CN115561823A - Logging-while-drilling transmitting device based on nuclear magnetic resonance - Google Patents

Abstract

The invention belongs to the technical field of nuclear magnetic resonance logging while drilling, and provides a logging while drilling transmitting device based on nuclear magnetic resonance, which comprises: the device comprises a main control acquisition processing module, a driving module, a power pulse transmitting module, an antenna interface module and a high-voltage power supply. The master control acquisition processing module is used for receiving master control signals, converting the signals, outputting the converted signals to the driving module and serving as driving signals; the driving module is used for receiving the front-stage signal and outputting the front-stage signal to the rear-stage power pulse transmitting circuit; the power pulse transmitting module is used for bootstrap and lifting the supplied direct current to generate a pulse meeting the nuclear magnetic resonance transmitting requirement; the antenna interface module adopts parallel resonance, so that the voltage provided by the power transmitting circuit is the transmitted resonance voltage; the high-voltage power supply provides required power supply electric energy for the circuit. The radio frequency transmitting circuit can be realized under the conditions of high temperature, high pressure, strong vibration and narrow space, and provides high-power and high-energy-efficiency indexes for the development of a nuclear magnetic resonance logging instrument while drilling.

Description

Logging-while-drilling transmitting device based on nuclear magnetic resonance

Technical Field

The invention belongs to the technical field of nuclear magnetic resonance logging while drilling, and particularly relates to a nuclear magnetic resonance-based logging while drilling transmitting device.

Background

Compared with the traditional single measurement technology, the nuclear magnetic resonance logging can provide more abundant stratum parameters, three basic problems of hole, seepage and saturation of logging are covered comprehensively, the inversion speed is high, the signal intensity is high, the method is not influenced by stratum characteristics, the method is the only method capable of distinguishing the water-bound fluid in the stratum, the free fluid seepage volume characteristics in any rock stratum can be directly detected, a large number of valuable reference bases are provided for evaluating the geological structure and the reservoir characteristics, the method has great advantages for measuring complex terrains, landforms, stratum permeability and the like, and the method is the most advanced logging means at present.

The nuclear magnetic resonance detector is a multidisciplinary cross instrument system with high complexity and difficulty. Especially for ultra-low field nuclear magnetic resonance exploration for geophysical exploration, it is extremely difficult to generate a magnetic field that can transition protons (hydrogen nuclei) from a low energy state to a high energy state.

Disclosure of Invention

In order to generate a magnetic field for enabling protons (hydrogen nuclei) to jump from a low energy state to a high energy state, the invention provides a logging-while-drilling transmitting device based on nuclear magnetic resonance. The device produces the reference signal under the larmor frequency under the control effect of host computer to cooperation high voltage power supply through the control of two full bridge circuit, realizes the bootstrapping of transmitting voltage, is connected with the antenna through antenna interface module, forms the magnetic field that can form resonance with proton (hydrogen nucleus), makes the nuclear magnetic moment that is in the low-energy state, through absorbing the energy that alternating magnetic field provided, moves to high-energy state more. The nuclear magnetic resonance survey transmitting device realizes the excitation effect on the transmitting antenna by generating a series of high-power pulses with the pulse frequency, the pulse amplitude and the transmitting period meeting the nuclear magnetic resonance requirement, effectively excites the stratum to generate nuclear magnetic resonance echo signals, and is the core for realizing the nuclear magnetic resonance logging detection task. The high-power pulse meeting the nuclear magnetic resonance requirement mainly comprises the following two points: 1. the frequency of the emitted pulses is the larmor frequency, because at the larmor frequency, the magnetic energy levels of the hydrogen nuclei can shift due to resonance; 2. because the while-drilling probe adopts an 'Inside-out' scheme, namely a permanent magnet is placed in a borehole (Inside), a static magnetic field which is far higher than a geomagnetic field and is uniform in a certain area is established in a formation (Outside) Outside the borehole, so that formation signals are monitored, and the excitation power of an antenna is high. Therefore, for the nuclear magnetic resonance emitting device, the power output by the power pulse emitting module is required to be high, and the high-power radio frequency pulse is transmitted to the antenna and emitted into the formation by the antenna to excite hydrogen nuclei so as to generate nuclear magnetic resonance.

The master control acquisition processing module is used for receiving a master control signal, converting the master control signal and inputting the converted master control signal into the driving module, wherein the master control signal is a control signal given by an upper computer, and the frequency of a reference signal of the control signal is Larmor frequency;

the driving module is used for receiving an output signal of the front-stage main control acquisition processing module and outputting the output signal to the rear-stage power pulse transmitting module;

the power pulse transmitting module is used for bootstrapping and lifting direct current provided by a high-voltage power supply to generate pulses meeting the nuclear magnetic resonance transmitting requirement;

the high-voltage power supply provides required power supply electric energy for the transmitting device;

compared with the prior art, the invention requires the pulse transmitting circuit to create the pulse excitation stratum nuclear magnetic resonance echo with high frequency, high power, high voltage and large current, needs the power semiconductor device and the electronic circuit support with excellent performance, and the silicon carbide metal-oxide semiconductor field effect transistor (SiC MOSFET) shows excellent performance characteristics in high-frequency, high-voltage and high-temperature environments, so that the power semiconductor devices adopted by the invention are all SiC MOSFETs, and can provide high-power and high-energy-efficiency radio frequency transmitting signals for developing a nuclear magnetic resonance logging instrument while drilling under the conditions of high temperature, high voltage, strong vibration and narrow space. Wide transmission frequency bandwidth and high resolution.

Drawings

FIG. 1, system block diagram;

FIG. 2 is a logic diagram of the operation of the driving chip;

FIG. 3 is a diagram of a power pulse transmitting module;

FIG. 4, timing diagram of control signals;

FIG. 5a is a current flow diagram of a preferred embodiment of the present invention;

FIG. 5b is a current flow diagram of a preferred embodiment of the present invention;

FIG. 5c is a current flow diagram of a preferred embodiment of the present invention;

FIG. 5d is a current flow diagram of a preferred embodiment of the present invention;

the antenna comprises a commutation full-bridge circuit 3-1, a bootstrap isolation circuit 3-2, a transmission full-bridge circuit 3-4 and an antenna module, wherein Q1-Q8 are field effect transistors, C1 and C2 are energy storage short section capacitors, D1 and D2 are diodes, R1-R4 are resistors, and T1-T8 are field effect transistor working stages.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the following drawings and examples further describe the embodiments of the present invention in detail. The following examples are merely illustrative of the present invention and are not intended to limit the invention.

Referring to fig. 1, the present invention comprises a main control acquisition processing module, a driving module, a power pulse transmitting module, an antenna module and a high voltage power supply. The driving module consists of a digital control and signal conversion circuit and a signal monitoring and protecting circuit; the power pulse transmitting module consists of an isolating circuit, a reversing full-bridge circuit, a bootstrap isolating circuit and a transmitting full-bridge circuit.

The pulse transmitting module needs to be matched with the natural frequency of the antenna to create a required radio frequency field B1 which is perpendicular to the static magnetic field B of the antenna magnet ₀ The hydrogen nuclear atoms in the detection area can be rotated in the direction, and nuclear magnetic resonance conditions are created. To make the radio frequency field B ₁ Is sufficient and requires a large pulse current to pass through the transmitting antenna coil. Nuclei with magnetic moments have a resonance frequency, called larmor frequency, which depends on the magnetic separation ratio and the strength of the externally applied magnetic field F = γ B ₀ And/2 pi, where gamma is the rotation ratio or scale factor. Determining emission reference frequency according to Larmor frequency, generating driving control signal, and outputting control signal based on self-selecting echo CPMG pulse sequenceThe differential signal of (2). The master control acquisition processing module receives the differential signal given by the upper computer, converts the differential signal into a single-ended signal and outputs the single-ended signal to the driving module.

The driving module receives the converted master control signal, amplifies the 5V control signal into a high-current 20V control signal, and enables the master control acquisition processing module to rapidly control the on and off of a field effect transistor in the power pulse transmitting module. The driving module comprises a driving chip and a magnetic ring, wherein the driving chip adopts CHT-HADES2P and CHT-HADES2S, the CHT-HADES2P is used for modulation, the CHT-HADES2S is used for demodulation, and the magnetic ring is used for signal isolation. Referring to fig. 2, a logic diagram for processing driving signals for two chips is shown. The control signal is input to CHT-HADES2P, the chip is modulated by OOK (binary on-off keying), the converted main control signal is modulated into a high-frequency signal according to the characteristics of the CHT-HADES2P chip and transmitted to the rear stage, and the working frequency bands are different due to the fact that magnetic rings made of different materials pass through a specific magnetic ring, so that the nickel-zinc magnetic ring is adopted to isolate strong and weak current signals of the front stage and the rear stage and input the strong and weak current signals to CHT-HADES2S, and the chip demodulates the modulated high-frequency signal transmitted from the front stage and outputs a 20V drive control signal amplified into a large current. And then the power is transmitted to the backward stage and is input into a field effect transistor in the power pulse transmitting circuit, so that the field effect transistor can be controlled to be switched on and off by the driving circuit.

Referring to fig. 3, the power pulse transmitting module is configured to convert a 600V direct current provided by a high-voltage power supply into a 2400V high-power radio frequency pulse after chopping, and is specifically divided into three parts, namely, a commutating full bridge circuit, a bootstrap isolation circuit, and a transmitting full bridge circuit; the commutation full-bridge circuit comprises 4 field effect transistors Q1, Q2, Q7 and Q8, wherein the Q1 and the Q2 form a bridge arm, the Q7 and the Q8 form a bridge arm, the two bridge arms are respectively connected with a high-voltage power supply, the commutation full-bridge circuit is connected with the bootstrap isolation circuit, and control signals of the 4 field effect transistors are 20V control signals of large current output by the driving module; the bootstrap isolation circuit comprises energy storage pup joint capacitors C1 and C2, isolation diodes D1 and D2, and resistors R1-R4, wherein R1> R2, R3> R4; the isolation between the commutation full-bridge circuit and the emission full-bridge arm is realized through D1 and D2 and resistors R1 and R3, and energy storage short-circuit capacitors C1 and C2 are connected with the resistors R1 and R3 in parallel, so that the function of bootstrap over-high voltage which is nearly one time is realized; the bootstrap isolation circuit is connected with the preceding stage commutation full bridge to realize bootstrap lifting of voltage; the lifted circuit is connected with the transmitting full bridge circuit; the transmitting full-bridge circuit comprises 4 field effect transistors Q3, Q4, Q5 and Q6, wherein a bridge arm is formed by the Q3 and the Q4, a bridge arm is formed by the Q5 and the Q6, control signals of the 4 field effect transistors are 20V control signals of large current output by the driving module, and the output end of the transmitting full-bridge circuit is connected with the transmitting antenna module.

The working process of the power pulse transmitting module is as follows: the high-voltage power supply is used as an electric energy source and is input into the reversing full-bridge circuit, the reversing full-bridge circuit realizes the reversing of the power transmitting pulse, the phase matching of the transmitting full-bridge circuit is ensured, and symmetrical dynamic voltage is created for the power transmitting pulse; the bootstrap isolation circuit is connected with the preceding stage commutation full bridge to realize bootstrap lifting of voltage; the bootstrap isolation circuit inputs to the transmission full bridge circuit, and the transmission full bridge circuit is parallelly connected with the antenna module, and the transmission antenna interface adopts low inductance design and resonant circuit to be the simple parallel resonance circuit of frequency modulation to guarantee that the maximum voltage that power pulse emission module provided is the resonant voltage of antenna promptly, wherein, high voltage power supply be the DC power supply of 600V power supply. The specific working process is as follows:

referring to fig. 4, a timing diagram of the driving control signals is shown. The on and off of each field effect transistor in the double full-bridge circuit can be divided into different working stages, and each working stage corresponds to T1-T8 in a time sequence, and eight working stages are total. Wherein Q1Q8 is turned on to be in a T1 stage, Q3Q6 is turned on to be in a T2 stage, Q3Q6 is turned off to be in a T3 stage, Q1Q8 is turned off to be in a T4 stage, Q2Q7 is turned on to be in a T5 stage, Q4Q5 is turned on to be in a T6 stage, Q4Q5 is turned off to be in a T7 stage, and Q2Q7 is turned off to be in a T8 stage. Wherein T1-T4 create a positive voltage for the transmit pulse and T5-T8 create a negative voltage for the transmit pulse.

Referring to FIG. 3, in order to be able to create as high a bootstrap voltage as possible, R1> > R2, R3> > R4 should be satisfied. Before the start of operation, all driving signals are set low, all field effect transistors are turned off, and because R1> > R2 and R3> > R4, the voltage between the two ends of C1 and C2 is close to 600V, and the voltage between the two ends of the antenna is 0.

In the stage T1, Q1 and Q8 are conducted, at this time, the potential at point B is 600V, the potential at point A is 1200V, the potential at point D is 0V, and the voltage across point C2 is supplemented from nearly 600V to 600V. As shown in fig. 5a, the current flow diagram is shown in the T1 operation phase.

And in the stage T2, Q3 and Q6 are conducted, at the moment, Q1 and Q8 are still in an on state, the voltage of the point A is applied to the upper end of the antenna, and the lower end of the antenna is connected with 0V. If the initial transmission period is adopted, the voltage at the two ends of the antenna is 0, the voltage is applied to the antenna, the resonant capacitor is equivalent to a short circuit, most of current can generate large charging current for charging the resonant capacitor, and the voltage at the two ends of the resonant capacitor rises sharply; if the working period is normal, the resonant capacitors at the two ends of the antenna resonate until the two ends of the capacitor are close to the maximum forward value, the voltages at the two ends of the capacitor are supplemented to the forward direction of 1200V after the Q3 and the Q6 are conducted, at the moment, the current on the antenna coil is in the process from negative to positive, and when the voltage reaches the highest point, the current begins to increase in the forward direction. As shown in fig. 5b, the current flow diagram is shown in the T2 operation phase.

And in the stage T3, Q3 and Q6 are turned off, the antenna freely oscillates, the voltage at two ends of the resonant capacitor is reduced from the vicinity of 1200V, and the current of the coil is positively increased. As shown in fig. 5c, the current flow diagram is shown in the T3 operation phase.

And in the stage T4, Q1 and Q8 are switched off, the antenna is still in a free resonance state, the voltages at two ends of the antenna resonance capacitor are reduced from positive to negative, the positive direction of the coil current reaches the maximum and begins to be gradually reduced, and the resonance capacitor begins to be reversely charged. As shown in fig. 5d, the current flow diagram is shown in the T4 operation phase.

Since the principle of the positive and negative working processes is the same, only the T1-T4 working processes will be described.

Because the working voltage is very large, the requirement of the double full bridges on the accuracy of control signals is very strict, and in order to prevent potential safety hazards caused by direct connection of upper and lower field effect transistors, a special signal monitoring and protecting circuit directly cuts off power supply input of a high-voltage power supply if a signal is found to be in a problem.

Generally, the 600V direct-current high-voltage chopped wave is converted into a high-power radio-frequency pulse with the peak value of 2400V, the radio-frequency pulse is transmitted to an antenna, and the radio-frequency pulse is emitted into a stratum by the antenna to excite hydrogen nuclei, so that nuclear magnetic resonance is generated.

Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims (9)

1. The utility model provides a well logging while drilling emitter based on nuclear magnetic resonance, includes and follows the boring probe, its characterized in that includes: the device comprises a main control acquisition processing module, a driving module, a power pulse transmitting module, a high-voltage power supply and an antenna interface module; the upper computer sends a master control signal under Larmor frequency to a master control acquisition processing module, the master control acquisition processing module converts the master control signal and outputs 8 paths, each converted master control signal is respectively input into a driving module, the driving module generates a driving signal capable of driving a field effect tube in a power pulse transmitting module, the power pulse transmitting module boosts direct current provided by a high-voltage power supply under the control of the driving signal to generate a series of high-power pulses with pulse frequency, pulse amplitude and transmitting period meeting the nuclear magnetic resonance requirement, the excitation effect on a transmitting antenna is realized, and a stratum is effectively excited to generate a nuclear magnetic resonance echo signal; the high-power pulse meeting the nuclear magnetic resonance requirement comprises the following two points: 1. the emitted pulse frequency is Larmor frequency, and under the Larmor frequency, resonance transition can occur between magnetic energy levels of hydrogen nuclei; 2. the probe while drilling adopts an 'Inside-out' scheme, wherein Inside means that a permanent magnet is placed in a borehole, and out means that a static magnetic field which is far higher than a geomagnetic field and is uniform in a certain area is established in a stratum Outside the borehole, so that formation signals are monitored, and high-power pulses output by a power pulse transmitting module are transmitted to an antenna and transmitted to the stratum by the antenna to excite hydrogen nuclei to generate nuclear magnetic resonance.

2. The logging-while-drilling transmitting device based on nuclear magnetic resonance as recited in claim 1, further characterized in that the main control signal given by the upper computer is a differential signal, and the conversion of the main control signal by the main control acquisition processing module means that the differential signal is converted into a single-ended signal.

3. The logging-while-drilling transmitting device based on nuclear magnetic resonance as recited in claim 1, further characterized in that the driving module amplifies the converted 5V master control signal into a 20V control signal with a large current, so that the master control acquisition processing module can rapidly control the on/off of the field effect transistor in the power pulse transmitting module; furthermore, by arranging a monitoring and protecting circuit, the accuracy of the converted master control signal is monitored in real time, and the potential safety hazard of direct connection of a field effect tube bridge arm in the power pulse transmitting module is prevented.

4. The logging-while-drilling transmitting device based on nuclear magnetic resonance as recited in claim 3, wherein the driving module comprises a driving chip and a magnetic ring, the driving chip adopts CHT-HADES2P and CHT-HADES2S, wherein the CHT-HADES2P is used for modulation, the CHT-HADES2S is used for demodulation, and the magnetic ring is used for signal isolation; the working process of the driving module is that the converted main control signal is input to CHT-HADES2P, the chip is modulated by OOK binary on-off keying, the converted main control signal is modulated into a high-frequency signal and transmitted to the rear stage, the high-frequency signal and the low-frequency signal are isolated from the front stage and the rear stage through the magnetic ring and input to CHT-HADES2S, and the chip demodulates the modulated high-frequency signal transmitted from the front stage into the original driving control signal with Larmor frequency.

5. The logging-while-drilling transmitting device based on nuclear magnetic resonance as recited in claim 1, wherein the driving module and the power pulse transmitting module are connected through an isolation circuit to achieve isolation of front and rear level strong and weak electric signals.

6. The transmitting device for logging while drilling based on nuclear magnetic resonance as claimed in claim 1, wherein the power pulse transmitting module is configured to convert the 600V direct current provided by the high voltage power supply into 2400V high power radio frequency pulses after chopping.

7. The logging-while-drilling transmitting device based on nuclear magnetic resonance as recited in claim 6, wherein the power pulse transmitting module is specifically divided into three parts, namely a commutating full bridge circuit, a bootstrap isolating circuit and a transmitting full bridge circuit;

the commutation full-bridge circuit comprises 4 field effect transistors Q1, Q2, Q7 and Q8, wherein the Q1 and the Q2 form a bridge arm, the Q7 and the Q8 form a bridge arm, the two bridge arms are respectively connected with a high-voltage power supply, the commutation full-bridge circuit is connected with the bootstrap isolation circuit, and control signals of the 4 field effect transistors are 20V control signals of large current output by the driving module;

the bootstrap isolation circuit comprises energy storage pup joint capacitors C1 and C2, isolation diodes D1 and D2, resistors R1, R2, R3 and R4, wherein R1> R2 and R3> R4; d1, C1 and R2 are connected in series, the anode of D1 is connected with the drain electrode of Q1, R2 is connected with the source electrode of Q2, the other end of R2 is connected with the drain electrode of Q2, D2, C2 and R4 are connected in series, the anode of D2 is connected with the drain electrode of Q7, R4 is connected with the source electrode of Q8, the other end of R4 is connected with the drain electrode of Q8, a resistor R1 is connected with an energy storage short-circuit capacitor C1 in parallel, a resistor R3 is connected with the energy storage short-circuit capacitor C2 in parallel, and the function of raising the voltage by nearly one time by bootstrap is achieved; the isolation between the commutation full-bridge circuit and the emission full-bridge arm is realized through the D1 and the D2 and the resistors R1 and R3, and the bootstrap isolation circuit is connected with the preceding stage commutation full-bridge to realize the bootstrap lifting of voltage; the lifted circuit is connected with the transmitting full bridge circuit;

the emitting full-bridge circuit comprises 4 field effect transistors Q3, Q4, Q5 and Q6, wherein a bridge arm is formed by the Q3 and the Q4, a bridge arm is formed by the Q5 and the Q6, the negative electrode of the D1 is connected with the drain electrode of the Q3, the negative electrode of the D2 is connected with the drain electrode of the Q5, the control signals of the 4 field effect transistors are 20V control signals of large current output by the driving module, and the output end of the emitting full-bridge circuit is connected with the emitting antenna module.

8. The while drilling logging-while-drilling transmitting device based on nuclear magnetic resonance as recited in claim 7,

the working process of the power pulse transmitting module is as follows: the high-voltage power supply is used as an electric energy source and is input into the reversing full-bridge circuit, the reversing full-bridge circuit realizes the reversing of the power transmitting pulse, the phase matching of the transmitting full-bridge circuit is ensured, and symmetrical dynamic voltage is created for the power transmitting pulse; the bootstrap isolation circuit is connected with the preceding stage commutation full bridge to realize bootstrap lifting of voltage; the bootstrap isolation circuit inputs to the transmission full bridge circuit, and the transmission full bridge circuit is parallelly connected with antenna interface module, and antenna interface module adopts low inductance design and resonant circuit to be the simple parallel resonance circuit of frequency modulation to guarantee that the maximum voltage that power pulse emission module provided is the resonant voltage of antenna promptly, wherein, high voltage power supply be the DC power supply of 600V power supply.

9. The logging-while-drilling transmitting device based on nuclear magnetic resonance as claimed in claim 7, wherein the power pulse transmitting module includes 8 field effect transistors Q1-Q8, the on and off of the field effect transistors can be divided into different working stages, each working stage corresponds to T1-T8 in the time sequence, the total of eight working stages is eight, wherein Q1Q8 is turned on as T1 stage, Q3Q6 is turned on as T2 stage, Q3Q6 is turned off as T3 stage, Q1Q8 is turned off as T4 stage, Q2Q7 is turned on as T5 stage, Q4Q5 is turned on as T6 stage, Q4Q5 is turned off as T7 stage, and Q2Q7 is turned off as T8 stage, wherein T1-T4 is a process of generating a forward voltage for transmitting pulses, and T5-T8 is a process of generating a negative voltage for transmitting pulses.

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