WO2020078003A1 - Time-domain transient electromagnetic wave well logging far-boundary detection method - Google Patents

Time-domain transient electromagnetic wave well logging far-boundary detection method Download PDF

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Publication number
WO2020078003A1
WO2020078003A1 PCT/CN2019/088711 CN2019088711W WO2020078003A1 WO 2020078003 A1 WO2020078003 A1 WO 2020078003A1 CN 2019088711 W CN2019088711 W CN 2019088711W WO 2020078003 A1 WO2020078003 A1 WO 2020078003A1
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boundary
time
electromagnetic wave
formation
domain
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PCT/CN2019/088711
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French (fr)
Chinese (zh)
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袁习勇
邓少贵
张盼
刘天淋
李海涛
蔡联云
姜春阳
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中国石油大学(华东)
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Publication of WO2020078003A1 publication Critical patent/WO2020078003A1/en

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    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B47/00—Survey of boreholes or wells
    • E21B47/12—Means for transmitting measuring-signals or control signals from the well to the surface, or from the surface to the well, e.g. for logging while drilling
    • E21B47/13—Means for transmitting measuring-signals or control signals from the well to the surface, or from the surface to the well, e.g. for logging while drilling by electromagnetic energy, e.g. radio frequency
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B49/00—Testing the nature of borehole walls; Formation testing; Methods or apparatus for obtaining samples of soil or well fluids, specially adapted to earth drilling or wells

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  • the invention relates to the field of petroleum exploration and development, and belongs to the category of electric logging methods, in particular to a time domain transient electromagnetic wave logging boundary remote detection method.
  • Electromagnetic wave logging tools have become one of the key technologies for geosteering and reservoir evaluation because of their advantages such as greater detection depth and stronger azimuth detection capabilities.
  • the widely used electromagnetic logging tools at home and abroad generally use specific frequency time-harmonic excitation and measurement modes: the traditional electromagnetic wave logging transmitter and receiver antennas are coaxially arranged, the detection range is about 2m, and there is no azimuth detection capability; Electromagnetic wave logging adopts coaxial / tilt / orthogonal measurement mode, while adding low-frequency mode, the detection depth can reach 5m, and can simultaneously obtain the azimuth information of the interface; in recent years, the ultra-deep exploration while drilling reservoir imaging survey launched by Schlumberger Geosphere, through the combination of multi-component signals, has achieved geological steering at the reservoir scale.
  • the detection range can reach tens of meters, but there are problems such as long source distance and difficulty in signal synchronization.
  • the detection depth of the electromagnetic wave logging excited by the time harmonic source is limited to the geometric relationship between the transmitting and receiving coils, that is, in order to increase the detection depth, the frequency must be reduced and the source distance must be increased, which requires high construction technology and field application.
  • Transient electromagnetic waves contain rich information in the wide frequency domain and the time domain.
  • an induced electromotive force is generated in the formation, which in turn generates an induced eddy current.
  • the diffusion of the eddy current generates a secondary field.
  • the scattered field will cause the difference of the measurement signal of the receiving antenna in the time domain, so it has the ability to detect the boundary far. Combined with the multi-component transmitting and receiving antenna coupling arrangement measurement method, it is helpful to improve the azimuth sensitivity of transient electromagnetic logging to the boundary.
  • transient electromagnetic wave downhole pulse excitation signals the combined arrangement relationship of transmitting and receiving antennas, the acquisition of time-domain logging signals, the way of signal definition and the response characteristics of transient electromagnetic waves to geological structures, the use of transient electromagnetic waves
  • the remote detection of the time domain logging boundary is of great significance.
  • the present invention proposes a time-domain transient electromagnetic wave logging boundary remote detection method, which has a reasonable design, overcomes the deficiencies of the prior art, and has a good effect.
  • a time-domain transient electromagnetic wave logging remote boundary detection method including the following steps:
  • Step 1 Establish a stratum model and design a combined transmit and receive antenna mode
  • Step 2 Select the transient electromagnetic wave pulse source excitation mode to emit current into the formation; after excitation, turn off the current source and measure the pure secondary field in the formation after shutdown;
  • Step 3 Obtain the time-domain induced electromotive force
  • Step 4 Build a transient electromagnetic wave logging boundary detection signal definition method to extract formation conductivity and formation boundary position information
  • Step 5 Transient electromagnetic wave logging is used to detect the boundary under the conditions of different distance, dip angle and formation resistivity.
  • a single-transmitting and dual-receiving transmitting and receiving mode is adopted.
  • the antenna is composed of a group of transmitting coils and two groups of receiving coils.
  • the transmitting coils are arranged coaxially.
  • the distances between the two receiving coils and the transmitting coil are the same.
  • the zz and zx components of the layered medium can be measured simultaneously in one shot.
  • step 3 the following steps are specifically included:
  • Step 3.1 Use the vector bit function method to obtain the frequency-domain induced electromotive force V ( ⁇ ) of the magnetic dipole source in any direction of the layered medium;
  • Step 3.2 Perform time-frequency information processing, select a time-frequency conversion algorithm, convert the frequency domain logging response V ( ⁇ ) to the time domain, and obtain the time domain induced electromotive force V (t).
  • step 4 the following steps are specifically included:
  • Step 4.1 Under uniform formation conditions, the expression of induced electromotive force V zz is shown in formula (2):
  • ⁇ is the magnetic permeability
  • ⁇ is the electrical conductivity
  • r is the distance between the measurement point and the source point
  • e x , e y , and e z are the unit vectors in the x, y, and z directions, respectively;
  • the measurement signal is linearly related to the formation conductivity, and V zz is used to extract formation conductivity; under layered formation conditions, V zz is used to extract formation conductivity;
  • Step 4.2 Based on the principle of electromagnetic wave scattering, define the induced electromotive force difference ⁇ V zz between the total field of the zz component of the layered medium and the background field of the zz component of the current layer where the antenna is located, as shown in formula (3):
  • V zz V zz total field- V zz background field (3);
  • ⁇ V zz reflects the contribution of the interface to the logging response
  • V Geosignal V zx (4)
  • azimuth detection is performed on the boundary.
  • step 5 under different formation dip angles, for look ahead geological model appearing in geosteering while drilling, that is, the transmitting and receiving antenna is located in front of the interface, the interface is detected by ⁇ V zz ; for look around appearing in geosteering while drilling
  • the geological model that is, under the conditions of wells with high inclination / horizontal wells, adopts ⁇ V zz or V Geosignal detection interface to guide the geological steering.
  • the invention can realize the long-distance detection of the formation interface under the condition that the instrument is short, and solves the problem that the current logging tool is too long and applied in the deep logging detection Inconvenience and other problems; the transient electromagnetic wave measurement process is not disturbed by the primary field, including rich information in the wide frequency domain and the time domain. When the electromagnetic wave encounters an interface during the propagation process, the scattered field will cause the difference of the receiving antenna measurement signal in the time domain.
  • the advantage of extracting target information in the time domain; the multi-component coil arrangement method can determine the formation conductivity and interface position at the same time, and has the ability to detect azimuth.
  • the time-domain transient electromagnetic wave logging boundary detection method provided by the invention has a long detection distance and can be applied to geosteering while drilling, which can adjust the trajectory of the borehole in time, realize the accurate landing of horizontal wells in highly deviated wells, and improve the exploration and development of oil and gas resources. s efficiency.
  • FIG. 1 is a schematic diagram of the structure of a single-transmission dual-reception coaxial / orthogonal antenna used in the present invention
  • FIG. 2 is a schematic diagram of a stratum model according to a specific embodiment of the present invention, the coil system is located above the interface;
  • FIG. 3 is a schematic diagram of a stratum model according to a specific embodiment of the present invention, and the coil system is located below the interface;
  • FIG. 4 is a schematic diagram of a pulse excitation source used in the present invention.
  • FIG. 5 is a schematic diagram of the zz component logging response at different distances on the interface when the coil system is perpendicular to the formation in a specific embodiment of the present invention
  • FIG. 6 is a schematic diagram of zz component logging response at different distances on the interface when the angle between the coil system and the formation is 60 °;
  • FIG. 7 is a schematic diagram of the zx component logging response at different distances on the interface when the angle between the coil system and the formation is 60 ° according to a specific embodiment of the present invention
  • FIG. 8 is a schematic diagram of the zx component logging response when the angle between the coil system and the formation of the present invention is 0 °, and they are respectively below and above the interface;
  • FIG. 9 is a schematic diagram of the zz component logging response at different angles between the coil system and the interface of the present invention.
  • FIG. 10 is a schematic diagram of the zz component logging response of different resistivities of a uniform formation in the present invention.
  • FIG. 11 is a schematic diagram of the zz component logging response of different resistivity of the layered formation of the present invention.
  • the object of the present invention is to provide a time domain transient electromagnetic wave logging boundary detection method, using a short source distance to achieve the far detection of the formation boundary.
  • the invention adopts a single-transmitting and double-receiving coil arrangement mode, the transmitting coil is coaxially arranged, and the two receiving coils are coaxially and orthogonally arranged and have the same source distance; the pulse source is used as the excitation signal source to measure the current in the formation after the current is turned off Pure secondary field; construct a transient electromagnetic wave logging signal definition method to extract formation conductivity, interface position and other information.
  • the transient electromagnetic wave logging source distance is small, the detection is deep, and it is sensitive to the interface orientation, which shows its great potential for application in geosteering while drilling.
  • Step 1 Establish a stratum model and design a combined transmit and receive antenna mode.
  • FIG. 1 is a schematic diagram of an antenna structure for time-domain transient electromagnetic logging provided by the present invention for remote boundary detection.
  • a single-transmission and dual-receive antenna structure is adopted, and the source distance from the transmitting antenna (coil) T to the receiving antennas (coil) R1 and R2 is shown in FIG.
  • the transmitting coil T is coaxially arranged
  • the receiving coil R1 is coaxially arranged
  • the receiving coil R2 is orthogonally arranged.
  • the source distance is the same, 40in, so the zz and zx components can be measured simultaneously in one transmission.
  • the formation model includes medium I and medium II, medium I has a resistivity of 10 ⁇ ⁇ m, and medium II has a resistivity of 1 ⁇ ⁇ m, the coil system is located in the medium I, respectively above and below the interface.
  • Step 2 Select the transient electromagnetic wave pulse source excitation mode to emit current into the formation; after excitation, turn off the current source and measure the pure secondary field in the formation after shutdown;
  • the pulse source as the excitation source as shown in Figure 4, which are the next step current source, Gaussian pulse, and sawtooth wave, which emits current into the formation, and the excitation is long enough to eliminate the transient effect caused by the current turn-on After the current is turned off, the pure secondary field in the formation, the rest of the calculation content of the present invention is the following step current source as an example.
  • Step 3 Perform time-frequency information processing, select an appropriate time-frequency conversion algorithm, convert the frequency domain logging response of different frequencies ⁇ to the time domain, and obtain the time-domain induced electromotive force.
  • Step 3.1 Use the vector bit function method to obtain the frequency-domain induced electromotive force V ( ⁇ ) of the magnetic dipole source in any direction of the layered medium;
  • Step 3.2 Perform time-frequency information processing, select a time-frequency conversion algorithm, convert the frequency domain logging response V ( ⁇ ) to the time domain, and obtain the time domain induced electromotive force V (t).
  • V (t) Taking the Gaver-Stehfest inverse Laplace transform method as an example, after obtaining V ( ⁇ ), let V (t) can be expressed as:
  • J is the filter coefficient
  • m is The integer part of.
  • Step 4 Build a transient electromagnetic wave logging boundary detection signal definition method to extract formation conductivity and formation interface position information.
  • Step 4.1 Under uniform formation conditions, the expression of induced electromotive force V zz is:
  • ⁇ is the magnetic permeability
  • ⁇ is the electrical conductivity
  • r is the distance between the measurement point and the source point
  • e x , e y , and e z are the unit vectors in the x, y, and z directions, respectively;
  • V zz is used to extract the formation conductivity; under layered formation conditions, V zz is used to extract the formation apparent conductivity.
  • Step 4.2 Based on the principle of electromagnetic wave scattering, define the induced electromotive force difference ⁇ V zz of the zz component total field of the layered medium and the zz component background field of the current layer where the coil system is located: ie ( ⁇ zz total field- ⁇ zz background field ) reflects the adjacent layer pair logging The contribution of the response; the presence of the boundary leads to the cross component zx not being 0, and the induced electromotive force V zx of the zx component is defined as the azimuth geological signal V Geosignal , reflecting the position of the formation boundary. According to the coil system being above or below the interface, the time domain induced electromotive force The negative changes are different, and azimuth detection is performed on the stratum boundary.
  • Step 5 Transient electromagnetic logging at different distances, dips, and formation resistivities to detect the boundary
  • the transmitting and receiving antenna is located in front of the interface and the angle between the antenna and the interface is large, at this time, the total field of the zz component of the layered medium and the current layer of the antenna
  • the induced electromotive force difference ⁇ V zz of the zz component background field is detected on the interface.
  • the angle between the antenna and the formation interface is 90 °.
  • the intersection of the curve and the x axis in the time domain reflects the boundary distance DTB. The closer the interface distance, The earlier the measurement signal ⁇ V zz appears;
  • the interface can be probed with ⁇ V zz , as shown in Figure 6, the angle between the antenna and the formation interface is 30 °; or The zx component azimuth geological signal V Geosignal is used to detect the interface. As shown in Figure 7, the angle between the antenna structure and the formation interface is 30 °. The intersection of ⁇ V zz and V Geosignal with the x axis is basically the same. The detection effect on the interface distance the same;
  • V Geosignal contains azimuth detection characteristics.
  • the antenna is located in the medium I, at a distance of 10m from the boundary and parallel to the interface, respectively below and above the interface .
  • the induced electromotive force value in the time domain is the same, but when the antenna is above the interface, the induced electromotive force is positive (solid line) in the early stage and negative (dashed line) in the late stage; when the antenna is below the interface, the extreme value
  • the positive and negative changes of the induced electromotive force on both sides of the point are just the opposite.
  • the relative position of the antenna and the interface is judged according to this changing characteristic of V zx .
  • the distance between the electrode system and the boundary is 10m
  • the angle between the electrode system and the formation interface is 90 °, 60 °, 45 °, 30 °, 15 °, 5 °, 0 °, respectively.
  • the detection of the boundary under the condition of inclination is shown in Figure 9.
  • the greater the formation dip angle the greater the absolute value of ⁇ V zz ; meanwhile, as the apparent thickness of the formation increases, the boundary distance increases, and the extreme point of the curve shifts to the left.
  • the resistivities are 1, 5, 10, and 20 ⁇ ⁇ m, as shown in Figure 10; when the ground interface exists, the angle between the electrode system and the formation interface is 90 °, The distance between the formation boundaries is 5m and 10m respectively, and the resistivity contrast on both sides of the interface is: 10: 1, 10: 5.
  • the boundary detection is performed under different resistivity contrast conditions. When the formation resistivity is the same, the measurement is performed under different boundary distances. Late curves coincide.
  • the logging response of the zz component of different resistivity of the layered formation of the present invention is shown in FIG. 11.

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Abstract

Disclosed is a time-domain transient electromagnetic wave well logging far-boundary detection method, related to the field of oil exploration, comprising the following steps: step 1: establishing a stratum model, designing a transmitting/receiving antenna combination mode; step 2: selecting a transient electromagnetic wave well logging pulse source excitation mode, transmitting a current into a stratum, performing excitation then cutting off a current source, measuring a pure secondary field in the stratum after the cutoff; step 3: acquiring a time-domain induced electromotive force; step 4: constructing a transient electromagnetic signal defining scheme, extracting information such as electric conductivity of the stratum and the boundary of the stratum; and step 5: performing boundary detections of transient electromagnetic wave well logging under different distances, inclination angles, and stratum resistivity conditions. Compared with a prior time-harmonic source electromagnetic wave well logging method, the method is free from interferences of a primary field while measuring, a pulse source comprises rich information of a wide frequency domain, the advantage of time-domain extraction of stratum information is provided, and a shorter source distance can be used to implement a remote detection of the boundary of the stratum for geosteering with well drilling and logging.

Description

一种时间域瞬变电磁波测井边界远探测方法Method for detecting far boundary of transient electromagnetic wave logging in time domain 技术领域Technical field
本发明涉及石油勘探开发领域，属于电测井方法范畴，具体地说是涉及一种时间域瞬变电磁波测井边界远探测方法。The invention relates to the field of petroleum exploration and development, and belongs to the category of electric logging methods, in particular to a time domain transient electromagnetic wave logging boundary remote detection method.
背景技术Background technique
随钻地质导向的关键在于实现地层边界的方位探测，随着复杂油气勘探及高效开发技术的发展，对随钻地质导向提出了更高要求，需要对井周数米到数十米范围内的边界(地层边界、断层)进行探测。电磁波类测井仪器因其具有较大的探测深度、较强的方位探边能力等优势，成为地质导向与储层评价的关键技术之一。The key to geo-drilling while drilling is to realize the azimuth detection of the formation boundary. With the development of complex oil and gas exploration and efficient development technology, higher requirements are placed on geo-drilling while drilling. Detection of boundaries (stratigraphic boundaries, faults). Electromagnetic wave logging tools have become one of the key technologies for geosteering and reservoir evaluation because of their advantages such as greater detection depth and stronger azimuth detection capabilities.
目前国内外广泛使用的随钻电磁波类测井仪器通常采用特定频率时谐激励及测量模式：传统电磁波测井发射接收天线同轴布置，探测范围2m左右，不具备方位探边能力；随钻方位电磁波测井，采用同轴/倾斜/正交的测量模式，同时增加了低频模式，探测深度可达5m，可同时获取界面的方位信息；近年来Schlumberger推出的超深探测随钻储层成像测井仪Geosphere，通过多分量信号的组合实现了油藏尺度的地质导向，探测范围可达数十米，但存在源距过长及信号同步困难等问题。时谐源激励的电磁波测井的探测深度局限于发射和接收线圈的几何关系，即为了增加探测深度，必须降低频率，增大源距，对施工工艺和现场应用要求很高。At present, the widely used electromagnetic logging tools at home and abroad generally use specific frequency time-harmonic excitation and measurement modes: the traditional electromagnetic wave logging transmitter and receiver antennas are coaxially arranged, the detection range is about 2m, and there is no azimuth detection capability; Electromagnetic wave logging adopts coaxial / tilt / orthogonal measurement mode, while adding low-frequency mode, the detection depth can reach 5m, and can simultaneously obtain the azimuth information of the interface; in recent years, the ultra-deep exploration while drilling reservoir imaging survey launched by Schlumberger Geosphere, through the combination of multi-component signals, has achieved geological steering at the reservoir scale. The detection range can reach tens of meters, but there are problems such as long source distance and difficulty in signal synchronization. The detection depth of the electromagnetic wave logging excited by the time harmonic source is limited to the geometric relationship between the transmitting and receiving coils, that is, in order to increase the detection depth, the frequency must be reduced and the source distance must be increased, which requires high construction technology and field application.
瞬变电磁波包含了宽频域和时间域的丰富信息，当脉冲源关断时，在地层中产生感应电动势，进而产生感应涡流，涡流的扩散产生二次场，当井周存在地质构造时，其散射场会造成接收天线测量信号在时域中的差异，因而具有边界远探测能力。结合多分量的发射与接收天线耦合布置测量手段，有利于提高瞬变电磁波测井对边界的方位敏感性。Transient electromagnetic waves contain rich information in the wide frequency domain and the time domain. When the pulse source is turned off, an induced electromotive force is generated in the formation, which in turn generates an induced eddy current. The diffusion of the eddy current generates a secondary field. When there are geological structures around the well, The scattered field will cause the difference of the measurement signal of the receiving antenna in the time domain, so it has the ability to detect the boundary far. Combined with the multi-component transmitting and receiving antenna coupling arrangement measurement method, it is helpful to improve the azimuth sensitivity of transient electromagnetic logging to the boundary.
因此，研究瞬变电磁波井下脉冲激励信号的选取，发射及接收天线的组合布置关系、时间域测井信号的获取、信号定义方式以及瞬变电磁波对地质构造的响应特性，对利用瞬变电磁波进行时间域测井边界的远探测有重要意义。Therefore, to study the selection of transient electromagnetic wave downhole pulse excitation signals, the combined arrangement relationship of transmitting and receiving antennas, the acquisition of time-domain logging signals, the way of signal definition and the response characteristics of transient electromagnetic waves to geological structures, the use of transient electromagnetic waves The remote detection of the time domain logging boundary is of great significance.
发明内容Summary of the invention
针对现有技术中存在的上述技术问题，本发明提出了一种时间域瞬变电磁波测井边界远探测方法，设计合理，克服了现有技术的不足，具有良好的效果。In view of the above technical problems existing in the prior art, the present invention proposes a time-domain transient electromagnetic wave logging boundary remote detection method, which has a reasonable design, overcomes the deficiencies of the prior art, and has a good effect.
为了实现上述目的，本发明采用如下技术方案：In order to achieve the above objectives, the present invention adopts the following technical solutions:
一种时间域瞬变电磁波测井边界远探测方法，包括以下步骤：A time-domain transient electromagnetic wave logging remote boundary detection method, including the following steps:
步骤1：建立地层模型，设计发射接收天线组合模式；Step 1: Establish a stratum model and design a combined transmit and receive antenna mode;
步骤2：选择瞬变电磁波测井脉冲源激励模式，向地层中发射电流；进行激励后关断电 流源，测量关断后地层中的纯二次场；Step 2: Select the transient electromagnetic wave pulse source excitation mode to emit current into the formation; after excitation, turn off the current source and measure the pure secondary field in the formation after shutdown;
步骤3：获取时间域感应电动势；Step 3: Obtain the time-domain induced electromotive force;
步骤4：构建瞬变电磁波测井边界探测信号定义方式，提取地层电导率和地层边界位置信息；Step 4: Build a transient electromagnetic wave logging boundary detection signal definition method to extract formation conductivity and formation boundary position information;
步骤5：进行不同距离、倾角、地层电阻率条件下瞬变电磁波测井对边界的探测。Step 5: Transient electromagnetic wave logging is used to detect the boundary under the conditions of different distance, dip angle and formation resistivity.
优选地，步骤1中，采用单发双收的发射接收模式，该天线由一组发射线圈和两组接收线圈组成，发射线圈同轴布置，两个接收线圈距离发射线圈距离相同，分别采用同轴和正交的布置方式，一次发射能够同时测得层状介质zz和zx分量。Preferably, in step 1, a single-transmitting and dual-receiving transmitting and receiving mode is adopted. The antenna is composed of a group of transmitting coils and two groups of receiving coils. The transmitting coils are arranged coaxially. The distances between the two receiving coils and the transmitting coil are the same. With the axis and orthogonal arrangement, the zz and zx components of the layered medium can be measured simultaneously in one shot.
优选地，在步骤3中，具体包括如下步骤：Preferably, in step 3, the following steps are specifically included:
步骤3.1：利用矢量位函数法获取层状介质任意方向磁偶极子源的频率域感应电动势V(ω)；Step 3.1: Use the vector bit function method to obtain the frequency-domain induced electromotive force V (ω) of the magnetic dipole source in any direction of the layered medium;
步骤3.2：进行时频信息处理，选择时频转换算法，将频率域测井响应V(ω)转换到时间域，获取时间域感应电动势V(t)。Step 3.2: Perform time-frequency information processing, select a time-frequency conversion algorithm, convert the frequency domain logging response V (ω) to the time domain, and obtain the time domain induced electromotive force V (t).
优选地，在步骤4中，具体包括如下步骤：Preferably, in step 4, the following steps are specifically included:
步骤4.1：均匀地层条件下，感应电动势V zz的表达式如公式(2)所示： Step 4.1: Under uniform formation conditions, the expression of induced electromotive force V zz is shown in formula (2):
Figure PCTCN2019088711-appb-000001
Figure PCTCN2019088711-appb-000001
其中，m为磁偶极矩，μ为磁导率，σ为电导率，r为测量点距源点的距离，e x、e y、e z分别为x、y、z方向的单位向量； Where m is the magnetic dipole moment, μ is the magnetic permeability, σ is the electrical conductivity, r is the distance between the measurement point and the source point, and e x , e y , and e z are the unit vectors in the x, y, and z directions, respectively;
均匀地层测量后期满足感应电动势
Figure PCTCN2019088711-appb-000002
测量信号与地层电导率线性相关，利用V zz提取地层电导率；层状地层条件下，利用V zz提取地层视电导率； Meet the induced electromotive force in the later stage of uniform formation measurement
Figure PCTCN2019088711-appb-000002
The measurement signal is linearly related to the formation conductivity, and V zz is used to extract formation conductivity; under layered formation conditions, V zz is used to extract formation conductivity;
步骤4.2：基于电磁波散射原理，定义层状介质的zz分量总场与天线所在当前层zz分量背景场的感应电动势差值ΔV zz，如公式(3)所示： Step 4.2: Based on the principle of electromagnetic wave scattering, define the induced electromotive force difference ΔV zz between the total field of the zz component of the layered medium and the background field of the zz component of the current layer where the antenna is located, as shown in formula (3):
ΔV zz＝V zz总场-V zz背景场   (3)； ΔV zz = V zz total field- V zz background field (3);
ΔV zz反映界面对测井响应的贡献； ΔV zz reflects the contribution of the interface to the logging response;
边界的存在导致交叉分量zx不为0，定义zx分量的感应电动势V zx为方位地质信号V Geosignal，如公式(4)所示： The existence of the boundary results in the cross component zx not being 0, and the induced electromotive force V zx of the zx component is defined as the azimuth geological signal V Geosignal as shown in formula (4):
V Geosignal＝V zx   (4)； V Geosignal = V zx (4);
根据线圈系位于界面上方或者下方时，时间域感应电动势正负变化情况不同，对边界进行方位探测。According to the difference between the positive and negative changes of the induced electromotive force in the time domain when the coil system is located above or below the interface, azimuth detection is performed on the boundary.
优选地，步骤5中：不同地层倾角情况下，针对随钻地质导向中出现的look ahead地质模型，即发射接收天线位于界面前方，采用ΔV zz探测界面；针对随钻地质导向中出现的look around地质模型，即大斜度井/水平井条件下，采用ΔV zz或者V Geosignal探测界面，指导地质导向。 Preferably, in step 5: under different formation dip angles, for look ahead geological model appearing in geosteering while drilling, that is, the transmitting and receiving antenna is located in front of the interface, the interface is detected by ΔV zz ; for look around appearing in geosteering while drilling The geological model, that is, under the conditions of wells with high inclination / horizontal wells, adopts ΔV zz or V Geosignal detection interface to guide the geological steering.
本发明所带来的有益技术效果：The beneficial technical effects brought by the present invention:
本发明与现有的时谐源随钻电磁波测井方法相比，在仪器较短的情况下，可以实现地层界面的远距离探测，解决了目前测井深探测中测井仪器过长、应用不便等问题；瞬变电磁波测量过程不受一次场的干扰，包含宽频域和时间域的丰富信息，电磁波传播过程中遇到界面，散射场会造成接收天线测量信号在时域中的差异，具有时域提取目标信息的优点；采用多分量的线圈布置方式，可同时确定地层电导率、界面位置，具备方位探测能力。本发明提出的时间域瞬变电磁波测井边界远探测方法，探测距离远，可应用于随钻地质导向，及时调整井眼轨迹，实现大斜度井水平井的准确着陆，提高油气资源勘探开发的效率。Compared with the existing time-harmonic source LWD electromagnetic logging method, the invention can realize the long-distance detection of the formation interface under the condition that the instrument is short, and solves the problem that the current logging tool is too long and applied in the deep logging detection Inconvenience and other problems; the transient electromagnetic wave measurement process is not disturbed by the primary field, including rich information in the wide frequency domain and the time domain. When the electromagnetic wave encounters an interface during the propagation process, the scattered field will cause the difference of the receiving antenna measurement signal in the time domain. The advantage of extracting target information in the time domain; the multi-component coil arrangement method can determine the formation conductivity and interface position at the same time, and has the ability to detect azimuth. The time-domain transient electromagnetic wave logging boundary detection method provided by the invention has a long detection distance and can be applied to geosteering while drilling, which can adjust the trajectory of the borehole in time, realize the accurate landing of horizontal wells in highly deviated wells, and improve the exploration and development of oil and gas resources. s efficiency.
附图说明BRIEF DESCRIPTION
图1为本发明采用的单发双收同轴/正交天线结构示意图；1 is a schematic diagram of the structure of a single-transmission dual-reception coaxial / orthogonal antenna used in the present invention;
图2为本发明具体实施例的地层模型示意图，线圈系位于界面以上；2 is a schematic diagram of a stratum model according to a specific embodiment of the present invention, the coil system is located above the interface;
图3为本发明具体实施例的地层模型示意图，线圈系位于界面以下；3 is a schematic diagram of a stratum model according to a specific embodiment of the present invention, and the coil system is located below the interface;
图4为本发明采用的脉冲激励源示意图；4 is a schematic diagram of a pulse excitation source used in the present invention;
图5为本发明具体实施特例的线圈系与地层垂直时界面不同距离的zz分量测井响应示意图；5 is a schematic diagram of the zz component logging response at different distances on the interface when the coil system is perpendicular to the formation in a specific embodiment of the present invention;
图6为本发明具体实施特例的线圈系与地层夹角60°时界面不同距离的zz分量测井响应示意图；FIG. 6 is a schematic diagram of zz component logging response at different distances on the interface when the angle between the coil system and the formation is 60 °;
图7为本发明具体实施特例的线圈系与地层夹角60°时界面不同距离的zx分量测井响应示意图；7 is a schematic diagram of the zx component logging response at different distances on the interface when the angle between the coil system and the formation is 60 ° according to a specific embodiment of the present invention;
图8为本发明线圈系与地层夹角0°，分别位于界面下方和上方时zx分量测井响应示意图；8 is a schematic diagram of the zx component logging response when the angle between the coil system and the formation of the present invention is 0 °, and they are respectively below and above the interface;
图9为本发明线圈系与界面不同夹角的zz分量测井响应示意图；9 is a schematic diagram of the zz component logging response at different angles between the coil system and the interface of the present invention;
图10为本发明均匀地层不同电阻率的zz分量测井响应示意图；10 is a schematic diagram of the zz component logging response of different resistivities of a uniform formation in the present invention;
图11为本发明层状地层不同电阻率的zz分量测井响应示意图。FIG. 11 is a schematic diagram of the zz component logging response of different resistivity of the layered formation of the present invention.
具体实施方式detailed description
本发明的目的提供一种时间域瞬变电磁波测井边界探测方法，用短源距实现地层边界的远探测。本发明采用单发双收的线圈布置方式，发射线圈同轴布置，两个接收线圈分别同轴、正交布置且源距相同；采用脉冲源作为激励信号源，测量电流关断后地层中的纯二次场；构 建瞬变电磁波测井信号定义方式，提取地层电导率，界面位置等信息。与现有的时谐激励源电磁波测井方法相比，瞬变电磁波测井源距小，探测深，对界面方位敏感，显示其应用于随钻地质导向的巨大潜力。The object of the present invention is to provide a time domain transient electromagnetic wave logging boundary detection method, using a short source distance to achieve the far detection of the formation boundary. The invention adopts a single-transmitting and double-receiving coil arrangement mode, the transmitting coil is coaxially arranged, and the two receiving coils are coaxially and orthogonally arranged and have the same source distance; the pulse source is used as the excitation signal source to measure the current in the formation after the current is turned off Pure secondary field; construct a transient electromagnetic wave logging signal definition method to extract formation conductivity, interface position and other information. Compared with the existing time-harmonic excitation source electromagnetic wave logging method, the transient electromagnetic wave logging source distance is small, the detection is deep, and it is sensitive to the interface orientation, which shows its great potential for application in geosteering while drilling.
下面结合附图以及具体实施方式对本发明作进一步详细说明：The present invention will be further described in detail below with reference to the drawings and specific embodiments:
步骤1：建立地层模型，设计发射接收天线组合模式。Step 1: Establish a stratum model and design a combined transmit and receive antenna mode.
图1为本发明提供的时间域瞬变电磁波测井进行边界远探测的天线结构示意图，采用单发双收的天线结构，发射天线(线圈)T到接收天线(线圈)R1、R2的源距相同，发射线圈T同轴布置，接收线圈R1同轴布置，接收线圈R2正交布置，源距相同，为40in，所以一次发射可同时测得zz、zx分量。1 is a schematic diagram of an antenna structure for time-domain transient electromagnetic logging provided by the present invention for remote boundary detection. A single-transmission and dual-receive antenna structure is adopted, and the source distance from the transmitting antenna (coil) T to the receiving antennas (coil) R1 and R2 is shown in FIG. In the same way, the transmitting coil T is coaxially arranged, the receiving coil R1 is coaxially arranged, and the receiving coil R2 is orthogonally arranged. The source distance is the same, 40in, so the zz and zx components can be measured simultaneously in one transmission.
对随钻地质导向中遇到的向前看(look ahead)、向远看(look around)地质情况进行简化，同时将随钻过程中仪器自上而下或自下而上由泥岩层钻进砂岩层的情况考虑在内，建立瞬变电磁波测井边界探测地质模型，如图2、3所示：地层模型包括介质I和介质II，介质I电阻率10Ω·m，介质II电阻率1Ω·m，线圈系位于介质I中，分别位于界面上方和下方。Simplify the look ahead and look around geological conditions encountered during geosteering while drilling, and at the same time, the instrument will be drilled from the mudstone layer from top to bottom or from bottom to top during drilling Taking the sandstone layer into consideration, the geological model of transient electromagnetic logging boundary detection is established, as shown in Figures 2 and 3: The formation model includes medium I and medium II, medium I has a resistivity of 10Ω · m, and medium II has a resistivity of 1Ω · m, the coil system is located in the medium I, respectively above and below the interface.
步骤2：选择瞬变电磁波测井脉冲源激励模式，向地层中发射电流；进行激励后关断电流源，测量关断后地层中的纯二次场；Step 2: Select the transient electromagnetic wave pulse source excitation mode to emit current into the formation; after excitation, turn off the current source and measure the pure secondary field in the formation after shutdown;
选择脉冲源作为激励源，如图4所示，分别为下阶跃电流源、高斯脉冲、锯齿波，向地层中发射电流，激励足够长的时间以消除电流接通引起的瞬变效应，测量电流关断后地层中的纯二次场，本发明其余计算内容以下阶跃电流源为例。Select the pulse source as the excitation source, as shown in Figure 4, which are the next step current source, Gaussian pulse, and sawtooth wave, which emits current into the formation, and the excitation is long enough to eliminate the transient effect caused by the current turn-on After the current is turned off, the pure secondary field in the formation, the rest of the calculation content of the present invention is the following step current source as an example.
步骤3：进行时频信息处理，选择合适的时频转换算法，将不同频率ω的频率域测井响应转换到时间域，获取时间域感应电动势。Step 3: Perform time-frequency information processing, select an appropriate time-frequency conversion algorithm, convert the frequency domain logging response of different frequencies ω to the time domain, and obtain the time-domain induced electromotive force.
步骤3.1：利用矢量位函数法获取层状介质任意方向磁偶极子源的频率域感应电动势V(ω)；Step 3.1: Use the vector bit function method to obtain the frequency-domain induced electromotive force V (ω) of the magnetic dipole source in any direction of the layered medium;
步骤3.2：进行时频信息处理，选择时频转换算法，将频率域测井响应V(ω)转换到时间域，获取时间域感应电动势V(t)。Step 3.2: Perform time-frequency information processing, select a time-frequency conversion algorithm, convert the frequency domain logging response V (ω) to the time domain, and obtain the time domain induced electromotive force V (t).
以Gaver-Stehfest逆拉普拉斯变换法为例，获得V(ω)后，令
Figure PCTCN2019088711-appb-000003
V(t)可表示为： Taking the Gaver-Stehfest inverse Laplace transform method as an example, after obtaining V (ω), let
Figure PCTCN2019088711-appb-000003
V (t) can be expressed as:
Figure PCTCN2019088711-appb-000004
Figure PCTCN2019088711-appb-000004
其中，
Figure PCTCN2019088711-appb-000005
J为滤波系数，
Figure PCTCN2019088711-appb-000006
m是
Figure PCTCN2019088711-appb-000007
的整数部分。 among them,
Figure PCTCN2019088711-appb-000005
J is the filter coefficient,
Figure PCTCN2019088711-appb-000006
m is
Figure PCTCN2019088711-appb-000007
The integer part of.
步骤4：构建瞬变电磁波测井边界探测信号定义方式，提取地层电导率，地层界面位置信息。Step 4: Build a transient electromagnetic wave logging boundary detection signal definition method to extract formation conductivity and formation interface position information.
步骤4.1：均匀地层条件下，感应电动势V zz的表达式为： Step 4.1: Under uniform formation conditions, the expression of induced electromotive force V zz is:
Figure PCTCN2019088711-appb-000008
Figure PCTCN2019088711-appb-000008
其中，m为磁偶极矩，μ为磁导率，σ为电导率，r为测量点距源点的距离，e x、e y、e z分别为x、y、z方向的单位向量； Where m is the magnetic dipole moment, μ is the magnetic permeability, σ is the electrical conductivity, r is the distance between the measurement point and the source point, and e x , e y , and e z are the unit vectors in the x, y, and z directions, respectively;
均匀地层测量晚期满足感应电动势
Figure PCTCN2019088711-appb-000009
测量信号与地层电导率线性相关，利用V zz提取地层电导率；层状地层条件下，利用V zz提取地层视电导率。 Even formation measurement meets the induced electromotive force in the late stage
Figure PCTCN2019088711-appb-000009
The measurement signal is linearly related to the formation conductivity. V zz is used to extract the formation conductivity; under layered formation conditions, V zz is used to extract the formation apparent conductivity.
步骤4.2：基于电磁波散射原理，定义层状介质zz分量总场与线圈系所在当前层zz分量背景场的感应电动势差值ΔV zz：即(Δzz 总场-Δzz 背景场)反映邻层对测井响应的贡献；边界的存在导致交叉分量zx不为0，定义zx分量的感应电动势V zx为方位地质信号V Geosignal，反映地层边界位置，根据线圈系位于界面上方或者下方时，时间域感应电动势正负变化情况不同，对地层边界进行方位探测。 Step 4.2: Based on the principle of electromagnetic wave scattering, define the induced electromotive force difference ΔV zz of the zz component total field of the layered medium and the zz component background field of the current layer where the coil system is located: ie (Δzz total field- Δzz background field ) reflects the adjacent layer pair logging The contribution of the response; the presence of the boundary leads to the cross component zx not being 0, and the induced electromotive force V zx of the zx component is defined as the azimuth geological signal V Geosignal , reflecting the position of the formation boundary. According to the coil system being above or below the interface, the time domain induced electromotive force The negative changes are different, and azimuth detection is performed on the stratum boundary.
步骤5：进行不同距离、倾角、地层电阻率条件下的瞬变电磁波测井对边界的探测Step 5: Transient electromagnetic logging at different distances, dips, and formation resistivities to detect the boundary
上述不同距离情况下，针对随钻地质导向中出现的look ahead地质模型，即发射接收天线位于界面前方，与界面夹角较大，此时用层状介质的zz分量总场与天线所在当前层zz分量背景场的感应电动势差值ΔV zz探测界面，如图5所示，天线与地层界面的夹角为90°，时间域中曲线与x轴的交点反映边界距离DTB，界面距离越近，测量信号ΔV zz出现时间越早； In the case of the above different distances, for the look ahead geological model that appears in the geosteering while drilling, that is, the transmitting and receiving antenna is located in front of the interface and the angle between the antenna and the interface is large, at this time, the total field of the zz component of the layered medium and the current layer of the antenna The induced electromotive force difference ΔV zz of the zz component background field is detected on the interface. As shown in Figure 5, the angle between the antenna and the formation interface is 90 °. The intersection of the curve and the x axis in the time domain reflects the boundary distance DTB. The closer the interface distance, The earlier the measurement signal ΔV zz appears;
针对随钻地质导向中出现的look around地质模型，即大斜度井/水平井条件下，此时可用ΔV zz探测界面，如图6所示，天线与地层界面的夹角为30°；或者用zx分量的方位地质信号V Geosignal探测界面，如图7所示，天线结构与地层界面的夹角为30°，ΔV zz和V Geosignal与x轴的交点位置基本一致，对界面距离的探测效果相同； For the look around geological model that appears in the geosteering while drilling, that is, under the conditions of high-angle well / horizontal well, the interface can be probed with ΔV zz , as shown in Figure 6, the angle between the antenna and the formation interface is 30 °; or The zx component azimuth geological signal V Geosignal is used to detect the interface. As shown in Figure 7, the angle between the antenna structure and the formation interface is 30 °. The intersection of ΔV zz and V Geosignal with the x axis is basically the same. The detection effect on the interface distance the same;
但是，与ΔV zz相比，V Geosignal包含方位探测特性，如图8(a)、8(b)所示，天线位于介质I中，与边界距离10m且与界面平行，分别位于界面下方和上方。两种情况下，时间域内的感应电动势数值相同，但是当天线位于界面上方时，极值点前期感应电动势为正(实线)，晚期为负(虚线)；当天线位于界面下方时，极值点两侧感应电动势的正负变化恰好相反。根据V zx的这种变化特征判断天线与界面的相对位置。 However, compared with ΔV zz , V Geosignal contains azimuth detection characteristics. As shown in Figures 8 (a) and 8 (b), the antenna is located in the medium I, at a distance of 10m from the boundary and parallel to the interface, respectively below and above the interface . In both cases, the induced electromotive force value in the time domain is the same, but when the antenna is above the interface, the induced electromotive force is positive (solid line) in the early stage and negative (dashed line) in the late stage; when the antenna is below the interface, the extreme value The positive and negative changes of the induced electromotive force on both sides of the point are just the opposite. The relative position of the antenna and the interface is judged according to this changing characteristic of V zx .
上述不同地层倾角条件下，电极系到边界的距离为10m，电极系与地层界面的夹角分别为90°、60°、45°、30°、15°、5°、0°，进行不同地层倾角条件下对边界的探测，如图9所示。 地层倾角越大，ΔV zz的绝对值越大；同时由于地层视厚度增加，边界距离增大，曲线的极值点左移。 Under the above different formation dip angles, the distance between the electrode system and the boundary is 10m, and the angle between the electrode system and the formation interface is 90 °, 60 °, 45 °, 30 °, 15 °, 5 °, 0 °, respectively. The detection of the boundary under the condition of inclination is shown in Figure 9. The greater the formation dip angle, the greater the absolute value of ΔV zz ; meanwhile, as the apparent thickness of the formation increases, the boundary distance increases, and the extreme point of the curve shifts to the left.
上述不同电阻率条件下：均匀地层条件下，电阻率分别为1、5、10和20Ω·m，如图10所示；当地层界面存在时，电极系与地层界面的夹角为90°，地层边界的距离分别为5m，10m，界面两侧电阻率对比度分别为：10:1、10:5，进行不同电阻率对比度条件下的边界探测，地层电阻率相同时，不同边界距离情况下测量晚期曲线重合。本发明层状地层不同电阻率的zz分量测井响应如图11所示。Under the above different resistivity conditions: under uniform formation conditions, the resistivities are 1, 5, 10, and 20 Ω · m, as shown in Figure 10; when the ground interface exists, the angle between the electrode system and the formation interface is 90 °, The distance between the formation boundaries is 5m and 10m respectively, and the resistivity contrast on both sides of the interface is: 10: 1, 10: 5. The boundary detection is performed under different resistivity contrast conditions. When the formation resistivity is the same, the measurement is performed under different boundary distances. Late curves coincide. The logging response of the zz component of different resistivity of the layered formation of the present invention is shown in FIG. 11.
当然，上述说明并非是对本发明的限制，本发明也并不仅限于上述举例，本技术领域的技术人员在本发明的实质范围内所做出的变化、改型、添加或替换，也应属于本发明的保护范围。Of course, the above description does not limit the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions, or replacements made by those skilled in the art within the essential scope of the present invention should also belong to this The scope of protection of the invention.

Claims (5)

  1. 一种时间域瞬变电磁波测井边界远探测方法，其特征在于：包括以下步骤：A time-domain transient electromagnetic wave logging boundary remote detection method, characterized in that it includes the following steps:
    步骤1：建立地层模型，设计发射接收天线组合模式；Step 1: Establish a stratum model and design a combined transmit and receive antenna mode;
    步骤2：选择瞬变电磁波测井脉冲源激励模式，向地层中发射电流；进行激励后关断电流源，测量关断后地层中的纯二次场；Step 2: Select the transient electromagnetic wave pulse source excitation mode to emit current into the formation; after excitation, turn off the current source and measure the pure secondary field in the formation after shutdown;
    步骤3：获取时间域感应电动势；Step 3: Obtain the time-domain induced electromotive force;
    步骤4：构建瞬变电磁波测井边界探测信号定义方式，提取地层电导率和地层边界位置信息；Step 4: Build a transient electromagnetic wave logging boundary detection signal definition method to extract formation conductivity and formation boundary position information;
    步骤5：进行不同距离、倾角、地层电阻率条件下瞬变电磁波测井对边界的探测。Step 5: Transient electromagnetic wave logging is used to detect the boundary under the conditions of different distance, dip angle and formation resistivity.
  2. 根据权利要求1所述的时间域瞬变电磁测井边界远探测方法，其特征在于：步骤1中，采用单发双收的发射接收模式，该天线由一组发射线圈和两组接收线圈组成，发射线圈同轴布置，两组接收线圈距离发射线圈距离相同，分别采用同轴和正交的布置方式，一次发射能够同时测得层状介质zz和zx分量。The remote detection method for time-domain transient electromagnetic logging boundary according to claim 1, characterized in that: in step 1, a single-transmission and dual-reception transmission and reception mode is adopted, and the antenna is composed of a group of transmitting coils and two groups of receiving coils The transmitting coils are coaxially arranged. The two sets of receiving coils are at the same distance from the transmitting coils. The coaxial and orthogonal arrangements are used respectively. The zz and zx components of the layered medium can be measured at the same time.
  3. 根据权利要求1所述的时间域瞬变电磁波测井边界远探测方法，其特征在于：在步骤3中，具体包括如下步骤：The time-domain transient electromagnetic wave logging boundary remote detection method according to claim 1, characterized in that: in step 3, specifically includes the following steps:
    步骤3.1：利用矢量位函数法获取层状介质任意方向磁偶极子源的频率域感应电动势V(ω)；Step 3.1: Use the vector bit function method to obtain the frequency-domain induced electromotive force V (ω) of the magnetic dipole source in any direction of the layered medium;
    步骤3.2：进行时频信息处理，选择时频转换算法，将频率域测井响应V(ω)转换到时间域，获取时间域感应电动势V(t)。Step 3.2: Perform time-frequency information processing, select a time-frequency conversion algorithm, convert the frequency domain logging response V (ω) to the time domain, and obtain the time domain induced electromotive force V (t).
  4. 根据权利要求1所述的时间域瞬变电磁波测井边界远探测方法，其特征在于：在步骤4中，具体包括如下步骤：The time-domain transient electromagnetic wave logging boundary remote detection method according to claim 1, characterized in that: in step 4, specifically includes the following steps:
    步骤4.1：均匀地层条件下，感应电动势V zz的表达式如公式(2)所示： Step 4.1: Under uniform formation conditions, the expression of induced electromotive force V zz is shown in formula (2):
    Figure PCTCN2019088711-appb-100001
    Figure PCTCN2019088711-appb-100001
    其中，m为磁偶极矩，μ为磁导率，σ为电导率，r为测量点距源点的距离，e x、e y、e z分别为x、y、z方向的单位向量； Where m is the magnetic dipole moment, μ is the magnetic permeability, σ is the electrical conductivity, r is the distance between the measurement point and the source point, and e x , e y , and e z are the unit vectors in the x, y, and z directions, respectively;
    均匀地层测量后期满足感应电动势
    Figure PCTCN2019088711-appb-100002
    测量信号与地层电导率线性相关，利用V zz提取地层电导率；层状地层条件下，利用V zz提取地层视电导率；     Meet the induced electromotive force in the later stage of uniform formation measurement
    Figure PCTCN2019088711-appb-100002
    The measurement signal is linearly related to the formation conductivity, and V zz is used to extract formation conductivity; under layered formation conditions, V zz is used to extract formation conductivity;
    步骤4.2：基于电磁波散射原理，定义层状介质的zz分量总场与天线所在当前层zz分量背景场的感应电动势差值ΔV zz，如公式(3)所示： Step 4.2: Based on the principle of electromagnetic wave scattering, define the induced electromotive force difference ΔV zz between the total field of the zz component of the layered medium and the background field of the zz component of the current layer where the antenna is located, as shown in formula (3):
    ΔV zz＝V zz总场-V zz背景场       (3)； ΔV zz = V zz total field- V zz background field (3);
    ΔV zz反映界面对测井响应的贡献； ΔV zz reflects the contribution of the interface to the logging response;
    边界的存在导致交叉分量zx不为0，定义zx分量的感应电动势V zx为方位地质信号V Geosignal，如公式(4)所示： The existence of the boundary results in the cross component zx not being 0, and the induced electromotive force V zx of the zx component is defined as the azimuth geological signal V Geosignal as shown in formula (4):
    V Geosignal＝V zx        (4)； V Geosignal = V zx (4);
    根据线圈系位于界面上方或者下方时，时间域感应电动势正负变化情况不同，对边界进行方位探测。According to the difference between the positive and negative changes of the induced electromotive force in the time domain when the coil system is located above or below the interface, azimuth detection is performed on the boundary.
  5. 根据权利要求1所述的时间域瞬变电磁波测井边界远探测方法，其特征在于：步骤5中：不同地层倾角情况下，针对随钻地质导向中出现的look ahead地质模型，即发射接收天线位于界面前方，采用zz分量的信号差ΔV zz探测界面；针对随钻地质导向中出现的look around地质模型，即大斜度井/水平井条件下，采用ΔV zz或者V Geosignal探测界面，指导地质导向。 The time-domain transient electromagnetic wave logging boundary remote detection method according to claim 1, characterized in that: in step 5: under different formation dip angles, for the look ahead geological model appearing in the geosteering while drilling, that is, the transmitting and receiving antenna Located in front of the interface, the signal difference ΔV zz is used to detect the interface; for the look around geological model that appears in the geosteering while drilling, that is, under the conditions of high-angle wells / horizontal wells, the ΔV zz or V Geosignal detection interface is used to guide the geology guide.
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