Note: Descriptions are shown in the official language in which they were submitted.
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METHOD FOR A PRESSURE RELEASE ENCODING SYSTEM FOR
COMMUNICATING DOWNHOLE INFORMATION THROUGH A WELLBORE TO A
SURFACE LOCATION
FIELD OF THE INVENTION
[01] The present invention relates to a system and method for transmitting
information
from a downhole location to surface location. More particularly, the present
invention
relates to a system and method for communicating the inclination angle at the
bottom of
a wellbore to a surface location in a generally real-time fashion without the
need for
wirelines or remote transmission. The present invention also relates to the
association
of pressure transducer measurements to monitor pressure changes as a method of
transmission of information.
BACKGROUND OF THE INVENTION
[02] Drilling In underground drilling, such as gas, oil or geothermal
drilling, a bore is
drilled through a formation deep in the earth. Such bores are formed by
connecting a
drill bit to sections of long pipe, referred to as a "drill pipe," so as to
form an assembly
commonly referred to as a "drill string" that extends from the surface to the
bottom of
the borehole. The drill bit is rotated so that it advances into the earth,
thereby forming
the bore. In rotary drilling, the drill bit is rotated by rotating the drill
string at the surface.
In directional drilling, the drill bit is rotated by a downhole mud motor
coupled to the drill
bit.; In a steerable drill string, the mud motor is bent at a slight angle to
the centerline
of the drill bit so as to create a side force that directs the path of the
drill bit away from a
straight line. The drill pipe is rotated slowly so as to avoid being stuck to
the formation.
The drill pipe is not the main source of the drill bit rotation. In any event,
in order to
lubricate the drill bit and flush cuttings from its path, pumps on the surface
pump fluid
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referred to as "drilling mud", at a high pressure, through an internal passage
in the drill
string and out through the drill bit. The drilling mud then flows to the
surface through the
annular passage formed between the drill string and the cut formation
borehole.
[03] Depending on the drilling operation, the surface measured pressure of
the
drilling mud flowing through the drill string will typically be between 500
psi and 5000
psi. Some of this pressure is lost at the drill bit so that the pressure of
the drilling mud
flowing outside the drill string is less than that flowing inside the drill
string. In addition,
the components of the drill string are also subjected to wear and abrasion
from drilling
mud, as well as the vibration of the drill string.
[04] The distal end of a drill string is the bottom hole assembly (BHA),
which
includes the drill bit, the drilling sub and drill collars. In "measurement
while drilling"
(MWD) applications, sensing modules in the BHA provide information concerning
the
direction of the drilling. This information can be used, for example, to
control the
direction in which the drill bit advances in a steerable drill string. Such
sensors may
include magnetometers and accelerometers to sense inclination, azimuth and
tool face
orientation.
[05] Historically, information concerning the conditions in the well, such
as
information about the formation being drilled through, was obtained by
stopping drilling,
and lowering sensors into the bore through the center of the drill pipe using
a wireline
cable, which were then retrieved after the measurements had been taken. This
approach was known as wireline logging. More recently, sensing modules have
been
incorporated into the BHA to provide the drill operator with essentially real-
time
information concerning one or more aspects of the drilling operation as the
drilling
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progresses. In "logging while drilling" (LWD) applications, the drilling
aspects about
which information is supplied comprise characteristics of the formation being
drilled
through. For example, resistivity sensors may be used to transmit, and then
receive,
high frequency wavelength signals (e.g., electromagnetic waves) that travel
through the
formation surrounding the sensor. By comparing the transmitted and received
signals,
information can be determined concerning the nature of the formation through
which the
signal traveled, such as whether it contains water or hydrocarbons. Other
sensors are
used in conjunction with magnetic resonance imaging (MRI). Still other sensors
include
gamma scintillators, which are used to determine the natural radioactivity of
the
formation, and nuclear detectors, which are used to determine the porosity and
density
of the formation.
[06] In traditional LWD and MWD systems, electrical power is supplied
either by a
turbine driven by the mud flow or a , battery modules. In both LWD and MWD
systems,
the information collected by the sensors must be transmitted to the surface,
where it can
be analyzed. Such data transmission is typically accomplished using a
technique
referred to as "mud pulse telemetry." In a mud pulse telemetry system, signals
from the
sensor modules are typically received and processed in a microprocessor-based
data
encoder embodied in a collar as part of the BHA, which digitally encodes the
sensor
data. A controller in the control module then actuates a pulser, also
incorporated into
the BHA, that generates pressure pulses within the flow of drilling mud that
contains the
encoded information. The pressure pulses are defined by a variety of
characteristics,
including amplitude (the difference between the maximum and minimum values of
the
pressure), duration (the time interval during which the pressure is
increased), shape,
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and frequency (the number of pulses per unit time). Various encoding systems
have
been developed using one or more pressure pulse characteristics to represent
binary
data (i.e., bit 1 or 0)--for example, a pressure pulse of 0.5 second duration
represents
binary 1, while a pressure pulse of 1.0 second duration represents binary 0.
The
pressure pulses travel up the column of drilling mud flowing down to the drill
bit, where
they are sensed by a strain gauge-based pressure transducer. The data from the
pressure transducer are then decoded and analyzed by the drilling rig
operating
personnel.
[07] In the past, various patents have issued relating to the transmission
of
downhole conditions to a surface location. U.S. Patent No. 3,867,714, issued
on
February 18, 1975 to B.J. Patton, describes a logging-while-drilling (LWD)
system,
which is positioned within the drill string of a well drilling apparatus. The
system
includes a tool which has a turbine-like, signal-generating valve which
rotates to
generate a pressure wave signal in the drilling fluid which is representative
of a
measured downhole condition.
[08] U.S. Patent No. 4,520,468, issued on May 28, 1985 to S.A.
Scherbatskoy,
provides measurement-while-drilling (MWD) systems. The measurements are
transmitted to the earth by a pulser, which produces common responses to
electrical
signals from a measuring instrument, and pressure pulses in the drilling fluid
which are
detected and decoded at the surface of the earth. The pulser is mounted in a
special
pulser sub which is of short length and enlarged internal diameter compared to
the
standard drill sub and which is threadedly secured at each end to the BHA
collars. drill
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string. An elongated housing is supported by the pulser sub. This elongated
housing
contains instrumentation or batteries and is connected to the pulser.
[09] U.S. Patent No. 4,562,560, issued on December 31, 1985 to A.W. Kamp,
provides a method and means for transmitting data through a drill string in a
borehole.
The data is in the form of pressure waves (such as pressure pulses) which are
generated by means of a downhole mud motor that is driven by the drilling mud.
The
pressure waves are generated by varying the load on the mud motor according to
a
predetermined pattern that is representative of the data to be transmitted.
[10] U.S. Patent No. 5,679,894, issued on October 21, 1997 to Kruger et
al.,
describes a drilling system in which sensors are placed at selected locations
in the drill
string so as to continually measure various downhole operating parameters,
including
the differential pressure across the mud motor, rotational speed of the mud
motor,
torque, temperature, pressure differential between the fluid passing through
the mud
motor and the annulus between the drill string and the borehole, and the
temperature of
the circulating fluid. A downhole control circuit has a microprocessor so as
to process
signals from the sensors and transmit the process data uphole to a surface
control unit
by way of suitable telemetry.
[11] U.S. Patent No. 6,105,690, issued on August 22, 2000 to Biglin, Jr. et
al.,
provides a method and apparatus for communicating with a device downhole in a
well,
such as a sub in the BHA at the end of the drill string. Pressure pulses, such
as those
generated by the pistons of the mud pump, are transmitted through the drilling
mud to a
pressure pulsation sensor in the BHA. Based on its analysis of the pressure
pulsations,
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the sensor can decipher a command from the surface so as to direct the
steering of a
steerable drill string.
[12] U.S. Patent No. 6,443,228, issued on September 3, 2002 to Aronstam et
al., is
a method for utilizing flowable devices in wellbores. These flowable devices
are used to
provide communication between surface and the downhole instruments so as to
establish a communication network in the wellbore. The flowable devices are
adapted
to move with a fluid flowing in the wellbore. The flowable device can be a
memory
device or a device that can provide a measurement of a parameter of interest.
The
flowable devices are introduced into the flow of a fluid flowing through a
wellbore. The
fluid moves the device in the wellbore. The flowable device is returned to the
surface
with the returning fluid.
[13] U.S. Patent No. 6,691,804, issued on February 17, 2004 to W.H.
Harrison,
describes a directional borehole drilling system and method. Instrumentation
located
near the bit measures the present position when the bit is static and a
dynamic tool face
measures position when the bit is rotating. The data is processed to determine
the error
between present position and a desired trajectory.
[14] U.S. Patent No. 6,714,138, issued on March 30, 2004 to Turner et al.,
discloses a method and apparatus for transmitting information to the surface
from
downhole in a well in which a pulser is incorporated into the BHA of a drill
string, the
pulser generating pressure coded pulses to contain information concerning the
drilling
operation. The pressure pulses travel to the surface where they are detected
and
decoded so as to decipher the information. The pulser includes a stator
forming
passages through which drilling fluid flows on its way to the drill bit. The
rotor has
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blades that obstruct the flow of the drilling fluid through the passage when
the rotor is
rotated into a first orientation and when rotated into a second orientation,
such that the
oscillation of the rotor generates the encoded pressure pulses. An electric
motor, under
the operation of a controller, drives a drive train that oscillates the rotor
between the first
and second orientation. The controller controls one or more characteristics of
the
pressure pulses by varying the oscillation of the rotor. The controller may
receive
information concerning the characteristics of the pressure pulses from a
pressure
sensor mounted proximate to the BHA, as well as information concerning the
angular
orientation of the rotor by means of an encoder. The controller may also
receive
instructions for controlling the pressure pulse characteristics from the
surface by means
of encoded pressure pulses transmitted to the pulser from the surface that are
sensed
by the pressure sensor and decoded by the controller.
[15] U.S. Patent No. 6898150, issued on May 24, 2005 to Hahn, teaches a
hydraulically balanced reciprocating pulser valve for mud pulse telemetry.
Pressure
fluctuations are generated by a reciprocating pulser system in a flowing
drilling fluid.
The system includes a reciprocating poppet and a stationary valve assembly
with axial
flow passages. The poppet reciprocates in close proximity to the valve
assembly, at
least partially blocking the flow through the valve assembly and generating
oscillating
pressure pulses. The poppet passes through two zero speed positions during
each
cycle, enabling rapid changes in signal phase, frequency, and/or amplitude
thereby
facilitating enhanced data encoding. The poppet is driven by a linear electric
motor
disposed in a lubricant filled housing.
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[16] Conventional downhole tools, MWD tools and steering tools typically
will use a
dedicated mud pulser (valve) that requires a large amount of power to actuate
the valve
and modulate the mud pressures in a manner that can be detected with a
pressure
transducer at the surface. These tools use mud pulsers or other means to
generate
oscillatory signals or mud pulses that create decreases and corresponding
increases in
the mud circulatory system. The significant proportion of the energy
associated with
conventional MWD pressure signals is the part of the signal waveform that
increases
the pressure of the system, whereas the part of the signal waveform that
releases the
system pressure uses a very small amount of energy. This invention capitalizes
upon
the energy savings associated with the pressure release encoded system that
only
releases pressures in the circulatory system as a transmission means. MWD
tools are
cost prohibitive as a means of transmitting the direction of the borehole when
drilling
vertical boreholes. Typically, periodic measurement of the "verticality of the
well" is
required by measuring the inclination of the borehole as the well is drilled
deeper. Most
vertically drilled wells use a cost-effective mechanical "drift indicator"
that is lowered via
a wireline into the well to make the inclination measurements at the required
depth and
pulled out of the hole to read the inclination. Mechanical drift tools are
currently being
replaced by newer electronic drift indicators. Thus, the industry has a need
for a cost
effective tool that can send inclination information to the surface without
requiring the
stopping of the drilling operation and the running of the wireline tool into
the wellbore. A
"real-time" tool that could replace wireline tools would have to be compact,
relatively
inexpensive, be robust and have a long operational life.
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[17] It is an object of the present invention to provide a cost effective
system for
communicating downhole information to the surface.
[18] It is another object of the present invention to provide a method of
sensing
flow to activate the encoding system for communicating downhole information.
[19] It is another object of the present invention to provide a method that
uses flow
as a switch for activating and de-activating the encoding system.
[20] It is a further object of the present invention to provide a pressure
release
encoding system and method, which minimizes the amount of power for activating
the
system for transmission of pressure information to the surface.
[21] It is a further object of the present invention to extend the battery
life of the
system by making use of the oil rig mud pumps as the primary energy source of
the
pressure release encoded system, thus enabling the system of the present
invention to
activate the encoding system and to progressively release the pressure across
the float
valve in an energy efficient manner.
[22] It is a further object of the present invention to use a brake as a
control and a
differential pressure sensor as a control feedback source to accurately
dictate the
desired differential pressure drop across the valve.
[23] It is a further object of the present invention to use a pressure
sensor within a
hydraulic brake to detect a pressure level at a first position.
[24] It is a further object of the present invention to use a brake to
standardize a
desired differential pressure across the valve.
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[25] It is a further object of the present invention to use a brake to
derive a
predetermined differential pressure across the valve independent of fluid
density and
fluid velocities.
[26] It is a further object of the present invention to use a return spring
within the
hydraulic brake to close the main valve once the drilling interval has been
completed
and the mud pumps are turned off.
[27] These and other objects and advantages of the present invention will
become
apparent from a reading of the attached specification and appended claims.
BRIEF SUMMARY OF THE INVENTION
[28] The present invention is a system for communicating downhole
information
through a wellbore to a surface location. This system comprises a valve for
providing a
flow restriction to fluid passing in the wellbore, a sensor positioned in the
wellbore for
sensing a downhole condition in the wellbore, a brake device being cooperative
with the
valve and restricting the valve from fully opening during the commencement of
fluid flow
in at least in two fixed positions that are a timed relation to the downhole
condition
sensed by the sensor, and a detector positioned at the surface location and
cooperative
with the fluid passing in the wellbore for providing a measurement value at
the surface
location correlative to the time between the changes of the pressure of the
fluid in the
wellbore.
[29] The system of the present invention further includes a drilling sub
interconnected between the drill collars and the drill bit. The valve and
brake device are
positioned within the drilling sub.
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[30] The valve includes a float valve that is mounted in the drilling sub
in a
manner suitable for controlling flow of drilling mud in the wellbore. The
float valve is
normally used for controlling only reverse flow in the BHA, which is disclosed
in the prior
art. The present invention utilizes a ruggedized float valve to restrict the
fluid flow
therethrough using a pressure release encoding system. The brake device serves
to
hold the float valve in at least two partially open positions to create fixed
pressure drops
across the valve at the commencement of fluid flow through the drilling sub.
The float
valve, in particular, includes a housing positioned in the drilling sub, a
valve seat and
valve member slidably movable in the housing with a piston stem connected to
the
piston of the valve and extending outwardly of the housing. The brake piston
of the
brake member bears on the piston stem opposite the piston of the float valve
so as to
impede an axial advancement of the piston of the valve so as to move the
piston of the
float valve in the housing in timed relation between the two positions. In
particular, the
brake device or brake member includes an actuatable brake piston movable
between a
first fixed position and a second fixed position representing two
predetermined fixed
pressure drops across the valve.
[31] A pumping means is positioned at the surface location for pumping
drilling
mud into the wellbore. The detector serves to detect a change of pressure of
the drilling
mud. A logic system correlates the sensed time between the changes of pressure
to the
downhole condition. A display serves to provide a generally real-time humanly
perceivable indication of this downhole condition.
[32] In the preferred embodiment of the present invention, the sensor is an
inclination sensor for sensing an angle of inclination of the drilling sub. It
is this angle of
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inclination of the drilling sub, which is the downhole condition of well bore
inclination.
The logic system serves to correlate the sensed time between pressure drops to
the
angle of inclination.
[33] The present invention includes the pressure release encoding system
using
a method of communicating within a wellbore that comprises the steps of: (1)
sensing a
quiet downhole condition corresponding to a non-pumping and non-drilling rig
operation;
(2) sensing a quantifiable downhole condition; (3) sensing the commencement of
mud
flow due to the starting of the mud pumps (4) forming a flow restriction
within the
circulation system in the wellbore; (5) using a brake device to govern the
quantified
pressure restriction of the drilling mud in the circulation system; (6)
measuring the force
at the brake control device proportional to the differential pressure across
the flow
restriction; (7) using a brake control means to form a predetermined first
steady state
flow restriction; (8) releasing a first percentage of the pressure within the
flow restriction
at a first time; (9) releasing a second percentage of the pressure within the
flow
restriction at a second time such that the time between the first time and the
second
time is correlative of the downhole conditions; and (10) determining the
downhole
condition at a surface location by sensing the time between the changes of
pressure;
and (11) increasing the flow restriction to the original state when the flow
through the
flow restriction has returned to zero.
[34] In the method of the present invention, the valve means is a
ruggedized
float valve positioned in the fluid passageway in the drilling sub. The float
valve creates
the flow restriction. Additionally, a hydraulic brake is positioned in the
drilling sub such
that a hydraulic brake piston cooperates with the float valve piston rod. The
hydraulic
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brake piston is controlled via a solenoid pilot valve allowing a processor
command to
release the float valve to a partially open static position corresponding to a
desired
pressure drop across the float valve. After a pre-determined steady state
pressure has
been established across the float valve, the float valve is allowed to further
open to a
first fixed position and then a second fixed position so as to cause the float
valve to
release the first percentage of pressure and the second percentage of
pressure. The
step of detecting includes measuring a time between the release of the first
percentage
of pressure and the release of the second percentage of pressure and then
correlated
this time to the downhole condition.
[35] In the preferred method of the present invention, the step of sensing
includes sensing an angle of inclination of a drill bit within the wellbore. A
time value is
assigned to the sensed angle of inclination. The brake allows the float valve
to open to
a first fixed position and the second fixed position at a time equal to the
assigned time
value.
[36] The present application claims the subject matter of activating the
encoding
system, setting the brake positions for the pressure drops, and setting a
first brake
position based on a predetermined pressure level. The steps of encoding are
claimed in
a related patent application. The present steps were also disclosed in the
related patent
application.
[37] These and other objects and advantages of the present invention will
become
apparent from a reading of the attached specification and appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
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[38] FIGURE 1 is a schematic view illustrating the system of the present
invention
in association with components of a conventional drilling rig, showing the
relative
location of the present invention.
[39] FIGURE 2 is a partial sectional view, showing the drilling sub and
present
invention in relation to the drill string.
[40] FIGURE 3 is a detailed perspective view of the valve means of the
present
invention.
[41] FIGURE 4 is a cross-sectional view of the float valve in a closed
attitude.
[42] FIGURE 5 is a top plan view of the float valve of Figure 4.
[43] FIGURE 6 is a cross-sectional view of the float valve in a semi-open
attitude.
[44] FIGURE 7 is a cross-sectional view of the present invention, showing
the float
valve, hydraulic brake, electronics system and end centralizer.
[45] FIGURE 8 is an exploded and isolated cross-sectional view of the
hydraulic
brake of Figure 7.
[46] FIGURE 9 is a graph illustration, showing the sensing of timed
pressure
changes.
[47] FIGURE 10 is a block diagram of the microprocessor-based electronics
section of the downhole tool of the present invention.
DETAILED DESCRIPTION OF THE DRAWINGS
[48] FIGURE 1 illustrates the system 1 of the present invention, including
a
conventional drilling rig located at a site above the borehole 2. The drill
string 3 is
supported by the derrick 4 and includes drill collars 7 and a drill bit 6. A
float valve 36
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resides inside the drill sub 5. The system 1 includes a downhole electronics
module 8
also resides inside the drill sub 5 and includes a hydraulic brake 44, an
inclination
sensing device and a processing device. The downhole electronics module 8 is
described in greater detail in FIGURE 2.
[49] The system 1 includes a pumping means, usually comprised of a drilling
rig
with a mud pump system. The flow of the mud pump system is generated by mud
pumps 9 through the stand pipe 10, the mud hose 11, the swivel 12, the kelly
13, down
the drill pipe 14, through the drill collars 7 and drill sub 5. Mud then exits
out through
the drill bit 6 and travels up the annulus 15 of the wellbore 2 to the surface
where it is
carried back to the mud pit 16 by way of a conduit 17.
[50] The pressure of the mud that passes through the mud pump system is
monitored by a pressure sensor 18 at the surface location, which is mounted on
the
stand pipe 10. The pressure sensor 18 conveys the pressure of the mud pump
system
to a surface computer 20 via a wired interface box 19.
[51] The downhole electronics module 8 of the present invention measures
the
wellbore inclination every time the mud pump 9 transitions from an on-state to
an off-
state creating a quiet downhole environment to record the inclination
measurement. All
information gathered by the electronics module tool 8 will be saved to the
internal
memory of the electronics module 8. This information can be retrieved later
after the
downhole electronics module 8 is brought to the surface.
[52] In the present invention, when specifically directed, the information
gathered
by the downhole electronics module 8 is communicated via the pressure sensor
18,
through the wired interface box 19, to the surface computer 20, through the
mud pump
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system by way of a pressure release communications method. This innovative
pressure
release communications method is initiated when the mud pump system is turned
on
and the resulting flow through the valve means is detected by downhole
electronics
module 8. The present invention enables the downhole electronics module 8 to
automatically activate and de-activate according to the status of the
drilling. For
example, vibration due to the drilling process can cause the tool to power
down; thus,
no downhole conditions are being sensed during the power down. Then, the lack
of
drilling vibration can cause the tool to wake up.
[53] On the next off-cycle of the pumps of the mud pump system, the
downhole
tool 8 measures the wellbore inclination as the downhole condition and
activates the
pressure transducer that detects the start of the mud flow through the float
valve 36. A
hydraulic brake restricts the opening of the float valve 36 in a controlled
routine dictated
by electronics system 34. On the next on-cycle of the pumps of the mud pump
system,
pressure will be generated across the float valve 36 because of its restricted
movement.
The mud pump system will also generate a pressure observed by the surface
computer
20 by way of the interface box 19 to the pressure sensor 18 mounted on the
stand pipe
10.
[54] The hydraulic brake 44 also contains a pressure sensing device sensed
by
electronic module 8. Once the downhole electronics module 8 has established a
stable
pressure across the float valve 36, it will release the hydraulic brake 44 so
as to allow
the float valve 36 to partially open. The encoding system has now been
activated.
When a portion of the pressure across the float valve 36 has been released,
the
downhole electronics module 8 will reactivate the hydraulic brake 44 so as to
stop the
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opening of float valve 36. This reduction of pressure across the float valve
36 will be
seen throughout the mud pump system and will be transmitted to the surface
computer
20 via interface box 19 and pressure transducer 18 on the stand pipe 10.
[55] After a period of time that is proportional to the inclination of the
wellbore 2,
and as described hereinafter, the downhole electronics module 8 will
deactivate the
hydraulic brake 44 so as to allow the remaining pressure across the float
valve 36 to be
released. This second release of pressure will be seen at the surface computer
20 just
as the first release of pressure was observed by the surface computer 20. The
time
between the first release of pressure across the float valve 36 and the second
release
of pressure across the float valve 36 is proportional to the inclination of
the wellbore 2.
This time between pressure releases is measured by the surface computer 20.
This
information is used to calculate the inclination of the wellbore and is
displayed to an
operator.
[56] FIGURE 2 is a cut-away view showing the drilling sub 5 that is secured
to an
end of the drill collars 7 and drill string 14. The drilling sub 5 includes an
interior
passageway extending axially longitudinally therethrough. A float valve 36 is
positioned
to one end of the drilling sub 5 within the fluid passageway as the valve
means of the
present invention. The float valve 36 itself is a modified float valve that is
commonly
used on drilling subs in the prior art. As such, the present invention does
not
significantly modify the basic construction of the drilling sub 5 or a
particular float valve
36. However, in the present invention, the system includes a downhole
electronics
module 8 including a float valve 36 and a hydraulic brake 44 placed within the
fluid
passageway so as to provide a proper action onto the float valve 36 so as to
allow
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changes of pressure in the drilling mud to be provided in timed relation to
the downhole
condition. This arrangement is not disclosed by the prior art.
[57] The drilling sub 5 has a threaded connection at one end and another
threaded
connection at an opposite end. One connection is suitable for joining with the
drill bit
the opposite threaded connection is suitable for joining with the drill
collars. The float
valve 36 is positioned on a hanger seat 50 a conventional bore back machined
in the
internal diameter of drilling sub 5. This method securing float valve 36 and
sealing the
float valve 36 with seals 54 within drilling sub 5 is commonly used in the
prior art.
[58] The downhole electronics module 8 is assembled with an actuator
section 44
and a stabilizer/centralizer 48 positioned at one end of the electronic
section 34
opposite the hydraulic brake 44. A hanger 50 serves to position float valve 36
and
electronics module 8 in alignment with the float valve 36. Within the concept
of the
present invention, the determination of the pressure sensing device can be
easily
accomplished by installing the downhole electronics module 8 within a
conventional or
slightly modified drill sub 5. Besides pressure sensing, other types of
downhole
conditions at the brake may be used to communicate through the downhole
electronics
module 8 for purposes of activating or calibrating the encoding through
pressure drops.
[59] FIGURE 3 is a more detailed three-dimensional illustration of valve
means or
flow valve assembly 36 of the present invention. The preferred embodiment of
the
invention utilizes a strengthen float valve assembly 36 above conventional
float valves
to allow for the additional forces and wear demands associated with the
controlled flow
restrictions demanded by the invention. A standard float valve housing form
has been
improved. A ceramic seat lining 82 protects the valve housing from erosion
when fluid
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passes along opening 100 through the float valve housing 80. Valve poppet 92
can
slide axially and outwardly from seat 82 via shaft 88 within ceramic bushings
98 and 99
held in association with valve housing 80. Upper ceramic bushing 98 and lower
ceramic
bushing 99 centralize shaft 88 from potentially damaging vibrations caused by
the
forces resulting from restricting flow through aperture 100.
[60] FIGURE 6 is a cross sectional illustration of float valve 36 with
valve poppet 92
in a semi open position in relation to seat 82 within float valve housing 80.
Valve shaft
88 associated with poppet 92 is displaced outwardly from valve adaptor 96 when
poppet
92 is displaced off its seat due to flow through aperture 100.
[61] FIGURE 4 is a cross sectional illustration of float valve 36 with
valve poppet 92
in a closed position in relation to seat 82 within float valve housing 80.
FIGURE 3 shows
an end view of the float valve 36.
[62] FIGURE 7 is cross-sectional view of a portion of the downhole
electronics
module 8 in accordance with the teachings of the preferred embodiment of the
present
invention. There is an electronic section 34, the hydraulic brake section 44
and a float
valve 36. The stabilizer/centralizer 48 is provided at one end of the downhole
electronics module 8. It is this hydraulic brake section 44 which serves to
impart the
necessary action onto the float valve 36 so as to allow the present invention
to carry out
its intended purpose.
[63] FIGURE 8 illustrates an expanded cross-sectional view of the hydraulic
brake
means 44 for further clarification of the preferred embodiment of the
invention. The
hydraulic brake 44 includes a generally tubular body, extending longitudinally
from the
stabilizer/centralizer 48 at one end to the float valve 36 with adaptor 96 at
the opposite
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end. The hydraulic brake section 44 includes the hydraulic actuator piston 78
fixed to
piston rod 62 extends outwardly of brake housing 44. The piston rod has end 62
suitable for abutting the piston stem 88 of the float valve 36 (in the manner
to be
described hereinafter). Piston 78 has hydraulic oil 68 inserted rearwardly
within the
interior of the hydraulic chamber of section 44.
[64] A control manifold 72 uses a solenoid pilot valve 46 to control the
flow of oil
through the manifold 72. When piston 78 is pushed by the poppet shaft 88 of
float valve
36, oil 68 is displaced through manifold 72 via solenoid control valve 46
positioned
within the manifold. If control valve 46 is closed, oil 68 will be prevented
from flowing
through manifold 72, hydraulically locking piston 62 and poppet shaft 88 from
moving in
the presence of mud flow through float valve 36.
[65] Hydraulic brake 44 is hydraulically compensated via compensating
piston 79
that moves accordingly and compliantly with piston 78. A return spring 66 is
incorporated into the oil filled space 68 so as to return the hydraulic brake
piston 78,
and float valve 36 into its retracted position when fluid flow through float
valve 36 has
ceased.
[66] A differential pressure transducer 76 is housed in manifold 72 to
measure the
differential pressure across manifold 72. The electronic section 34 includes a
battery
assembly 70 located within the interior of the electronic section 34. An
inclination sensor
404 is placed adjacent to the electronics 74 and rearwardly of the hydraulic
brake
section 44. A high-pressure electrical bulkhead 78 will be positioned between
the
actuator section 44 and the electronic section 34.
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[67] In the present invention, the inclination sensor 404 is of a type
presently
available and utilized within the prior art for downhole conditions. The
electronics 74
are similarly available in the prior art. The electronics will process the
information from
the inclination sensor 404 so as to provide an output that would indicate the
orientation
of the drill bit within the wellbore. However, unlike the prior art, the
system of the
present invention has electronics 74 suitably connected to solenoid valve 46.
As such,
the electronics 74 of the present invention will serve to hydraulically
control the
reseeding of the piston 78 to a first position and a second position in timed
relation. The
timed relation can be based upon the angular inclination of the drill bit. For
example,
the movement between the first position and the second position can be a one
second
interval if the angular inclination is one degree. Alternatively, if the
angular inclination is
two degrees, then the interval between the movement of the first reseeded
position and
the second further reseeded position of the hydraulic brake 78 can be two
seconds.
Still further, if there is a five degree angle of inclination, then the time
interval between
the first reseeded position and the second further reseeded position can be
five
seconds. As will be described hereinafter, these controlled restrictions of
float valve
opening will cause pressure static pressure changes in the drilling mud that
can be
sensed from the surface location. As such, if the pressure changes would occur
two
seconds apart, then the operator would know that there was a two degree angle
of
inclination. Various fractional angles can also be conveyed in a similar
manner from the
downhole condition to the surface location. All of the electronics are self-
contained
within the downhole electronics module 8. As a result, no wireline connections
are
necessary to the surface location and no telemetry systems are required.
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[68] FIGURES 7 and 8 illustrate the operation of the downhole electronics
module
8, also referred to as the downhole tool, in the preferred embodiment of the
invention.
The downhole tool can take a survey during the normal rig operation of
connecting an
additional drill pipe. Then, the rig pumps are turned off the fluid flow
through a valve
means, such as a flow valve 36, ceases, the resulting axial force from the
poppet shaft
88 and hydraulic brake piston shaft 62 is reduced allowing spring 66 to return
the float
valve to a closed position. Once the electronics or tool electronics system 74
senses a
quiet condition associated with a non drilling condition via a shock sensor or
accelerometer. The tool electronics system 74 measures the inclination of the
system
via inclination sensor 404. The inclination measurement is stored in the
electronics
system 74 memory. When the mud pumps are started the resulting flow through
float
valve 36 starts to move oil through the open solenoid valve 46 housed in
manifold 72.
The resulting initial pressure in oil 68 is measured by pressure transducer 76
and
processed by electronics system 74. The micro controller system in electronics
system
74 now having detected the commencement of flow due to the starting of the
rigs
pumps, energizes solenoid valve 46 sealing oil flow through manifold 72. As
such,
rearward movement of the piston 78 is hydraulically blocked preventing the
further
opening of float valve 36. The simple impeding of this axial movement requires
a
minimum of energy. The pressure drop across partially open float valve 36
increases
as the fluid flow rises. The differential pressure drop across float valve 36
can be
measured by the single pressure transducer 76 downstream of float valve 36 via
the
resulting proportion force in shaft 88 conveying to the same force in shaft 62
and piston
78. Piston 78 loads oil 68 forming a hydraulic pressure within the oil in the
brake
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chamber. The pressure drop across float valve 36 can be controlled during the
commencement of flow to a predetermined pressure drop across the valve.
Electronics
74 micro controller switches the electrical drive to hydraulic brake solenoid
pilot valve 46
in a control routine cooperative with pressure sensor 76 to reach the
predetermined
pressure drop across float valve 36.
[69] After electronics system 74 and pressure sensor 76 have established
that a
first predetermined stable static pressure has been reached, electronics
system 74 will
open the solenoid pilot valve allowing hydraulic oil 68 to flow through
manifold 72.
Piston 78 can then axially move allowing the mechanically coupled float valve
36 to
open further, until electronics system 74 and pressure sensor 76 have
established a
second predetermined stable static pressure. This second pressure is
controlled by
electronics system 74 to be a programmable percentage of the first
predetermined
pressure. After a period of time proportionally corresponding to the prior
recorded
inclination measurement, electronics system 74 will open the solenoid pilot
valve 46
allowing flow valve 36 to fully open.
[70] Under certain circumstances, it may be necessary to incorporate three
or more
movements to the piston 78 so as to accurately and properly convey information
pertaining to the downhole condition to the surface location.
[71] FIGURE 9 illustrates the manner in which the pressure release encoding
of
the present invention relates to the change of time of pressure changes
conveyed to the
surface. In FIGURE 9, the horizontal axis represents time while the vertical
axis
represents pressure. Line 110 is illustrated as pressure building up in the
system. This
build-up of pressure occurs when the valve poppet 92 is seated within its seat
82 in float
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valve 36. Eventually, when the system pressure has equalized, the pressure
will level
out. When the valve poppet 92 opens, in the manner of FIGURE 6, a pressure
drop
112 will occur. When the valve poppet 92 opens further, another pressure drop
114
occurs. Since the cause of the pressure drops is the relay of information from
the
sensor, through the electronics, to the hydraulic brake, and, in turn, to the
stem 88 of
the valve poppet 92, the time of these pressure changes, represented by delta
t 116 is
correlative of the downhole condition. As stated previously, and merely as an
example,
if the delta t is two seconds, then the surface location will know that the
drill bit has two
degrees of deviation. If the delta t is 3.25 seconds, then the surface
location will know
that the change of orientation is 3.25 . It is believed that the system of the
present
invention can also be adapted to various other downhole sensor tools. In the
present
invention, the amount of pressure change is not very important. It is only the
existence
of the pressure change which is important to monitor. As such, the time
between the
pressure changes (regardless of the amount of pressure) provides the necessary
information to the operator at the surface so as to determine the downhole
condition.
[72] FIGURE 10 shows the microprocessor-based electronic system 400 of the
downhole electronics module 8. This electronic system 400 includes a
microprocessor
402, an inclination sensor 404, a shock sensor 406, a temperature sensor 408,
a real-
time clock 410, and a serial port 412 in order to communicate outwardly of the
downhole
tool. The electronic system 400 also includes differential pressure sensor
electronics
414 and an electrically-controlled solenoid valve controller 416. Solenoid
pilot valve 46
and the pressure sensor 76 are wired to the controller and are both
incorporated in
manifold 72 within hydraulic brake 44.
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[73] The downhole electronics module 8 is mounted in the drill sub 5 in the
manner
shown in FIGURE 2. When the pumps 9 in the mud pump system are turned on,
drilling
mud is forced down the drill string 3 into the drill sub 5 and around the
downhole
electronics module 8 before exiting out the drill bit 6 and returning to the
surface mud
pits 16 by way of the annulus 15 of the wellbore 2. Shock sensor 406 detects
the shock
and vibration associated with the rotary drilling of drill bit 6 cutting
formation 2. When
the drilling stops shock sensor 406 turns off. This stoppage wakes the
microprocessor
402 from a low powered sleep state. When the microprocessor 402 wakes up, it
first
verifies a quiet downhole state identifying a stoppage of the drilling
process, then it
reads the inclination from the inclination sensor 404, the temperature from
the
temperature sensor 408, and the present time from the real-time clock 410.
This
information is stored in the electronic memory and can be retrieved at a later
time by
way of the serial port 412 when the downhole tool is at the surface.
[74] After storing this information into memory, microprocessor 402 will
monitor
differential pressure sensor 76 via the sensor electronics 414 to detect the
commencement of mud flow as described previously.
Once mud flow has been
detected microprocessor 402 will initiate the pressure release communication
procedure
also described in section (21). Once the pressure release communication
procedure
has been conducted the microprocessor 402 will return to its low power sleep
state until
the next quite event associated with the cessation of the drilling process.
[75] The system and method of the present invention provides a cost
effective
system for communicating downhole directional information to the surface. The
use of
shock and movement sensors allow the downhole electronic module to
automatically
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activate when in a borehole and automatically shut down when not needed, such
that
surface communication is not required prior to running. The activation of the
mud pumps
can start the readings of the downhole condition without any separate need to
activate
the system. The present invention uses a pressure sensor within a hydraulic
brake to
detect the starting of the rig mud pumps. The downhole electronics module has
a return
spring within the hydraulic brake to close the main valve once the drilling
interval has
been completed and the mud pumps are turned off.
[76] The system and method of the present invention effectively
incorporates
existing elements of drilling rigs. The pressure release encoding system also
increases
the usefulness of existing float valves, which can be efficient adapted for
the innovative
method of the present invention. Furthermore, the system and method does not
require
significant modification of the drilling sub, which is already employed in the
BHA. The
system and method still allow monitoring of the downhole condition in a
relatively real-
time manner at a surface location.
[77] The present invention improves energy and power usage. The pressure
release encoding system minimizes the amount of power for the transmission of
pressure information to the surface. Only a small amount of power is needed
for the
downhole module or tool of the present invention itself. The battery life of
the system is
extended by making use of the oil rig mud pumps as the primary energy source
of the
pressure release encoded system, thus enabling the system of the present
invention to
progressively release the pressure across the float valve in an energy
efficient manner.
[78] The system and method of the present invention disclose a hydraulic
brake
means, solenoid pilot valve, and only a single pressure sensor in an
innovative manner.
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These elements control feedback to accurately dictate the desired differential
pressure
drop across the float valve and derive a desired differential pressure across
the float
valve. The single sensor in the drilling sub is an important innovation over
the prior art
systems with at least two sensors. The installation of two pressure sensors,
sometimes
on both sides of a valve means is no longer required by the present invention.
Previously, the technology required two pressure transducers positioned
physically
below and above the pressure restriction, such as the main valve and seat. The
hydraulic brake, pressure sensor and solenoid pilot valve control also derive
a
predetermined differential pressure across the float valve independent of
fluid density
and fluid velocities.
[79] The foregoing disclosure and description of the invention is
illustrative and
explanatory thereof. Various changes in the details of the illustrated
construction or in
the steps of the described method may be made within the scope of the appended
claims without departing from the true spirit of the invention. The present
invention
should only be limited by the following claims and their legal equivalents.
