patent application number 12/495736 was filed with the patent office on 2009-10-29 for intelligent efficient servo-actuator for a downhole pulser.
Invention is credited to Kenneth A. Lambe, F. Dale Pratt, Axel M. Schmidt.
Application Number | 20090267791 12/495736 |
Document ID | / |
Family ID | 35095753 |
Filed Date | 2009-10-29 |
United States Patent
Application |
20090267791 |
Kind Code |
A1 |
Pratt; F. Dale ; et
al. |
October 29, 2009 |
INTELLIGENT EFFICIENT SERVO-ACTUATOR FOR A DOWNHOLE PULSER
Abstract
An improved energy efficient intelligent pulser driver used for
generating a mud pulse in a MWD (measurement while drilling)
application. In the pulser driver, a direct current (DC) powered
control circuit activates a three-phase DC brushless motor that
operates a servo-valve. Opening of the servo-valve equalizes
pressure in a plenum causing the operation of a main valve reducing
flow area and causing a pressure spike in the mud column. Closing
of the servo-valve creates a reduction in mud pressure that
operates the main valve and increases the flow area causing an end
to the pressure spike. The servo-valve is powered both in opening
and closing operations by the motor.
Inventors: |
Pratt; F. Dale; (Calgary,
CA) ; Schmidt; Axel M.; (Calgary, CA) ; Lambe;
Kenneth A.; (Calgary, CA) |
Correspondence
Address: |
BLAKELY SOKOLOFF TAYLOR & ZAFMAN LLP
1279 OAKMEAD PARKWAY
SUNNYVALE
CA
94085-4040
US
|
Family ID: |
35095753 |
Appl. No.: |
12/495736 |
Filed: |
June 30, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11101033 |
Apr 6, 2005 |
7564741 |
|
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12495736 |
|
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|
60560047 |
Apr 6, 2004 |
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Current U.S.
Class: |
340/855.4 |
Current CPC
Class: |
E21B 47/24 20200501;
G01V 11/002 20130101 |
Class at
Publication: |
340/855.4 |
International
Class: |
G01V 3/00 20060101
G01V003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 6, 2004 |
CA |
2,463,354 |
Claims
1-15. (canceled)
16. A servo-controller for use with a downhole
measurement-while-drilling pulser actuator, the servo-controller
comprising a sensor, memory, control circuitry, and an operator
interface.
17. The servo-controller of claim 16 wherein the sensor is a
mudflow sensor, pressure sensor, temperature sensor, rotation-step
counter, position sensor, velocity sensor, current level sensor,
battery voltage sensor, timer, or error monitor.
18. The servo-controller of claim 16 wherein the memory stores
time-stamped or counted sensed events together with an event-type
indication.
19. The servo-controller of claim 16 wherein the control circuitry
is programmable to cause an action within the actuator responsive
to a sensed event, a time, an elapsed time, a series of sensed
events, or any combination thereof.
20. The servo-controller of claim 16 wherein the operator interface
provides information from memory to the operator.
21. The servo-controller of claim 16 wherein the operator interface
allows an operator to alter the programming of the control
circuitry.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/560,047, filed Apr. 6, 2004, and Canadian
Application No. 2,463,354, filed Apr. 6, 2004, which are
incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates generally to a telemetry
system, and in particular to a measurement while drilling (MWD)
system. More particularly, the present invention relates to a
servo-actuator for a downhole mud pulser for sending information
from downhole to surface.
BACKGROUND OF THE INVENTION
[0003] The desirability and effectiveness of well logging systems
where information is sensed in the well hole and transmitted to the
surface through mud pulse telemetry has long been recognized. Mud
pulse telemetry systems provide the driller at the surface with
means for quickly determining various kinds of downhole
information, most particularly information about the location,
orientation and direction of the drill string at the bottom of the
well in a directional drilling operation. During normal drilling
operations, a continuous column of mud is circulating within the
drill string from the surface of the well to the drilling bit at
the bottom of the well and then back to the surface. Mud pulse
telemetry repeatedly restricts the flow of mud to propagate signals
through the mud upward to the surface, thereby providing a very
fast communication link between the drill bit and the surface.
Depending on the type of drilling fluid used, the velocity may vary
between approximately 3000 and 5000 feet per second.
[0004] A telemetry system may be lowered on a wireline located
within the drill string, but is usually formed as an integral part
of a special drill collar inserted into the drill string near the
drilling bit. The basic operational concept of mud pulse telemetry
is to intermittently restrict the flow of mud as it passes through
a downhole telemetry valve, thereby creating a pressure pulse in
the mud stream that travels to the surface of the well. The
information sensed by instrumentation in the vicinity of the
drilling bit is encoded into a digital formatted signal and is
transmitted by instructions to pulse the mud by intermittently
actuating the telemetry valve, which restricts the mud flow in the
drill string, thereby transmitting pulses to the well surface where
the pulses are detected and transformed into electrical signals
which can be decoded and processed to reveal transmitted
information.
[0005] Representative examples of previous mud pulse telemetry
systems may be found in U.S. Pat. Nos. 3,949,354; 3,958,217;
4,216,536; 4,401,134; and 4,515,225.
[0006] Representative samples of mud pulse generators may be found
in U.S. Pat. Nos. 4,386,422; 4,699,352; 5,103,420; and
5,787,052.
[0007] A telemetry system capable of performing the desired
function with minimal control energy is desirable, since the
systems are typically powered by finite-storage batteries. One such
example is found in U.S. Pat. No. 5,333,686, which describes a mud
pulser having a main valve biased against a narrowed portion of the
mud flowpath to restrict the flow of mud, with periodic actuation
of the main valve to allow mud to temporarily flow freely within
the flowpath. The main valve is actuated by a pilot valve that can
be moved with minimal force. The pilot valve additionally provides
for pressure equalization, thereby increasing the life of downhole
batteries.
[0008] Another example of an energy efficient mud pulser is
described in U.S. Pat. No. 6,016,288, the mud pulser having a DC
motor electrically powered to drive a planetary gear which in turn
powers a threaded drive shaft, mounted in a bearing assembly to
rotate a ball nut lead screw. The rotating threaded shaft lifts the
lead screw, which is attached to the pilot valve.
[0009] Solenoid-type pulser actuators have also been used to
actuate the main pulser valve, however, there are many problems
with such a system. The use of a spring to bias the solenoid
requires the actuator (servo) valve to overcome the force of the
spring (about 6 pounds) and of the mud prior to actuating the main
valve. A typical solenoid driven actuator valve is capable of
exerting only 11 pounds of pressure, leaving only 5 pounds of
pressure to actuate the pulser assembly. Under drilling conditions
requiring higher than normal mud flow, the limited pressures
exerted by the solenoid may be unable to overcome both the pressure
of the return spring and the increased pressure of the flowing mud,
resulting in a failure to open the servo-valve, resulting in the
main valve remaining in a position in which mud flow is not
restricted, and therefore failing to communicate useful information
to the surface.
[0010] A further problem with the use of a solenoid to actuate the
pulser assembly is the limited speed of response and recovery that
is typical of solenoid systems. Following application of a current
to a solenoid, there is a recovery period during which the magnetic
field decays to a point at which it can be overcome by the force of
the solenoid's own return spring to close the servo-valve. This
delay results in a maximum data rate (pulse width) of approximately
0.8 seconds/pulse, limiting the application of the technology.
[0011] Moreover, the linear alignment of the solenoid must be
exactly tuned (i.e. the magnetic shaft must be precisely positioned
within the coil) in order to keep the actuator's power
characteristics within a reliable operating range. Therefore,
inclusion of a solenoid within the tool adds complexity to the
process of assembling and repairing the pulser actuator, and
impairs the overall operability and reliability of the system.
[0012] Existing tools are also prone to jamming due to accumulation
of debris, reducing the range of motion of the pilot valve.
Particularly when combined with conditions of high mud flow, the
power of the solenoid is unable to clear the jam, and the tool is
rendered non-functional. The tool must then be brought to the
surface for service.
[0013] Stepper motors have been used in mud pulsing systems,
specifically, in negative pulse systems (see for example U.S. Pat.
No. 5,115,415). The use of a stepper motor to directly control the
main pulse valve, however, requires a large amount of electrical
power, possibly requiring a turbine generator to supply adequate
power to operate the system for any length of time downhole.
[0014] Repair of previous pursers has been an as yet unresolved
difficulty. Typically, the entire tool has been contained within
one housing, making access and replacement of small parts difficult
and time-consuming. Furthermore, a bellows seal within the
servo-poppet has typically been the only barrier between the mud
flowing past the pilot valve's poppet and the pressurized oil
contained within the servo-valve actuating tool, which is required
to equalize the hydrostatic pressure of the downhole mud with the
tool's internal spaces. Therefore, in order to dissemble the tool
for repair, the bellows seal had to be removed, causing the
integrity of the pressurized oil chamber to be lost at each
repair.
[0015] Furthermore, a key area of failure of MWD pulser drivers has
been the failure of the bellows seal around the servo-valve
activating shaft, which separates the drilling mud from the
internal oil. In existing systems, the addition of a second seal is
not feasible, particularly in servo-drivers in which the
servo-valve is closed by a spring due to the limited force which
may be exerted by the spring, which is in turn limited by the
available force of the solenoid, and cannot overcome the friction
or drag of an additional static/dynamic linear seal.
[0016] It remains desirable within the art to provide a pulse
generator that has an energy efficiency sufficient to operate
reliably and to adapt to a variety of hostile downhole conditions,
has reduced susceptibility to jamming by debris, and is simpler to
repair than previous systems.
SUMMARY OF THE INVENTION
[0017] It is an object of the present invention to obviate or
mitigate at least one disadvantage of previous mud pulsers and
pulse generators.
[0018] In a first aspect, the present invention provides a downhole
measurement-while-drilling pulser actuator comprising a servo valve
movable between an open position which permits mud flow through a
servo-orifice and a restricted position which restricts mud flow
through the servo-orifice, the servo-valve powered to the open
position and powered to the closed position by a reversible
electric motor.
[0019] In one embodiment, the servo valve includes a servo-poppet
powered by the motor in reciprocating linear movement towards and
away from the servo-orifice.
[0020] In a further embodiment, the actuator may include a rotary
to linear conversion system for converting rotary motion of the
reversible electric motor into linear reciprocating movement of the
poppet. The rotary to linear conversion system may include a
threaded lead screw held stationary and driven in rotation by a
rotary motor. In this embodiment, the lead screw may be threadably
attached to a ball nut from which the poppet depends, whereby the
rotary motion of the motor causes rotation of the screw to result
in driven linear movement of the ball nut and the poppet in either
direction.
[0021] In a further embodiment, there is provided a
servo-controller for controlling the powering of the servo-valve by
the electric motor. The servo-controller may further be capable of
sensing the position of the poppet with respect to the
servo-orifice, such that the poppet position is sensed when mud
flow through the servo-orifice is restricted or unrestricted, and
wherein the amount and direction of rotation of the motor from the
sensed poppet position is counted and stored by the controller.
[0022] In another embodiment, the sensed position of the orifice
restriction is calibrated as the fully closed position of the
poppet. The poppet's travel is thereby monitored and controlled
during operation to avoid unneeded collision or frictional wear
between the poppet and the servo-orifice. The servo controller may
sense the position of the poppet by sensing whether movement of the
poppet is impeded, and the servo-controller counts the number of
rotations of the motor until the poppet is impeded and compares the
number of rotations to an expected number of rotations to determine
the position of the poppet with respect to the servo-orifice. The
expected number of rotations can be preset to allow a predetermined
rate of mud flow past the servo-orifice when the poppet is moved
away from the servo-orifice by the preset expected number of
rotations.
[0023] In a still further embodiment, the servo-controller may
include a debris clearing command that is initiated when the number
of rotations counted is not equal to the expected number of
rotations. The debris clearing command may cause the motor to
rapidly reciprocate the poppet to dislodge any debris present
between the poppet and the servo-orifice.
[0024] In another embodiment, the attachment between the poppet and
the motor comprises a dynamic seal to isolate the motor, rotary to
linear conversion system and related drive components from the
drilling mud in which the poppet and orifice are immersed when in
operation.
[0025] In a further aspect, the present invention provides a method
for causing the generation of a mud pulse by a controlled pulser's
main pulse valve comprising the steps of: powering a pulser
servo-valve in a first direction using a rotary motor such that mud
is permitted to flow past a servo-orifice to activate a main mud
pulse valve; and powering the servo-valve in a second direction
using the rotary motor such that mud flow past the servo-orifice is
restricted to deactivate the main mud pulse valve.
[0026] In one embodiment, the method further comprises the step of
cutting power to the motor to hold the servo-valve in a particular
position within its range of motion to tailor the actuator's effect
on the main pulse valve and thereby tailor the pressure and
duration characteristics of a mud pulse.
[0027] In another aspect, the invention provides a servo-controller
for use with a downhole measurement-while-drilling pulser actuator,
the servo-controller comprising a sensor, memory, control
circuitry, and an operator interface.
[0028] In one embodiment, the sensor is a mudflow sensor, pressure
sensor, temperature sensor, rotation-step counter, position sensor,
velocity sensor, current level sensor, battery voltage sensor,
timer, or an error monitor.
[0029] In another embodiment, the memory stores time-stamped or
counted sensed events together with an event-type indication. The
servo-controller may be programmable to cause an action within the
actuator responsive to a sensed event, a time, an elapsed time, a
series of sensed events, or any combination thereof.
[0030] In a further embodiment, the user interface provides
information from memory to the operator, and may allow an operator
to alter the programming of the control circuitry. Other aspects
and features of the present invention will become apparent to those
ordinarily skilled in the art upon review of the following
description of specific embodiments of the invention in conjunction
with the accompanying figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] Embodiments of the present invention will now be described,
by way of example only, with reference to the attached Figures,
wherein:
[0032] FIGS. 1A and B are a longitudinal cross sectional view of
the upper and lower portions of an embodiment of the mud pulser
during mud flow through the servo orifice; and
[0033] FIGS. 2A and 2B are a longitudinal cross sectional view of
the upper and lower portions of an embodiment of the mud pulser
during mud flow restriction by the poppet.
DETAILED DESCRIPTION
[0034] The present invention relates to an apparatus and method for
actuating a mud pulser telemetry system used during well-drilling
operations. The present apparatus allows a servo-valve to be
powered both in opening and closing to activate a main mud pulser
valve, and does not rely on a solenoid system. The powered opening
and closing of the servo-valve results in various functional and
economic advantages, including the ability to clear debris from the
restricted portion of the mud flowpath, and faster data rates due
to elimination of inherent operating delays in the solenoid systems
of previous tools, with the end result of providing a pulser driver
which consumes a minimal amount of DC power while providing more
force with which to drive the servo-valve's poppet in each
direction. Therefore, the actuator remains functional at a
comprehensive range of downhole drilling conditions.
[0035] Furthermore, in the embodiment shown in the Figures, the
present device is designed to have several independent,
interconnected housings, and employs a double seal between the oil
compartment and the drilling mud, which simplifies assembly and
repair of the tool. The assembly/disassembly is simplified to
reduce repair turnaround time by using modular components.
[0036] Additionally, the use of a stepper motor, electric load
sensors, and control circuitry in a powered-both-directions
servo-valve system will allow for self-calibration of the tool and
self-diagnosis and error correction unavailable in other systems.
In an embodiment of the invention, as shown in FIGS. 1A and 1B, a
three-phase stepper rotary motor 1 is monitored and controlled by a
servo-controller 10, the rotary movement of the motor 1 being
converted into linear movement of a poppet 21, thereby opening and
closing a servo-valve 20 to actuate a mud pulser main valve (not
shown). Communication of information to the well surface is
accomplished by encoded signals, which are translated to produce
pressure surges in the downward flow of the pressurized mud. It is
recognized that although the drilling fluid is generally referred
to as mud, other drilling fluids are also suitable for use with the
present invention, as is well known in the art.
[0037] With reference to the Figures, the mud pulser actuator is
lowered downhole and, in the embodiment shown, generally includes a
plurality of serially interconnected housings 2, 3, 4, 5, 6, 7, and
8, an electrical connector 9, a servo-controller 10 for controlling
the operation of a rotary motor 1, and a servo-valve assembly 20
that is driven in linear motion by the rotary motor 1. The
servo-valve assembly includes a poppet 21 capable of linear
reciprocating movement to and from a seal surface 22 of a servo
orifice 23, thereby opening and closing the servo orifice 23 to
allow or prevent the passage of pressurized mud and thereby actuate
a pulser (not shown, connected to the lower end 2a of the lowermost
housing 2) to generate a pressure pulse for telemetric
purposes.
Mechanical System
[0038] A rotary-to-linear coupling system 30a, 30b (hereinafter
referred to as coupling system 30) is used to translate the torque
from the rotary motor 1 into linear movement of the servo-valve
shaft 24, which is preferably a series of connected shafts for
transferring linear movement from the coupling system 30 to the
servo poppet 21. Preferably, the servo shaft includes a spline
shaft 24a, which passes through a spline coupling 24b that can be
used to prevent rotation of the shaft 24a when necessary. The
coupling system 30 also includes seals which serve to isolate the
rotating mechanism from the downhole mud.
[0039] In the embodiment pictured in FIGS. 1A and 1B, the rotary
motor 1, is electrically powered through an electrical connection
9, by a power source (not shown). When activated, the motor 1
rotates a lead screw 31 that is mounted within a bearing support
32, causing a ball nut 33 to move threadably along the lead screw
31. Linear movement of the ball nut 33 results in dependent linear
movement of the servo shaft 24, and servo poppet 21. When driven in
the forward direction, the rotary motor 1 will cause linear
movement of the poppet 21 away from the servo-valve seat 22, to
allow passage of pressurized mud through the servo-orifice 23 to
activate the main mud pulser valve to close. When the motor 1
drives the lead screw 31 in the reverse direction, poppet 21 is
urged towards the seal surface 22 to cover the servo orifice 23, as
shown in FIG. 2B, and mud is therefore prevented from passing
through the servo orifice 23 to actuate the mud pulser main valve
to open.
[0040] The spline shaft 24 is surrounded by lubricating fluid,
which must be pressurized against the downhole hydrostatic
pressure. As shown, a pressure compensator in the form of a
membrane or bellows 42 allows reservoir fluid to substantially
equalize the pressure via a part 43. The pressure compensator be a
membrane, bellows, piston type or other type known in the industry.
In addition to a bellows seal 40, an additional seal 41 may be
added to hold oil inside the chamber of the tool, with the bellows
seal 40 preventing mud from reaching the additional seal 41. The
dual seal 40, 41 maintains the integrity of the lubrication chamber
during operation and during replacement of the bellows seal 40
during maintenance. The addition of this seal 41 does not
negatively impact performance of the actuator due to the improved
power characteristics of the system, as will be discussed
below.
[0041] In a preferred embodiment, the construction of the device
allows most downhole clogs, where debris in the mud may stop the
poppet 21 from sealing with the seal surface 22, to be easily
cleared as will be described below, and the serially interconnected
housing design allows simple and rapid repair of the tool when
necessary.
[0042] The valve assembly 20 is preferably composed of a wear
resistant material such as tungsten carbide or ceramic to maximize
the efficiency of the tool and to minimize maintenance of the tool,
and is preferably replaceable.
Operation
[0043] When restriction of mud flow by the main valve is desired,
the rotary motor 1 will be activated by the servo-controller 10 in
the forward direction. As shown in FIG. 1B, forward powering of the
rotary motor 1 will cause the lead screw 31 to turn in the forward
(for example, clockwise) direction, thereby raising the ball nut 33
and lifting the servo poppet 21 from the servo-valve seat 22. This
will allow mud flow to pass unrestricted through the servo-orifice
23 to actuate the main mud pulse valve, restricting mud flow to
generate a pulse that is transmitted to the surface. The
current-consuming portion of the circuit is then shut down until a
further signal is received from the servo-controller 10. The lack
of current to the motor 1 results in the motor 1 being immovable
and therefore acting as a brake to prevent further movement of the
poppet 21 until further activation of the motor 1.
[0044] Subsequently, when the servo-controller 10 initiates reverse
motion by the motor 1, the lead screw 31 is rotated in the reverse
direction (in the example, counterclockwise) by the motor 1,
causing the ball nut 33 and servo shaft 24 to move towards the
servo-valve seat 22 as shown in FIG. 2B. Closure of the servo-valve
20 causes opening of the main mud pulser valve to allow mud to flow
unrestricted to the surface. The current-consuming portion of the
circuit is then shut down until a further signal is received from
the servo-controller 10. The motor again acts as a brake until
further power is applied (by shorting its coils together).
[0045] The lead screw 31 and ball nut 33 may be replaced by an
alternate system of rotary to linear conversion, however a lead
screw 31 and ball nut 33 are advantageous as they are relatively
small in size and may be provided with bearings to provide a
low-friction mechanism with high load capacity, durability, and low
backlash tolerance. The lead screw 31 may be held in contact with
the motor 1 by a bearing support 32 or any other suitable
means.
[0046] The presently described system of using a stepper motor 1 to
drive a servo-valve has several advantages. The powering of the
servo-valve 20 in both directions allows greater direct control of
the servo-valve 20, avoids the previous necessity of using a return
spring in the servo assembly, and therefore the energy required is
similar to that of the force of the downhole mud flow. This results
in an energy efficient system, and results to date indicate that
the presently described system can supply a force of 100 pounds of
pressure for less energy than previous systems, particularly than
those which employ a solenoid activator. Thus, the present system
can overcome higher pressures on the poppet valve 21, allowing the
system to clear itself of debris, and permitting use in a wide
range of downhole conditions, including conditions of higher
pressure and higher volume mud flow, and in conditions when the mud
is contaminated or is very dense.
[0047] Use of a rotary motor powering the servo-valve in both
directions also allows the system to be more responsive than
solenoid systems, resulting in a faster data rate with more
accurate or precise pulse-edge timing. Experimental results
indicate that data rates of 0.25 seconds/pulse are possible with
this system, as compared to 0.8 to 1.5 seconds/pulse in solenoid
systems.
Flow Detection & Diagnostic Software
[0048] The servo controller detects the position of the poppet 21
against the servo-valve seal 22 by counting the number of rotations
made by the motor until further movement of the poppet is impeded.
For example, if the poppet 21 is generally programmed to attain an
unseated position that is three forward motor rotations away from
the seated position, upon seating activation by the
servo-controller 10, the motor will turn three reverse rotations,
at which point further rotation will be impeded due to seating of
the poppet 21 on the seal 23. On unseating activation by the servo
controller 10, the motor will turn three complete forward rotations
to return the poppet to its pre-programmed unseated position.
Seating can be sensed by an increase in current drawn by the motor,
from which a large opposing force (like stopped motion due to valve
seating) is inferred. The control circuitry also senses rotation of
the motors and can count rotations and direction of rotation.
[0049] Debris may enter the device with the mud, potentially
causing jamming of the poppet. The servo controller 10 can be
programmed to detect and clear jams from the servo-valve 20. For
example, debris may become lodged at the servo-valve seal 22,
preventing the poppet from fully sealing against the valve seal 22.
In such a situation, the motor would be prevented from completing
its three reverse rotations. This is sensed by the servo-controller
10, which will then attempt to dislodge the debris. The dislodging
sequence may include rapid reciprocation of the poppet 21 towards
and away from the seal 22, or may include further reverse rotations
on the subsequent reverse rotation. For example, if the motor was
able to turn only two reverse rotations, the servo-controller 10
will recognize that the valve did not properly close, and will
adjust one or more subsequent forward and/or reverse rotations to
ensure that the poppet 21 is able to seat against the valve seal
22. Similarly, debris may cause the poppet to not fully open,
resulting in appropriate corrective action by the servo-controller
on the next motor 1 activation. In either case, a processor
provides a report of measurements recorded and controls the
following cycle of the brushless motor's rotation accordingly.
[0050] The ability to detect and clear most jams within the tool
allows a more robust design of the tool in other respects. For
example, as the tool can easily clear particulate matter from the
servo-valve assembly, the tool can be provided with larger and
fewer mud ports, and may include reduced amounts of screening.
Screening is susceptible to clogging, and so reducing screening
leads to longer mean time between operation failure of the device
in-hole; and will reduce the velocity of any mud flow through the
tool, reducing wear on the bladder and other parts. Further, the
removal of several previously necessary components (such as the
return spring, transformer, and solenoid and related electronics)
contributes to a tool of smaller size (in both length and diameter)
that is more versatile in a variety of situations. For example,
embodiments with outside diameter less than 13/8'' (approaching
1'') or length less than four feet have been achieved, although
these dimensions are not by way of limitation, but by example
only.
[0051] Custom software also has the ability to track downhole
conditions, and also uses a sensor to detect mudflow. When mudflow
is detected, a signal is sent to the Directional Module Unit (not
shown), to activate the overall system. The system also has the
ability to time stamp events such as start or end of mudflow,
incomplete cycles or system errors, low voltages, current, and the
like, as well as accumulated run-time, number of pulses, number of
errors, running totals of rotations or motor pulses. Wires or
conductors may also be easily passed by the pulser section to
service additional near-bit sensors or other devices. The software
that detects the mudflow can be configured for different time
delays to enable it to operate under a larger variety of downhole
drilling conditions than its predecessors. The mudflow detection
capability can also be used to calibrate or confirm the closed
position of the poppet.
[0052] In addition, a user may monitor such data as well as any
downhole sensors using a user interface attachable to the tool.
Such sensors may include pressure or temperature sensors, rotation
step-counters, travel or depth sensors, current levels, battery
voltage, or timers. The user could monitor each component of the
actuator to determine when the tool must be removed from downhole
for repair. A user may, in turn, program an activity to cause an
action or correction in response to a sensed event.
[0053] The above-described embodiments of the present invention are
intended to be examples only. Alterations, modifications and
variations may be effected to the particular embodiments by those
of skill in the art without departing from the scope of the
invention, which is defined solely by the claims appended
hereto.
* * * * *