This disclosu re relates generally t o methods and apparatus for
gen erating pulses in a fluid colu mn, as. may be used for telemetry between a
surface location and downhole instru mentation within a subterranean well.
[0002] Drilling fluid circulated down a drill string to lu bricate the drill bit and
remove cuttings is typically broadly referred to as drilling "mud." The use of
pulses in a drilling flu id column is typically termed "mud pulse telemetry."
Numerous fluid pulsing systems have been used for generating such pulses in
the fluid colu mn. Such systems include various forms of valve mechanisms to
produce fluid pulses. A "poppet" valve, for example, may have a valve member
that linearly reciprocates, t o open and close a fluid passageway. A rotary valve,
by comparison, may have a rotor that rotates t o selectively control flow t o a
fluid passageway. A rotary valve may either rotate reciprocally, t o relatively
open and close a fluid passage t o generate pulses, or continually, wherein the
speed of the rotor may be varied to facilitate pulses at a momentary selected
frequency t o execute a desired communication protocol. Each of these systems
offers various features and characteristics.
BRIEF DESCRIPTION OF THE DRAWINGS
[0003] Figure 1 depicts is a schematic representation of an exemplary tool
string within a wellbore, the tool string including a mud pulse generator in
accordance with the present disclosure.
[0004] Figure 2A-C depict example structures for use in generating fluid pulses;
wherein Figure 2A schematically depicts an illustrative example valve assembly
in an "open" position, and Figure 2B schematically depicts the example valve
assembly of Figure 2A in a "closed" position; while Figure 2C depicts an
example embodiment of a mud pulse generator, including an example valve
assembly, depicted partially in vertical section.
[0005] Figures 3A-B depict the valve assembly of the example mud pulse
gen erator of Figure 2C in greater detail, depicted in longitudinal cross-section in
Figure 3A, and in lateral cross-section in Figure 3B.
[0006] Figure 4 depicts a vertical cross-section of an alternative embodiment of
a mud pulse generator valve assembly.
[0007] Figure 5 depicts a vertical cross-section of yet another alternative
embodiment of a mud pulse generator valve assembly.
[0008] Figure 6 depicts a vertical cross-section of an alternative configuration
for use with a mud pulse generator such as that of Figure 2C.
[0009] Figure 7 depicts a vertical cross-section of another alternative
configuration for use with a mud pulse generator such as that of Figure 2C.
[0010] Figure 8 depicts a block diagram of an example electronics section
suitable for use in the mud pulse generator of Figu re 2C.
[0011] Figu re 9 depicts a flow chart of an example method for using a mud
pulse generator valve assembly of any of the types described herein.
DETAILED DESCRIPTION
[0012] The present disclosu re includes new methods and apparatus for
gen erating fluid pulse telemetry signals, wherein a linearly moving valve
member, such as a piston, moves within a piston chamber defined at least in
part by a su rface, t o selectively obstruct fluid flow and thereby control a rate of
fluid flow through openings in that surface. The surface opening(s) may
represent or be defined by the respective intersection of one or more fluid flow
passage(s) with the piston chamber. In some example embodiments, the fluid
flow passage will extend around a portion of the piston chamber, t o intersect a
downstream portion of the piston chamber. In some example embodiments,
the piston will move along a linear axis and the fluid flow passage will intersect
the piston chamber surface at an angle relative t o that linear axis of movement.
[0013] The linearly moving valve member may fully, or at least partially,
obstruct flow to, or from, the fluid flow passage when in a first position (i.e., t o
close or at least red uce flow relative t o a second position) and t o allow and/or
increase flow to, or from, the fluid flow passage when moved from the first
position t o the second position. This description is not intended to limit the
linearly moving valve member t o having two positions, nor t o only discrete
positions. Rather, in at least some embodiments, the linearly moving valve
member may be varied over a range of positions to selectively obstruct the fluid
passage and thus vary fluid flow by an amou nt that varies with position of the
linearly moving valve member and corresponding obstruction of the fluid flow
passage.
[0014] In some embodiments, the moveable valve member will include a
closu re member configured to open or close flow t hrough one or fluid flow
passages in a desired manner. In some embodiments, the valve closure
member will generally open or close a fluid passage that is radially disposed
relative t o the axis of linear movement of the valve member. In some
embodiments, the piston chamber will have a region with surfaces defining a
generally uniform bore for a selected distance, and the valve will include one or
more fluid passages that extend to opening(s) in a that surface, and the closure
member is linearly moveable within the bore t o open or close fluid flow
through the openings.
[0015] The following detailed description describes example embodiments of
the new mud pulse generator and associated methods with reference t o the
accompanying drawings, which depict various details of examples that show
how the disclosure may be practiced. The discussion addresses various
examples of novel methods, systems and apparatus in reference t o these
drawings, and describes the depicted embodiments in sufficient detail t o
enable those skilled in the art t o practice the disclosed su bject matter. Many
embodiments other than the illustrative examples discussed herein may be
used to practice these techniques. Structural and operational changes in
addition t o the alternatives specifically discussed herein may be made without
departing from the scope of this disclosu re.
[0016] In this description, references to "one embodi ment" or "an
embodiment," or to "one example" or "an example" in this description are not
intended necessarily to refer t o the same embodiment or example; however,
neither are such embodiments mutually exclusive, unless so stated or as will be
readily apparent to those of ordinary skill in the art having the benefit of this
disclosure. Thus, a variety of combinations and/or integrations of the
embodiments and examples described herein may be included, as well as
further embodiments and examples as defined within the scope of all claims
based on this disclosure, as well as all legal equivalents of such claims.
[0017] A mud pulse generator as described herein will be used to generate
pulses in a fluid column within a downhole well to facilitate "mud pulse
telemetry." This terminology embraces communication through pulses in a
fluid column of any kind of well servicing fluid (or produced fluid) that may be
in a well. One example of such use is for the mud pulse generator t o be placed
in a drillstring along with MWD (or LWD) tools, t o communicate data from the
WD/ LWD tools upwardly and t o the surface through the fluid column flowing
downwardly through the drillstring to exit the drill bit. The pulses will be
detected and decoded at the surface, thereby communicating data from tools
or other sensors in the bottom whole assembly, or elsewhere in the drillstring.
The described example mud pulse generator relatively open and closes fluid
passages t o create pulses in the fluid column of a selected duration and pattern
which are detectable at the surface. In other contemplated systems, a mud
pulse generator as described may be placed proximate the surface for providing
downlink pulse communication t o a downhole tool.
[0018] Referring now t o Figure 1, the figure schematically depicts an example
directional drilling system 100 configured to form wellbores at a variety of
possible trajectories, including those that deviate from vertical. Directional
drilling system 100 includes a land drilling rig 112 t o which is attached a drill
string, indicated generally at 104, with a bottom hole assembly, indicated
generally at 144 (hereinafter BHA), in accordance with this disclosure. The
present disclosu re is not limited to land drilling rigs, and example systems
according t o this disclosure may also be employed in drilling systems associated
with offshore platforms, semi-submersible, drill ships, and any other drilling
system satisfactory for forming a wellbore extending through one or more
downhole formations. Drilling rig 112 and associated surface control and
processing system 140 can be located proximate the well head 110 at the
Earth's surface. Drilling rig 112 can also include a rotary table and rotary drive
motor (not specifically depicted), and other equipment associated with rotation
or other movement of drill string 104 within wellbore 116. Other components
for drilling and/or managing the well, such as blow out preventers (not
expressly shown) will also be provided proximate well head 110. An annulus
118 is formed between the exterior of drill string 104 and the formation
surfaces defining wellbore 116.
[0019] One or more pumps will be provided to pump drilling fluid, indicated
generally at 128, from a fluid reservoir 126 to the upper end of drill string 104
extending from well head 110. Return drilling fluid, formation cuttings, and/or
downhole debris from the bottom end 132 of wellbore 116 will return through
the annulus 118 through various condu its and/or other devices t o fluid
reservoir 126. Various types of pipes, tubing, and/or other conduits may be
used to form the complete fluid paths.
[0020] BHA 106 at the lower end of drill string 104 terminates in a drill bit 134.
Drill bit 134 includes one or more fluid flow passageways with respective
nozzles disposed therein. Various types of well fluids can be pumped from
reservoir 126 to the end of drill string 104 extending from wellhead 110. The
well fluid(s) flow through a longitudinal bore (not expressly shown) in drill string
104, and exit from nozzles formed in drill bit 134. During drilling operations
drilling fluid will mix with formation cuttings and other downhole debris
proximate drill bit 134. The drilling fluid will then flow upwardly through
annulus 118 to return the formation cuttings and other downhole debris to the
surface. Various types of screens, filters, and/or centrifuges (not expressly
shown) will typically be provided to remove formation cuttings and other
downhole debris prior to returning drilling fluid to reservoir 126.
[0021] Bottom hole assembly (BHA) 106 can include various components, for
example one or more measurement while drilling (MWD) or logging while
drilling (LWD) tools 136, 148 that provide logging data and other information t o
be communicated from the bottom of wellbore 116 to surface equ ipment 108.
In this example string, BHA 106 includes mud pulse generator 144 to provide
mud pulse telemetry of such data and/or other information through the fluid
column within the drill string to a surface receiver location, for example,
proximate the wellhead 110. Mud pulse generator 144 will be constructed in
accordance with the example device of Figure 2 and/or any of the other
example embodiments described herein. At the surface receiver location, the
pressure pulses in the fluid column will be detected and converted t o electrical
signals for commu nication to su rface equipment, and potentially from there t o
other locations.
[0022] The communicated logging data and/or other information
communicated to a receiver uphole can then be communicated to a data
processing system 140. Data processing system 140 can include a variety of
hardware, software, and combinations thereof, including, e.g., one or more
programmable processors configured t o execute instructions on and retrieve
data from and store data on a memory t o carry out one or more functions
attributed to data processing system 140 in this disclosure. The processors
employed to execute the functions of data processing system 140 may each
include one or more processors, such as one or more microprocessors, digital
signal processors (DSPs), application specific integrated circuits (ASICs), field
programmable gate arrays (FPGAs), programmable logic circuitry, and the like,
either alone or in any su itable combination.
[0023] For some applications, data processing system may have an associated
printer, display, and/or additional devices t o facilitate monitoring of the drilling
and logging operations. For many applications, outputs from data processing
system will be communicated to various components associated with operating
drilling rig 112 and may also be communicated to various remote locations
monitoring the performance of the operations performed through directional
drilling system 100.
[0024] Referring now to Figu re 2A, the figure schematically depicts an example
valve mechanism 150 illustrated in simplified form, to depict the movement
and function of the valve closure mechanism. The mechanism 150 includes a
ported sub 152 within a housing 154. In this example configu ration, ported sub
152 in combination with housing 154 defines a plurality of fluid flow passages,
which include channels 156. In many examples, channels 156 are in fluid
communication with a fluid-containing annular region (not depicted in this
figu re) above the valve mechanism within housing 154, through which well
fluids are pumped. The fluid flow passages further include radially extending
passages 158 that each communicating with a channels 156 and extend t o
intersect a central bore 162, through which fluid will flow. Central bore 162 is a
downstream portion of a chamber, indicated generally at 174, containing a
longitudinally movable valve member, here in the form of a piston 164
configured for reciprocating movement in response t o a drive mechanism 170.
Each radially extending passage 158 terminates at an opening 160 in a surface
176 defining central bore 162 of piston chamber 174. The fluid flow passages
will be sized t o allow passage of anticipated particulates that may be dispersed
in a drilling fluid, such as various forms of "lost circulation materials" that may
be introduced into a fluid t o address fluids being lost into formations
penetrated by the wellbore.
[0025] In the depicted example, drive mechanism 170 can be of any of a variety
of mechanisms, such as mechanical, electrical, hydraulic mechanisms, etc., and
thus is depicted generically in the figure. As will be described later herein,
electrical mechanisms are believed t o be well suited as drive mechanisms, and
example alternatives for electromagnetic drive mechanisms are discussed later
herein.
[0026] In this example, piston 164 includes a radially enlarged closure member,
indicated generally at 166. Closure member 166 includes a radially outward
surface 168. Piston 164 is linearly movable between at least first and second
positions along a longitudinal axis of movement 172, and may be movable
relative t o one or more additional positions between the first and second
positions or to one side of either of those first and second positions. In Figure
2A, piston 164 is in a relatively retracted position, in which valve assembly is
"open," because outward su rface 168 of closure member 166 is longitudinally
above (or "uphole") of openings 160, and thus openings 160 are unobstructed,
to provide free flow of fluid from channels 156, through passages 158 and
associated openings 160, into central bore 162 of the piston chamber.
[0027] Referring now also t o Figure 2B, that figure depicts the piston 164 in a
second longitudinal position, in which the piston 164 is relatively extended, and
the valve mechanism 150 is "closed" by virtue of the radially outward surface
168 of closure member 166 being longitudinally adjacent openings 160 t o
relatively restrict, or block, fluid flow from passages 158 into central bore 162.
For purposes of generating fluid pulses, complete blockage or "sealing" of
openings 160 is not required . In this example, closure member 166 has
openings within the perimeter defined by outward su rface 168 to allow closure
member 166 t o reciprocate t hrough fluids with less resistance; and surfaces of
closu re member 166 may be configu red t o minimize such resistance. In this
example, piston 164 moves linearly relative t o flow flowing radially inwardly, at
an angle relative t o the axis of movement 172. Thus, in this example
configuration, valve mechanism 150 operates primarily in shear relative to the
flowing fluid, and movement of piston 164 does not have to overcome the
weight of the fluid column above valve mechanism in either direction of
reciprocating movement.
[0028] Referring now to Figu re 2C, that figure depicts an example mud pulse
generator 200, depicted partially in vertical section. Mud pulse generator 200
will use a valve assembly that operates generally in accordance with the
schematic example above (which may be implemented in a variety of
configurations, including but not limited t o example configurations as described
herein). In this example, mud pulse generator 200 includes a housing assembly
202, which in this example, includes an outer housing 204 having box and pin
connections 206, 207, respectively, at the upper and lower ends, as well as a
central insert 206 and an exit bore insert 208 as will be further discussed later
herein in reference to Figure 3A.
[0029] Mud pulse generator 200 includes three primary assemblies that will be
discussed below: a power sou rce for operating the device (in this example, a
generator assembly, indicated generally at 210); an electronics section 226 and
a valve assembly 230. Generator assembly 210 includes a generator section,
indicated generally at 212, which will include a stator and rotor (not specifically
Illustrated) cooperatively configured to generate electrical cu rrent for use by
mud pulse generator 200 in response to rotation of the rotor relative to the
stator. Generator assembly 212 also includes, in this example, a multi-stage
adjustable flow gear 214, comprising a plurality of vanes configured to engage
fluid flowing downwardly in annulus 216 su rrounding generator assembly 210
within outer housing 204, and gearing for coupling to generator 212. Flow gear
214 is operatively coupled to the rotor of the generator 212 to cause rotation
thereof to generate the electrical current. At an upper end, generator assembly
210 includes a tapered nose 222 to direct flu id flow to the annulus 216, where
the fluid will engage the vanes of the first and second stages, 228A, 228B,
respectively. In some systems, tapered nose 222, or another component in its
place, may be configured to facilitate connections to another tool, such as any
one or more of electrical, optical, hydraulic, pneumatic, and/or mechan ical
connections (as discussed herein in reference to Figure 6). In this example, a
centralizer 224 is coupled between flow gear 214 and generator 212 to keep
the generator assembly 210 centralized within outer housing 204, thereby
defining a portion of an annulus 216 surround ing generator assembly 210
with in outer housing 204.
[0030] In this example, mud pulse generator 200 includes an electronics section
226 beneath generator assembly 210, and operatively coupled thereto. Again,
a centralizer 232 is located between generator assembly 210 and electron ics
section 226. Due to the communication of electrical current between the
generator and the electronics section, a hermetic seal 234 will be provided
between the two sections. In the depicted example, the seal is located within
the centralizer 232, but can alternatively be located either in either the
gen erator assembly 210 or electronics section 226, or in another interveni ng
component.
[0031] Electronics section 226 will typically include a sealed housing 236 to
isolate the contained circuitry and components from the exterior environ ment.
In this example, electronics section 226 includes both an electrical storage
mechanism for receiving electrical current produced by generator assembly 210
and control circu itry for operating mud pulse generator 200.
[0032] Referring now t o Figu re 8, that figure depicts a block diagram
representation of an example electronics section 226 suitable for use as a
component of mud pulse generator 200. As shown in that figure, electronics
section 226 includes an electrical storage device 802, in this example, coupled
t o receive an input 804 of electrical current from generator assembly 210.
Electrical storage device 802 may be of any known type suitable for the
requ irements of the remainder of mud pulse generator 200, such as a battery
or capacitor. Electronics section 226 also includes a power controller 806
operatively coupled to electrical storage device 802. Power controller 806 is
typically structured to perform a number of functions, including regulation of
the voltage and/or current supplied t o other components. This power
regu lation will often include various forms of filtering of the electrical signal t o
remove noise or other anomalies. Although power controller 806 is depicted as
being downstream from electrical storage device 802, many functions of the
controller may be performed before the electrical signal from generator 212 is
coupled t o the electrical storage device 802, and thus the current from
generator 212 may be coupled to power controller 806 instead of electrical
storage device 802. In such configurations, power controller 806 may also
include appropriate battery/storage management functionality.
[0033] Electrical current will be commu nicated from either power controller
806 or electrical storage device 802 to other electrical components in the
system. In the depicted example, these include a data signal
processing/encoding module 808 providing functional ity as described later
herein in reference t o Figu re 6, t o receive one or more data signals through one
or more inputs, as indicated at 810, and t o prepare such signal(s) for
communication through a series of mud pulses. Once a portion of a data
stream is ready for transmission, the data stream will be communicated t o a
valve controller 812 to provide appropriate control signa ls to the valve
assembly 230.
[0034] In some example systems, one or more feedback signals are received at
an input 814 and used t o optimize the performance of mud pulse generator
200, such as through adjustment of the operation of the valve controller 812.
Such feedback signal can be from a variety of potential sources. For example,
one or more sensors may be located relatively uphole in the tool string
containing mud pulse generator 200 where they can sense the generated
pulses or other conditions in the wellbore to provide appropriate feedback
signal. Such a feedback signal may be analyzed within the valve controller 812
t o adjust operation of the valve. For example, if the analysis of the feedback
signal were to indicate less than a desired threshold of pulse identification or
discrimination, valve controller 812 can be actuated t o adjust the valve
operation, for example by controlling the valve either t o reduce the
transmission rate (and possibly expand the pulse duration) and/or t o increase
the pulse amplitude. In some situations, valve controller 812 might determine
that a different commu nication protocol would be better suited to existing
downhole conditions, and can communicate (as indicated at 818) t o data signal
processing/encoding module 808 an instruction t o make such change.
[0035] Other sou rces of feedback signals are also contemplated. For example,
feed back might be obtained from the pulse receiver proximate the wellhead,
and communicated downhole by any suitable mechanism, such as a fluid pulse
downlink, wired pipe, or a communication chan nel including some portion
which is a wireless communication link. Further, in addition t o sensing fluid
pulses, other types of sensors might be utilized, such as acoustic sensors for
sensing noise in the wellbore, vibration or other movement sensors (for
example, accelerometers) sensing movement associated with the tool string,
etc.
[0036] In order t o provide the described functionality, the electron ics section
226 will typically include one or more processing resources such as a
programmable processor or a controller, and where a programmable device is
used, may also include random access memory (RAM), hardware and/or
software control logic, other storage for containing data and/or operating
instructions, read only memory (ROM), and/or other types of nonvolatile
memory. For pu rposes of this disclosure, all such memory devices, whether
volatile or non-volatile, and storage drives are considered non-transitory
storage devices. In addition, electronics section 226 comprises suitable
interface circuits 820 for communicating and receiving data from sensors
located at the surface and/or downhole, and may include one or more ports for
communicating with external devices, as well as any additional necessary input
and output (I/O) devices.
[0037] In one exa mple, electronics section 226 has programmed instructions
stored in the memory that when executed performs the described control
operations. While the described functionalities of electronics system are
described and depicted as separate in reference t o Figure 8, such depiction is
for clarity of description, any or all of such functionalities may be performed by
a single processor or controller, if desired.
[0038] Referring again to Figu re 2C, in the depicted example, electronics
section 226 is coupled to the valve assembly 230 through use of a connecting
block 238 between the two units. Again, a hermetic seal 240 will be provided
between the two units to isolate the electrical connections between the two
components. Although in the depicted example, generator assembly 210 and
electronics section 226 are depicted as being located up hole from the valve
assembly 230, these components may instead be located downhole from the
valve assembly 230. In other examples, the structu re and functionality of
electronics section 226 may be provided by two or more separate assemblies
within a mud pulse generator, an example of which is discussed herein in
reference t o Figure 7.
[0039] Referring now also t o Figures 3A-B, Figure 3A depicts valve assembly
230 in greater detail, and partially in longitudina l cross-section, while Figure 3B
depicts a lateral cross-section of valve assembly 230 through closure member
254. As can be seen in Figu re 3A, in this region, housing assembly 202 includes
not only outer housing 204, but a central insert 206 and an exit bore insert 208.
Central insert 206 sealingly engages the inner bore of outer housing 204. In a
relatively upper section, central insert 206 includes a plu rality of flutes arou nd
its outer surface extending generally t o the inner diameter of outer housing 204
t o define passageways 242A, 242B in communication with annu lus 216 above.
In a relatively lower portion, central insert includes a plurality of generally
radially extending passageways 244A, 244B connecting the passageways 242A,
242B defined by said flutes within outer housing 204. In this example
configuration, each passageway 244A, 244B terminates at a respective opening,
each indicated at 248, t o a central bore 240 in central insert 206. Passageways
244A, 244B will preferably extend at some angle relative t o central bore 240.
While this angle can be any that is desired, in many examples the included
angle between each passageway 244A, 244B and a longitudinal axis through
central bore 240 will be less than 90 degrees t o minimize obstructions of fluid
flow, and in many examples will be less than about 45 degrees, as in the
depicted example.
[0040] Valve assembly 230 includes a valve member configured for linear,
reciprocating motion within the valve assembly 230, which is identified as
piston 250. In the depicted example, piston 250 is constructed of at least two
parts, a drive member 252 and a closure mem ber 254 coupled to the drive
member 252 for movement together, so that the reciprocating motion of drive
member 252 causes closure member 254 t o move between one or more
positions relatively in registry with openings 248, t o relatively close the fluid
path into central bore 240, and one or more positions relatively out of registry
with openings 248 to relatively open the fluid path into central bore 240.
Closu re mem ber 254 can be of many possible configurations that will restrict
fluid between openings 248 and central bore 240 when in a first position, and
will allow such fluid communication when in a second position. In the depicted
example, closure member includes an outer ring 270 supported by a plurality of
spokes 272 relative to a central hub 274. Central hub 274 facilitates the
attachment of closu re member 254 to drive member 252. Although closure
member 254 has been described as a separate structure from drive member
252, in other examples both can be formed as a single component.
[0041] In the depicted example, the flu id will flow into central bore 240 from
passageways 244A, 244B. However, configurations are possible which would
allow the flow to be in the opposite direction, such as if the described
components were reversed in orientation. The described configuration is
desirable, however, as it removes the piston 250 from the pressure exerted by
the fluid column in the tool string, and allows closu re member t o open and
close the fluid passages while acting essentially in shear relative t o the flowing
fluid. Piston 250 being placed for movement outsid e of the fluid column allows
easier movement in both directions, as the drive mechanism does not need t o
overcome the weight and force of the fluid column when moving in either
direction. Examples of this configu ration offer a significant advantage over
valves with a moving structure member that is exposed to the fluid column
above (such as conventional poppet valves), which have t o overcome the
weight and pressure of the column when moving in one of the two directions.
[0042] In the depicted example, outer ring 270 of closure member 254 has a
circumferential periphery having a central section 276 having a generally
cylindrical profile, providing a "sealing" su rface. Closure member 254 is sized
such that central section 276 provides a relatively small tolerance within central
bore 256 to substantially block flu id flow between openings 248 and central
bore 240. It should be understood that complete closure (i.e., literal "sealing")
of the fluid flow passages is not necessa ry for the generation of the fluid pulses.
In fact, in some examples, closure member 254 may be configured t o leave
"open" (i.e. unblocked) one or more openings 248 even when in a relatively
"closed" position, so as to always allow some degree of flu id flow; or some fluid
flow may be permitted through the dimensions of closu re member 254 being
selected to allow a desired gap, even when in registry with the openings (i.e., in
a "closed" position). Thus, the "opening" and "closing" of the valve are not
absolute terms, but are relative t o one another, indicating permitting and
obstructing fluid flow to a degree desired to generate fluid pulses, while
meeting operations requirements of downhole operations (such as fluid flow to
the drill bit during drilling operations).
[0043] In this example configuration, closure member 254 is configu red to
block all openings 248, and therefore has a continuous outer periphery. Outer
ring 270 includes tapering sections 278A, 278B on each side of central section
276 tapering in the radially inward direction, which minimize fluid resistance t o
movement of closure member 254 in both directions. Additionally, the
depicted tapers will assist in freeing closure member 254 from any solids which
might otherwise become trapped and thereby block or impede movement of
close member. Closure member 254 will preferably be constructed of a
relatively lightweight material which is capable of withstanding the fluid
pressures and downhole environments in which it will be used. One suitable
material for closure member 254 is titanium, to minimize the mass of closure
member 254 thereby facilitating relatively rapid reciprocal or other movement
within central bore 240. Other suitable materials would be ceramic, stellite,
and or tungsten carbide, each of which may offer particular advantages relative
to specific downhole conditions).
[0044] A driver section, indicated generally at 280, is configured to move piston
250 back and forth along the linear path. Driver section 280 can be of many
possible configurations, and may be operated for example either electrically or
hydraulically. In the depicted example, driver section 280 is electrically
operated. The drive mechanism may be a solenoid or other su itable
mechanism, for example a voice coil selectively generating a magnetic field t o
interact with a magnetic field established by one or more permanent magnets
to cause the reciprocating movement of piston 250. For this type of driver
mechanism, the coils can be most easily placed in a valve housing 256 which
will remain stationary relative t o central insert 206, thereby facilitating the
practical considerations of electrical connections from electronics section 226
t o one or more coils 258A, 258B located in respective recesses 260A, 260B in
the inner periphery of valve housing 256. The valve housing 256 will be formed
of a non-magnetic material. Drive member 252 will include one or more
recesses 262A, 262B extending at least partially around the periphery of drive
member 252 with each recess housing one or more respective permanent
magnets, indicated generally at 264A, 264B.
[0045] The described drive mechanism, using coils interacting with the
magnetic fields established by permanent magnets can be implemented in
ways that offer particular advantages. For example, as can be seen in driver
section 280, no physical engagement with drive member 252 is required to
cause the desired movement; and the movement will occur even with well
fluids su rrounding drive member 252 in valve housing 256. As a resu lt, no
dynamic seal is required between drive member 252 and valve housing 256 (or
a similar structure). Such dynamic seals can, in some implementations, impede
movement of a moving member (here, drive member 252) and/or serve as a
potential point of failure. While such a dynamic seal could be added t o driver
section 280 if desired for some applications or configu rations, in the depicted
embodiment, one is not necessary for the described functioning of driver
section 280.
[0046] A number of specific configurations for the coils and the permanent
magnets are envisioned. In some cases, multiple coils may be actuated with
opposite polarities of electrical cu rrent t o generate the reciprocal movement of
the piston 250. In other examples, however, each coil ay be actuated with a
single polarity of electrical current, with the change in direction achieved
through orientation of the magnetic fields of the permanent magnets and the
relative placement of the permanent magnets. In either type of system,
multiple coils may be sequentially actuated to obtain the desired movement of
the piston 250. In this example, the valve housing 256 and coils 258 extend
concentrically around drive member 252. While this configu ration offers
advantages, it should be understood that other mechanisms may be used in
which the coils or other electromagnetic structures are not concentric to drive
member 252 but are placed relatively radially outwardly of drive member 252.
[0047] In the depicted embodiment of valve assembly 230, central bore 240
has a generally circular cross-section . However other configu rations may be
utilized, such as an oval cross-section to the bore, which could be utilized t o
prevent rotation of closure member 254, if such were desired for a particu lar
implementation. Whatever the cross-sectional configuration of central bore
240, it will preferably have a generally uniform lateral cross-section (as depicted
in Figu re 3B), at least across the intended range of travel of closu re member
254.
[0048] In some configurations, valve assembly 230 as can be configured such
that closu re member 254 can reciprocate between a first position generally
opening openings 248 for fluid flow and a second position generally closing
openings 248 for fluid flow. In such configurations, closure member 254 need
only reciprocate from one side of openings 248 t o a position generally in
registry with openings 248. This type of configuration lends itself t o design
configurations of the arrangement of openings and of piston travel and
configuration t o optimize the valve for rapidity of movement between open
and closed positions, to facilitate a high density of pulses per time unit.
However, other configu rations are expressly contemplated. As one example,
closure member might move from a first position above openings 248, to a
second position closing openings 248, and then to a third position on the
opposite side of openings 248.
[0049] As another alternative, closure member 254 may move not only
between essentially a relatively full "open" position, fully uncovering all
openings, and a full "closed" position, fully covering all, or a su bset, of openings
248, but may also move t o one or more intermediate positions only partially
blocking either all or a subset of open ings 248. In this type of configu ration,
valve assembly 230 would be able t o generate multiple amplitudes of pulses.
As another alternative configuration to achieve multiple amplitudes, openings
248 may be cooperatively arranged with closure member 254 such that only
some openings are closed with closure member in a first position, and all
openings are closed with closure member 254 in an axially offset position.
Different cooperative arrangements of openings 248 and the configu ration of
closu re member 254 can be envisioned t o achieve this result. As one example,
one or more openings 248 might be arranged to intersect central bore 240 at a
first longitu dinal position, with one or more other openings 248 arranged to
intersect central bore 240 at a nearby, but longitudinally offset, position.
Closu re member 254 can be configured with a dimension sufficient to block
both sets of openings in one position, and with sufficient travel to allow only
blocking either set of openings at two additional positions. An additional
possible configuration would be for the two sets of openings to define different
cumulative flow areas, such that blocking of a first set of openings 248 wou ld
block a selected percentage of the total fluid flow, while blocking of the second
set of open ings 248 wou ld block a different selected percentage of the total
fluid flow, thereby enabling at least three pulse amplitudes.
[0050] Referring now t o Figu re 4, the figure depicts an alternative configuration
of a mud pulse generator valve assembly, indicated generally at 400. Valve
assembly 400 is depicted in an operating environment within an outer housing
402. Valve assembly 400 includes a valve housing assembly, indicated generally
at 404, sealingly received with an outer housing 402. In the depicted example,
housing assembly 404 includes a lower block 406 and an upper block 408.
Additionally, a conduit section 410 provides a path 412 for routing electrical
conductors into upper block 408 and down through lower block 406 t o other
devices below valve assembly 400 (only a portion of the path is visible in the
depicted cross section). Either upper block 408 or conduit section 410 will be
configured t o provide a plurality of centralizing ribs (for example three ribs) t o
maintain the centralized orientation of upper block 408. As with valve section
assembly 230 of Figu res 2 and 3, the centralizing ribs will define a plurality of
passageways, as indicated at 414, in communication with the annulus 416
above valve assembly 400, and extending past upper block 408, and
terminating in one or more passageways 418 in lower block 406 extending t o
respective openings 420 in a surface defining at a central bore 422, in a manner
generally analogous to valve assembly 230, discussed above.
[0051] As can be seen from Figure 4, valve assembly 400 includes a moveable,
generally annular drive piston, indicated generally at 424, having a drive section
426 and an integrally formed closure section 428. Drive section 426 is
supported in concentric relation to a guide rod 432 by a pair of bearings 430A,
430B. Drive section 426 extends with in a drive housing 434, and where the
support of guide rod 432 maintains a close, but spaced relation between
adjacent surfaces of drive section 426 and drive housing 436.
[0052] Valve assembly 400, like valve assembly 230 of Figu res 2 and 3, will be
electrically actuated, such as though use of one or more voice coil assemblies.
Thus, drive section 426 includes a plurality of permanent magnets 438, secu red
within one or more recesses 440 on the outer diameter of drive piston 442.
Drive housing 436 supports a plurality of selectively actuable coils extending in
concentric relation t o drive piston 442. In the depicted example, drive housing
436 supports four coils 444A-D. The same options for the configuration and
control of coils 444A-D discussed relative t o valve assembly 230 of Figu re 2C are
applicable t o this valve assembly 400.
[0053] In some examples, coils 444 will be in an oil bath in a sealed chamber
446. Sealed chamber 446 is sealed at a lower extent by a sealed engagement,
at 448, between drive housing 430 and upper block 408, and at an upper extent
by a seal plate 450. Seal plate 450 sealingly engages both gu ide rod 432 and
drive housing 436. Thus, coils 444 and any other electrical circuitry that may be
included within sealed chamber 446, are within oil, and isolated from the well
fluid surrounding drive piston 442.
[0054] As can be seen from Figure 4, closure section 428 does not define
merely a solid cylindrical sealing su rface (as discussed relative t o central su rface
276 of closure member 254, as depicted in Figures 3A-B). Instead, closure
section 428 defines a plurality of openings 452 each of which will engage with a
respective opening 420 in surface 450 defining a central bore 422. All
longitudinally extending surfaces of closu re section, including those defining
openings 452 and lower surface 454 are again tapered t o reduce restrictions on
movement through the flu id.
[0055] In operation, in a manner as previously described, actuation of the voice
coils will cause either forward or backward linear movement of drive piston
section, causing closure section 428 t o move such that openings 452 are moved
into or out of registry with openings 420, thereby selectively relatively opening
or blocking flow between openings 420 and central bore 422 to establish pulses
in the moving fluid column as described previously.
[0056] Referring now t o Figu re 5, therein is depicted an alternative
configuration for a mud pulse generator valve assembly 500, depicted in
vertical section. Mud pulse valve 500 shares many structural and operational
characteristics with valve assembly 400 of Figu re 4. Accordingly, those
similarities will not be specifically addressed here. Components having a
structu ral and functional similarity t o components in valve assembly 400 will be
numbered similarly in Figure 5, without implying that such components are fully
identical in all respects t o those of Figu re 4.
[0057] In some example systems, it may be preferable t o have a "fail-safe"
mechanism, such that if the mud pulse valve were t o fail, it would fail in an
"open " position in which mud flow through the valve, toward the drill bit or
other mechanisms below, would still occur. This resu lt can be achieved by
providing a biasing mechanism arranged t o bias closure section 428 such that
openings 452 are moved into registry with openings 420 thereby opening flow
t o the passages. This biasing mechanism can be one of various types, such as
hydraulic, pneumatic (such as an air chamber serving as a spring) or
mechanical. In many example systems the biasing mechanism will be
mechanical, including one or more springs, which may be of various
configurations.
[0058] Valve assembly 500 again includes an electrically actuated drive section,
indicated generally at 502, with a generally annular drive piston, indicated
generally at 504, that includes a drive section 506 coupled to form a
functionally integral unit with closure section 428. A spring assembly 506
extends between a lower portion of upper block 408 and an upper portion of
drive piston 504. In the depicted example, spring assembly 506 includes at
least one conduit configured to have two spaced legs 508A, 508B separated by
a bridge section 510 such that spaced legs 508A-B, when compressed toward
one another, provide a bias toward a relatively separated position, in which
drive piston 504 is biased t o a position, as illustrated, wherein openings 452 of
closure section 428 are in registry with openings 420, allowing fluid flow
therethrough. When drive piston 504 is electrically actuated to move toward a
relatively retracted position, the generally laterally extend ing legs (relative t o a
longitudinal axis extending through the valve assembly 500) are compressed
towards one another, establishing the bias.
[0059] In this example, spring assembly 506 is formed of tubes, which allows
spring 506 also serve as a conduit, which can house electrical conductors t o
facilitate communication with mechanisms on drive piston 504. As noted
above, the positions of the permanent magnets and coils can be arranged with
either type of component on either the stationary components or movable
components of the drive section. In this example, a plurality of coils 512A-C are
supported on moveable drive piston 504 while a plurality of permanent
magnets 514A-E are supported by the stationa ry central rod 516. In this
configuration, coils 512A-C can receive electrical control signals through
conductors extending through the tubes forming spring assembly 506. The
electrical conductors will be in communication with electronics section such as
described at 226 in Figure 2C (or relative to element 702 in Figure 7, later
herein). Spring assembly 506 can be formed of any material capable of
withstanding the downhole conditions and provided acceptable fatigue
resistance t o withstand the cycling of the valve assembly. For a tubular spring
mechanism as in the example, titanium is contemplated t o be an acceptable
material. In place of a single spring assembly 506, multiple springs may be
used, and the springs may be of configurations other than the example
depicted herein. Spring assembly 506 and coils 512A-C will again preferably be
in an oil bath, generally as described relative t o valve assembly 400 of Figure 4.
[0060] As is apparent from the above discussion, in mud pulse generator
assembly 200 of Figure 2C, all of the fluid flow is directed around tapered nose
222 t o reach generator assembly 210, and particularly t o encou nter the vanes
thereof, before flowing through passageways 242A, 242B. Referring now to
Figure 6, therein is depicted an upper portion of an alternate mud pulse
generator configuration, indicated generally at 600, which may be utilized. In
this example, components serving essentially the same functionality as in mud
pulse generator 200 of Figure 2C are numbered similarly. In mud pulse
generator 600, in order t o allow control of fluid by generator assembly 210,
generator assembly is housed within a sleeve assembly 602 that fits within
housing assembly 202. Sleeve assembly 602 defines a central bore 616, and an
external bypass channel 604.
[0061] Generator assembly 210 is housed within central bore 616, which
extends longitudinally, past at least multi-stage adjustable flow gear 214, t o an
exit port (not shown) in communication with an annulus in communication with
bypass chan nel 604. Sleeve assembly 602 includes an upper sub 606 that
houses a valve assembly, indicated generally at 608. Valve assembly 608
includes a movable sleeve 610 that is longitudinally movable relative t o housing
assembly 202, and relative t o a bypass port 612. In this example, valve
assembly 608 includes a biasing spring 614 arranged t o bias movable sleeve 610
into a position closing bypass port 612. Thus, in the depicted example valve
assembly 608 is arranged such that all flow will be directed t hrough central
bore 616, and thereby t o generator assembly 210, in the absence of actuation
of the valve t o open bypass port 612. Valve assembly 608 may be actuated by
any desired actuation mechanism. For example, an electrical control
mechanism as described relative to valve assem bly 230 in Figure 2C may be
utilized. Alternatively, other actuation mechanisms including other forms of
electrical, hydraulic, or mechanical mechanisms may be utilized.
[0062] Mud pulse generator 600 and is also configured to allow communication
of signals through the device. Accord ingly, in this example, upper sub 606
includes a connector 620 supported on a centralizing snorkel 622 to facilitate
engagement with a complementary connector centralized within housing
assembly 202. In many examples, connector 620 will be an electrical
connector, and wi ll be coupled t o electrical conductors housed within isolated
channel through sleeve assembly 602. In other examples, connector 620 may
be an optical connector or a hybrid optical and electrical connector; or may be
a hydraulic connector. In the depicted example, snorkel 622 is depicted as a
separate component from upper sub 606, and therefore includes a portion of a
connector assembly 626A, which engages a complementary connector
assembly 626B in upper su b 606. Thus, in a configu ration in which connector
620 is an electrical connector, electrical signals may be communicated through
condu ctors within channel 628 of snorkel 622 and through connector assembly
626A-B t o conductors with in channel 624 (the conductors are not specifically
depicted, for clarity).
[0063] As identified above in reference t o mud pulse generator assembly 200
of Figu re 2C, other configurations are possible, including the mud pulse valve
assembly 230, being arranged at the top of the mud pulse generator, with the
remainder of the identified components being located beneath the valve
assembly. Referring now to Figure 7, that figu re depicts yet another alternative
configuration for a mud pu lse generator 700 in which the electronics section
(226, as described in reference t o Figure 2C) is divided into two parts. In this
example, storage mechan isms, such as capacitors and/or batteries, as
previously described will still be located above the valve assembly in a first
electronics section as depicted in Figure 2C (not depicted here). However,
other electronics, such as control circu itry and other systems previously
described relative t o electronics section 226 will be located within a separate
electronics section 702 placed below valve assembly 230 (partially depicted).
Electronics section 702 is configured to extend concentrically around a fixed
sleeve 704 defining a portion of central bore 240 (of Figure 3A) within a housing
assembly 202. Electrical communication is provided through one or more
passageways, such as depicted at 706 in valve assembly 700, and t hrough fixed
sleeve 704 (passageways not visible in the depicted cross section). Such
passageway 706 will preferably extend to reach other passageways in the valve
assembly (as depicted at 412 in Figure 4) t o reach at least to the electronics
section 226 above the valve assembly; and in some cases will extend t o an
upper connector (such as depicted at 620 in Figure 6), t o facilitate connection
with other tools located above mud pulse generator 700. Additionally, other
passageways 710 and/or connectors 712 may be provided to facilitate
communication of electronics section 702 and/or other structures above it,
with tools located beneath mud pulse generator 700.
[0064] Referring now to Figure 9, the figure depicts a high level flow chart 800
of an example method of operation of any of valve assembly 200, valve
assembly 400, or valve assembly 500. As a first step, a controller assembly will
receive data t o be communicated, as indicated at 902. This receiving of data
may be performed in another mechanism such as an MWD or LWD tool in the
tool string, or by another control assembly, such that the data may be gathered
for transmission by the valve assembly.
[0065] Next, the data will be prepared for communication. This will typically
include encoding the data pursuant t o a selected communication protocol, as
indicated at 904. Any of a wide variety of communication protocols for
communicating data through a pu lse series can be implemented, including
frequency-shift keying (FSK), phase-shift keying (PSK), amplitude-shift keying
(ASK), and combinations of the above, as well as other communication
protocols. An appropriate controller will then control the drive assembly of the
valve assembly, as indicated at 906. This functionality can be performed, for
example, within a down hole electronics section, as described in reference t o
Figure 8. In the case of the described voice coil drive mechanisms, this will
include selectively applying cu rrent t o one or more of the voice coils t o cause
linear movement of the closure element as described above, in accordance
with the selected communication protocol, and a selected data rate. As noted
above, for some example valve configurations this can include moving the
closu re member t o positions in addition to (respectively) fully "open" and fully
"closed," as may be used to provide one or more additional levels of pulse
amplitude. Also as noted above, this actuation can include sequential actuation
of multiple coils.
[0066] Many variations may be made in the structures and techniques
described and illustrated herein without departing from the scope of the
inventive subject matter. For example, the alternative structures and
operations discussed above with respect t o each of valve assembly 230, valve
assembly 400 and valve assembly 500 should be understood to be applicable to
the other valve assemblies. As just one example, closure member 252 of valve
assembly 230 (Figure 3), could be configu red to include a generally solid section
and a section with radial openings as depicted relative to closure section 428 at
452. Similarly the alternative configurations as discussed in reference t o
Figures 6 and 7 may be used in systems with any of valve assemblies 230, 400,
and/or 500. Additionally, many variations may be made relative t o the
described example systems in view of the disclosure herein. Accordingly, the
scope of the inventive subject matter is t o be determined only by the scope of
the following claims and all additional claims supported by the present
disclosure, and all equivalents of such claims.

We claim:
1. A flu id pulse generator valve, comprising,
a housing;
a piston chamber within the housing, the piston chamber having a downstream
portion;
a flu id flow passage within the housing extending around a portion of the
piston chamber to intersect the downstream portion of the piston
chamber; and
a piston disposed within the piston chamber and linearly moveable t o
selectively obstruct flow at the intersection between the fluid flow
passage and the downstream portion of the piston chamber.
2. The fluid pulse generator valve of claim 1, wherein the fluid flow
passage extends inwardly at an angle to where the fluid flow passage intersects
the downstream portion of the piston chamber.
3. The fluid pulse generator valve of claim 1, wherein the valve comprises a
plurality of fluid flow passages extending around a portion of the piston
chamber.
4. The fluid pulse generator valve of claim 1, wherein the fluid flow
passage is sized t o pass particulates that may be dispersed in a drilling fluid
when flowed through the fluid flow passage.
5. The fluid pulse generator valve of claim 1, further comprising a drive
mechanism operably coupled to the piston t o control movement of the piston
over a range of linear movement.
6. The fluid pulse generator valve of claim 5, wherein the range of linear
movement includes a plurality of different positions, each corresponding t o a
different degree of flow obstruction at the intersection between fluid flow
passage and the downstream portion of the piston chamber.
7. The fluid pulse generator valve of claim 5, wherein the drive mechanism
comprises an electromagnetic mechanism includ ing a controller for controlling an
amplitude of linear reciprocation of the piston.
8. The fluid pulse generator valve of claim 5, wherein the drive mechanism
is sufficiently powered to clear particulates dispersed in a drilling fluid with the
piston when the particulates are present at the intersection of the flu id flow
passage with the downstream portion of the piston chamber.
9. The fluid pulse generator valve of claim 1, wherein the piston is sealed
with an inner wall of the piston chamber.
10. The fluid pulse generator valve of claim 9, further comprising a dynamic
seal isolating at least a portion of the drive mechanism from a fluid flowing in
the downstream portion of the piston chamber.
11. The fluid pulse generator valve of claim 1, further comprising a radial
gap between the piston and an inner wall of the piston chamber, whereby
some fluid flowing through the fluid passage outside of the piston chamber may
enter the piston chamber regardless of the position of the piston.
12. A fluid pulse generator valve, comprising:
a housing;
a piston chamber within the housing, the piston chamber having a portion
defined by a su rface;
a fluid flow passage within the housing extending t o intersect the piston
chamber at one or more openings in the su rface; and
a piston disposed within the piston chamber and linearly moveable within the
piston chamber to selectively obstruct flow and allow flow through the
one or more openings in the piston chamber surface.
13. The fluid pu lse generator valve of claim 12, wherein the valve comprises
a plurality of fluid flow passages intersecting the downstream portion of the
piston chamber.
14. The fluid pulse generator valve of claim 12, wherein the piston
comprises a closu re member which will obstruct flow through the openings
when it is in registry with the openings.
15. The fluid pulse generator valve of claim 14, wherein the surface of the
piston chamber defines a portion having a uniform bore in which the closure
member of the piston reciprocates.
16. A flu id pulse generator, comprising:
a housing assembly defining at least one flow passage; and
a shear valve assembly within the housing, the shear valve assembly including an
actuation member moveable along a linear axis, the actuation member
including a closure section to open or close a fluid passage opening that is
radially disposed relative t o the linear axis.
17. The fluid pulse generator of claim 16, further comprising a drive
mechanism, at least a portion of the drive mechanism physically coupled to the
actuation member.
18. A flu id pulse generator, comprising:
a valve housing assembly defining a flow passage, the flow passage extending t o a
plurality of openings disposed around the perimeter of a su rface defining a
uniform bore for an established distance;
a valve piston having a closu re member linearly moveable within the generally
uniform bore, the closu re member moveable between a first position
allowing flow of fluid between the openings and the uniform bore, and a
second position obstructing the flow of fluid between at least some of the
openings and the uniform bore;
a drive mechanism operably coupled t o the valve piston; and
a controller operably coupled t o the drive mechanism to move the closure
member between the first and second positions.
19. The fluid pulse generator of claim 18, wherein the valve assembly is
further moveable t o at least a third position.
20. The fluid pu lse generator of claim 18, wherein the drive mechanism is an
electromagnetic mechanism.
21. The fluid pulse generator of claim 20, wherein the electromagnetic drive
mechanism includes at least one permanent magnet on a first component and
at least one coil on a second component.
22. The fluid pu lse generator of claim 18, wherein the controller will actuate
the drive mechanism in accordance with at least one protocol selected from the
grou p of: FSK, PSK, ASK, and combinations of the above.
23. The fluid pulse generator of claim 18, wherein the generally uniform bore
has a circular cross-section for the established distance.
24. The fluid pulse generator of claim 18, wherein the closure member
comprises a generally cylindrical outer surface su pported relative t o a central hub
by a plurality of spokes.
25. A flu id pulse generator, comprising:
a housing;
a piston chamber within the housing, the piston chamber having a portion defined
by a surface;
a flu id flow passage within the housing extending t o intersect the piston chamber
at one or more openings in the surface; and
a piston disposed within the piston chamber and linearly moveable within the
piston chamber to selectively obstruct flow and allow flow t hrough the
one or more openings in the piston chamber surface;
a drive mechanism operably coupled to move the piston between positions to
obstruct or allow flow through the openings;
a power source; and
a controller coupled to the power source and drive mechanism to control the
drive mechanism t o move the piston to generate a series of fluid pulses.
26. The fluid pulse generator of claim 25, f rther comprising a plurality of fluid
flow passages within the housing and extending to intersect the piston chamber at
one or more openings.
27. The fluid pu lse generator of claim 25, wherein the fluid flow passage
extends around a portion of the piston chamber t o intersect the downstream
portion of the piston chamber.
28. The fluid pulse generator of claim 25, wherein a portion of the drive
mechanism is radially disposed relative t o a portion of the piston.
29. The fluid pulse generator of claim 26, wherein a portion of the drive
mechanism extends concentric to a portion of the piston.
30. A method of generating fluid pulses in a fluid column, comprising:
actuating a fluid pulse generator disposed in a tool string within a wellbore, the
tool string containing the flu id colu mn, the fluid pulse generator
comprising,
a housing assembly defining a flow passage, the flow passage extending t o
a plurality of openings disposed in a surface defining a generally
uniform bore for an established distance;
a valve assembly having a closure member linearly moveable within the
gen erally uniform bore, the closu re member su pporting a sealing
surface, wherein the closure member is moveable between a first
position in which the sea ling surface allows relatively free flow of
fluid between the openings and the generally uniform bore, and a
second position in which the sealing su rface relatively restricts the
flow of fluid between the plu rality of openings and the bore; and
a drive mechanism operably coupled to the closure member to move the
closu re member between the first and second positions; and
wherein actuating the fluid pulse generator comprises,
receiving information to be communicated through the fluid column,
encoding the information in accordance with a selected communication
protocol, and
controlling the drive mechanism t o move the closure member in
accordance with the encoded information t o generate a
corresponding series of fluid pulses in the flu id column.
31. The method of claim 30, wherein the closure member is further movable
t o a third position, and wherein the drive mechanism is further operable t o move
the closure member t o the third position as well as t o the first and second
positions.
32. The method of claim 31, wherein controlling the drive mechanism further
comprises:
receiving feedback inputs from the sensors outside the valve mechanism, and
adjusting the drive mechanism in response t o such feedback.