U.S. patent application number 14/658929 was filed with the patent office on 2015-10-15 for system and method for determining the start time of a pressure pulse from a downhole explosive device.
The applicant listed for this patent is RECON PETROTECHNOLOGIES LTD., STAR GENERAL MICRO SYSTEMS LTD.. Invention is credited to Michael BOYLE, David Edwin SENGER.
Application Number | 20150292318 14/658929 |
Document ID | / |
Family ID | 54258902 |
Filed Date | 2015-10-15 |
United States Patent
Application |
20150292318 |
Kind Code |
A1 |
SENGER; David Edwin ; et
al. |
October 15, 2015 |
SYSTEM AND METHOD FOR DETERMINING THE START TIME OF A PRESSURE
PULSE FROM A DOWNHOLE EXPLOSIVE DEVICE
Abstract
A system and method for use in determining the start time of a
pressure pulse created by a downhole explosive device detonated by
a firing signal includes a downhole tool with a pressure pulse
detector that detects the pressure pulse and generates an input
signal in response thereto, and a circuit path configured to output
a signaling pulse distinguishable from the firing signal. A surface
unit receives and discriminates the signaling pulse from the firing
signal, and outputs a start time signal in response to receiving
the signaling pulse. Alternatively, the downhole tool includes a
processor that measures and stores the time that the pressure pulse
detector generates the input signal.
Inventors: |
SENGER; David Edwin;
(Edmonton, CA) ; BOYLE; Michael; (Calgary,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
STAR GENERAL MICRO SYSTEMS LTD.
RECON PETROTECHNOLOGIES LTD. |
Edmonton
Calgary |
|
CA
CA |
|
|
Family ID: |
54258902 |
Appl. No.: |
14/658929 |
Filed: |
March 16, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61977409 |
Apr 9, 2014 |
|
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|
Current U.S.
Class: |
166/250.01 ;
166/66 |
Current CPC
Class: |
E21B 47/06 20130101;
E21B 43/11857 20130101 |
International
Class: |
E21B 47/12 20060101
E21B047/12; E21B 47/06 20060101 E21B047/06; E21B 43/116 20060101
E21B043/116 |
Claims
1. A system for creating a start time signal in response to a
pressure pulse created by a downhole explosive device detonated by
a firing signal, the system comprising: (a) a downhole tool
comprising: (i) a pressure pulse detector for detecting the
pressure pulse and generating an input signal in response to
detecting the pressure pulse; and (ii) a circuit path operatively
connected to the pressure pulse detector, and configured to output
a signaling pulse having a signal parameter distinguishable from
the signal parameter of the firing signal, in response to the input
signal; and (b) a surface unit comprising a circuit path
operatively connected to the downhole tool circuit path, and
configured to discriminate the signaling pulse from the firing
signal, and to output the start time signal in response to
receiving the signaling pulse.
2. The system of claim 1, wherein the downhole tool is powered
solely by a power source located at the surface.
3. The system of claim 1, wherein the downhole tool circuit path is
further configured to amplify the input signal.
4. The system of claim 1 wherein the downhole tool circuit path is
further configured to discriminate the input signal from the firing
signal by comparing a parameter of the input signal to a
predetermined parameter associated with the firing signal, and to
output the signaling pulse only if the input signal is
discriminated from the predetermined parameter associated with the
firing signal.
5. The system of claim 1 wherein the downhole tool circuit path is
configured to output the signaling pulse with a greater voltage, a
greater current, or both a greater voltage and a greater current
than the firing signal.
6. The system of claim 1 wherein the surface unit circuit path is
configured to discriminate the signaling pulse from the firing
signal by comparing a parameter of the signaling pulse to a
predetermined parameter associated with the firing signal.
7. The system of claim 1 wherein the surface unit circuit path is
configured to analogically attenuate electrical noise associated
with the firing signal that is transmitted with the signaling pulse
and/or is configured to digitally extract the firing signal from
the signaling pulse to output the start time signal.
8. The system of claim 1 wherein the downhole tool circuit path is
operatively connected to the surface unit circuit path by a
transmission path that also transmits the firing signal to the
downhole explosive device.
9. A method for creating a start time signal in response to a
pressure pulse created by a downhole explosive device detonated by
a firing signal, the method comprising the steps of: (a) using a
downhole tool for: (i) detecting the pressure pulse and generating
an input signal in response to detecting the pressure pulse; (ii)
in response to detecting the pressure pulse, generating a signaling
pulse distinguishable from the firing signal; (b) using a surface
unit for: (i) receiving the signaling pulse; (ii) discriminating
between the signaling pulse and the firing signal; and (iii) in
response to receiving the signaling pulse, outputting the start
time signal.
10. The method of claim 9, wherein the downhole tool is powered
solely by a power source located at the surface.
11. The method of claim 9 wherein the downhole tool is further used
for amplifying the input signal.
12. The method of claim 9 wherein the downhole tool is further used
for discriminating the input signal from the firing signal by
comparing a parameter of the input signal to a predetermined
parameter associated with the firing signal, and wherein generating
the signaling pulse is conditional on the input signal being
discriminated from the firing signal.
13. The method of claim 9 wherein the signaling pulse is
distinguishable from the firing pulse by a greater voltage, a
greater current, or both a greater voltage and a greater current
than does the firing signal.
14. The method of claim 9 wherein the surface unit discriminates
the signaling pulse from the firing signal by comparing a parameter
of the signaling pulse to a predetermined parameter associated with
the firing signal.
15. The method of claim 9 further comprising, before receiving the
signaling pulse at the surface unit, the step of analogically
attenuating electrical noise associated with the firing signal that
is transmitted with the signaling pulse to the surface unit and/or
the step of digitally extracting the firing signal from the
signaling pulse to output the start time signal.
16. The method of claim 9 wherein the surface unit receives the
signaling pulse in a transmission path that also transmits the
firing signal to the downhole explosive device.
17. A downhole tool for creating a signaling pulse in response to a
pressure pulse created by a downhole explosive device detonated by
a firing signal, the downhole tool comprising: (a) a pressure pulse
detector for detecting the pressure pulse and generating an input
signal in response to detecting the pressure pulse; and (b) a
circuit path operatively connected to the pressure pulse detector,
and configured to output a output the signaling pulse
distinguishable from the firing signal, in response to the input
signal.
18. The downhole tool of claim 17 wherein the downhole tool is
powered solely by a power source located at the surface and used to
create the firing signal.
19. A downhole tool for determining the time of a pressure pulse
created by a downhole explosive device detonated by a firing
signal, the downhole tool comprising: (a) a pressure pulse detector
for detecting the pressure pulse and generating an input signal in
response to detecting the pressure pulse; and (b) a processor
operatively connected to the pressure pulse detector by a circuit
path, the processor comprising an internal clock and a memory
component storing a set of instructions executable by the processor
to determine a time at which the processor receives the input
signal, and store the time in the memory component.
20. The downhole tool of claim 19 wherein the set of instructions
is executable by the processor to further store the input signal in
the memory component in association with the time.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the priority benefit of U.S.
Provisional Patent Application No. 61/977,409 filed on Apr. 9, 2014
entitled "Downhole Perforation Timing System", the contents of
which are incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a system and method for
determining the start time of a downhole pressure pulse, such as
created by a downhole explosive device.
BACKGROUND OF THE INVENTION
[0003] The conventional method used to determine the location of
micro-seismic events (i.e., those events resulting from induced
seismicity related to hydraulic fracturing) relies upon velocity
models derived from dipole sonic logs. An inversion process is used
to minimize the misfit error between actual and theoretical event
arrival times using a multiplicity of receivers. However, sonic
tools use acoustic energy in the 10,000 to 30,000 Hz range to
measure formation velocities, a range which greatly exceeds the
typical frequency content of micro-seismic events. Since seismic
energy in the earth is dispersive (i.e., velocity varies with
frequency), error is introduced into the velocity model.
[0004] The seismic energy from multiple perforation shots from a
perforating gun can be used to calibrate and improve the velocity
model derived from sonic logs. Receivers are positioned in a nearby
borehole, on the surface, or both, to detect pressure pulses
created by the perforation shots. Every ray path between a
perforation shot location and a receiver contributes to a more
complete mapping of the three-dimensional velocity structure. If
both the ray path distance and ray path travel time are known, then
the pressure pulse velocity can be determined for each ray path.
Information regarding velocity anisotropy enhances the
understanding of the petro-physical properties of the rock, leading
to a better correlation with surface seismic data, and a further
reduction in event location error.
[0005] In order to accurately determine the ray path travel time,
it is necessary to accurately determine the detonation time of the
explosive device used in the perforating gun. Unfortunately, the
firing signal used to detonate the explosive device is not a
reliable indicator of the actual detonation time because of
variable and unpredictable delays between the generation of the
firing signal and the detonation of the explosive device. For
example, blasting caps typically have moisture sensors. If downhole
moisture invades the blasting cap, this can delay detonation by
wetting electrical conductors between the firing system and the
explosive device itself. The firing system may have a safety
lockout which introduces a time delay between generation of the
firing signal and its transmission to the explosive device.
Different firing systems are associated with different delays
between sending the firing signal and actual detonation. Further,
the electrical firing signal typically interferes with any up-hole
transmitted signaling pulses. It has thus not been possible to
reliably and accurately determine when the explosive was actually
detonated downhole.
SUMMARY OF THE INVENTION
[0006] The present invention relates to a system and method for
determining the start time of a downhole pressure pulse created by
the firing of a downhole explosive device.
[0007] In one aspect, the present invention comprises a downhole
tool for creating a signaling pulse in response to a pressure pulse
created by a downhole explosive device detonated by a firing
signal. The downhole tool comprises a pressure pulse detector for
detecting the pressure pulse and generating an input signal in
response to detecting the pressure pulse, and a circuit path
operatively connected to the pressure pulse detector, and
configured to output a signaling pulse distinguishable from the
firing signal, in response to the input signal.
[0008] In one embodiment, the downhole tool is configured as a sub
that can be lowered downhole by a wireline.
[0009] In one embodiment, the downhole tool is powered solely by a
power source located at the surface and used to create the firing
signal.
[0010] In one embodiment, the downhole tool circuit path is further
configured to amplify the input signal.
[0011] In one embodiment, the downhole tool circuit path is further
configured to discriminate the input signal from the firing signal
by comparing a parameter of the input signal to a predetermined
parameter associated with the firing signal, and to output the
signaling pulse only if the input signal is discriminated from the
predetermined parameter.
[0012] In one embodiment, the downhole tool circuit path is
configured to output the signaling pulse with a greater voltage, a
greater current, or both a greater voltage and a greater current
than the firing signal.
[0013] In another aspect, the present invention comprises a system
for creating a start time signal in response to a pressure pulse
created by a downhole explosive device detonated by a firing
signal. The system comprises a downhole tool, as described above,
and a surface unit. The surface unit comprises a circuit path
operatively connected to the downhole tool circuit path, and
configured to discriminate the signaling pulse from the firing
signal, and to output the start time signal in response to
receiving the signaling pulse.
[0014] In one embodiment, the surface unit circuit path is
configured to discriminate the signaling pulse from the firing
signal by comparing a parameter of the signaling pulse to a
predetermined parameter associated with the firing signal.
[0015] In one embodiment, the surface unit circuit path is
configured to analogically attenuate electrical noise associated
with the firing signal that is transmitted with the signaling
pulse.
[0016] In one embodiment, the surface unit circuit path is
configured to digitally extract the firing signal from the
signaling pulse to output the start time signal.
[0017] In one embodiment, the downhole tool circuit path is
operatively connected to the surface unit circuit path by a
transmission path that also transmits the firing signal to the
downhole explosive device.
[0018] In another aspect, the present invention comprises a method
for creating a start time signal in response to a pressure pulse
created by a downhole explosive device detonated by a firing
signal, the method comprising the steps of:
[0019] (a) using a downhole tool for: [0020] (i) detecting the
pressure pulse and generating an input signal in response to
detecting the pressure pulse; [0021] (ii) in response to detecting
the pressure pulse, generating a signaling pulse distinguishable
from the firing signal;
[0022] (b) using a surface unit for: [0023] (i) receiving the
signaling pulse; [0024] (ii) discriminating between the signaling
pulse and the firing signal; and [0025] (iii) in response to
receiving the signaling pulse, outputting the start time
signal.
[0026] In one embodiment, the downhole explosive device comprises a
perforating gun or an electric blasting cap.
[0027] In one embodiment, the downhole tool is powered solely by a
power source located at the surface and used to create the firing
signal.
[0028] In one embodiment, the downhole tool is further used for
amplifying the input signal.
[0029] In one embodiment, the downhole tool is further used for
discriminating the input signal from the firing signal by comparing
a parameter of the input signal to a predetermined parameter
associated with the firing signal, and wherein generating the
signaling pulse is conditional on the input signal being
discriminated from the firing signal.
[0030] In one embodiment, the signaling pulse is distinguishable
from the firing pulse by a greater voltage, a greater current, or
both a greater voltage and a greater current than does the firing
signal.
[0031] In one embodiment, the surface unit discriminates the
signaling pulse from the firing signal by comparing a parameter of
the signaling pulse to a predetermined parameter associated with
the firing signal.
[0032] In one embodiment, the method further comprises, before
receiving the signaling pulse at the surface unit, the step of
analogically attenuating electrical noise associated with the
firing signal that is transmitted with the signaling pulse to the
surface unit.
[0033] In one embodiment, the method further comprises, before
receiving the signaling pulse at the surface unit, the step of
digitally extracting the firing signal from the signaling pulse to
output the start time signal.
[0034] In one embodiment, the surface unit receives the signaling
pulse in a transmission path that also transmits the firing signal
to the downhole explosive device.
[0035] In another aspect, the present invention provides a downhole
tool for determining the time of a pressure pulse created by a
downhole explosive device detonated by a firing signal. The
downhole tool comprises a pressure pulse detector for detecting the
pressure pulse and generating an input signal in response to
detecting the pressure pulse, and a processor operatively connected
to the pressure pulse detector by a circuit path. The processor
comprises an internal clock and a memory component storing a set of
instructions executable by the processor to determine a time at
which the processor receives the input signal, and store the time
in the memory component.
[0036] In one embodiment, the downhole tool is configured by a sub
that can be lowered downhole by a wireline.
[0037] In one embodiment, the downhole tool is powered solely by a
power source located at the surface and used to create the firing
signal.
[0038] In one embodiment, the downhole tool circuit path is further
configured to amplify the input signal.
[0039] In one embodiment, the downhole tool circuit path is
configured to discriminate the input signal from the firing signal
by comparing a parameter of the input signal to a predetermined
parameter associated with the firing signal, and to transmit the
input signal to the processor only if the input signal is
discriminated from the firing signal.
[0040] In one embodiment, the set of instructions is executable by
the processor to further store the input signal in the memory
component in association with the time.
[0041] Additional aspects and advantages of the present invention
will be apparent in view of the description, which follows. It
should be understood, however, that the detailed description and
the specific examples, while indicating preferred embodiments of
the invention, are given by way of illustration only, since various
changes and modifications within the spirit and scope of the
invention will become apparent to those skilled in the art from
this detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0042] The invention will now be described by way of an exemplary
embodiment with reference to the accompanying simplified,
diagrammatic, not-to-scale drawings.
[0043] FIG. 1 is a schematic block diagram showing use of one
embodiment of a system of the present invention in a field
installation.
[0044] FIG. 2 is a schematic block diagram of one embodiment of a
downhole tool of the system of FIG. 1.
[0045] FIG. 3 is a schematic diagram of one embodiment of a circuit
path of a downhole tool of the present invention.
[0046] FIG. 4 is a schematic block diagram of one embodiment of a
surface unit of the system of FIG. 1.
[0047] FIG. 5 is a schematic diagram of one embodiment of a circuit
path of a surface unit of the present invention.
[0048] FIG. 6 is a schematic diagram of an alternative embodiment
of a circuit path of a surface unit of the present invention.
[0049] FIG. 7 is a schematic depiction of one embodiment of a
memory-based downhole tool of the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0050] The present invention relates generally to systems and
methods for determining a start time of a downhole pressure pulse
created by the firing of a downhole explosive. When describing the
present invention, all terms not defined herein have their common
art-recognized meanings. To the extent that the following
description is of a specific embodiment or a particular use of the
invention, it is intended to be illustrative only, and not limiting
of the claimed invention. The following description is intended to
cover all alternatives, modifications and equivalents that are
included in the spirit and scope of the invention, as defined in
the appended claims.
[0051] As used herein, the term "explosive device" refers to any
type of device capable of creating a "pressure pulse" in a
surrounding medium upon the explosive device's activation or
detonation. Suitable explosive devices include, but are not limited
to, a perforating gun, an electric blasting cap, and the like. As
used herein, the term "pressure pulse" refers to a pressure
variation that propagates in a gas, liquid or solid medium, and
includes sound, vibration, ultrasound, and infrasound waves and
pulses. Sound propagates primarily as a pressure wave or pulse.
[0052] One embodiment of the system (10) of the present invention
as shown in FIG. 1 comprises a downhole tool (12) and a surface
unit (14), with such components being operatively connected. In one
embodiment, the surface unit (14) is also operatively connected to
a firing device (16) which generates a firing signal to detonate a
downhole explosive device (18) positioned within a wellbore (20).
As used herein, the term "operatively connected" in describing the
relationship between components means a connection for conveying
signals between components, such as, for example, the electric
wireline (22), the cable (24), or a wireless transmitter and
receiver. In one embodiment, the electrical wireline (22) is the
same transmission path that is used by the firing device (16) to
transmit the firing signal to the explosive device (18).
[0053] In general, the downhole tool (12) detects a pressure pulse
(36) created by the detonation of the downhole explosive device
(18), using for example a pressure transducer, and transmits a
signaling pulse (44) up-hole through the electric wireline (22) to
the surface unit (14), which can be used to provide accurate
indicator of the time at which the firing of the explosive device
(18) occurred downhole (t=0). The surface unit (14) processes the
signaling pulse (44) to provide a start time signal (54). The
system (10) may be used in conjunction with a remotely located
receiver (not shown) which generates a signal in response to the
pressure pulse. A computer (not shown) equipped with a timing
system is operatively connected to the surface unit (14) to
determine the time elapsed between the start time signal (54) and
the signal subsequently received from the receiver. The elapsed
time represents the travel time of the pressure pulse from the
downhole tool (12) to the remote receiver. This travel time can be
used to determine the velocity of the pressure pulse if the
distance between the downhole tool (12) and the remote receiver is
known.
[0054] As shown in one embodiment in FIG. 2, the downhole tool (12)
comprises a pressure pulse detector (26) operatively connected to a
circuit path comprising an amplifier (28), a discriminator and
logic unit (30), a signal generator (32), and a power supply
(34).
[0055] The pressure pulse detector (26) detects an acoustic
pressure pulse (36) created by the firing of the explosive device
(18), and generates an input signal (38) in response to detecting
the pressure pulse (36). The pressure pulse detector (26) may be
any suitable device known in the art, such as a pressure
transducer, which without limitation, may include piezoresistive,
capacitive, electromagnetic, or optical devices.
[0056] The amplifier (28) increases the amplitude of the input
signal (38) to yield a relatively larger output signal (40). In one
embodiment, the amplifier (28) modulates the output signal (40) to
match the input signal (38) shape, but with a relatively larger
amplitude. The amplifier (28) transmits the amplified output signal
(40) to the discriminator and logic unit (30).
[0057] In one embodiment, the pressure pulse detector (26) produces
an analog signal (38). The discriminator of the discriminator and
logic unit (30) converts the analog input signal (38), after
amplified by amplifier (28), into a standardized output pulse (42)
whenever the amplified input signal (38) amplitude exceeds a
predetermined threshold voltage. The logic unit of the
discriminator and logic unit (30) performs the logical operations
(for example, AND, NAND, OR, NOR and NOT). The input signal (38)
and output pulse (42) amplitude corresponds to two possible states:
"0" (or "TRUE") or "1" ("FALSE"). In one embodiment, the logic unit
signals are joined so that the output pulse (42) is "1" or "TRUE"
only when the input signal (38) corresponds to a predetermined
pattern. In one embodiment as shown in FIG. 3, the discriminator
and logic cunit (30) comprises one or more comparators to compare
the voltage of the input signal (38) to the predetermined threshold
voltage and outputs a "1" or "TRUE" output pulse (42) if the input
signal (38) exceeds the predetermined threshold voltage. One
comparator may be configured for a negative signal and the other
comparator may be configured for a positive signal to accommodate
input signals (38) of either polarity. The output pulse (42) from
the discriminator and logic unit (30) is then sent to the signal
generator (32).
[0058] The signal generator (32) receives the output pulse (42)
from the discriminator and logic unit (30), and processes the
output pulse (42) into a signaling pulse (44) distinguishable from
the firing signal. In one embodiment, the signal generator (32)
amplifies the energy of the signaling pulse (44) so that it is
greater than the energy of the firing signal in order to be
detectable by the surface unit (14). The signaling pulse (44) may
have a greater voltage, or a larger current, or both, than the
firing signal. In other embodiments, the signaling pulse (44) may
have other distinguishable parameters in comparison with the firing
signal. In one embodiment as shown in FIG. 3, the signal generator
(32) may comprise one or more integrated circuits that amplify the
output pulse (42) to produce the signaling pulse (42). The signal
generator (32) transmits the high energy signaling pulse (44) to
the surface unit (14).
[0059] The power supply (34) provides operating power (46) to the
amplifier (28), the discriminator and logic unit (30), and the
signal generator (32). In one embodiment, as a safety feature, the
downhole tool (12) lacks any intrinsic power source which might
accidentally detonate the explosive device (18). The power supply
(34) uses power (46) from the same source which operates the firing
device (16) to initiate the detonation of the explosive device
(18). In one embodiment, the operating power (46) is about 12 V DC.
In one embodiment, the power supply (34) is "fast settling" in the
sense that it quickly stabilizes so that the amplifier (28) and the
discriminator (30) are ready to detect an input signal (38)
generated by the pressure pulse detector (26).
[0060] By transmitting the signaling pulse (44) to the surface unit
(14), the downhole tool (12) thus provides the surface unit (14)
with a relatively accurate indicator of the time at which the
firing of the explosive device (18) occurred. The wireline
delay--i.e., the time required by the signaling pulse (44) to
travel through the electric wireline (22) to the surface unit--may
be the major source of inaccuracy, but is practically very brief.
In one embodiment, the wireline delay may vary by .+-.10 .mu.s
because of transmission velocity of the signaling pulse (44)
through the electric wireline (22). This wireline delay depends
upon the length of the wireline or electrical connection (22). The
wireline delay is typically estimated to be about 40 .mu.s for a
wireline having a length of about 5000 m. As the wireline delay is
a measurable constant delay, it can be predicted or measured, and
accounted for, if greater accuracy is required in determining the
firing time of the downhole explosive device (18).
[0061] In one embodiment, the downhole tool (12) may be configured
as a sub which can be lowered downhole by the electric wireline
(22) to be positioned proximate to the explosive device (18). The
sub is preferably rated to withstand elevated temperature and
pressure, in one example, a minimum of about 100.degree. C. and
about 135 MPa.
[0062] As shown in FIG. 4, in one embodiment, the surface unit (14)
comprises a circuit path comprising an analog signal filter (48), a
digital filter (49), discriminator (50), and a power source (60).
The circuit path of the surface unit (14) receives the high energy
signaling pulse (44) from the circuit path of the downhole tool
(12) through an operative connection, such as the electric wireline
(22).
[0063] It will be appreciated that in practical implementation, the
time that elapses between the transmission of the firing signal and
transmission of the signaling pulse (44) is very brief. If the
firing signal and signaling pulse (44) are transmitted on the same
electric wireline (22) or electric wirelines in proximity to each
other, the signaling pulse may be contaminated with the firing
signal, and possibly interference signal from other devices. Thus,
in one embodiment, the analog filter (48) and digital filter (49)
conduct signal separation and signal restoration on the signaling
pulse (44) received from the downhole tool (12). Signal separation
is needed when a signal has been contaminated with interference,
noise, or other signals such as interference signals associated
with the firing signal or firing device. Signal restoration is used
when a signal has been distorted in some manner. The analog signal
filter (48) processes the signaling pulse (44) received from the
downhole tool (12) by attenuating any electrical firing noise. In
embodiments as shown in FIGS. 5 and 6, the analog filter (48)
comprises one or more resistor and capacitor elements. The analog
signal filter (48) transmits the filtered signal (52) to the
digital filter (49) for further processing.
[0064] The digital filter (49) enhances the filtered signal (52) to
output a start time signal (54) to a computer system (not shown).
In embodiments, as shown in FIGS. 5 and 6, the digital filter (49)
comprises one or more integrated circuits. The integrated circuits
are programmed or programmable with algorithms that account for
known firing signals and interference signal generated by different
firing devices (16). In this manner, the digital filter (49) may be
customized and adapted for use with a variety of different firing
devices (16). The algorithms subtract the known firing signal and
interference signal generated by a selected firing device from the
filtered signal (52), thus extracting only the signaling pulse (44)
for use as the start time signal (54).
[0065] The discriminator (50) tracks the firing voltages and sets
the detection levels from the filtered signal (52) so as to
distinguish it from the firing signal or other interference
signals. In embodiments, as shown in the FIGS. 5 and 6, the
discriminator comprises one or more comparators to compare the
voltage of the filtered signal (52) to a pre-determined threshold
voltage associated with the firing signal for a standard blasting
cap. If the voltage of the filtered signal (52) exceeds the
pre-determined threshold voltage, the comparator outputs a "1" or
"TRUE" start time signal (54). One comparator may be configured for
a negative signal and the other comparator may be configured for a
positive signal to accommodate filtered signals (38) of either
polarity. In one embodiment as shown in FIG. 6, the filtered signal
(52) may by-pass the discriminator (50), and proceed directly to
the digital filter (49) for processing, as described above. In such
an embodiment, the digital filter (49) effectively discriminates
the filtered signal (52) from the firing signal or other
interference signals.
[0066] The power source (60) provides operating power to the
components of the surface unit (14).
[0067] In one embodiment, at least one noise filter (56) is
included on each of the lines (22, 24) between the surface unit
(14) and the firing device (16), respectively, to filter such
unwanted components such as background noise or interfering
signals. Optionally, a custom firing power supply (58) may be used
to activate or detonate the explosive device (18), which may
enhance the signal to noise ratio.
[0068] A display (not shown) which is either operatively connected
to or integral with the surface unit (14) may display indication
signals (for example, system status, errors, alarms, output
messages, instructions, audible buzzers, indicator lights) to
perform a test of the system (10) to ensure proper connection of
all components before operation, and to inform a user whether
firing of the downhole explosive device (18) has been detected. For
example, a lengthy continuous beep or illumination might indicate
that the explosive device (18) has detonated successfully, and a
short fast beep or illumination might indicate that the explosive
device (18) has misfired or a malfunction has occurred in the
system (10).
[0069] The surface unit (14) may include an operational switch so
that a user can specify the particular type of explosive device
(18) from which the start time signal pulse (54) will originate.
Types of explosive devices (18) to which the surface unit (14) may
be responsive include, but are not limited to, non-radio frequency
type detonators, PX-1.TM. detonators (Teledyne RISI, Inc., Tracy,
Calif.), and DynaEnergetics.TM. detonators (DynaEnergetics GmbH
& Co. KG, Troisdorf, Germany). As discussed above, the digital
filter (49) may be configured with algorithms that account for
known firing signals and interference signal generated by firing
devices (16) used with different types of explosive devices
(18).
[0070] A remote unit (not shown) may be included in the system (10)
in order to transmit the start time signal pulse output (54) to a
separate remote unit (not shown) to be read at a different location
or site. Display means may be integral with the remote unit to
display indication signals (for example, audible buzzers, indicator
lights) to confirm firing of the downhole explosive device (18) in
order that the user can then transmit the start time signal pulse
(54) to the remote unit. Transmitting acoustic data remotely
conveniently enables another user to obtain the data without having
to read the display of the surface unit (14) in person, or risk
injury by being present in a detonation area.
[0071] In use and operation, a computer which comprises a timing
clock system may be operatively connected to both the surface unit
(14) and a remote receiver comprising conventional acoustic
measuring equipment. The computer may be a separate physical
component, physically integrated with the surface unit (14) or the
remote receiver, or a combination of the foregoing. The remote
receiver generates a signal upon being actuated by the pressure
pulse. Since the distance between the remote receiver and the
explosive device is greater than the distance between the remote
receiver and the downhole tool (12), the computer receives the
signal generated by the remote receiver after receiving the start
time signal from the surface unit (14). The computer uses start
time signal (54) transmitted from the surface unit (14) to
accurately mark the time of detonation of the explosive device
(18), and uses the signal transmitted from the remote receiver to
accurately mark the time that the pressure pulse reached the remote
receiver. By knowing these two times, it is possible to accurately
determine an elapsed time for the acoustic pulse to travel to the
receiver based on the difference between these two times, and
accounting for wireline delay as necessary. The velocity of the
pressure pulse between the explosive device (18) and the remote
receiver may be determined if the distance between them is
known.
[0072] In an alternative embodiment as shown in FIG. 7, a
memory-based downhole tool (120) is provided. In this case, the
memory downhole tool (120) is configured similarly to downhole tool
(12) shown in FIG. 2 in that it comprises a pressure pulse detector
(126), an amplifier (128), and a discriminator and logic unit (130)
that operate in a similar manner to the corresponding components of
the downhole tool (12) described above. However, in this
embodiment, the memory-based downhole tool (120) need not be
operatively connected to a surface unit (14). Rather than
transmitting the output pulse (42), to a signal generator (32) and
uphole to the surface unit (14), the output pulse (42) is received
by a processor (132) having an internal clock and a memory
component, which forms part of the memory-based downhole tool (20).
The internal clock may include temperature compensation, as is well
known in the art. In response to the output pulse (42), the
processor (132) determines the timing of the output pulse and
stores the output pulse (36) into the memory component with an
associated time tag, in a time data file. In this embodiment, a
battery power supply (150) may be used to power the amplifier
(128), the discriminator and logic unit (130) and the processor
(132). In one embodiment, there is no electrical connection between
the electric wireline (22) that is used to power the explosive
device (18) and the battery-powered circuit path of the
memory-based downhole tool (120) to reduce the possibility of the
battery power supply (130) accidentally activating or detonating
the explosive device.
[0073] Before use downhole, the processor (132) of the memory-based
downhole tool (120) is operatively connected to a computer (not
shown) by any conventional means (160), such as USB, serial port or
wireless means such as Bluetooth or WiFi. The computer includes or
is connected to a standalone timing clock system, which the
computer synchronizes to the internal clock of the memory downhole
tool (120). In this manner, the internal clock of the memory
downhole tool (120) may be synchronized with a timing clock system
that is used to determine when an output signal is received from a
remote receiver.
[0074] The memory-based downhole tool (120) may then be deployed
and used downhole to detect pressure pulses.
[0075] The surface timing clock system may also be connected to a
receiving device (conventional seismic device) and receives time
entries corresponding to pressure pulses received by the remote
receiver. When the memory downhole tool (120) is brought back to
the surface, it is re-connected to the computer and resynchronized
with the surface timing clock system. The time difference drift
from the memory downhole tool (120) can then be determined and
corrected.
[0076] By knowing the time tagged to the output pulse (42) by the
processor (142) and the time that the remote receiver generated the
output pulse, it is possible to accurately determine an elapsed
time for the acoustic pulse to travel to the receiver based on the
difference between these two times. The velocity of the pressure
pulse may be determined if the distance between the explosive
device (18) and the remote receiver is known.
[0077] The flowchart and block diagrams and schematics in the
Figures illustrate the architecture, functionality, and operation
of possible implementations of systems, methods and computer
program products according to various embodiments of the present
invention. In this regard, each block in the flowchart or block
diagrams may represent a module, segment, or portion of code, which
comprises one or more executable instructions for implementing the
specified logical function(s). It should also be noted that, in
some alternative implementations, the functions noted in the block
may occur out of the order noted in the figures. For example, two
blocks shown in succession may, in fact, be executed substantially
concurrently, or the blocks may sometimes be executed in the
reverse order, depending upon the functionality involved. It will
also be noted that each block of the block diagrams and/or
flowchart illustration, and combinations of blocks in the block
diagrams and/or flowchart illustration, can be implemented by
special purpose hardware-based systems that perform the specified
functions or acts, or combinations of special purpose hardware and
computer instructions.
[0078] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of
the invention. As used herein, the singular forms "a", "an" and
"the" are intended to include the plural forms as well, unless the
context clearly indicates otherwise. It will be further understood
that the terms "comprises" and/or "comprising," when used in this
specification, specify the presence of stated features, integers,
steps, operations, elements, components and/or groups, but do not
preclude the presence or addition of one or more other features,
integers, steps, operations, elements, components, and/or groups
thereof. The terms "preferably," "preferred," "prefer,"
"optionally," "may," and similar terms are used to indicate that an
item, condition or step being referred to is an optional (not
required) feature of the invention.
[0079] The corresponding structures, materials, acts, and
equivalents of all means or steps plus function elements in the
claims below are intended to include any structure, material, or
act for performing the function in combination with other claimed
elements as specifically claimed. The description of the present
invention has been presented for purposes of illustration and
description, but it is not intended to be exhaustive or limited to
the invention in the form disclosed. Many modifications and
variations will be apparent to those of ordinary skill in the art
without departing from the scope and spirit of the invention. The
embodiment was chosen and described in order to best explain the
principles of the invention and the practical application, and to
enable others of ordinary skill in the art to understand the
invention for various embodiments with various modifications as are
suited to the particular use contemplated.
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