Electromagnetic wave antenna system and measurement method for pre-drilling detection

Abstract

The present invention discloses a pre-drilling electromagnetic wave antenna system and a measurement method, wherein the system includes a front short section, a screw and a remote detection instrument, wherein the front end of the front short section is connected to the drill bit, and the rear end of the front short section is connected to the remote detection instrument via a screw. The front short section includes an inclined transmitting antenna and a group of axial receiving antennas, and the remote detection instrument includes an inclined transmitting antenna, a group of axial receiving antennas and multiple groups of three-axis orthogonal receiving antennas. The present invention can realize the function of pre-drilling at a large distance in front of the drill bit, and multiple groups of receiving antennas with different source distances can ensure that electromagnetic wave responses within different ranges of the surrounding space can be received, so that information on undrilled strata at different depths in front of the drill bit can be obtained through inversion. The present invention helps to solve difficult problems such as precise landing in complex reservoir drilling, elimination of pilot wells, improvement of drilling encounter rate, drilling risk control, reservoir optimization, and comprehensive and detailed evaluation of oil reservoirs.

Description

Technical Field

[0001] The present invention relates to the technical field of pre-detection well logging, and in particular to a pre-detection while drilling electromagnetic wave antenna system and a measurement method. Background Art

[0002] According to its measurement principle, the resistivity pre-detection logging technology while drilling can be divided into: lateral current resistivity logging while drilling and electromagnetic wave logging while drilling.

[0003] Existing LWD lateral current resistivity logging tools and related technologies primarily include the RAB, GVR, and MicroScope instruments released by Schlumberger in 1993, 1998, and 2008, respectively, and the newly developed AFR (azimuthally focused resistivity) tool by Halliburton. These instruments utilize the principle of current lateral measurement to perform lateral resistivity, drill bit resistivity, and resistivity imaging. Their drill bit resistivity offers forward-looking detection capabilities, but the depth of detection is relatively shallow, with a forward-looking measurement range generally limited to less than 1.2 meters. In China, the China Petroleum Drilling Research Institute launched the NBRt near-bit resistivity tool in 2003, which also offers forward-looking drill bit resistivity measurements within a range similar to those of international LWD lateral current resistivity logging tools.

[0004] Of the existing pre-drilling electromagnetic logging tools, the only one currently available is Schlumberger's EMLA, launched in 2016 and later renamed IriSphere. IriSphere consists of a tilted transmitting antenna and two to three receiving sections, each with three orthogonal tilted receiving antennas. The total length of the instrument is over 23 meters.

[0005] The existing LWD resistivity pre-probe logging instruments have the following main shortcomings: the existing LWD lateral current resistivity logging instruments have a limited detection range and a short pre-probe distance; the existing LWD pre-probe electromagnetic wave logging instrument combination is too long, and the measurement signal is greatly affected by the bending and vibration of the drill collar, which is not conducive to drilling inclination and poses a high safety risk to on-site construction operations. Summary of the Invention

[0006] The present invention aims to overcome the shortcomings of existing instruments by providing a forward detection antenna system and measurement method while drilling. This antenna system design combines a front-end sub, a screw, and a remote detection instrument to obtain spatial responses within different surrounding ranges. Using geometric factor technology, it obtains information such as the formation interface and resistivity ahead of the drill bit, achieving a longer forward detection distance. To achieve this objective, the present invention provides the following technical solutions:

[0007] A front-end detection electromagnetic wave antenna system for drilling, comprising a front short section, a screw and a remote edge detection instrument, wherein the front end of the front short section is connected to the drill bit, and the rear end of the front short section is connected to the remote edge detection instrument via a screw, wherein:

[0008] The front sub includes an inclined transmitting antenna and a group of axial receiving antennas, wherein the front end of the inclined transmitting antenna is connected to the drill bit, and the axial receiving antenna is connected to the rear end of the inclined transmitting antenna.

[0009] The remote edge detection instrument includes an inclined transmitting antenna, a group of axial receiving antennas and multiple groups of three-axis orthogonal receiving antennas. The front end of the axial receiving antenna is close to the inclined transmitting antenna, and the rear end of the axial receiving antenna is close to the orthogonal receiving antenna.

[0010] Preferably, the axial receiving antenna includes a first receiving antenna and a second receiving antenna; the first receiving antenna is close to the tilted transmitting antenna.

[0011] Preferably, the source distances of the first receiving antenna and the second receiving antenna of the axial receiving antenna are different, and the normal direction of the first receiving antenna and the normal direction of the second receiving antenna are in the same direction as the axis of the drilling direction.

[0012] Preferably, the three-axis orthogonal receiving antenna includes an axial antenna, a first orthogonal antenna and a second orthogonal antenna; the front end of the axial antenna is close to the first orthogonal antenna, and the rear end of the axial antenna is close to the second orthogonal antenna.

[0013] Preferably, the axial antenna is in the same direction as the axis of the drilling direction, the first orthogonal antenna and the second orthogonal antenna are perpendicular to the axis of the drilling direction, and the normal direction of the axial antenna; the normal direction of the first orthogonal antenna and the normal direction of the second orthogonal antenna are orthogonal to each other.

[0014] A measurement method for an electromagnetic wave antenna for pre-drilling detection, the method includes an antenna system according to the present invention, and the method is performed according to the following steps: tilting the transmitting antenna to transmit electromagnetic wave signals of different frequencies;

[0015] The receiving antenna receives the electromagnetic wave signals of different frequencies; the tilted transmitting antenna transmits electromagnetic wave signals of different frequencies and the receiving antenna receives the electromagnetic wave signals of different frequencies, forming a transmitting antenna-receiving antenna combination, and obtaining a direct measurement signal G n (σ, F), where σ represents the formation conductivity, F represents the function of the instrument frequency, n represents the nth group of transmitting antenna-receiving antenna combination, n = 1, 2, 3 ... n; according to the direct measurement signal G n (σ,F), the transmit antenna-receive antenna combination measurement signal coefficient δ is calculated by the geometric factorn ; Each group of transmitting and receiving antennas measures the signal coefficient δ n and directly measure the signal G n (σ,F) is used to calculate the forward detection signal Fw at different detection depths n According to the forward signal Fw n Calculate the forward distance LA n .

[0016] Preferably, the inclined transmitting antenna that transmits electromagnetic wave signals of different frequencies refers to a front short section or an inclined transmitting antenna of a remote edge detection instrument.

[0017] Preferably, the receiving antenna that receives the electromagnetic wave signals of different frequencies refers to the axial receiving antenna of the front short section or the axial receiving antenna of the remote detection instrument, or the three-axis orthogonal receiving antenna of the remote detection instrument.

[0018] Preferably, the axial receiving antenna of the front short section, the axial receiving antenna of the remote edge detection instrument and the three-axis orthogonal receiving antenna of the remote edge detection instrument can receive the electromagnetic wave signal simultaneously.

[0019] Preferably, the direct measurement signal refers to the measurement voltage signal of the same transmitting-receiving antenna combination, which represents the sum of contributions from all spatial directions in front, behind and on the sides of the instrument within a certain range, and is expressed as the measurement voltage G n (σ,F) represents.

[0020] Preferably, the directly measured signal G n (σ, F), n = 1, 2, 3...n, wherein the measurement signal G1(σ, F) of the first transmitting antenna-receiving antenna combination refers to the voltage measured by the electromagnetic wave signal transmitted by the inclined transmitting antenna on the front short section and the nth group of three-axis orthogonal receiving antennas of the remote edge detection instrument.

[0021] The measurement signal G2(σ,F) of the second transmitting antenna-receiving antenna combination refers to the voltage measured by the electromagnetic wave signal transmitted by the inclined transmitting antenna on the front short section and the n-1th group of three-axis orthogonal receiving antennas of the remote edge detection instrument.

[0022] The measurement signal G3(σ,F) of the third transmitting antenna-receiving antenna combination refers to the voltage measured by the electromagnetic wave signal transmitted by the inclined transmitting antenna on the front short section and the n-2th group of three-axis orthogonal receiving antennas of the remote edge detection instrument.

[0023] By analogy, the measurement signal G of the nth transmitting antenna-receiving antenna combination is n (σ, F) refers to the voltage measured by the electromagnetic wave signal transmitted by the inclined transmitting antenna on the front short section and the axial receiving antenna of the remote edge detection instrument.

[0024] The measurement signal G of the n+1th transmitting antenna-receiving antenna combination n+1 (σ, F) refers to the voltage measured between the electromagnetic wave signal transmitted by the inclined transmitting antenna on the front short section and the axial receiving antenna of the front short section.

[0025] The measurement signal G of the n+2th transmitting antenna-receiving antenna combination n+2 (σ, F) refers to the voltage measured by the axial receiving antenna pair of the remote edge detection instrument when the electromagnetic wave signal transmitted by the tilted transmitting antenna of the remote edge detection instrument and the electromagnetic wave signal transmitted by the nth group of tilted transmitting antennas of the remote edge detection instrument are measured.

[0026] The measurement signal G of the n+3th transmitting antenna-receiving antenna combination n+3 (σ, F) refers to the voltage measured by the electromagnetic wave signal transmitted by the tilted transmitting antenna of the remote edge detection instrument and the n-1th group of three-axis orthogonal receiving antennas of the remote edge detection instrument.

[0027] By analogy, the measurement signal G of the 2n+2th transmitting antenna-receiving antenna combination is 2n+2 (σ, F) refers to the voltage measured by the electromagnetic wave signal transmitted by the tilted transmitting antenna of the remote edge detection instrument and the axial receiving antenna of the remote edge detection instrument.

[0028] Preferably, the coefficient δ of the measurement signal n , determined by the equipotential surface with 90% contribution of the three-dimensional geometric factor in the drilling direction.

[0029] Preferably, the forward detection signal Fw of different detection depths is calculated n The calculation formula is as follows:

[0030] Pre-sound signal of the first detection depth:

[0031]

[0032] Pre-detection signal of the second detection depth:

[0033]

[0034] Pre-detection signal at the third detection depth:

[0035]

[0036] Similarly, the forward signal of the nth detection depth is:

[0037]

[0038] Wherein, n represents the nth group of transmitting antenna-receiving antenna combination, n=1, 2, 3...n; i represents the ith group of transmitting antenna-receiving antenna combination, i=n+1, n=1, 2, 3...n; G n (σ,F) is the measured voltage, which represents the contribution of the signals received by the nth group of transmitting antennas and receiving antennas to the total response; δ is the measured signal coefficient, which represents G n (σ, F) is the difference in contribution of the received signal at each location in the space to the total response; the Fw n It is the forward signal, indicating G n (σ,F) The distance signal from the front end of the detection range to the instrument drill bit.

[0039] Preferably, the forward signal Fw n Calculate the forward distance LA n , the 10% change of the measurement signal is used as the criterion for identifying the undrilled formation, that is, Fw n The boundary distance corresponding to a 10% change in the curve is LA n .

[0040] Technical effects and advantages of the present invention:

[0041] 1. Place the measuring point as far forward as possible. The instrument's forward detection distance needs to be subtracted from the distance from the measuring point to the drill bit. The distance from the measuring point to the drill bit depends on the specific instrument and downhole tool combination. To achieve a larger forward detection distance, the measuring point is placed as far forward as possible. In this invention, a forward short sub is designed that can be placed directly behind the drill bit.

[0042] 2. Increase the source distance without increasing the instrument length. According to the principle of electromagnetic wave logging, the instrument detection range is an increasing function of the source distance between the transmitting antenna and the receiving antenna. To maximize the front detection range and increase the source distance without increasing the instrument length, the screw required for drilling is placed between the front short section and the remote detection instrument, making full use of the screw length and increasing the source distance.

[0043] 3. The use of antennas with multiple angles, such as axial, inclined, and orthogonal, and antenna combinations with different source distances can measure stratum information in different detection ranges. Through geometric factor calculation, the stratum information at different depths in front of the drill bit can be accurately extracted.

[0044] In summary, the electromagnetic wave antenna system and measurement method for pre-drilling detection described in the present invention propose an antenna system with a front short section connected to a remote detection instrument, which can realize the function of pre-drilling detection at a large distance ahead of the drill bit. Multiple groups of receiving antennas with different source distances ensure that they can receive electromagnetic wave responses within different ranges of the surrounding space, so that information about undrilled formations at different depths ahead of the drill bit can be obtained through geometric factors. Conventional receiving antenna pairs can measure the resistivity near the wellbore. Using the antenna system described in the present invention, the resistivity of the formation at different detection depths can be measured separately. Through data processing and geometric factor calculation, the interface in the undrilled formation, the conductivity on both sides of the interface, and the distance between the instrument and the interface can be predicted. In formations with a resistivity contrast of 1:100, the pre-drilling distance is over 10 meters. The application of the present invention can help solve difficult problems such as precise landing in complex reservoir drilling, eliminating pilot wells, improving the drilling rate, controlling drilling risks, optimizing reservoirs, and realizing comprehensive and detailed evaluation of oil reservoirs.

[0045] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a structural schematic diagram of the present invention;

[0047] Figure 2 Schematic diagram of measurement of signals with different source distances in the present invention;

[0048] Figure 3 Contribute 90% of the 3D geometry factor to the isosurface map;

[0049] Figure 4 Schematic diagram of the detection depth corresponding to different source distance signals in the present invention;

[0050] Figure 5 Schematic diagram of the detection range of the present invention;

[0051] Figure 6 The measurement curve of the tool at different well inclination angles; DETAILED DESCRIPTION

[0052] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0053] In order to solve the deficiencies of the prior art, the present invention discloses an electromagnetic wave antenna system and a measurement method for detecting electromagnetic waves before drilling. Figure 1 As shown, the system includes a front sub, a screw, and a remote edge detection instrument. The front end of the front sub is connected to the drill bit, and the rear end of the front sub is connected to the remote edge detection instrument via the screw. The front sub includes an inclined transmitting antenna and a set of axial receiving antennas. The front end of the inclined transmitting antenna is connected to the drill bit, and the axial receiving antenna is connected to the rear end of the inclined transmitting antenna. The remote edge detection instrument includes an inclined transmitting antenna, a set of axial receiving antennas, and several sets of three-axis orthogonal receiving antennas. The three-axis orthogonal receiving antennas of the remote edge detection instrument are long-source-range receiving antennas. The front end of the axial receiving antenna is close to the inclined transmitting antenna, and the rear end of the axial receiving antenna is close to the three-axis orthogonal receiving antenna.

[0054] Furthermore, the axial receiving antenna includes a first receiving antenna and a second receiving antenna; the first receiving antenna is close to the tilted transmitting antenna; the source distances between the first receiving antenna and the second receiving antenna of the axial receiving antenna are different, and the normal direction of the first receiving antenna and the normal direction of the second receiving antenna are in the same direction as the axis of the drilling direction; the three-axis orthogonal receiving antenna includes an axial antenna, a first orthogonal antenna, and a second orthogonal antenna; the front end of the axial antenna is close to the first orthogonal antenna, and the rear end of the axial antenna is close to the second orthogonal antenna. The axial antenna is in the same direction as the axis of the drilling direction, the first orthogonal antenna and the second orthogonal antenna are perpendicular to the axis of the drilling direction, and the normal directions of the axial antennas; the normal directions of the first orthogonal antenna and the second orthogonal antenna are orthogonal to each other.

[0055] A method for measuring an electromagnetic wave antenna before drilling is provided, wherein the method adopts the system of the present invention and is performed according to the following steps:

[0056] The tilted transmitting antenna transmits electromagnetic wave signals of different frequencies;

[0057] The receiving antenna receives the electromagnetic wave signals of different frequencies;

[0058] According to the tilted transmitting antenna transmitting electromagnetic wave signals of different frequencies and the receiving antenna receiving the electromagnetic wave signals of different frequencies, a transmitting antenna-receiving antenna combination is formed, and a direct measurement signal G is obtained. n (σ,F);

[0059] According to the direct measurement signal G n (σ,F), the measurement signal coefficient δ of the transmitting antenna-receiving antenna combination is calculated by the geometric factor n ;

[0060] The measured signal coefficient δ for each transmit-receive antenna combination n and directly measure the signal G n (σ,F) is used to calculate the forward detection signal Fw at different detection depths n ;

[0061] According to the forward signal Fw n Calculate the forward distance LA n .

[0062] Furthermore, the inclined transmitting antenna that transmits electromagnetic wave signals of different frequencies refers to the inclined transmitting antenna of the front short section or the remote edge detection instrument.

[0063] Furthermore, the receiving antennas for receiving the electromagnetic wave signals of different frequencies are the axial receiving antennas of the front sub, the axial receiving antennas of the remote edge detection instrument, or the three-axis orthogonal receiving antennas of the remote edge detection instrument. The axial receiving antennas of the front sub, the axial receiving antennas of the remote edge detection instrument, and the three-axis orthogonal receiving antennas of the remote edge detection instrument are capable of simultaneously receiving the electromagnetic wave signals.

[0064] Furthermore, the direct measurement signal refers to the measurement voltage signal of the same transmitting and receiving antenna combination, which represents the sum of contributions from all spatial directions in front, behind and on the sides of the instrument within a certain range. n (σ, F), where σ represents the formation conductivity, F represents the function of the instrument frequency, and n represents the nth transmitting antenna-receiving antenna combination, n = 1, 2, 3...n.

[0065] Further, if Figure 2 As shown, the measurement signal G1 (σ, F) of the first transmitting antenna-receiving antenna combination refers to the voltage measured by the electromagnetic wave signal transmitted by the inclined transmitting antenna on the front short section and the nth group of three-axis orthogonal receiving antennas of the remote edge detection instrument; the measurement signal G2 (σ, F) of the second transmitting antenna-receiving antenna combination refers to the voltage measured by the electromagnetic wave signal transmitted by the inclined transmitting antenna on the front short section and the n-1th group of three-axis orthogonal receiving antennas of the remote edge detection instrument; the measurement signal G3 (σ, F) of the third transmitting antenna-receiving antenna combination refers to the voltage measured by the electromagnetic wave signal transmitted by the inclined transmitting antenna on the front short section and the n-2th group of three-axis orthogonal receiving antennas of the remote edge detection instrument; and so on. n (σ, F) refers to the voltage measured between the electromagnetic wave signal transmitted by the inclined transmitting antenna on the front short section and the axial receiving antenna of the remote edge detection instrument.

[0066] Furthermore, the measurement signal G of the n+1th transmitting antenna-receiving antenna combination n+1(σ, F) refers to the voltage measured by the electromagnetic wave signal transmitted by the inclined transmitting antenna on the front short section and the axial receiving antenna of the front short section; the measurement signal G of the n+2th transmitting antenna-receiving antenna combination n+2 (σ, F) refers to the voltage measured by the electromagnetic wave signal transmitted by the tilted transmitting antenna of the remote edge detection instrument and the electromagnetic wave signal transmitted by the nth group of tilted transmitting antennas of the remote edge detection instrument, and the axial receiving antenna pair of the remote edge detection instrument; the measurement signal G of the n+3th transmitting antenna-receiving antenna combination n+3 (σ, F) refers to the voltage measured by the electromagnetic wave signal transmitted by the tilted transmitting antenna of the remote edge detection instrument and the n-1th set of three-axis orthogonal receiving antennas of the remote edge detection instrument; and so on, the measurement signal G of the 2n+2th transmitting antenna-receiving antenna combination 2n+2 (σ,F) refers to the voltage measured between the electromagnetic wave signal transmitted by the tilted transmitting antenna of the remote edge detection instrument and the axial receiving antenna of the remote edge detection instrument.

[0067] Direct measurement of signal G n (σ,F) represents the sum of all spatial contributions from the front, back, and sides of the instrument within a certain range. For different transmit and receive antenna combinations, G n Each region of the received space (σ,F) contributes differently to the total response, and its measurement signal coefficient can be expressed by δ.

[0068] With the system of the present invention, the detection range of the measurement signal G1(σ, F) of the first transmitting antenna-receiving antenna combination is large, and the detection range of the measurement signals G2(σ, F), G3(σ, F)...G of the second, third...n transmitting antenna-receiving antenna combinations is large. n The detection range of (σ,F) decreases in sequence, and the signal coefficient δ is measured according to each set of transmitting and receiving antennas. n and directly measure the signal G n (σ,F) is used to calculate the forward detection signal Fw at different detection depths n According to the forward signal Fw n Calculate the forward distance LA n .

[0069] Further, according to Figure 5 As shown in the figure, the measurement signal G1(σ, F) of the first transmitting antenna-receiving antenna combination has a larger detection range. The measurement signal is the sum of the responses from layer 1 and layer 2, but the contributions of layer 1 and layer 2 are different. Similarly, the measurement signals G2(σ, F), G3(σ, F)...G n The (σ, F) detection range decreases successively, and the measured signal is also the sum of the responses from formations 1 and 2, except that the contribution from formation 2 is greater. Formation 1 is a drilled formation, and its resistivity can be measured.

[0070] Further, if Figure 3 As shown, through the geometric factor, 90% of the contribution is in the equipotential surface of the drilling direction. Let the source distance between the transmitting antenna and the receiving antenna be L, then Figure 3 The equipotential surface in the drilling direction is at 2L. Calculate the measurement signal coefficients of each set of transmitting and receiving antennas, namely G1(σ,F), G2(σ,F), G3(σ,F)...G n Coefficients δ1, δ2, δ3...δ of (σ,F) n .

[0071] Furthermore, the signal coefficient δ is measured n The equipotential surface at which 90% of the three-dimensional geometric factor contributes in the drilling direction is determined. The position of the equipotential surface at which 90% of the three-dimensional geometric factor contributes for each set of source distances between the transmitting and receiving antennas is determined, and the weight of the geometric factor for each set of source distances between the transmitting and receiving antennas is calculated, which is the measurement signal coefficient.

[0072] Furthermore, the measurement signal with a larger detection depth is subtracted from the measurement signal with a smaller detection depth, and the coefficient of the measurement signal is calculated by the three-dimensional geometric factor. The forward detection signal reflects the distance between the instrument and the interface, as well as the formation resistivity at different detection depths on both sides of the interface. n (σ,F) and δ n Calculate the forward detection signal Fw at different detection depths n The calculation formula is as follows:

[0073] Pre-sound signal of the first detection depth:

[0074]

[0075] Pre-detection signal of the second detection depth:

[0076]

[0077] Pre-detection signal at the third detection depth:

[0078]

[0079] Similarly, the forward signal of the nth detection depth is:

[0080]

[0081] Wherein, n represents the nth group of transmitting antenna-receiving antenna combination, n=1, 2, 3...n; G n (σ,F) is the measured voltage, which represents the contribution of the signals received by the nth group of transmitting antennas and receiving antennas to the total response; the δ is the different detection depths, which represents G n(σ, F) is the difference in contribution of the received signal at each location in the space to the total response; the Fw n It is the forward signal, indicating G n (σ,F) is the distance signal from the front end of the detection range to the instrument drill head.

[0082] Furthermore, the forward signal Fw n Calculate the front detection distance LA n , the 10% change of the measurement signal is used as the criterion for identifying the undrilled formation, that is, Fw n The boundary distance corresponding to a 10% change in the curve is LA n .

[0083] The present invention will be further described with reference to specific embodiments.

[0084] Taking the present invention as an example of vertical well drilling in two layers of strata, Figure 5 As shown, using the antenna system of the present invention, the detection range of the measurement signal G1 (σ, F) of the first transmitting antenna-receiving antenna combination is larger, and the measurement signal is the sum of the responses from formation 1 and formation 2, except that the contributions of formation 1 and formation 2 are different. Similarly, the detection range of the measurement signals G2 (σ, F), G3 (σ, F), and G4 (σ, F) of the second, third, and fourth transmitting antenna-receiving antenna combinations is smaller, and the measurement signal is also the sum of the responses from formation 1 and formation 2, except that the contribution of formation 2 is greater. Formation 1 is a drilled formation, and its resistivity can be measured, and then the conductivity can be calculated based on the inverse of the resistivity. Through the equipotential surface with 90% contribution of the geometric factor in the drilling direction, let the source distance between the transmitting antenna and the receiving antenna be L, then Figure 3 The equipotential surface in the drilling direction is at 2L. Calculate the geometric factor weights of each group of transmitting and receiving antennas, that is, the coefficients δ1, δ2, δ3, and δ4 of G1(σ, F), G2(σ, F), G3(σ, F), and G4(σ, F). Then, the forward detection signals at different detection depths can be obtained:

[0085] The forward signal of the instrument's first detection depth:

[0086]

[0087] The forward signal of the instrument's second detection depth:

[0088]

[0089] The forward signal of the instrument's third detection depth:

[0090]

[0091] The instrument's forward signal at the fourth detection depth:

[0092]

[0093] Combine Figure 4 , through the geometric factor 90% contribution in the drilling direction of the equipotential surface, the source distance between the transmitting antenna and the receiving antenna is L, further, according to the forward signal Fw n The measurement signal change of 10% is used as the criterion for identifying undrilled formations, that is, Fw n The boundary distance corresponding to a 10% change in the curve is LA n , n=1,2,3,4.

[0094] Figure 6 In a 1:100 single-interface formation, the resistivities on both sides of the interface are 1Ω·m and 100Ω·m respectively. The conductivity σ can be obtained based on the resistivity, and the forward exploration curves Fw1, Fw2, Fw3, and Fw4 of the four detection depths are further obtained. Among them, Fw1 has the largest detection depth and is the first to predict the existence of the interface. Taking a 10% change in the measurement signal as the criterion for identifying undrilled formations, the forward detection distance of Fw1 is greater than 10m. Since Fw1 has the largest detection range, the resistivity Rt1 of the first underground layer is greatly affected by the resistivity Rt2 of the second underground layer, that is, the conductivity σ1 of the first underground layer is greatly affected by the conductivity σ2 of the second underground layer. Taking the measurement signal Fw n A change of 10% is used as the criterion for identifying undrilled formations, that is, Fw n The boundary distance corresponding to a 10% change in the curve is LA n .

[0095] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A front-end detection electromagnetic wave antenna system for drilling, comprising a front sub, a screw and a remote detection instrument, characterized in that: The front end of the front short section is connected to the drill bit, and the rear end of the front short section is connected to the remote edge detection instrument through a screw, wherein: The front sub includes an inclined transmitting antenna and a set of axial receiving antennas, wherein the front end of the inclined transmitting antenna is connected to the drill bit, and the axial receiving antenna is connected to the rear end of the inclined transmitting antenna; The remote edge detection instrument includes an inclined transmitting antenna, a group of axial receiving antennas and multiple groups of three-axis orthogonal receiving antennas, the front end of the axial receiving antenna is close to the inclined transmitting antenna, and the rear end of the axial receiving antenna is close to the orthogonal receiving antenna; The axial receiving antenna includes a first receiving antenna and a second receiving antenna; the first receiving antenna is close to the tilted transmitting antenna; The normal direction of the first receiving antenna and the normal direction of the second receiving antenna are in the same direction as the axis of the drilling direction; The three-axis orthogonal receiving antenna includes an axial antenna, a first orthogonal antenna and a second orthogonal antenna; The front end of the axial antenna is close to the first orthogonal antenna, and the rear end of the axial antenna is close to the second orthogonal antenna; The axial antenna is in the same direction as the axis of the drilling direction, the first orthogonal antenna and the second orthogonal antenna are perpendicular to the axis of the drilling direction, and the normal direction of the axial antenna; the normal direction of the first orthogonal antenna and the normal direction of the second orthogonal antenna are orthogonal to each other.

2. The electromagnetic wave antenna system for pre-drilling detection according to claim 1, characterized in that: The first receiving antenna and the second receiving antenna of the axial receiving antenna have different source distances.

3. A method for measuring an electromagnetic wave antenna for pre-drilling detection, the method using the electromagnetic wave antenna system for pre-drilling detection according to claim 1 or 2, characterized in that: The method is carried out according to the following steps: The tilted transmitting antenna transmits electromagnetic wave signals of different frequencies; wherein the tilted transmitting antenna transmitting electromagnetic wave signals of different frequencies refers to the tilted transmitting antenna of the front short section or the remote edge detection instrument; The receiving antenna receives the electromagnetic wave signals of different frequencies; wherein the receiving antenna that receives the electromagnetic wave signals of different frequencies refers to the axial receiving antenna of the front short section or the axial receiving antenna of the remote detection instrument, or the three-axis orthogonal receiving antenna of the remote detection instrument; the axial receiving antenna of the front short section, the axial receiving antenna of the remote detection instrument, and the three-axis orthogonal receiving antenna of the remote detection instrument can simultaneously receive the electromagnetic wave signals; According to the tilted transmitting antenna, electromagnetic wave signals of different frequencies are transmitted and the receiving antenna receives the electromagnetic wave signals of different frequencies, forming a transmitting antenna-receiving antenna combination and obtaining a direct measurement signal , where σ represents the formation conductivity, F represents the function of the instrument frequency, and n represents the nth transmitting antenna-receiving antenna combination, n = 1, 2, 3...n; According to the direct measurement signal , the transmit antenna-receive antenna combination measurement signal coefficient is calculated by geometric factor ; Measure the signal coefficient for each transmit-receive antenna pair and directly measure the signal Calculate the forward detection signal at different detection depths ; According to the pre-probe signal Calculate the forward distance .

4. The method for measuring an electromagnetic wave antenna before drilling according to claim 3, wherein: The direct measurement signal refers to the measurement voltage signal of the same transmitting-receiving antenna combination, which represents the sum of all spatial contributions from the front, rear and side of the instrument within a certain range. express.

5. The method for measuring an electromagnetic wave antenna before drilling according to claim 4, characterized in that: The direct measurement signal , n=1, 2, 3...n, where, Measurement signal of the first transmitting antenna-receiving antenna combination It refers to the voltage measured by the electromagnetic wave signal transmitted by the inclined transmitting antenna on the front short section and the nth group of three-axis orthogonal receiving antennas of the remote edge detection instrument; Measurement signal of the second transmitting antenna-receiving antenna combination It refers to the voltage measured by the electromagnetic wave signal transmitted by the inclined transmitting antenna on the front short section and the n-1th group of three-axis orthogonal receiving antennas of the remote edge detection instrument; Measurement signal of the third transmitting antenna-receiving antenna combination It refers to the voltage measured by the electromagnetic wave signal transmitted by the inclined transmitting antenna on the front short section and the n-2 group of three-axis orthogonal receiving antennas of the remote edge detection instrument; By analogy, the measurement signal of the nth transmitting antenna-receiving antenna combination is It refers to the voltage measured by the electromagnetic wave signal transmitted by the inclined transmitting antenna on the front short section and the axial receiving antenna of the remote edge detection instrument; Measurement signal of the n+1th transmitting antenna-receiving antenna combination It refers to the voltage measured by the electromagnetic wave signal transmitted by the inclined transmitting antenna on the front short section and the axial receiving antenna on the front short section; Measurement signal of the n+2th transmitting antenna-receiving antenna combination It refers to the electromagnetic wave signal transmitted by the tilted transmitting antenna of the remote edge detection instrument and the electromagnetic wave signal transmitted by the nth group of tilted transmitting antennas of the remote edge detection instrument, and the voltage measured by the axial receiving antenna of the remote edge detection instrument; Measurement signal of the n+3th transmitting antenna-receiving antenna combination It refers to the voltage measured by the electromagnetic wave signal transmitted by the tilted transmitting antenna of the remote edge detection instrument and the n-1th group of three-axis orthogonal receiving antennas of the remote edge detection instrument; By analogy, the measurement signal of the 2n+2th transmitting antenna-receiving antenna combination is It refers to the electromagnetic wave signal transmitted by the tilted transmitting antenna of the remote edge detection instrument and the voltage measured by the axial receiving antenna of the remote edge detection instrument.

6. The method for measuring an electromagnetic wave antenna before drilling according to claim 3, characterized in that: The coefficients of the measurement signal , determined by the equipotential surface where 90% of the three-dimensional geometric factor contributes in the drilling direction.

7. The method for measuring an electromagnetic wave antenna before drilling according to claim 3, wherein: Calculate the forward detection signal at different detection depths The calculation formula is as follows: Pre-sound signal of the first detection depth: Pre-detection signal of the second detection depth: Pre-detection signal at the third detection depth: Similarly, the forward signal of the nth detection depth is: Where n represents the nth transmit antenna-receive antenna combination, n=1, 2, 3...n; i represents the i-th transmit antenna-receive antenna combination, i=n+1, n=1, 2, 3...n; is the measured voltage, which represents the contribution of the signals received at various locations in the space by the nth transmitting antenna-receiving antenna combination to the total response; is the measurement signal coefficient, which is expressed as The difference in contribution of the received signals at various locations in the space to the total response; It is the forward signal, indicating The distance signal from the front end of the detection range to the instrument drill head.

8. The method for measuring an electromagnetic wave antenna before drilling according to claim 3, wherein: According to the pre-probe signal Calculate the forward distance , takes the 10% change of the measurement signal as the criterion for identifying the undrilled formation, that is, The boundary distance corresponding to a 10% change in the curve is .

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