WO2021035881A1 - 核磁共振线圈阵列及其去耦合方法、核磁共振探测装置 - Google Patents

核磁共振线圈阵列及其去耦合方法、核磁共振探测装置 Download PDF

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WO2021035881A1
WO2021035881A1 PCT/CN2019/110305 CN2019110305W WO2021035881A1 WO 2021035881 A1 WO2021035881 A1 WO 2021035881A1 CN 2019110305 W CN2019110305 W CN 2019110305W WO 2021035881 A1 WO2021035881 A1 WO 2021035881A1
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Prior art keywords
coil
circuit
decoupling
nuclear magnetic
magnetic resonance
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PCT/CN2019/110305
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English (en)
French (fr)
Inventor
肖立志
罗嗣慧
廖广志
汪正垛
凡永恒
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中国石油大学(北京)
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Publication of WO2021035881A1 publication Critical patent/WO2021035881A1/zh
Priority to US17/681,289 priority Critical patent/US20220179018A1/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
    • G01R33/32—Excitation or detection systems, e.g. using radio frequency signals
    • G01R33/36—Electrical details, e.g. matching or coupling of the coil to the receiver
    • G01R33/3642—Mutual coupling or decoupling of multiple coils, e.g. decoupling of a receive coil from a transmission coil, or intentional coupling of RF coils, e.g. for RF magnetic field amplification
    • G01R33/365—Decoupling of multiple RF coils wherein the multiple RF coils have the same function in MR, e.g. decoupling of a receive coil from another receive coil in a receive coil array, decoupling of a transmission coil from another transmission coil in a transmission coil array
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N24/00—Investigating or analyzing materials by the use of nuclear magnetic resonance, electron paramagnetic resonance or other spin effects
    • G01N24/08—Investigating or analyzing materials by the use of nuclear magnetic resonance, electron paramagnetic resonance or other spin effects by using nuclear magnetic resonance
    • G01N24/081—Making measurements of geologic samples, e.g. measurements of moisture, pH, porosity, permeability, tortuosity or viscosity
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
    • G01R33/32—Excitation or detection systems, e.g. using radio frequency signals
    • G01R33/34—Constructional details, e.g. resonators, specially adapted to MR
    • G01R33/34046—Volume type coils, e.g. bird-cage coils; Quadrature bird-cage coils; Circularly polarised coils
    • G01R33/34069—Saddle coils
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
    • G01R33/32—Excitation or detection systems, e.g. using radio frequency signals
    • G01R33/36—Electrical details, e.g. matching or coupling of the coil to the receiver
    • G01R33/3628—Tuning/matching of the transmit/receive coil
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
    • G01R33/32—Excitation or detection systems, e.g. using radio frequency signals
    • G01R33/36—Electrical details, e.g. matching or coupling of the coil to the receiver
    • G01R33/3664—Switching for purposes other than coil coupling or decoupling, e.g. switching between a phased array mode and a quadrature mode, switching between surface coil modes of different geometrical shapes, switching from a whole body reception coil to a local reception coil or switching for automatic coil selection in moving table MR or for changing the field-of-view
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V3/00—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation
    • G01V3/18—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation specially adapted for well-logging
    • G01V3/32—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation specially adapted for well-logging operating with electron or nuclear magnetic resonance

Definitions

  • the embodiments of the present application relate to nuclear magnetic resonance logging technology, in particular to a nuclear magnetic resonance coil array and its decoupling method, and a nuclear magnetic resonance detection device.
  • Nuclear magnetic resonance is a physical process in which atomic nuclei with non-zero magnetic moments undergo Zeeman splitting of the spin energy levels under the action of an external magnetic field and resonantly absorb radio frequency radiation of a certain frequency.
  • Nuclear magnetic resonance logging technology uses nuclear magnetic resonance detection devices to detect the formation around the borehole.
  • the probe is one of the most important components of the nuclear magnetic resonance detection device. It is mostly a single radio frequency antenna structure, which can measure 360° omnidirectional area or 60°, 120° single azimuth area, but it has no circumferential direction to the downhole formation. Resolving power.
  • the existing nuclear magnetic resonance detection device measures the formation based on a simple homogeneous formation model structure, and the measured signal is a circumferential omnidirectional or single-azimuth average signal of the formation, and the average signal is used to reflect the nature of the formation.
  • the measured downhole environment is mostly complex stratum environments, such as complex heterogeneous stratum, partial mud intrusion stratum, or wellbore collapsed stratum.
  • the average signal cannot accurately reflect the nature of the formation, resulting in poor detection accuracy of the nuclear magnetic resonance detection device.
  • Array detection technology can perform per-well imaging of the formation around the borehole to obtain richer formation information.
  • the inductive coupling between the coil arrays of the nuclear magnetic resonance detection device makes the coil unit unable to transmit and receive signals normally. Therefore, the inductive coupling problem of the nuclear magnetic resonance array coil needs to be solved urgently.
  • the embodiments of the present application provide a nuclear magnetic resonance coil array, a decoupling method thereof, and a nuclear magnetic resonance detection device to solve the inductive coupling problem of a downhole nuclear magnetic resonance coil.
  • an embodiment of the present application provides a nuclear magnetic resonance coil array, including a coil resonance unit and a decoupling network unit;
  • the coil resonance unit includes a plurality of coil resonance circuits
  • the decoupling network unit includes a plurality of decoupling circuits, wherein each coil resonance circuit includes a coil and a resonance capacitor;
  • the resonant capacitor in the resonant circuit of each coil is connected in parallel with the coil, and the coils in the resonant circuit of each coil are distributed at equal intervals on the circumference, and a decoupling circuit is set between the same-named and different-named ends of adjacent coils;
  • Each coil is connected to the antenna switching circuit of the nuclear magnetic resonance detection device at the same time, and is used to sequentially transmit nuclear magnetic resonance signals under the control of the antenna switching circuit, and each tuning capacitor is used to tune the transmission frequency of the corresponding nuclear magnetic resonance signal, and the decoupling
  • the circuit is used to eliminate the mutual inductance coupling between adjacent coils.
  • each coil resonant circuit also includes a resistor
  • the resistor After the resistor is connected in series with the coil, it is then connected in parallel with the resonant capacitor, a decoupling circuit connector is provided between the resistor and the resonant capacitor, and a decoupling circuit is provided between the coil and the resonant capacitor Connector, the decoupling circuit connector is used to connect with the decoupling circuit.
  • a decoupling circuit is provided between the same-named end and the different-named end of the spacer coil in each coil resonance circuit to eliminate the mutual inductance coupling between the spacer coils.
  • the coil in each coil resonant circuit is a plane-wound saddle-shaped or figure-eight-shaped double-turn coil
  • the coil in each coil resonance circuit is a saddle-shaped or figure eight-shaped multi-turn coil that is wound on a plane.
  • the positions of two adjacent coils in each coil resonant circuit are orthogonal.
  • the resonant capacitors in the resonant circuit of each coil are respectively located in the capacitor compartment at the front end of the corresponding coil, and the structure of each resonant capacitor is the same.
  • each decoupling circuit is located in the cabin at the front end of the corresponding resonant capacitor, and the structure of each decoupling circuit is the same.
  • the decoupling circuit includes a decoupling capacitor with an adjustable capacitance.
  • the embodiments of the present application provide a decoupling method based on the nuclear magnetic resonance coil array described in the first aspect and various possible designs of the first aspect, including:
  • each unit of the nuclear magnetic resonance coil array When each unit of the nuclear magnetic resonance coil array is in a disconnected state, respectively tune the electrical parameters of each resonant capacitor to the same state;
  • each resonant capacitor Connect each resonant capacitor with the same electrical parameter to the corresponding coil resonance circuit at the same time, and connect a decoupling circuit between the same-named and different-named ends of adjacent coils in each coil resonant circuit;
  • an embodiment of the present application provides a nuclear magnetic resonance detection device, including: the nuclear magnetic resonance coil array described in the first aspect and various possible designs of the first aspect.
  • the nuclear magnetic resonance coil array and its decoupling method, and the nuclear magnetic resonance detection device provided by this embodiment include a coil resonance unit and a decoupling network unit; the coil resonance unit includes a plurality of coil resonance circuits, and the decoupling network unit includes Multiple decoupling circuits, among which, a coil resonant circuit includes a coil and a resonant capacitor; the resonant capacitor in the resonant circuit of each coil is connected in parallel with the coil, and the coils in the resonant circuit of each coil are distributed at equal intervals on the circumference.
  • a decoupling circuit is set between the same-named terminal and the different-named terminal; each coil is connected to the antenna switching circuit of the nuclear magnetic resonance detection device at the same time, and is used to sequentially transmit nuclear magnetic resonance signals under the control of the antenna switching circuit, and each tuning capacitor is used for tuning Corresponding to the transmission frequency of the nuclear magnetic resonance signal, the decoupling circuit is used to eliminate the mutual inductance coupling between adjacent coils.
  • the coil array has a simple structure and excellent performance, and can effectively eliminate the coupling effect between the coil resonant circuits, thereby realizing precise positioning of oil and gas positions and obtaining high-quality borehole formation data.
  • FIG. 1 is a schematic structural diagram of a nuclear magnetic resonance coil array provided by an embodiment of the application.
  • FIG. 2 is a schematic diagram of a three-dimensional structure of a nuclear magnetic resonance coil array provided by an embodiment of the application;
  • FIG. 3 is a circuit diagram of a nuclear magnetic resonance coil array provided by an embodiment of the application.
  • FIG. 4 is a schematic flowchart of a decoupling method for a nuclear magnetic resonance coil array provided by an embodiment of the application;
  • FIG. 5 is a schematic structural diagram of a nuclear magnetic resonance detection device provided by an embodiment of the application.
  • Nuclear magnetic resonance logging technology uses nuclear magnetic resonance detection devices to detect the formation around the borehole.
  • the probe is one of the most important components of the nuclear magnetic resonance detection device. It is mostly a single radio frequency antenna structure, which can measure 360° omnidirectional area or 60°, 120° single azimuth area, but it has no circumferential direction to the downhole formation. Resolving power. Therefore, the existing nuclear magnetic resonance detection device measures the formation based on a simple homogeneous formation model structure, and the measured signal is a circumferential omnidirectional or single-azimuth average signal of the formation, and the average signal is used to reflect the nature of the formation.
  • the measured downhole environment is mostly complex stratum environments, such as complex heterogeneous stratum, partial mud intrusion stratum, or wellbore collapsed stratum.
  • the average signal cannot accurately reflect the nature of the formation, resulting in poor detection accuracy of the nuclear magnetic resonance detection device.
  • Array detection technology can perform per-well imaging of the formation around the borehole to obtain richer formation information.
  • the inductive coupling between the coil arrays of the nuclear magnetic resonance detection device makes the coil unit unable to transmit and receive signals normally. Therefore, the inductive coupling problem of downhole nuclear magnetic resonance array coils needs to be solved urgently.
  • this embodiment provides a nuclear magnetic resonance coil array, a decoupling method thereof, and a nuclear magnetic resonance detection device.
  • the coil array includes a coil resonance unit and a decoupling network unit; the coil resonance unit includes a plurality of coil resonances.
  • the above-mentioned decoupling network unit includes a plurality of decoupling circuits, wherein a coil resonant circuit includes a coil and a resonant capacitor; the resonant capacitor in the resonant circuit of each coil is connected in parallel with the coil, and the coil in the resonant circuit of each coil is on the circumference Distributed at equal intervals, a decoupling circuit is set between the same-named and different-named ends of adjacent coils; each coil is connected to the antenna switching circuit of the nuclear magnetic resonance detection device at the same time, and is used to sequentially transmit nuclear magnetic resonance under the control of the antenna switching circuit Signal, each tuning capacitor is used to tune the transmission frequency of the corresponding nuclear magnetic resonance signal, and the decoupling circuit is used to eliminate the mutual inductance coupling between adjacent coils.
  • the coil array has a simple structure and excellent performance, and can effectively eliminate the coupling effect between the coil resonant circuits, thereby realizing precise positioning of oil and gas positions and obtaining high-quality borehole
  • FIG. 1 is a schematic diagram of the structure of a nuclear magnetic resonance coil array provided by an embodiment of the application
  • FIG. 2 is a schematic diagram of a three-dimensional structure of the nuclear magnetic resonance coil array provided by an embodiment of the application.
  • the output port of the coil array 1 is directly connected to the antenna switching circuit 2.
  • the coil array 1 may include a coil resonance unit and a decoupling network unit.
  • Figures 1 and 2 take the coil resonant unit including four coil resonant circuits as an example for description, but the number of coil resonant circuits is not particularly limited in this embodiment, and the number of coil resonant circuits can be selected according to specific application scenarios.
  • the coil resonance unit includes a plurality of coil resonance circuits
  • the decoupling network unit includes a plurality of decoupling circuits.
  • each coil resonant circuit includes a coil and a resonant capacitor.
  • the resonant capacitor in the resonant circuit of each coil is connected in parallel with the coil.
  • the coils in the resonant circuit of each coil are distributed at equal intervals on the circumference.
  • Each coil is connected to the antenna switching circuit 2 of the nuclear magnetic resonance detection device at the same time, and is used to sequentially transmit nuclear magnetic resonance signals under the control of the antenna switching circuit 2.
  • each coil corresponds to a different detection orientation, and each coil can excite regions of interest in different orientations.
  • each coil can excite a thin tile shell-shaped region of interest with an arc of 90°.
  • the total area of interest is a 360° thin-walled hollow cylinder. Therefore, it is possible to transmit pulse energy and receive nuclear magnetic resonance signals for formations in different azimuths downhole, and the formation signals from different azimuths will not overlap, so the ability to distinguish formation information in different azimuths and angles can be improved.
  • the coil in the resonance circuit of each coil is a plane-wound saddle-shaped or figure-eight-shaped double-turn coil
  • the coils in the resonant circuit of each coil are plane-wound saddle-shaped or figure eight-shaped multi-turn coils.
  • the positions of two adjacent coils in each coil resonance circuit are orthogonal.
  • Each tuning capacitor is used to tune the transmission frequency of the corresponding nuclear magnetic resonance signal.
  • the resonant capacitors in the resonant circuits of each coil are respectively located in the capacitor compartment at the front end of the corresponding coil, and the structure of each resonant capacitor is the same, so that each coil can be adjusted to have the same transmission impedance, transmission frequency band, and performance. status.
  • a decoupling circuit is respectively arranged between the same-named end and the different-named end of the adjacent coils, and the decoupling circuit is used to eliminate the mutual inductance coupling between the adjacent coils.
  • each decoupling circuit is respectively located in a cabin at the front end of the corresponding resonant capacitor, and the structure of each decoupling circuit is the same.
  • a decoupling circuit can be set between the same-named and different-named ends of the spacer coils in each coil resonant circuit to eliminate the gap between the spacer coils.
  • the mutual inductance coupling can be set between the same-named and different-named ends of the spacer coils in each coil resonant circuit to eliminate the gap between the spacer coils.
  • the decoupling circuit includes a decoupling capacitor with an adjustable capacitance.
  • a decoupling capacitor with an adjustable capacitance Exemplarily, by adjusting the capacitance value of the decoupling capacitor, the electrical parameters of the coil resonant circuit affected by the inductive coupling are consistent.
  • the capacitance value of the decoupling capacitor can also be adjusted according to the mutual inductance coupling strength between the coils of each coil resonant circuit. For example: when the mutual inductance coupling between the coils increases, increase the capacitance of the decoupling capacitor.
  • each coil resonance circuit further includes a resistor
  • the resistor After the resistor is connected in series with the coil, it is then connected in parallel with the resonant capacitor, a decoupling circuit connector is provided between the resistor and the resonant capacitor, and a decoupling circuit is provided between the coil and the resonant capacitor Connector, the decoupling circuit connector is used to connect with the decoupling circuit.
  • Fig. 3 is a circuit diagram of the nuclear magnetic resonance coil array provided by an embodiment of the application.
  • Fig. 3 takes the coil resonant unit including four coil resonant circuits and the decoupling circuit including decoupling capacitors as an example for description, but this embodiment describes the coil resonant circuit
  • the number and decoupling circuits are not particularly limited.
  • the coil resonance unit includes: a first coil resonance circuit 31, a second coil resonance circuit 32, a third coil resonance circuit 33, and a fourth coil resonance circuit 34.
  • the first coil resonance circuit 31 includes a resistor R1, a coil L1, and a resonance capacitor C1.
  • the second coil resonance circuit 32 includes a resistor R2, a coil L2, and a resonance capacitor C1.
  • the third coil resonance circuit 33 includes a resistor R3, a coil L3, and a resonance capacitor C1.
  • the fourth coil resonance circuit 34 includes a resistor R4, a coil L4, and a resonance capacitor C1.
  • a decoupling circuit is set between the same-named and different-named ends of adjacent coils, namely between the same-named and different-named ends of coil L1 and coil L2, and between the same-named and different-named ends of coil L2 and coil L3,
  • a decoupling capacitor C2 is provided between the same-named end and the different-named end of the coil L3 and the coil L4, and between the same-named end and the different-named end of the coil L4 and the coil L1.
  • the same-named and different-named ends of the coil L1 and the coil L2 are respectively provided with a decoupling circuit connector
  • the same-named and different-named ends of the coil L2 and the coil L3 are respectively provided with a decoupling circuit connector
  • the coils L3 and L4 have the same names
  • a decoupling circuit connector is respectively provided on the end and the different name end
  • the same name and the different name end of the coil L4 and the coil L1 are respectively provided with a decoupling circuit connector, which is connected to the decoupling capacitor C2 through the decoupling circuit connector.
  • a decoupling circuit connector is provided between the resistor R1 and the resonant capacitor C1 in the first coil resonant circuit 31, and the connector is connected to a decoupling capacitor C2; in the second coil resonant circuit 32, a decoupling circuit connector is provided between the resistor R2 and the resonant capacitor C1. The coupling circuit connector is connected to the aforementioned decoupling capacitor C2.
  • a decoupling circuit connector is provided between the coil L1 and the resonant capacitor C1 in the first coil resonant circuit 31, and the connector is connected to another decoupling capacitor C2; in the second coil resonant circuit 32, a decoupling circuit connector is provided between the coil L2 and the resonant capacitor C1 Decoupling circuit connector, which is connected to the above-mentioned other decoupling capacitor C2.
  • the nuclear magnetic resonance coil array includes a coil resonant unit and a decoupling network unit; the coil resonant unit includes a plurality of coil resonant circuits, the decoupling network unit includes a plurality of decoupling circuits, wherein one coil resonant circuit includes A coil and a resonant capacitor; the resonant capacitor in the resonant circuit of each coil is connected in parallel with the coil, and the coils in the resonant circuit of each coil are distributed at equal intervals on the circumference.
  • a decoupling is set between the same-named and different-named ends of adjacent coils.
  • each coil is connected to the antenna switching circuit of the nuclear magnetic resonance detection device at the same time, and is used to sequentially transmit nuclear magnetic resonance signals under the control of the antenna switching circuit, and each tuning capacitor is used to tune the transmission frequency of the corresponding nuclear magnetic resonance signal, and the decoupling circuit is used To eliminate the mutual inductance coupling between adjacent coils.
  • the coil array has a simple structure and excellent performance, and can effectively eliminate the coupling effect between the coil resonant circuits, thereby realizing precise positioning of oil and gas positions and obtaining high-quality borehole formation data.
  • FIG. 4 is a schematic flowchart of a decoupling method for a nuclear magnetic resonance coil array provided by an embodiment of the application. As shown in FIG. 4, this embodiment is based on the decoupling method of the nuclear magnetic resonance coil array as in the foregoing embodiment, and includes:
  • the coil resonant capacitance of each coil resonant unit is tuned to the state of the same impedance, the same frequency, and the same electrical parameters such as the same Q value, so that the coil of each coil resonant circuit is in the state of Have the same transmitting impedance, transmitting frequency band and performance when transmitting.
  • S402 Connect the resonance capacitors with the same electrical parameters to the corresponding coil resonance circuit at the same time, and connect a decoupling circuit between the same-named end and the different-named end of the adjacent coils in each coil resonance circuit.
  • all resonant capacitors with the same electrical parameters are connected to the corresponding coil resonant circuit at the same time, and a decoupling circuit is respectively connected between the same-named and different-named ends of adjacent coil units in each coil resonant circuit, Check and record the impedance, frequency and Q value and other typical parameters between the resonant circuits of each coil.
  • S403 Adjust the decoupling capacitance value of each decoupling circuit to eliminate the mutual inductance coupling between adjacent coils.
  • the decoupling method of the nuclear magnetic resonance coil array provided by this embodiment is to tune the electrical parameters of the resonant capacitors to the same state when each unit of the nuclear magnetic resonance coil array is in the open state, and then set the electrical parameters of the same electrical parameters to the same state.
  • the resonant capacitor is connected to the corresponding coil resonant circuit at the same time, and a decoupling circuit is connected between the same-named and different-named ends of adjacent coils in each coil resonant circuit, and then the decoupling capacitance value of each decoupling circuit is adjusted to Eliminating the mutual inductance coupling between adjacent coils, the above decoupling method can effectively eliminate the coupling effect between the coil resonant circuits, improve the performance of the coil array, and then achieve precise positioning of oil and gas positions and obtain high-quality wellbore formation data.
  • FIG. 5 is a schematic structural diagram of a nuclear magnetic resonance detection device provided by an embodiment of the application. As shown in FIG. 5, the device includes: the nuclear magnetic resonance coil array 1 in the foregoing embodiment.
  • the nuclear magnetic resonance coil array 1 is used for receiving a switching instruction, and switching the coil resonance circuit according to the switching instruction.
  • the device further includes: an antenna switching circuit 2, a ground system 3, a transmitter module 4, a duplexer 5, and a receiver 6.
  • the above-mentioned antenna switching circuit 2 is used to send a switching command to the nuclear magnetic resonance coil array 1.
  • ground system 3 is used to send detection instructions and process data.
  • the above-mentioned transmitter module 4 is used to transmit high-power signals.
  • the aforementioned duplexer 5 is used to isolate the noise during pulse signal transmission and weak signal reception.
  • the above-mentioned receiver 6 is used to receive weak signals.
  • the nuclear magnetic resonance detection device provided in this embodiment can accurately locate the oil and gas position and obtain high-quality borehole formation data.

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Abstract

一种核磁共振线圈阵列（1）及其去耦合方法、核磁共振探测装置，该线圈阵列（1）包括：线圈谐振单元和去耦合网络单元；所述线圈谐振单元包括多个线圈谐振电路（31-34），所述去耦合网络单元包括多个去耦合电路，其中，一个线圈谐振电路（31-34）包括一个线圈（L1-L4）和一个谐振电容（C1）；各个线圈谐振电路（31-34）中的谐振电容（C1）与线圈（L1-L4）并联，各个线圈谐振电路（31-34）中的线圈（L1-L4）在圆周上等间隔分布，相邻线圈（L1-L4）的同名端和异名端之间分别设置一个去耦合电路；各个线圈（L1-L4）同时与核磁共振探测装置的天线切换电路（2）连接，用于在所述天线切换电路（2）的控制下依次发射核磁共振信号，各个谐振电容（C1）用于调谐相应的核磁共振信号的发射频率，所述去耦合电路用于消除相邻线圈（L1-L4）之间的互感耦合。

Description

核磁共振线圈阵列及其去耦合方法、核磁共振探测装置 技术领域
本申请实施例涉及核磁共振测井技术，尤其涉及一种核磁共振线圈阵列及其去耦合方法、核磁共振探测装置。
背景技术
核磁共振是磁矩不为零的原子核，在外磁场作用下自旋能级发生塞曼分裂，共振吸收某一定频率的射频辐射的物理过程。核磁共振测井技术是利用核磁共振探测装置对井眼周围的地层的进行探测。探头是核磁共振探测装置中的最重要的组成部分之一，其多为单射频天线结构，能够测量360°全方位区域或者60°、120°的单方位区域，但没有对井下地层的周向分辨能力。因此，现有核磁共振探测装置是基于简单的均质性地层模型结构对地层进行测量，测量得到的信号是地层的周向全方位或单方位的平均信号，采用该平均信号反映地层的性质。
然而，在核磁共振探测装置的实际应用中，测量的井下环境多为复杂的地层环境，例如复杂非均质性地层、部分泥浆侵入地层或者井眼垮塌地层等。在这种情况下，平均信号无法准确地反应地层的性质，导致核磁共振探测装置的探测精度较差。
阵列探测技术，能够对井眼周围的地层进行井周成像，获取更丰富的地层信息。然而，核磁共振探测装置的线圈阵列之间存在电感耦合作用，使得线圈单元无法正常地进行信号的发射与接收。因此，核磁共振阵列线圈的电感耦合问题亟需解决。
发明内容
本申请实施例提供一种核磁共振线圈阵列及其去耦合方法、核磁共振探测装置，以解决井下核磁共振线圈的电感耦合问题。
第一方面，本申请实施例提供一种核磁共振线圈阵列，包括线圈谐振单元和去耦合网络单元；
所述线圈谐振单元包括多个线圈谐振电路，所述去耦合网络单元包括多个去耦合电路，其中，每个线圈谐振电路包括一个线圈和一个谐振 电容；
各个线圈谐振电路中的谐振电容与线圈并联，各个线圈谐振电路中的线圈在圆周上等间隔分布，相邻线圈的同名端和异名端之间分别设置一个去耦合电路；
各个线圈同时与核磁共振探测装置的天线切换电路连接，用于在所述天线切换电路的控制下依次发射核磁共振信号，各个调谐电容用于调谐相应的核磁共振信号的发射频率，所述去耦合电路用于消除相邻线圈之间的互感耦合。
在一种可能的设计中，每个线圈谐振电路还包括一个电阻；
所述电阻与所述线圈串联后，再与所述谐振电容并联，所述电阻和所述谐振电容之间设置一个去耦合电路接头，所述线圈和所述谐振电容之间设置一个去耦合电路接头，所述去耦合电路接头用于与去耦合电路连接。
在一种可能的设计中，各个线圈谐振电路中间隔线圈的同名端和异名端之间分别设置一个去耦合电路，用于消除间隔线圈之间的互感耦合。
在一种可能的设计中，各个线圈谐振电路中的线圈为平面绕制的马鞍形或八字形的双匝线圈；
或者，各个线圈谐振电路中的线圈为平面绕制的马鞍形或八字形的多匝线圈。
在一种可能的设计中，各个线圈谐振电路中相邻两个线圈的位置正交。
在一种可能的设计中，各个线圈谐振电路中的谐振电容分别位于对应的线圈的前端的电容舱室内，且各个谐振电容的结构相同。
在一种可能的设计中，各个去耦合电路分别位于对应的谐振电容的前端的舱室内，且各个去耦合电路的结构相同。
在一种可能的设计中，所述去耦合电路包括电容值可调的去耦合电容。
第二方面，本申请实施例提供一种基于如上述第一方面以及第一方面各种可能的设计所述的核磁共振线圈阵列的去耦合方法，包括：
在所述核磁共振线圈阵列的各个单元处于断路状态时，分别调谐各个谐振电容的电性参数到相同的状态；
将各个电性参数相同的谐振电容同时接入相应的线圈谐振电路，在各个线圈谐振电路中相邻线圈的同名端和异名端之间分别接入一个去耦合电路；
调整各个去耦合电路的去耦合电容值，以消除相邻线圈之间的互感耦合。
第三方面，本申请实施例提供一种核磁共振探测装置，包括：如上述第一方面以及第一方面各种可能的设计所述的核磁共振线圈阵列。
本实施例提供的核磁共振线圈阵列及其去耦合方法、核磁共振探测装置，该线圈阵列包括线圈谐振单元和去耦合网络单元；上述线圈谐振单元包括多个线圈谐振电路，上述去耦合网络单元包括多个去耦合电路，其中，一个线圈谐振电路包括一个线圈和一个谐振电容；各个线圈谐振电路中的谐振电容与线圈并联，各个线圈谐振电路中的线圈在圆周上等间隔分布，相邻线圈的同名端和异名端之间分别设置一个去耦合电路；各个线圈同时与核磁共振探测装置的天线切换电路连接，用于在天线切换电路的控制下依次发射核磁共振信号，各个调谐电容用于调谐相应的核磁共振信号的发射频率，去耦合电路用于消除相邻线圈之间的互感耦合。该线圈阵列结构简单、性能优良，能够有效消除线圈谐振电路之间的耦合作用，进而实现精确定位油气位置，获取高质量的井眼地层数据。
附图说明
为了更清楚地说明本申请实施例或现有技术中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作一简单地介绍，显而易见地，下面描述中的附图是本申请的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动性的前提下，还可以根据这些附图获得其他的附图。
图1为本申请实施例提供的核磁共振线圈阵列的结构示意图；
图2为本申请实施例提供的核磁共振线圈阵列的立体结构示意图；
图3为本申请实施例提供的核磁共振线圈阵列的电路图；
图4为本申请实施例提供的核磁共振线圈阵列的去耦合方法的流程示意图；
图5为本申请实施例提供的核磁共振探测装置的结构示意图。
具体实施方式
为使本申请实施例的目的、技术方案和优点更加清楚，下面将结合本申请实施例中的附图，对本申请实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例是本申请一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域普通技术人员在没有作出创造性劳动前提下所获得的所有其他实施例，都属于本申请的保护的范围。
核磁共振测井技术是利用核磁共振探测装置对井眼周围的地层的进行探测。探头是核磁共振探测装置中的最重要的组成部分之一，其多为单射频天线结构，能够测量360°全方位区域或者60°、120°的单方位区域，但没有对井下地层的周向分辨能力。因此，现有核磁共振探测装置是基于简单的均质性地层模型结构对地层进行测量，测量得到的信号是地层的周向全方位或单方位的平均信号，采用该平均信号反映地层的性质。
然而，在核磁共振探测装置的实际应用中，测量的井下环境多为复杂的地层环境，例如复杂非均质性地层、部分泥浆侵入地层或者井眼垮塌地层等。在这种情况下，平均信号无法准确地反应地层的性质，导致核磁共振探测装置的探测精度较差。
阵列探测技术，能够对井眼周围的地层进行井周成像，获取更丰富的地层信息。然而，核磁共振探测装置的线圈阵列之间存在电感耦合作用，使得线圈单元无法正常地进行信号的发射与接收。因此，井下核磁共振阵列线圈的电感耦合问题亟需解决。
因此，考虑到上述问题，本实施例提供一种核磁共振线圈阵列及其去耦合方法、核磁共振探测装置，该线圈阵列包括线圈谐振单元和去耦合网络单元；上述线圈谐振单元包括多个线圈谐振电路，上述去耦合网络单元包括多个去耦合电路，其中，一个线圈谐振电路包括一个线圈和一个谐振电容；各个线圈谐振电路中的谐振电容与线圈并联，各个线圈 谐振电路中的线圈在圆周上等间隔分布，相邻线圈的同名端和异名端之间分别设置一个去耦合电路；各个线圈同时与核磁共振探测装置的天线切换电路连接，用于在天线切换电路的控制下依次发射核磁共振信号，各个调谐电容用于调谐相应的核磁共振信号的发射频率，去耦合电路用于消除相邻线圈之间的互感耦合。该线圈阵列结构简单、性能优良，能够有效消除线圈谐振电路之间的耦合作用，进而实现精确定位油气位置，获取高质量的井眼地层数据。
下面以具体地实施例对本申请的技术方案以及本申请的技术方案如何解决上述技术问题进行详细说明。下面这几个具体的实施例可以相互结合，对于相同或相似的概念或过程可能在某些实施例中不再赘述。下面将结合附图，对本申请的实施例进行描述。
图1为本申请实施例提供的核磁共振线圈阵列的结构示意图，图2为本申请实施例提供的核磁共振线圈阵列的立体结构示意图。线圈阵列1的输出端口直接接入到天线切换电路2当中，如图1所示，该线圈阵列1可以包括：包括线圈谐振单元和去耦合网络单元。图1和图2以线圈谐振单元包括四个线圈谐振电路为例进行说明，但本实施例对线圈谐振电路的个数不做特别限定，可以根据具体的应用场景选择线圈谐振电路的个数。
所述线圈谐振单元包括多个线圈谐振电路，所述去耦合网络单元包括多个去耦合电路。
其中，每个线圈谐振电路包括一个线圈和一个谐振电容。
各个线圈谐振电路中的谐振电容与线圈并联。
如图2所示，各个线圈谐振电路中的线圈在圆周上等间隔分布。
各个线圈同时与核磁共振探测装置的天线切换电路2连接，用于在所述天线切换电路2的控制下依次发射核磁共振信号。
示例性的，每个线圈分别对应不同的探测方位，每个线圈可以激励不同方位的感兴趣区域，以图2为例，每个线圈可以激励弧度为90°的薄瓦壳状感兴趣区域，总的感兴趣区域为360°薄壁中空型圆柱。因此，在井下可以对不同方位的地层进行脉冲能量的发射与核磁共振信号的接收，且不同方位地层信号不会发生重叠，因此可以提高对不同方位角度上地 层信息分辨能力。
可选地，各个线圈谐振电路中的线圈的为平面绕制的马鞍形或八字形的双匝线圈；
或者，各个线圈谐振电路中的线圈的为平面绕制的马鞍形或八字形的多匝线圈。
可选地，各个线圈谐振电路中相邻两个线圈的位置正交。
各个调谐电容用于调谐相应的核磁共振信号的发射频率。
可选地，各个线圈谐振电路中的谐振电容分别位于对应的线圈的前端的电容舱室内，且各个谐振电容的结构相同，以方便将各个线圈调至具有相同的发射阻抗、发射频带以及性能的状态。
相邻线圈的同名端和异名端之间分别设置一个去耦合电路，所述去耦合电路用于消除相邻线圈之间的互感耦合。
可选地，各个去耦合电路分别位于对应的谐振电容的前端的舱室内，且各个去耦合电路的结构相同。
可选地，当间隔线圈谐振电路之间的耦合作用较大时，可以在各个线圈谐振电路中间隔线圈的同名端和异名端之间分别设置一个去耦合电路，用于消除间隔线圈之间的互感耦合。
可选地，所述去耦合电路包括电容值可调的去耦合电容。示例性的，通过调节去耦合电容的电容值，使得受电感耦合影响的线圈谐振电路的电性参数达到一致。
可选地，为了更加有效地消除各线圈谐振电路的线圈之间的互感耦合，还可以根据各个线圈谐振电路的线圈之间的互感耦合强度，调节去耦合电容的容值。例如：当线圈之间的互感耦合增强时，增大去耦合电容的容值。
可选地，每个线圈谐振电路还包括一个电阻；
所述电阻与所述线圈串联后，再与所述谐振电容并联，所述电阻和所述谐振电容之间设置一个去耦合电路接头，所述线圈和所述谐振电容之间设置一个去耦合电路接头，所述去耦合电路接头用于与去耦合电路连接。
图3为本申请实施例提供的核磁共振线圈阵列的电路图，图3以线圈 谐振单元包括四个线圈谐振电路，去耦合电路包括去耦合电容为例进行说明，但本实施例对线圈谐振电路的个数和去耦合电路不做特别限定。如图3所示，线圈谐振单元包括：第一线圈谐振电路31、第二线圈谐振电路32、第三线圈谐振电路33和第四线圈谐振电路34。第一线圈谐振电路31包括电阻R1、线圈L1和谐振电容C1。第二线圈谐振电路32包括电阻R2、线圈L2和谐振电容C1。第三线圈谐振电路33包括电阻R3、线圈L3和谐振电容C1。第四线圈谐振电路34包括电阻R4、线圈L4和谐振电容C1。相邻线圈的同名端和异名端之间分别设置一个去耦合电路，即线圈L1和线圈L2的同名端和异名端之间、线圈L2和线圈L3的同名端和异名端之间、线圈L3和线圈L4的同名端和异名端之间，以及线圈L4和线圈L1的同名端和异名端之间，分别设置一个去耦合电容C2。具体的，线圈L1和线圈L2的同名端和异名端分别设置一个去耦合电路接头、线圈L2和线圈L3的同名端和异名端分别设置一个去耦合电路接头、线圈L3和线圈L4的同名端和异名端分别设置一个去耦合电路接头，以及线圈L4和线圈L1的同名端和异名端分别设置一个去耦合电路接头，通过去耦合电路接头与去耦合电容C2相连。
第一线圈谐振电路31中电阻R1和谐振电容C1之间设置一个去耦合电路接头，该接头与一去耦合电容C2连接；第二线圈谐振电路32中电阻R2和谐振电容C1之间设置一个去耦合电路接头，该接头与上述一去耦合电容C2连接。第一线圈谐振电路31中线圈L1和谐振电容C1之间设置一个去耦合电路接头，该接头与另一去耦合电容C2连接；第二线圈谐振电路32中线圈L2和谐振电容C1之间设置一个去耦合电路接头，该接头与上述另一去耦合电容C2连接。第二线圈谐振电路32、第三线圈谐振电路33与第二组去耦合电路的连接关系；第三线圈谐振电路33、第四线圈谐振电路34与第三组去耦合电路的连接关系；第四线圈谐振电路34、第一线圈谐振电路31与第四组去耦合电路的连接关系，均与上述第一线圈谐振电路31、第二线圈谐振电路32与第一组去耦合电路的连接关系基本相同，此处不再赘述。
本实施例提供的核磁共振线圈阵列，包括线圈谐振单元和去耦合网络单元；上述线圈谐振单元包括多个线圈谐振电路，上述去耦合网络单 元包括多个去耦合电路，其中，一个线圈谐振电路包括一个线圈和一个谐振电容；各个线圈谐振电路中的谐振电容与线圈并联，各个线圈谐振电路中的线圈在圆周上等间隔分布，相邻线圈的同名端和异名端之间分别设置一个去耦合电路；各个线圈同时与核磁共振探测装置的天线切换电路连接，用于在天线切换电路的控制下依次发射核磁共振信号，各个调谐电容用于调谐相应的核磁共振信号的发射频率，去耦合电路用于消除相邻线圈之间的互感耦合。该线圈阵列结构简单、性能优良，能够有效消除线圈谐振电路之间的耦合作用，进而实现精确定位油气位置，获取高质量的井眼地层数据。
图4为本申请实施例提供的核磁共振线圈阵列的去耦合方法的流程示意图。如图4所示，本实施例是基于如上述实施例的核磁共振线圈阵列的去耦合方法，包括：
S401：在所述核磁共振线圈阵列的各个单元处于断路状态时，分别调谐各个谐振电容的电性参数到相同的状态。
示例性的，在其他的单元为断路状态时，依次将各个线圈谐振单元的线圈谐振电容分别调谐到相同阻抗、相同频率及相同Q值等电性参数的状态，使各线圈谐振电路的线圈在发射时具有相同的发射阻抗，发射频带以及性能。
S402：将各个电性参数相同的谐振电容同时接入相应的线圈谐振电路，在各个线圈谐振电路中相邻线圈的同名端和异名端之间分别接入一个去耦合电路。
示例性的，将所有电性参数相同的谐振电容同时接入相应的线圈谐振电路，在各个线圈谐振电路中相邻的线圈单元的同名端和异名端之间分别接入一个去耦合电路，分别检查并记录各个线圈谐振电路之间的阻抗，频率以及Q值等典型参数。
S403：调整各个去耦合电路的去耦合电容值，以消除相邻线圈之间的互感耦合。
示例性的，调整去耦合电路的去耦合电容值，直到各个线圈谐振电路的线圈之间的频率及Q值相同且阻抗达到最大值，耦合的频谱完全消除。
本实施例提供的核磁共振线圈阵列的去耦合方法，通过在核磁共振线圈阵列的各个单元处于断路状态时，分别调谐各个谐振电容的电性参数到相同的状态，然后将各个电性参数相同的谐振电容同时接入相应的线圈谐振电路，在各个线圈谐振电路中相邻线圈的同名端和异名端之间分别接入一个去耦合电路，再调整各个去耦合电路的去耦合电容值，以消除相邻线圈之间的互感耦合，上述去耦合方法能够有效消除线圈谐振电路之间的耦合作用，提升线圈阵列的性能，进而实现精确定位油气位置，获取高质量的井眼地层数据。
图5为本申请实施例提供的核磁共振探测装置的结构示意图，如图5所示，该装置包括：上述实施例中的核磁共振线圈阵列1。
所述核磁共振线圈阵列1用于接收切换指令，根据所述切换指令切换线圈谐振电路。
可选地，该装置还包括：天线切换电路2、地面系统3、发射器模块4、双工器5、接收器6。
上述天线切换电路2，用于向所述核磁共振线圈阵列1发送切换指令。
上述地面系统3，用于发送检测指令和处理数据。
上述发射器模块4，用于发射大功率的信号。
上述双工器5，用于隔离在脉冲信号发射时与微弱信号接收时的噪声。
上述接收器6，用于接收微弱的信号。
本实施例提供的核磁共振探测装置，能够实现精确定位油气位置，获取高质量的井眼地层数据。
最后应说明的是：以上各实施例仅用以说明本申请的技术方案，而非对其限制；尽管参照前述各实施例对本申请进行了详细的说明，本领域的普通技术人员应当理解：其依然可以对前述各实施例所记载的技术方案进行修改，或者对其中部分或者全部技术特征进行等同替换；而这些修改或者替换，并不使相应技术方案的本质脱离本申请各实施例技术方案的范围。

Claims (10)

  1. 一种核磁共振线圈阵列，其特征在于，包括线圈谐振单元和去耦合网络单元；
    所述线圈谐振单元包括多个线圈谐振电路，所述去耦合网络单元包括多个去耦合电路，其中，每个线圈谐振电路包括一个线圈和一个谐振电容；
    各个线圈谐振电路中的谐振电容与线圈并联，各个线圈谐振电路中的线圈在圆周上等间隔分布，相邻线圈的同名端和异名端之间分别设置一个去耦合电路；
    各个线圈同时与核磁共振探测装置的天线切换电路连接，用于在所述天线切换电路的控制下依次发射核磁共振信号，各个调谐电容用于调谐相应的核磁共振信号的发射频率，所述去耦合电路用于消除相邻线圈之间的互感耦合。
  2. 根据权利要求1所述的线圈阵列，其特征在于，每个线圈谐振电路还包括一个电阻；
    所述电阻与所述线圈串联后，再与所述谐振电容并联，所述电阻和所述谐振电容之间设置一个去耦合电路接头，所述线圈和所述谐振电容之间设置一个去耦合电路接头，所述去耦合电路接头用于与去耦合电路连接。
  3. 根据权利要求1所述的线圈阵列，其特征在于，各个线圈谐振电路中间隔线圈的同名端和异名端之间分别设置一个去耦合电路，用于消除间隔线圈之间的互感耦合。
  4. 根据权利要求1所述的线圈阵列，其特征在于，各个线圈谐振电路中的线圈为平面绕制的马鞍形或八字形的双匝线圈；
    或者，各个线圈谐振电路中的线圈为平面绕制的马鞍形或八字形的多匝线圈。
  5. 根据权利要求1所述的线圈阵列，其特征在于，各个线圈谐振电路中相邻两个线圈的位置正交。
  6. 根据权利要求1所述的线圈阵列，其特征在于，各个线圈谐振电路中的谐振电容分别位于对应的线圈的前端的电容舱室内，且各个谐振 电容的结构相同。
  7. 根据权利要求1所述的线圈阵列，其特征在于，各个去耦合电路分别位于对应的谐振电容的前端的舱室内，且各个去耦合电路的结构相同。
  8. 根据权利要求1所述的线圈阵列，其特征在于，所述去耦合电路包括电容值可调的去耦合电容。
  9. 一种基于如权利要求1-8任一项所述的核磁共振线圈阵列的去耦合方法，其特征在于，包括：
    在所述核磁共振线圈阵列的各个单元处于断路状态时，分别调谐各个谐振电容的电性参数到相同的状态；
    将各个电性参数相同的谐振电容同时接入相应的线圈谐振电路，在各个线圈谐振电路中相邻线圈的同名端和异名端之间分别接入一个去耦合电路；
    调整各个去耦合电路的去耦合电容值，以消除相邻线圈之间的互感耦合。
  10. 一种核磁共振探测装置，其特征在于，包括：如权利要求1-8任一项所述的核磁共振线圈阵列。
PCT/CN2019/110305 2019-08-30 2019-10-10 核磁共振线圈阵列及其去耦合方法、核磁共振探测装置 WO2021035881A1 (zh)

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