U.S. patent application number 17/025105 was filed with the patent office on 2021-03-25 for near bit wireless constant current short distance transmission method and device.
The applicant listed for this patent is Institute of Geology and Geophysics, Chinese Academy of Sciences. Invention is credited to Wenxuan CHEN, Qingyun DI, Yuntao SUN, Wenxiu ZHANG, Jian ZHENG.
Application Number | 20210087926 17/025105 |
Document ID | / |
Family ID | 1000005148874 |
Filed Date | 2021-03-25 |
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United States Patent
Application |
20210087926 |
Kind Code |
A1 |
SUN; Yuntao ; et
al. |
March 25, 2021 |
NEAR BIT WIRELESS CONSTANT CURRENT SHORT DISTANCE TRANSMISSION
METHOD AND DEVICE
Abstract
A near-bit wireless constant current short-distance transmission
device has an emission part and a receiving part. The emission part
modulates a signal and then wirelessly transmits the modulated
signal to the receiving part. The emission part transmits an
emission signal into a stratum according to a set rated emission
constant current value, and dynamically monitors and adjusts the
rated emission constant current value of the emission signal to
obtain stable emission power.
Inventors: |
SUN; Yuntao; (Beijing,
CN) ; CHEN; Wenxuan; (Beijing, CN) ; DI;
Qingyun; (Beijing, CN) ; ZHENG; Jian;
(Beijing, CN) ; ZHANG; Wenxiu; (Beijing,
CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Institute of Geology and Geophysics, Chinese Academy of
Sciences |
Beijing |
|
CN |
|
|
Family ID: |
1000005148874 |
Appl. No.: |
17/025105 |
Filed: |
September 18, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E21B 47/13 20200501;
E21B 47/013 20200501 |
International
Class: |
E21B 47/13 20060101
E21B047/13; E21B 47/013 20060101 E21B047/013 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 18, 2019 |
CN |
201910882429.0 |
Claims
1. A near-bit wireless constant current short-distance transmission
system, comprising an emission part and a receiving part, the
emission part modulates a signal and then wirelessly transmits the
modulated signal to the receiving part at a short distance, wherein
the emission part emits an emission signal into a stratum according
to a set rated emission constant current value, and dynamically
monitors and adjusts the rated emission constant current value of
the emission signal to obtain stable emission power.
2. The near-bit wireless constant current short-distance
transmission system according to claim 1, wherein the emission part
comprises an emission processor part, a MOSFET driving part, a
feedback acquisition part, a constant current control part and an
emission electrode, the emission processor part is used for
carrying out binary frequency modulation on measurement information
of a near-bit measuring tool, generating a constant voltage
amplitude signal and controlling the constant current control part
to adjust the rated emission constant current value; the MOSFET
driving part is used for amplifying a constant voltage amplitude
signal and controlling a driving circuit after being driven by a
MOSFET; the feedback acquisition part is used for monitoring an
emission voltage value and an emission current value in real time
and feeding the emission voltage value and the emission current
value back to the emission processor part for dynamic monitoring
and adjustment; the constant current control part is used for
setting the rated emission constant current value, adjusting the
rated emission constant current value according to feedback
information obtained by the emission processor part, and feeding
the adjusted rated emission constant current value back to the
emission processor part; and the emission electrode is bridged with
an output end of the driving circuit, and emits an emission
constant current into the stratum.
3. The near-bit wireless constant current short-distance
transmission system according to claim 2, wherein the emission
processor part sets a constant analog voltage value by an analog
output port, and generates a constant voltage amplitude signal
after passing through an amplifying circuit.
4. The near-bit wireless constant current short-distance
transmission system according to claim 2, wherein adjusting the
rated emission constant current value by the constant current
control part according to the feedback information obtained by the
emission processor part specifically comprising: when the rated
emission constant current value is set to a maximum value during
initialization, then in the case that a total resistance in the
circuit is larger than a discharge resistance required by the rated
emission constant current value, reducing the rated emission
constant current value by the constant current control part, and in
the case that the total resistance in the circuit is less than the
discharge resistance required by the rated emission constant
current value, keeping the rated emission constant current value
unchanged by the constant current control part; and when the rated
emission constant current value is set to a minimum value during
initialization, then in the case that the total resistance in the
circuit is larger than the discharge resistance required by the
rated emission constant current value, increasing the rated
emission constant current value by the constant current control
part, and in the case that the total resistance in the circuit is
less than the discharge resistance required by the rated emission
constant current value, keeping the rated emission constant current
value unchanged by the constant current control part.
5. The near-bit wireless constant current short-distance
transmission system according to claim 2, wherein the emission
processor part obtains the emission voltage value and the emission
current value sent by the feedback acquisition part through
analog-to-digital converter interfaces ADC1 and ADC2.
6. A near-bit wireless constant current short-distance transmission
method adopting the near-bit wireless constant current
short-distance transmission system according to claim 1, comprising
the following steps: step 1, setting a rated emission constant
current value by a constant current control part; step 2, carrying
out binary frequency modulation on measurement information of a
near-bit measuring tool by an emission processor part and
generating a constant voltage amplitude signal; step 3: amplifying
the constant voltage amplitude signal by a MOSFET driving part, and
controlling a driving circuit after being driven by a MOSFET; step
4: monitoring an emission voltage value and an emission current
value in real time by a feedback acquisition part, and sending the
emission voltage value and the emission current value to the
emission processor part; step 5, adjusting the rated emission
constant current value by the constant current control part
according to feedback information obtained by the emission
processor part, and feeding the adjusted rated emission constant
current value back to the emission processor part; and step 6,
adjusting an emission constant current by the emission processor
part according to the adjusted rated emission constant current
value feedback by the constant current control part.
7. The near-bit wireless constant current short-distance
transmission method according to claim 6, wherein the emission
processor part sets a constant analog voltage value through an
analog output port, and generates a constant voltage amplitude
signal after passing through an amplifying circuit.
8. The near-bit wireless constant current short-distance
transmission method according to claim 6, wherein the step of
adjusting, by the constant current control part, the rated emission
constant current value according to feedback information obtained
by the emission processor part specifically comprises the following
steps: when the rated emission constant current value is set to a
maximum value during initialization, then in the case that a total
resistance in the circuit is larger than a discharge resistance
required by the rated emission constant current value, reducing the
rated emission constant current value by the constant current
control part, and in the case that the total resistance in the
circuit is less than the discharge resistance required by the rated
emission constant current value, keeping the rated emission
constant current value unchanged by the constant current control
part; and when the rated emission constant current value is set to
a minimum value during initialization, then if the total resistance
in the circuit is larger than the discharge resistance required by
the rated emission constant current value, increasing the rated
emission constant current value by the constant current control
part, and if the total resistance in the circuit is less than the
discharge resistance required by the rated emission constant
current value, keeping the rated emission constant current value
unchanged by the constant current control part.
9. The near-bit wireless constant current short-distance
transmission method according to claim 6, wherein the emission
processor part obtains the emission voltage value and the emission
current value sent by the feedback acquisition part through
analog-to-digital converter interfaces ADC1 and ADC2.
Description
FIELD
[0001] The present disclosure belongs to the technical field of
near-bit logging while drilling, and particularly relates to
near-bit wireless constant current short-distance transmission
method and device.
BACKGROUND
[0002] At present, near-bit logging while drilling technology is
developing rapidly. Compared with conventional logging while
drilling, a sensor probe of a near-bit logging instrument is closer
to a drill bit, and thus can obtain drilling stratigraphic
information in time to more accurately mark drilling trajectory,
reduce drilling operation risk and improve operation efficiency.
Generally speaking, a near-bit logging while drilling (LWD)
instrument consists of the following three parts: a near-bit
measuring tool, a near-bit short-distance transmission device and a
measurement while drilling (MWD) system, as shown in FIG. 1. The
near-bit measuring tool is arranged close to the drill bit, and an
accelerometer, a magnetic sensor and the like are installed inside
the near-bit measuring tool to measure the drilling trajectory
information. Some systems are also equipped with a gamma-ray probe
and a resistivity measuring tool, which can be used to measure
geological information of drilling strata in time. The near-bit
short-distance transmission system is composed of an emitter and a
receiver, and a screw is bridged between the emitter and the
receiver. The function of transmitting the information of the
near-bit measuring tool to the MWD system is realized. Due to the
structural characteristics of the screw, the screw usually has no
electrical connection performance (it is impossible to realize
wired communication between transmitting and receiving devices by
using a through wire), unless the screw structure is modified and
the through wire pre-embedded in the screw is used to realize the
wired communication (see the patent number CN201120323832.9), but
this structure has its limitations in use and is basically
abandoned. The development direction of near-bit short-distance
transmission is wireless transmission. Drilling Technology Research
Laboratory of China Petroleum Exploration and Development Research
Institute adopts an electromagnetic method. The method is that a
wireless electromagnetic short-distance transmission signal
generator with a transmitting antenna modulates data collected by
the near-bit measuring tool to generate electromagnetic signals
which are transmitted and output. A wireless electromagnetic
short-distance transmission receiver with a receiving antenna
receives the transmitted and output electromagnetic signals,
demodulates the received electromagnetic signals, and transmits the
demodulated data to an MWD measurement system (see patent number
CN100410488C). The third part, an MWD system, is mainly composed of
a probe tube, a battery and a mud pulse generator. The near-bit
short-distance transmission device sends the received near-bit
measurement information to a ground system by means of the mud
pulse generator for real-time monitoring by field engineers.
[0003] In the aspect of wireless short-distance transmission, in
addition to transmission by means of a wireless electromagnetism
mode, transmission by means of an electrode mode is also adopted.
The principle of the transmission by means of the electrode mode is
that an emitter, a screw and a receiver are divided into three
electrically isolated sections by inserting two GAP insulation
layers into the emitter and receiver. Wireless short-distance
transmission is realized by detecting weak signals at both ends of
the GAP at the receiver by emitting current from the emitter. This
method is easy to realize and convenient for machining, and thus
has been widely used.
[0004] However, in the actual development process, the applicant
finds that the power consumption of wireless short-distance
transmission by means of the electrode mode is quite different
under different strata and mud resistivity conditions. The dynamic
range of resistivity (influenced by mud resistivity and stratum
resistivity) of the drilling strata (near the bit during drilling)
can vary from 0.1.OMEGA.m to 200.OMEGA.m. Therefore, if the power
output of an emission circuit is not controlled effectively, once
the instrument encounters a low-resistivity stratum during
drilling, it means that a short circuit occurs at two ends of the
emitting GAP, and the power consumption of the emission circuit is
very large, which easily causes burning of the emission circuit of
the instrument. For example, the applicant has actually measured
that the actual equivalent resistance at both ends of the emission
electrode is about 10.OMEGA. in a mud environment of 1.OMEGA.m,
while the actual equivalent resistance at two ends of the emission
electrode is 200.OMEGA. in a mud environment of 37.OMEGA.m (clear
water). Therefore, in both of the two kinds of environment, if the
emission circuit emits at a constant voltage, the power consumption
in the case of low resistance is 20 times that in the case of high
resistance. With the decrease of mud resistivity, the difference is
larger, which easily results in the burning of the emission
circuit. Therefore, a constant-current near-bit emission method and
device are mainly proposed, and adjustment can be performed
according to the actual drilling situations, so as to avoid the
burning of the emission circuit due to excessive power
consumption.
[0005] At present, the constant current emission technology has not
been adopted in the method of near-bit wireless short-distance
transmission by means of the electrode mode. However, the
disadvantages of non-constant-current mode have been explained
above. Therefore, it is necessary to provide a method and device
for near-bit wireless short-distance transmission by adopting a
constant current emission mode.
SUMMARY
[0006] In order to achieve the above purpose, the present
disclosure provides a method and a system for near-bit wireless
constant current short-distance transmission, in order to avoid the
problem of transmission power consumption when drilling strata with
different resistivity during drilling, achieve simple structure and
easiness in implementation, and effectively avoid circuit damage
caused by excessive transmission power consumption.
[0007] According to a first aspect of the present disclosure,
provided is a near-bit wireless constant current short-distance
transmission system which comprises an emission part and a
receiving part, the emission part modulates a signal and then
wirelessly transmits the modulated signal to the receiving part at
a short distance, wherein the emission part emits an emission
signal into a stratum according to a set rated emission constant
current value, and dynamically monitors and adjusts the rated
emission constant current value of the emission signal to obtain
stable emission current.
[0008] Furthermore, the emission part comprises an emission
processor part, a metal-oxide-semiconductor field effect transistor
(MOSFET) driving part, a feedback acquisition part, a constant
current control part, an H-bridge driving part and an emission
electrode, wherein
[0009] the emission processor part is used for carrying out binary
frequency modulation on measurement information of a near-bit
measuring tool, generating a constant voltage amplitude signal and
controlling the constant current control part to adjust the rated
emission constant current value;
[0010] the MOSFET driving part is used for amplifying a constant
voltage amplitude signal and controlling the H-bridge driving part
after being driven by a MOSFET;
[0011] the feedback acquisition part is used for monitoring an
emission voltage value and an emission current value in real time
and feeding the emission voltage value and the emission current
value back to the emission processor part for dynamic monitoring
and adjustment;
[0012] the constant current control part is used for setting the
rated emission constant current value, adjusting the rated emission
constant current value according to feedback information obtained
by the emission processor part, and feeding the adjusted rated
emission constant current value back to the emission processor
part; and
[0013] the positive and negative poles of the emission electrode
are connected with the two poles of a load of the H-bridge driving
part respectively, and emits an emission constant current into the
stratum.
[0014] Furthermore, the emission processor part sets a constant
analog voltage value through an analog output port, and generates a
constant voltage amplitude signal after passing through an
amplifying circuit.
[0015] Furthermore, adjusting the rated emission constant current
value by the constant current control part according to the
feedback information obtained by the emission processor part
specifically comprises the following steps:
[0016] when the rated emission constant current value is set to a
maximum value during initialization, then,
[0017] if a total resistance in the circuit is larger than a
discharge resistance required by the rated emission constant
current value, the constant current control part reduces the rated
emission constant current value, and
[0018] if the total resistance in the circuit is less than the
discharge resistance required by the rated emission constant
current value, the constant current control part keeps the rated
emission constant current value unchanged; and
[0019] when the rated emission constant current value is set to a
minimum value during initialization, then,
[0020] if the total resistance in the circuit is larger than the
discharge resistance required by the rated emission constant
current value, the constant current control part increases the
rated emission constant current value, and
[0021] if the total resistance in the circuit is less than the
discharge resistance required by the rated emission constant
current value, the constant current control part keeps the rated
emission constant current value unchanged.
[0022] Furthermore, the emission processor part obtains the
emission voltage value and the emission current value sent by the
feedback acquisition part through analog-to-digital converter
interfaces ADC1 and ADC2.
[0023] According to a second aspect of the present disclosure,
provided is a near-bit wireless constant current short-distance
transmission method adopting the near-bit wireless constant current
short-distance transmission device according to the above
description, comprising the following steps:
[0024] step 1, setting a rated emission constant current value by a
constant current control part;
[0025] step 2, carrying out binary frequency modulation on
measurement information of a near-bit measuring tool through an
emission processor part and generating a constant voltage amplitude
signal;
[0026] step 3: amplifying the constant voltage amplitude signal by
a MOSFET driving part, and controlling an H-bridge driving circuit
after being driven by a MOSFET;
[0027] step 4: monitoring an emission voltage value and an emission
current value in real time through a feedback acquisition part, and
sending the emission voltage value and the emission current value
to the emission processor part;
[0028] step 5, adjusting, by the constant current control part, the
rated emission constant current value according to feedback
information obtained by the emission processor part, and feeding
the rated emission constant current value back to the emission
processor part; and
[0029] step 6, adjusting, by the emission processor part, an
emission constant current by the emission processor part according
to the adjusted rated emission constant current value feedback by
the constant current control part.
[0030] Furthermore, the emission processor part sets a constant
analog voltage value through an analog output port, and generates a
constant voltage amplitude signal after passing through an
amplifying circuit.
[0031] Furthermore, the step of adjusting, by the emission
processor part, the rated emission constant current value according
to the feedback information of the constant current control part
specifically comprises the following steps:
[0032] when the rated emission constant current value is set to a
maximum value during initialization, then
[0033] if a total resistance in the circuit is larger than a
discharge resistance required by the rated emission constant
current value, reducing the rated emission constant current value
by the constant current control part, and
[0034] if the total resistance in the circuit is less than the
discharge resistance required by the rated emission constant
current value, keeping the rated emission constant current value
unchanged by the constant current control part; and
[0035] when the rated emission constant current value is set to a
minimum value during initialization, then
[0036] if the total resistance in the circuit is larger than the
discharge resistance required by the rated emission constant
current value, increasing the rated emission constant current value
by the constant current control part, and
[0037] if the total resistance in the circuit is less than the
discharge resistance required by the rated emission constant
current value, keeping the rated emission constant current value
unchanged by the constant current control part.
[0038] Furthermore, the emission processor part obtains the
emission voltage value and the emission current value sent by the
feedback acquisition part through analog-to-digital converter
interfaces ADC1 and ADC2.
The Present Disclosure has the Following Beneficial Effects
[0039] according to the method and the device for near-bit wireless
constant current short-distance transmission provided by the
present disclosure, stable power consumption is guaranteed and
working time is prolonged by the constant current control part, the
condition that the maximum value of the emission current does not
exceed a set range in different strata and mud resistivity
environments can be ensured, effective wireless communication in
different strata and mud environments can be realized, the problem
of transmission power consumption when drilling strata with
different resistivity in the drilling process is avoided, the
structure is simple and implementation is easy, and circuit damage
caused by excessive transmission power consumption can be
effectively avoided. According to the present disclosure, a
constant current emission mode is adopted, which has a great
practical value in practical application.
BRIEF DESCRIPTION OF THE DRAWINGS
[0040] In order to explain the embodiments of the present
disclosure or the technical solution in the prior art more clearly,
the accompanying drawings required in the embodiments or the
description of the prior art will be briefly introduced below.
Obviously, the accompanying drawings in the following description
are only some embodiments of the present disclosure, and those
skilled in the art can obtain other accompanying drawings according
to the structures shown in these accompanying drawings without
paying creative labor.
[0041] FIG. 1 shows a structural diagram of a near-bit logging
while drilling instrument;
[0042] FIG. 2 shows a structural diagram of an emission part of a
near-bit wireless constant current short-distance transmission
system according to an embodiment of the present disclosure;
[0043] FIG. 3 shows a flow chart of a near-bit wireless constant
current short-distance transmission method according to an
embodiment of the present disclosure; and
[0044] FIG. 4 is a schematic diagram showing the operation of the
constant current control part and the feedback acquisition part
according to an embodiment of the present disclosure.
[0045] The realization, functional features and advantages of the
present disclosure will be further explained with reference to the
accompanying drawings in combination with the embodiments.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0046] Exemplary embodiments will be described in detail herein,
and examples thereof are shown in the accompanying drawings. When
the following description refers to the accompanying drawings,
unless otherwise indicated, the same numbers in different
accompanying drawings refer to the same or similar elements. The
embodiments described in the following exemplary embodiments do not
represent all embodiments consistent with the present disclosure.
On the contrary, they are merely examples of devices and methods
consistent with some aspects of the present disclosure as detailed
in the appended claims.
[0047] The terms "first", "second", etc., in the specification and
claims of the present disclosure are used to distinguish similar
objects, and are not necessarily used to describe a specific order
or sequence. It should be understood that the data thus used may be
interchanged under appropriate circumstances, so that the
embodiments of the present disclosure described herein can be
implemented, for example, in an order other than those illustrated
or described herein. In addition, the terms "include" and "have"
and any variations thereof are intended to cover non-exclusive
inclusion. For example, a process, method, system, product or
equipment including a series of steps or units do not need to be
limited to those steps or units explicitly listed, but may include
other steps or units not explicitly listed or inherent to these
processes, methods, products or equipment.
[0048] "Multiple" means including two or more.
[0049] It should be understood that the term "and/or" used in the
present disclosure is only an association relationship describing
the associated objects, indicating that there can be three
relationships. For example, A and/or B can indicate that A exists
alone, A and B exist simultaneously, and B exists alone.
[0050] The present disclosure discloses a near-bit wireless
constant current short-distance transmission device, as shown in
FIG. 2, which includes:
[0051] an emission processor part used for carrying out binary
frequency modulation (2FSK) on measurement information of a
near-bit measuring tool, setting a constant analog voltage value
and generating a constant voltage amplitude signal after passing
through an amplifying circuit;
[0052] a MOSFET driving part used for amplifying a modulated signal
and controlling an H-bridge driving circuit after being driven by a
MOSFET;
[0053] a feedback acquisition part used for monitoring an emission
voltage and an emission current in real time and feeding the
emission voltage and the emission current back to the emission
processor part for dynamic monitoring and adjustment;
[0054] a constant current control part used for adjusting an
emission current value according to feedback information obtained
by the emission processor part, and specifically, an output current
is adjusted continuously by outputting different voltages by a
digital-to-analog converter (DAC) of the emission processor part;
and
[0055] Positive and negative of emission electrodes are bridged
with an output end of the H-bridge driving circuit respectively,
and emits a preset constant current into the stratum.
[0056] The present disclosure further provides a near-bit wireless
constant current short-distance transmission method, as shown in
FIG. 3, including the following steps.
[0057] Step 101, setting a rated (first) emission constant current
value by a constant current control part.
[0058] Step 102, carrying out binary frequency modulation on
measurement information of a near-bit measuring tool through an
emission processor part, setting a constant analog voltage value
through an analog output port, and generating a constant voltage
amplitude signal after passing through an amplifying circuit,
wherein the emission processor part obtains an emission voltage
value and an emission current value sent by a feedback acquisition
part through analog-to-digital converter interfaces ADC1 and
ADC2.
[0059] Step 103: amplifying the constant voltage amplitude signal
by a MOSFET driving part, and controlling an H-bridge driving
circuit after being driven by a MOSFET.
[0060] Step 104: monitoring the emission voltage value and the
emission current value in real time through a feedback acquisition
part, and sending the emission voltage value and the emission
current value to the emission processor part.
[0061] Step 105, adjusting, by the constant current control part,
the first emission constant current value according to feedback
information obtained by the emission processor part, and feeding
the first emission constant current value back to the emission
processor part.
[0062] The step of adjusting, by the emission processor part, the
first emission constant current value according to the feedback
information of the constant current control part specifically
includes the following steps:
[0063] when the rated emission constant current value is set to a
maximum value (e.g., 1.0 A) during initialization,
[0064] if a total resistance in the circuit is larger than a
discharge resistance required by the first emission constant
current value, the constant current control part reduces the first
emission constant current value to a second emission constant
current value, and
[0065] if the total resistance in the circuit is less than the
discharge resistance required by the first emission constant
current value, the constant current control part keeps the rated
emission constant current value unchanged; and
[0066] when the rated emission constant current value is set to a
minimum value (e.g., 0.25 A) during initialization,
[0067] if the total resistance in the circuit is larger than the
discharge resistance required by the first emission constant
current value, the constant current control part increases the
first emission constant current value to a second emission constant
current value, and
[0068] if the total resistance in the circuit is less than the
discharge resistance required by the first emission constant
current value, the constant current control part keeps the rated
emission constant current value unchanged.
[0069] Step 106, adjusting, by the emission processor part, an
emission constant current according to the adjusted rated emission
constant current value feedback by the constant current control
part.
[0070] In the technical solution of the present application, the
constant current control part is the key to ensure stable power
consumption and prolong the working time. Different strata and mud
have different resistivity, ranging from 0.1.OMEGA.m to
200.OMEGA.m. Real-time monitoring of the emission current and the
emission voltage loaded to the stratum ensures that the maximum
value of the emission current does not exceed the set range in
different strata and mud resistivity environments, effective
wireless communication in different strata and mud environments can
be realized, and burning of the emission circuit due to a low load
can be avoided.
[0071] As shown in FIG. 4, the emission processor part sets a
constant analog voltage value through the analog output port, and
generates a constant voltage amplitude signal through the
amplifying circuit. The constant voltage amplitude signal is
connected with a collector end of a P-channel metal oxide
semiconductor (PMOS) power tube to realize a constant current
output discharge circuit from a power supply voltage to an H bridge
voltage. The constant current discharge circuit includes a power
resistance Rs, an H-bridge open-circuit resistance Ron, and a load
R at both ends of the emission electrode. If the total resistance
of RL=Rs+Ron+R is greater than the discharge resistance required by
constant current, the discharge circuit works at a current less
than the set constant current. If RL is less than the discharge
resistance required by constant current, the discharge circuit
works at a set constant current. In this way, it is ensured that
the emission circuit cannot be burned under the condition of low
stratum resistivity. At the same time, the device has a measuring
circuit that feeds back the current and voltage, and can monitor
the current of the discharge circuit and the voltage value of the
H-bridge high voltage in real time. According to these two measured
values, the emission processor part can obtain the present
equivalent resistance R at two ends of the emission electrode, so
that the apparent resistivity of the currently drilling stratum can
be obtained through inversion. The feedback voltage and the
feedback current can be simply obtained through analog-to-digital
converter interfaces ADC1 and ADC2 of the processor part.
[0072] In practical application, the selected power supply voltage
and the set constant current directly affect the working time of
the system (because the near-bit measuring tool is basically
powered by batteries) and a signal-to-noise ratio of a receiving
system (different transmission powers and stratum resistivity
directly affect the amplitude and signal-to-noise ratio of the
received signal). Therefore, setting is performed according to the
actual situations. At present, this method and device have been
applied to the near-bit electrode wireless short-distance
transmission system invented by the inventor.
Embodiment 1
[0073] In a system that has been realized at present, the power
supply voltage is 11 V, and the emission processor part sets the
maximum emission current to be 500 mA. The system sets the
collector voltage loaded to a PMOS to be 10 V through a DAC (an
analog-to-digital converter output port) of the processor part. The
power resistance is selected to be RS=2.OMEGA., so that if RL is
less than 22.OMEGA., the maximum current loaded by the system to a
high voltage end of an H bridge is 500 mA ((11 V-10 V)/2.OMEGA.).
Since the discharge circuit current is 500 mA and the power
consumption loaded on the Rs power resistance is 0.5*0.5*2=0.5 W,
it is necessary for Rs to select a high-power resistance to adapt
to a current being 500 mA or above.
Embodiment 2
[0074] By reforming the current system, a higher emission current
can be obtained, and the power supply voltage is 22 V. The emission
processor part sets the maximum emission current to be 2 A. The
system sets the collector voltage loaded to a PMOS to be 18 V
through a DAC (an analog-to-digital converter output port) of the
processor part. The power resistance is selected to be RS=2.OMEGA.,
so that if RL is less than 11.OMEGA., the maximum current loaded by
the system to the high voltage end of an H bridge is 2 A
((22V-18V)/2.OMEGA.). Since the discharge circuit current is 2 A,
and the power consumption loaded on the Rs power resistance is
2*2*2=8 W, the Rs needs to choose a high-power resistance to adapt
to a current being 2 A or above.
Embodiment 3
[0075] Under the condition of a high resistivity of the drilling
stratum, the power supply voltage is 11 V, and the emission
processor part sets the maximum emission current to be 0.5 A. The
system sets the collector voltage loaded to a PMOS to be 10 V
through a DAC (an analog-to-digital converter output port) of the
processor part. The power resistance is selected to be RS=2.OMEGA.,
so that if RL is less than 22.OMEGA., the maximum current loaded by
the system to the high voltage end of an H bridge is 2 A ((22 V-18
V)/2.OMEGA.). However, if the present equivalent resistance R at
two ends of the emission electrode is large and the total load RL
of the discharge circuit is greater than 22.OMEGA., the current of
the discharge circuit is less than 500 mA when the discharge
circuit works at a current of 11 V/RL.
[0076] According to the present disclosure, the constant current
emission function of the near-bit measuring tool can be realized,
and the practicability is high. The purpose of the present
disclosure is to solve the problem of electrode-type emission power
under the condition that different strata are actually drilled, so
as to avoid the problem that the emission power increases
uncontrollably and thus the circuit is burned under the condition
of a low-resistance stratum (the lower the resistivity of stratum,
the smaller the equivalent resistance at two ends of the emission
electrode).
* * * * *