A method and system for three-dimensional imaging based on directional drilling radar

Abstract

The application discloses a three-dimensional imaging method and system based on directional drilling radar, belongs to the field of engineering survey, mineral exploration and the like, and aims at identifying three-dimensional space distribution of abnormal stratum structures such as cracks, cavities and ore veins around a drilling hole, a well and a pipeline, and comprises an azimuthal drilling radar data acquisition device, which excites electromagnetic waves in a hole, the electromagnetic waves are reflected when encountering an abnormal body, the reflected electromagnetic waves are received by an azimuthal antenna, and then azimuthal electromagnetic wave data are obtained; then the azimuthal electromagnetic wave data are subjected to migration processing to return the diffracted waves and suppress interference waves, and migration results are obtained; three-dimensional imaging is completed according to azimuthal information obtained by a DOA method and radial distance and depth information obtained by migration; the application returns the diffracted waves by migration and suppresses some interference waves, achieves better identification effect for azimuthal detection of abnormal targets around a well, and greatly improves processing speed; and the application also has better identification and detection effect for horizontal cracks.

Description

Technical Field

[0001] This invention relates to the field of anomalous geological structure identification technology, and more specifically, to a three-dimensional imaging method and system based on directional borehole radar. Background Technology

[0002] Borehole radar is a special type of ground-penetrating radar whose antenna operates inside a borehole, allowing it to get closer to the target and be unaffected by surface weathering layers. Borehole radar is widely used in oil exploration, mineral prospecting, hydrological surveys, and engineering exploration. It is an effective method for detecting cracks.

[0003] To address the challenge of target azimuth identification in directional drilling radar, various methods have emerged, primarily including data matching algorithms and spatial spectrum methods. Data matching algorithms include the arctangent method and the residual method. The arctangent method involves calculating the tangent of the incident angle and can be divided into two approaches: coil-measured magnetic field and electric field-synthesized magnetic field. The residual method finds the most suitable incident angle by calculating the residual between the measured signal and the synthesized signal. The spatial spectrum method is a widely used approach for estimating the parameters of spatial signals using a spatial array. However, these methods suffer from several drawbacks: while the arctangent and residual methods offer some accuracy, and the residual method can be improved to apply to multiple targets, its precision is relatively low due to the inherent limitations of the algorithms. The spatial spectrum method, on the other hand, offers super-resolution and high noise tolerance, but also incurs a significant computational burden.

[0004] After obtaining the target's azimuth, the next step is to construct its three-dimensional morphology. Two-dimensional spatial spectrum algorithms can simultaneously obtain azimuth and elevation angles, but due to the limited number of array sources, small apertures, and various approximations, the accuracy of the obtained elevation angle is low. To address this issue, residual methods or linear predictions can be combined to obtain azimuth information, along with depth and radial distance information obtained through offset mapping, to achieve three-dimensional imaging of the target. However, these methods have limited applicability; for example, they can only handle single targets and plane waves incident on the array, and their performance is unsatisfactory for complex models such as rough cracks. Therefore, there is an urgent need for a three-dimensional imaging technology based on directional borehole radar to overcome at least one of the problems existing in the background technology. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to solve the issues of unsatisfactory processing effects in the prior art by employing a three-dimensional imaging technology based on directional drilling radar, which first performs offset analysis and then performs orientation recognition in three-dimensional imaging.

[0006] To achieve the above technical objectives, this application provides a three-dimensional imaging method based on directional borehole radar, comprising:

[0007] Based on directional drilling radar, an electromagnetic wave propagation velocity field is established according to the target being detected. The received raw radar data is then offset to obtain the offset result.

[0008] Based on the offset results, the target is imaged in three dimensions after orientation recognition.

[0009] Preferably, in the process of acquiring raw radar data, the data received by the directional drilling radar is preprocessed by removing DC, denoising, and deconvolution to generate raw radar data.

[0010] Preferably, during the offset processing of the original radar data, the offset processing of the original radar data is performed by a diffraction superposition offset method.

[0011] Preferably, during the offset processing, the underground area where the directional drilling radar is located is divided into grids, and each grid point is regarded as a diffraction point. The time-depth curve of the diffracted wave from the sub-wave source received by the antenna is a hyperbola.

[0012] By recording the corresponding track S on the hyperbola j When the diffracted wave travels, t j The amplitude values ​​are superimposed to achieve the offset processing.

[0013] Preferably, during the acquisition of the diffracted wave travel time t j During the process, the travel time of the diffracted wave is t j Represented as:

[0014]

[0015] Where n is the total number of records involved in the superposition, v is the electromagnetic wave velocity in the surrounding rock, D is the radial distance of the diffraction point, H is the ground depth corresponding to the diffraction point, and the distance between the radar's transmitting and receiving antennas is 2h. j This indicates the depth of the radar's corresponding diffraction point.

[0016] Preferably, during the azimuth identification process of the offset results, offset profiles of the receiving antenna data in the north, west, south and east directions on the UCA are obtained based on the offset results;

[0017] Based on the offset profile, the orientation of the diffraction point is identified using the DOA method.

[0018] Preferably, during the three-dimensional imaging process, the azimuth angle is obtained by azimuth identification using the DOA method, and the magnitude of the imaging point is determined based on the offset result to perform three-dimensional imaging of the target.

[0019] Preferably, in the process of acquiring the amplitude of the imaging point, the amplitude of the imaging point is expressed as:

[0020] M(D, H, θ(D, H)) = (A N (D, H) + A W (D, H) + A S (D, H) + A E (D, H) / 4

[0021] Among them, A N (D, H), A W (D, H), A S (D, H) and A E (D, H) represent the offset profiles of the received antenna data in the north, west, south, and east directions on the UCA, respectively, and θ(D, H) is the azimuth angle.

[0022] This invention discloses a three-dimensional imaging system based on directional borehole radar, comprising:

[0023] The data acquisition module is used to acquire raw radar data;

[0024] The offset module is used to establish an electromagnetic wave propagation velocity field based on the target of the directional drilling radar, perform offset processing on the original radar data, and obtain the offset result.

[0025] The 3D imaging module is used to perform 3D imaging of the target based on the offset results and after orientation recognition of the offset results.

[0026] Preferably, the data acquisition module is also used to preprocess the data received by the directional drilling radar by removing DC, denoising, and deconvolution to generate raw radar data.

[0027] The present invention discloses the following technical effects:

[0028] This invention uses offsetting to correct diffracted waves and suppress some interfering waves, making it easier to separate waveforms generated by different targets. Furthermore, the entire imaging process only requires one offset, resulting in faster computation. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of the method described in this invention;

[0031] Figure 2This is a schematic diagram of the diffraction superposition offset described in this invention, wherein (a) represents the relative position of the diffraction point and the antenna, and (b) represents the time-depth curve;

[0032] Figure 3 This invention describes a three-dimensional imaging process for a smooth crack, including: (a) simulation results (magnified view of the 15th channel at 47-52 ns); (b) migration results (magnified view of the 15th channel at 40-45 ns); (c) orientation recognition results; and (d) three-dimensional imaging results.

[0033] Figure 4 This is the three-dimensional imaging process of rough cracks described in this invention, wherein (a) simulation results (magnified display of the 15th channel at 47-52ns); (b) offset results (magnified display of the 15th channel at 40-45ns); (c) orientation recognition results; and (d) three-dimensional imaging results.

[0034] Figure 5 This is the three-dimensional imaging process of a horizontal rough crack as described in this invention, wherein (a) simulation results; (b) offset results; (c) orientation recognition results; and (d) three-dimensional imaging results.

[0035] Figure 6 This is a schematic diagram of the uniform circular array described in this invention. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0037] like Figure 1-6 As shown, this invention discloses a three-dimensional imaging method based on directional borehole radar, comprising:

[0038] Based on directional drilling radar, an electromagnetic wave propagation velocity field is established according to the target being detected. The received raw radar data is then offset to obtain the offset result.

[0039] Based on the offset results, the target is imaged in three dimensions after orientation recognition.

[0040] More preferably, the three-dimensional imaging method disclosed in this invention preprocesses the data received by the directional drilling radar during the acquisition of raw radar data by removing DC, denoising, and deconvolution to generate raw radar data.

[0041] More preferably, the three-dimensional imaging method disclosed in this invention performs offset processing on the original radar data by means of diffraction superposition offset.

[0042] More preferably, in the three-dimensional imaging method disclosed in this invention, during the offset processing, the underground area where the directional drilling radar is located is divided into grids, and each grid point is regarded as a diffraction point. The time-depth curve of the diffracted wave from the wavelet source received by the antenna is a hyperbola.

[0043] By recording the corresponding track S on the hyperbola j When the diffracted wave travels, t j The amplitude values ​​are superimposed to achieve the offset processing.

[0044] More preferably, the three-dimensional imaging method disclosed in this invention acquires the travel time t of the diffracted wave. j During the process, the travel time of the diffracted wave is t j Represented as:

[0045]

[0046] Where n is the total number of records involved in the superposition, v is the electromagnetic wave velocity in the surrounding rock, D is the radial distance of the diffraction point, H is the ground depth corresponding to the diffraction point, and the distance between the radar's transmitting and receiving antennas is 2h. j This indicates the depth of the radar's corresponding diffraction point.

[0047] More preferably, the three-dimensional imaging method disclosed in this invention, during the process of azimuth identification of the offset results, obtains offset profiles of the receiving antenna data in the north, west, south and east directions on the UCA based on the offset results;

[0048] Based on the offset profile, the orientation of the diffraction point is identified using the DOA method.

[0049] More preferably, the three-dimensional imaging method disclosed in this invention, during the three-dimensional imaging process, obtains the azimuth angle through the DOA method for orientation identification, determines the amplitude of the imaging point based on the offset result, and performs three-dimensional imaging of the detection target.

[0050] Further preferably, in the three-dimensional imaging method disclosed in this invention, the amplitude of the imaging point is represented as follows during the process of acquiring the amplitude of the imaging point:

[0051] M(D, H, θ(D, H)) = (A N (D, H) + A W (D, H) + A S (D, H) + A E (D, H) / 4

[0052] Among them, A N (D, H), A W (D, H), A S (D, H) and A E (D, H) represent the offset profiles of the received antenna data in the north, west, south, and east directions on the UCA, respectively, and θ(D, H) is the azimuth angle.

[0053] This invention discloses a three-dimensional imaging system based on directional borehole radar, comprising:

[0054] The data acquisition module is used to acquire raw radar data;

[0055] The offset module is used to establish an electromagnetic wave propagation velocity field based on the target of the directional drilling radar, perform offset processing on the original radar data, and obtain the offset result.

[0056] The 3D imaging module is used to perform 3D imaging of the target based on the offset results and after orientation recognition of the offset results.

[0057] More preferably, the data acquisition module of the three-dimensional imaging system disclosed in this invention is also used to preprocess the data received by the directional drilling radar by removing DC, denoising, and deconvolution to generate raw radar data.

[0058] Example 1: This invention provides a three-dimensional imaging technology based on directional borehole radar to identify the three-dimensional spatial distribution of abnormal geological structures such as cracks, cavities, and veins around boreholes, wells, and pipelines. The specific process includes the following:

[0059] 1. The method proposed in this invention is a three-dimensional imaging method that first performs offset and then performs orientation recognition. The process of this method is as follows:

[0060] (1) Data preprocessing mainly includes DC removal, noise reduction, deconvolution and other processing steps;

[0061] (2) Establish the electromagnetic wave propagation velocity field and perform offset processing on the raw radar data received by each antenna;

[0062] (3) Perform orientation identification on the offset results;

[0063] (4) Three-dimensional imaging is carried out based on the orientation information obtained by the DOA method and the radial distance and depth information obtained by the offset.

[0064] The advantage of this method is that the offset can correct the diffracted waves and suppress some interfering waves, making it easier to separate the waveforms generated by different targets. Furthermore, the entire imaging process only requires one offset, resulting in faster computation.

[0065] 2. Offset processing:

[0066] like Figure 2 As shown, the migration method chosen in this invention is diffraction superposition migration, which is a method based on ray theory. According to Huygens' principle, each reflection point of a geological body can be considered as a wavelet source, and the diffracted waves generated by these wavelet sources can be received by a receiving antenna. When applying diffraction superposition migration, the subsurface is divided into a grid, and each grid point is regarded as a diffraction point, see... Figure 2 (a) shows that the time-depth curve of the diffracted wave from the wavelet source received by the antenna is hyperbolic, as illustrated in (a). Figure 2 (b) In the hyperbola, the radial distance of the diffraction point P is D, the corresponding depth is H, the distance between the transmitting and receiving antennas is 2h, and the corresponding arbitrary recording channel S on the hyperbola is... j (corresponding depth is H) j The travel time of the diffracted wave is:

[0067]

[0068] In the formula, j = 1, 2, ..., n, where n is the total number of records participating in the superposition, and v is the electromagnetic wave velocity in the surrounding rock. Each record S... j Up t j The amplitude values ​​at each moment are summed up to obtain the total amplitude value at point P:

[0069]

[0070] At the reflecting interface or diffraction point, due to the amplitude value S of each recording channel... j (t j When the amplitude of the superimposed signal is close to that of the in-phase signal, the amplitude of the superimposed signal increases; conversely, in areas without a reflecting interface or diffraction point, the amplitude S of each recording track decreases. j (t j The non-in-phase waves partially cancel each other out, resulting in a relatively smaller total amplitude. This achieves automatic repositioning of reflected and diffracted waves while suppressing interference waves. By offsetting the data from each receiving antenna, A can be obtained. N (D, H), A W (D, H), A S (D, H) and A E (D, H) represent the offset profiles of the received antenna data in the north, west, south, and east directions on the UCA antenna, respectively.

[0071] 3. DOA estimation based on migration results:

[0072] This invention sets a threshold for the offset result A(D, H). Values ​​exceeding this threshold are considered to indicate the presence of a target, corresponding to a reflecting interface or diffraction point. As previously discussed, the offset result at the diffraction point is formed by superimposing signals from the diffraction hyperbola. These signals are nearly coherent, therefore the amplitude of the superimposed signal is a constant multiple of the amplitude of the unsuperimposed signal. Furthermore, due to in-phase superposition, the arrival time of the superimposed signal remains unchanged. This applies to receiving antennas on UCA. The azimuth obtained by superimposing the signals is equivalent to the azimuth of any recorded channel signal on the hyperbola. Therefore, the offset data can be used for DOA estimation.

[0073] Using A N (D, H), A W (D, H), A S (D, H) and A E (D, H) is used to identify the azimuth angle θ(D, H) using the MUSIC algorithm. Each D and H location corresponds to an azimuth value θ(D, H).

[0074] Suppose there are D far-field narrowband signals incident on the antenna array:

[0075]

[0076] Among them, u i (t) is the amplitude of the i-th signal, w0 is the angular frequency of the received signal, and j is the imaginary unit. When the array elements are isotropic and the effects of antenna mutual coupling are not considered, the signal received by the l-th element of the array can be expressed as:

[0077]

[0078] Where, n l (t) represents the noise of the l-th array element at time t, τ li This represents the time delay relative to the reference element when the i-th signal arrives at the l-th array element. Formula (6) can be written in vector form as:

[0079] X(t)=AS(t)+N(t) (7)

[0080] Where A=[a1(w0),L,a D [w0] is an array manifold. It is the steering vector of the i-th signal source, S(t)=[s1(t),L,s D (t)] T It is the signal source matrix, N(t)=[n1(t),L,n M (t)] TThis is the noise matrix, and the [·] here... T This represents the transpose. For a uniform circular matrix, with the center of the circle as the reference point, τ li It can be represented as

[0081]

[0082] Where r is the radius of the circular array, v is the propagation speed, and θ i It is the azimuth angle of the incident signal. It is the incident signal elevation angle, see Figure 6 Since this invention only estimates the azimuth angle, the elevation angle... It can be set to 0. At this point, the core issue is to determine the azimuth angle θ based on the received signal X(t). i .

[0083] Assuming N(t) is Gaussian white noise, the covariance matrix of the received signal X(t) can be expressed as:

[0084] R = E[XX] H ] = AE[SS H A H +E[NN H ] = AR S A H +σ 2 I (9)

[0085] Among them, R S It is the signal covariance matrix, σ 2 It's noise power, [·] H This represents the conjugate transpose. Eigendecomposition of R yields:

[0086] R = U S Σ S U S H +U N Σ N U N H (10)

[0087] Among them, U S It is the subspace spanned by the eigenvectors corresponding to the large eigenvalues, i.e., the signal subspace, while U N The signal subspace is the subspace spanned by the eigenvectors corresponding to the smaller eigenvalues, i.e., the noise subspace. Ideally, the signal subspace and noise subspace in the data space are orthogonal to each other; that is, the steering vector in the signal subspace is also orthogonal to the noise subspace, satisfying:

[0088] a H (θ)U N =0 (11)

[0089] For real-world data of finite length L, the maximum likelihood estimate of the data covariance matrix is:

[0090]

[0091] Similarly to By performing eigenvalue decomposition, the noise subspace vector matrix can be obtained. Due to the presence of noise, formula (11) is not entirely valid. In practice, the azimuth angle is obtained through a minimum optimization search, i.e.

[0092]

[0093] 4. 3D imaging:

[0094] Through the aforementioned offset processing and orientation recognition, this invention can obtain the target's azimuth, radial distance, and depth information. Let a three-dimensional imaging dataset be...

[0095] M(D, H, θ(D, H)) = (A N (D, H) + A W (D, H) + A S (D, H) + A E (D,H)) / 4, (13)

[0096] The spatial location of the imaging point is determined based on D, H, and θ, and the amplitude of the imaging point is determined based on the M value, ultimately yielding the three-dimensional imaging result.

[0097] (1) The data processing effect when the target is a smooth crack, such as Figure 3 As shown,

[0098] (2) The data processing effect when the target is a rough crack, such as Figure 4 As shown.

[0099] like Figure 5 As shown. During borehole radar detection, when the crack dip angle is horizontal or near-horizontal, it is difficult to detect the target shape because it does not meet the reflection conditions. With directional borehole radar, the positional information of diffraction points on the rough surface of the crack is used to further reconstruct the shape of cracks with unfavorable dip angles.

[0100] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0101] The three-dimensional imaging technology designed in this invention first performs offset imaging and then performs orientation recognition. By utilizing the offset imaging's ability to correct diffraction waves and suppress interference waves, it improves the recognition effect and processing speed. Furthermore, it also demonstrates better recognition and detection capabilities for horizontal cracks (near 0 tilt angle) that are typically undetectable due to their failure to meet reflection conditions.

[0102] In the description of this invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0103] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A three-dimensional imaging method based on directional borehole radar, characterized in that, include: Based on directional drilling radar, an electromagnetic wave propagation velocity field is established according to the target being detected. The received raw radar data is then offset to obtain the offset result. Based on the offset results, the target is imaged in three dimensions after orientation recognition is performed on the offset results. In the process of acquiring raw radar data, the data received by the directional drilling radar is preprocessed by removing DC, denoising, and deconvolution to generate the raw radar data. In the process of offsetting the original radar data, the original radar data is offset by a diffraction superposition offset method. During the process of azimuth identification of the offset results, offset profiles of the receiving antenna data in the north, west, south and east directions on the UCA are obtained based on the offset results. Based on the offset profile, the orientation of the diffraction point is identified using the DOA method.

2. The three-dimensional imaging method based on directional borehole radar according to claim 1, characterized in that: During the offset processing, the underground area where the directional drilling radar is located is divided into grids, and each grid point is regarded as a diffraction point. The time-depth curve of the sub-wave source diffraction wave received by the antenna is a hyperbola. By recording the corresponding paths on the hyperbola When the diffraction wave travels The amplitude values ​​are superimposed to achieve the offset processing.

3. The three-dimensional imaging method based on directional borehole radar according to claim 1, characterized in that: When obtaining the travel of diffraction waves During the process, the diffracted wave travels Represented as: Where j = 1, 2, ..., n, n is the total number of records involved in the superposition, v is the electromagnetic wave velocity in the surrounding rock, D is the radial distance of the diffraction point, H is the ground depth corresponding to the diffraction point, and the distance between the radar's transmitting and receiving antennas is 2h. This indicates the depth of the radar's corresponding diffraction point.

4. The three-dimensional imaging method based on directional borehole radar according to claim 1, characterized in that: During the three-dimensional imaging process, the azimuth angle is obtained by azimuth identification through the DOA method, and the magnitude of the imaging point is determined based on the offset result to perform three-dimensional imaging of the target.

5. The three-dimensional imaging method based on directional borehole radar according to claim 4, characterized in that: In the process of acquiring the amplitude of the imaging point, the amplitude of the imaging point is represented as follows: in, , , and These are the offset profiles of the received antenna data in the north, west, south, and east directions on the UCA, respectively. This is the azimuth angle.

6. A three-dimensional imaging system based on directional borehole radar, characterized in that, include: The data acquisition module, in the process of acquiring raw radar data, preprocesses the data received by the directional drilling radar by DC removal, noise reduction, and deconvolution to generate the raw radar data; used to acquire raw radar data; The offset module performs offset processing on the original radar data by using a diffraction superposition offset method. This is used to establish an electromagnetic wave propagation velocity field based on the detection target using directional drilling radar, and to perform offset processing on the original radar data to obtain the offset result. A three-dimensional imaging module is used to perform three-dimensional imaging of the detection target based on the offset result and after performing orientation recognition on the offset result; During the process of azimuth identification of the offset results, offset profiles of the receiving antenna data in the north, west, south and east directions on the UCA are obtained based on the offset results. Based on the offset profile, the orientation of the diffraction point is identified using the DOA method.

Images