CN107191181B - Well periphery interface detection method based on electromagnetic scattering - Google Patents
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Abstract
The invention provides a method for detecting a well periphery interface based on electromagnetic scattering, which comprises the following steps: a scattered field signal is extracted by using a symmetrical antenna structure, and a well periphery interface is represented by solving a difference signal; determining the relation between the edge detection capability and the emission frequency, the source distance and the inclination angle, and selecting appropriate parameters to achieve the optimal detection effect; and detecting by adopting a single-transmitting four-receiving antenna structure, and establishing a cross map to identify the relative position of an interface. The method for detecting the well-periphery interface fully considers the influence of the electromagnetic scattering field on the detection effect of the well-periphery interface, utilizes the amplitude difference of the symmetrical receiving antennas to represent electromagnetic scattering signals, realizes the quick identification of the well-periphery interface, utilizes the combination of the two groups of antenna structures to complete the determination of the relative position of the well-periphery interface, and has simple identification method and obvious effect.
Description
Technical Field
The invention relates to the technical field of electromagnetic wave logging, in particular to a method for detecting a well peripheral interface based on electromagnetic scattering.
Background
Geosteering drilling is an important means for efficient development of oil and gas, and early exploration and prediction of a well boundary are the key points of the geosteering drilling. The transmitting and receiving antennas of the traditional electromagnetic wave logging instrument are coaxially arranged, the detection range is only 2-3 m, and the traditional electromagnetic wave logging instrument does not have azimuth detection capability. The azimuth electromagnetic wave instrument adopts a coaxial/inclined/coplanar antenna on the basis of multi-frequency and multi-source distances to realize measurement of each component of an electromagnetic field, and the boundary detection range can reach 5-6 m. At present, electromagnetic wave logging generally distinguishes strata according to the geometric relationship of transmitting and receiving antennas, namely, in order to increase the detection depth, the working frequency needs to be reduced, the source distance of the antennas needs to be increased, so that an instrument with the capability of detecting a boundary far is overlong, the signal synchronization is difficult, and the requirements on the construction process and the field application are high.
Electromagnetic scattering occurs when electromagnetic waves meet a well-periphery interface in the propagation process, but the electromagnetic scattering information of the well-periphery interface is less taken into consideration at the present stage, and the macroscopic electrical property of a medium is usually depicted by utilizing the phase change or amplitude attenuation of a received signal by adopting electromagnetic wave logging, so that the remote detection capability of the well-periphery interface is weakened.
The well measurement signal is the superposition of a primary field and a scattering field, and the scattering signal is much weaker than the primary field, so that the research on how to optimize the antenna structure and parameters suppresses the primary field of the stratum background of the well bore, improves the scattering signal-to-noise ratio of the abnormal body, and has important significance for the detection of the well-periphery interface.
Disclosure of Invention
The invention provides a well-periphery interface detection method based on electromagnetic scattering, aiming at the defects of insufficient utilization of electromagnetic scattering signals and the like in the existing well-periphery interface detection method.
The technical solution adopted by the invention is as follows:
a method for detecting a well-periphery interface based on electromagnetic scattering comprises the following steps:
(1) method for establishing stratum model and extracting interface information
The antenna structure is composed of a transmitting antenna and two groups of receiving antennas, wherein one group of receiving antennas are obliquely arranged, each group of receiving antennas comprises two receiving antennas, and the two receiving antennas are symmetrically distributed on two sides of the transmitting antenna and have equal distances to the transmitting antenna; solving the signal difference strength of two groups of receiving antennas, and taking the signal difference strength as an identification mark of a well-periphery interface;
(2) optimizing antenna parameters
According to the method for detecting the interface by calculating the signal difference of the receiving antennas in the step (1), the influence of different factors on the edge detection capability of the method is researched, wherein the factors comprise the transmitting frequency, the source distance and the inclination angle; analyzing numerical simulation results under different factors, and finding out optimal parameters for detecting the well-periphery interface;
(3) simulating according to the optimal parameters of the well-periphery interface detection obtained in the step (2), carrying out numerical simulation aiming at stratum models under different inclination angles and distances, and establishing an intersection graph of a coaxial antenna and an inclined antenna, wherein the abscissa is the signal difference strength of the coaxial antenna, and the ordinate is the signal difference strength of the inclined antenna; and determining the relative position of the interface according to the position of the meeting data drop point.
Preferably, in step (1): the transmitting frequency of the transmitting antenna is 400kHz, the source distance from the transmitting antenna to the inclined receiving antenna is 1m, the stratum model comprises a medium I and a medium II, the resistivity of the medium I is 100 omega · m, and the resistivity of the medium II is 10 omega · m.
Preferably, in step (1), the method for determining the difference strength of the receiving antenna signal is as follows: the vector potential method is utilized to carry out the study of the forward modeling algorithm of the one-dimensional layered medium, the coil is equivalent to a magnetic dipole source, the interface is at the coordinate origin, and the spatial distribution of the electromagnetic field can be regarded as the superposition of the fields generated by a horizontal magnetic dipole source and a vertical magnetic dipole source independently;
in the formula (1), FiIs the vector potential of the i-th layer,
the component of the horizontal magnetic dipole in the ith layer in the vertical direction,
the component of the perpendicular magnetic dipole in the ith layer in the perpendicular direction,
is the component of the horizontal magnetic dipole in the i-th layer in the horizontal direction, ex、ezAre all unit vectors;
and (3) solving the following conditions according to the relation between the induced electromotive force and the vector potential:
in the formula (2), E is an induced electromotive force,
is a Hamiltonian.
Preferably, the frequency optimization method in the step (2) comprises the following steps: the single-transmitting and double-receiving antenna structure with the source distance of 1m is used, the antenna structure is vertical to an interface, and the edge detection characteristic of an antenna system under multiple frequencies is discussed aiming at an isotropic stratum; the resistivity of the medium I, II is 100 omega m and 10 omega m respectively, the power supply frequency is 200kHz, 400kHz, 800kHz and 1MHz respectively, the difference signals are extracted by adopting the method in the step (1), the detection characteristics under different frequency conditions are analyzed, the relation between the edge detection capability and the emission frequency is determined, and therefore the optimal detection frequency is found.
Preferably, the source distance optimization method in the step (2) comprises the following steps: selecting 0.5m, 1m, 1.2m and 2m from the source distances of the single-transmitting and double-receiving antenna structure respectively, enabling the antenna structure to be vertical to an interface, and discussing the edge detection characteristics of the antenna system under different source distances aiming at the isotropic stratum; the resistivity of the medium I, II is 100 omega m and 10 omega m respectively, and the power supply frequency selects 800kHz to transmit signals; and (2) extracting the difference signals by adopting the method in the step (1), analyzing the detection characteristics under the condition of different source distances, and determining the relation between the edge detection capability and the source distance so as to find out the optimal source distance.
Preferably, the inclination angle optimization method in the step (2) comprises the following steps: the method comprises the following steps of using a single-transmitting double-receiving antenna structure with a source distance of 1m, changing an included angle between the antenna structure and an interface, and discussing the edge detection characteristics of an antenna system under different dip angles aiming at an isotropic stratum; the resistivity of the medium I, II is 100 omega m and 10 omega m respectively, 800kHz emission signals are selected as power supply frequency, difference signals are extracted by adopting the method in the step (1), detection characteristics under different inclination angles are analyzed, the relation between the edge detection capability and the inclination angle is determined, and therefore the optimal inclination angle is found.
Preferably, in step (3): and connecting the difference signal data points of the same depth point under different inclination angles, and dividing the intersection map into a plurality of regions, wherein each region represents different positions of the well-periphery interface.
The beneficial technical effects of the invention are as follows:
the method for detecting the well-periphery interface fully considers the influence of the electromagnetic scattering field on the detection effect of the well-periphery interface, utilizes the amplitude difference of the symmetrical receiving antennas to represent electromagnetic scattering signals, realizes the quick identification of the well-periphery interface, and utilizes the combination of the two groups of antenna structures to complete the determination of the relative position of the well-periphery interface. The method for identifying the well-periphery interface by utilizing the electromagnetic scattering is simple and has obvious effect. Compared with the prior art, the method for detecting the boundary of the well periphery interface has the advantages that the measurement of the scattered field signals is completed by utilizing the symmetrical antenna structure, and the scattered waves have better capability of describing the details of the stratum, so that the method for detecting the boundary of the well periphery interface has simple identification effect, can accurately judge the position of the interface, and has a detection range which is obviously larger than that of the traditional boundary detection method under the condition of the same coil distance.
Drawings
The invention will be further described with reference to the following detailed description and drawings:
FIG. 1 is a schematic diagram of a single-transmitting and double-receiving coaxial antenna structure and a stratum model established by the structure (D is a boundary detection distance, L is a distance from a transmitting antenna to the front end of an instrument, D is a front detection distance, and R is a receiving antenna in the diagram)1And R2The distance from the transmitting antenna T is 0.8 m; receiving antenna R3And R4Distance of 1m from the transmitting antenna T);
FIG. 2 illustrates amplitude and phase signals of two receiving antennas according to an embodiment of the present invention;
FIG. 3 is a plot of amplitude difference and phase difference of signals according to an embodiment of the present invention;
FIG. 4 is a graph of difference signal versus frequency for an embodiment of the present invention;
FIG. 5 is a graph of difference signal versus source distance for an embodiment of the present invention;
FIG. 6 is a graph of a difference signal versus tilt angle according to an embodiment of the present invention;
FIG. 7 is a cross-sectional view of an identification interface location in accordance with an embodiment of the present invention.
Detailed Description
The invention aims to construct a method for extracting electromagnetic scattering signals of a well periphery interface and increasing a detection range. The invention adopts the design of a symmetrical antenna structure, extracts scattering signals of the abnormal body around the well, and obtains formation interface information by utilizing the amplitude difference of receiving antenna signals according to the signal response characteristics under different transmitting frequencies, source distances and inclination angles. The invention is used for detecting the well-periphery interface, the scattered field is measured according to the symmetrically-received antenna structure provided by the invention, and the boundary detection is completed by analyzing the scattered field. The detection method can obtain the interface scattering signal, and the scattering signal can better depict the well periphery interface, so the method has more definite physical significance and better edge detection effect. Compared with the traditional detection method which ignores the scattered signals, the detection method solves the problem of utilization of the scattered signals to a certain extent, and is more effective. The details will be described below.
A method for detecting a well-periphery interface based on electromagnetic scattering specifically comprises the following steps:
establishing stratum model and interface information extracting mode
The invention adopts a single-transmitting and double-receiving coaxial antenna structure, which consists of a transmitting antenna and two groups of receiving antennas, wherein one group of receiving antennas are obliquely arranged, the other group of receiving antennas are arranged in parallel with the transmitting antenna (coaxial antennas), each group of receiving antennas comprises two receiving antennas, and the two receiving antennas are symmetrically distributed on two sides of the transmitting antenna and have equal distance to the transmitting antenna. And (4) calculating the difference value of the two received induced electromotive forces, and using the difference value as an identification mark of the well periphery interface. When the instrument is far away from the ground interface, the signal amplitude and the phase of the two receiving antennas are completely the same; when the instrument is close to the interface of the stratum, the signal difference between the two receiving antennas is increased.
(II) optimizing antenna parameters
According to the method for detecting the interface by calculating the signal difference of the receiving antenna in the step (I), the influence of different factors on the edge detection capability of the method is researched, and the method mainly comprises the transmitting frequency, the source distance and the inclination angle. And finding out the optimal parameters of boundary detection by using numerical simulation as a means.
(III) determining the relative position of the interface
And (4) obtaining stratum boundary models with different inclination angles and distances on the basis of the optimal antenna parameters for detecting the well-periphery interface obtained in the step (two), and establishing an intersection graph of the differential signals of the coaxial antenna and the inclined antenna, wherein the abscissa is the differential signal intensity of the coaxial antenna, and the ordinate is the differential signal intensity of the inclined antenna. Connecting difference signal data points of the same depth point on different inclination angle curves, dividing the intersection map into a plurality of regions, wherein each region represents different positions of the well periphery interface, and determining the relative position of the interface according to the position of the intersection data falling point.
In the step (one), the transmitting frequency of the transmitting antenna is 400kHz, the source distance from the transmitting antenna to the tilted antenna is 1m, the resistivities of the medium I and the medium II are respectively 100 Ω · m and 10 Ω · m, and the method for obtaining the difference signal comprises the following steps:
the vector potential method is utilized to carry out one-dimensional layered medium forward modeling algorithm research, an antenna coil is equivalent to a magnetic dipole source, the interface is at the coordinate origin, and the electromagnetic field spatial distribution can be regarded as the superposition of fields generated by a horizontal magnetic dipole source and a vertical magnetic dipole source independently.
In the formula (1), FiIs the vector potential of the i-th layer,
the component of the horizontal magnetic dipole in the ith layer in the vertical direction,
the component of the perpendicular magnetic dipole in the ith layer in the perpendicular direction,
is the component of the horizontal magnetic dipole in the i-th layer in the horizontal direction, ex、ezAre all unit vectors;
and (3) solving the following conditions according to the relation between the induced electromotive force and the vector potential:
in the above method for optimizing antenna parameters, the frequency optimization method is as follows: the single-transmitting double-receiving antenna structure with the source distance from the transmitting antenna to the inclined antenna being 1m is used, an instrument is perpendicular to an interface, and the edge detection characteristic of the antenna system under multiple frequencies is discussed aiming at the isotropic stratum. The resistivity of the medium I, II was 100. omega. m and 10. omega. m, respectively, and the power supply frequencies were 200kHz, 400kHz, 800kHz, and 1MHz, respectively. And (3) extracting the difference signals by adopting the method in the step (I), analyzing the detection characteristics under different frequency conditions, and determining the relation between the edge detection capability and the emission frequency so as to find out the optimal detection frequency.
In the method for optimizing the antenna parameters, the source distance optimization method comprises the following steps: the source distances (the distances from the transmitting antenna to the inclined antenna) of the single-transmitting double-receiving antenna structure are respectively selected to be 0.5m, 1m, 1.2m and 2m, the instrument is vertical to the interface, and the edge detection characteristic of the antenna system under multiple frequencies is discussed aiming at the isotropic stratum. The resistivity of the medium I, II is 100 Ω · m and 10 Ω · m respectively, and 800kHz transmission signal is selected as the power supply frequency. And (3) extracting the difference signals by adopting the method in the step (I), analyzing the detection characteristics under the condition of different source distances, and determining the relation between the edge detection capability and the source distance so as to find out the optimal source distance.
In the above method for optimizing antenna parameters, the method for optimizing the tilt angle comprises: by using a single-transmitting double-receiving antenna structure with a source distance from a transmitting antenna to an inclined antenna being 1m, the included angle between an instrument and an interface is changed, and the edge detection characteristics of the antenna system under different inclined angles are discussed aiming at the isotropic stratum. The resistivity of the medium I, II is 100 Ω · m and 10 Ω · m respectively, and 800kHz transmission signal is selected as the power supply frequency. And (3) extracting the difference signals by adopting the method in the step (I), analyzing the detection characteristics under different inclination angles, determining the relation between the edge detection capability and the inclination angle, and optimizing the antenna structure.
The relative position of the well-periphery interface is determined by adopting a single-transmitting four-receiving antenna structure: and (3) extracting two groups of difference signals by adopting the method in the step (one) aiming at the isotropic stratum by using a tilted antenna structure with the source distance of 1m and a coaxial antenna structure with the source distance of 0.8 m. And continuously changing the included angle between the instrument and the stratum and simulating, making the simulated coaxial antenna difference signal and the simulated inclined antenna difference signal into a cross map, connecting the difference signal data points of the same depth point on the curve, and determining the relative position of the interface according to the area where the cross data falls.
The invention will be further explained with reference to the drawings.
A method for detecting a well-periphery interface based on electromagnetic scattering comprises the following steps:
step one
Fig. 1 is a schematic diagram of a single-transmitting and double-receiving coaxial antenna structure for performing well boundary detection based on electromagnetic scattering and a stratum model.
As shown in fig. 1, the employed single-transmitting and double-receiving coaxial antenna structure for the well periphery interface comprises: the antenna comprises a transmitting antenna and four receiving antennas, the number of turns of the antenna is 1, one group of receiving antennas and the transmitting antenna are coaxially arranged, the other group of receiving antennas and the transmitting antenna form an included angle of 45 degrees, the receiving antennas are symmetrically distributed on two sides of the transmitting antenna, and the distances from the two receiving antennas to the transmitting antenna in each group are equal. The stratum model adopts an isotropic laminar stratum, and an instrument forms a certain included angle with an interface.
Fig. 2 shows the amplitude and phase signals of the received signal in the receiving antenna of the single-transmitting and double-receiving coaxial antenna structure adopted by the present invention.
As shown in FIG. 2, the frequency of the transmitted signal is 400kHz, the resistivities of medium I and medium II are 100 Ω -m and 10 Ω -m respectively, and the borehole is perpendicular to the formation interface. When the instrument is far away from the stratum interface, the two receiving antennas are mainly influenced by signals transmitted through the stratum, and the amplitude and the phase of the received signals are completely the same; when the instrument is close to the interface of the stratum, the influence of electromagnetic scattering from the interface on the two receiving antennas is gradually enhanced, so that the signal difference is gradually increased.
Fig. 3 is a graph of the amplitude difference and phase difference of the receiving antenna in the antenna structure adopted in the present invention.
As shown in fig. 3, the difference between the original signals of the two receiving antennas in fig. 2 is obtained byAnd identifying the well-periphery interface by using the amplitude difference signal and the phase difference signal. The signal difference of the receiving antennas reaches a peak when the transmitting antenna is near the interface, wherein the signal amplitude difference is about 7 x 10-7V, phase difference is about 4 °; the interface is 9m before the instrument, or 4.3m after the instrument, and the amplitude difference is reduced to 1 × 10-9And V. At present, the signal intensity resolution of foreign instruments is 10nV, and if the number of turns of an antenna is properly increased, the detection range of the method for the interface can reach dozens of meters.
Step two
And under the conditions of the same stratum model and different transmitting frequencies, researching the change rule of the antenna structure on the boundary detection capability. The coil pitch is 1m, the resistivity of the medium I, II is 100 Ω · m and 10 Ω · m, respectively, and the power supply frequency is 200kHz, 400kHz, 800kHz, and 1MHz, respectively. And (3) extracting the difference signals by adopting the method in the step (I), and analyzing the detection characteristics under different frequency conditions, thereby determining the relation between the edge detection capability and the emission frequency. As shown in fig. 4, as the signal frequency increases, the signal difference amplitude of the receiving antenna increases significantly, and the signal change rate also increases significantly, which is beneficial to signal detection, but also causes the detection range to decrease, which is not beneficial to the far detection of the interface. Therefore, the frequency of the transmitted signal should be chosen to be 800 kHz.
And under the conditions of different source distances of the same stratum model, researching the change rule of the antenna structure on the boundary detection capability. The coil distances are respectively selected from 0.5m, 1m, 1.2m and 2m, and the edge detection characteristics of the antenna system under the multi-source distance are discussed respectively aiming at the conditions of a high-resistance stratum and a low-resistance stratum. The resistivity of the medium I, II is 100 Ω · m and 10 Ω · m respectively, and 800kHz transmission signal is selected as the power supply frequency. And (3) extracting the difference signals by adopting the method in the step (I), and analyzing the detection characteristics under the condition of different source distances so as to determine the relationship between the edge detection capability and the source distances. As shown in fig. 5, the peak value of the amplitude difference signal gradually decreases as the source distance increases, but the signal attenuation decreases as the source distance increases, so that the difference of the receiving antenna signals is large when the distance from the interface position is long, and the detection range is enlarged. However, the detection range does not increase in proportion to the source distance, and therefore, the source distance should be selected within a range of 1 m.
And under the conditions of different inclination angles of the same stratum model, researching the change rule of the antenna structure on the boundary detection capability. The coil pitch is 1m, the resistivity of the medium I, II is 100 omega m and 10 omega m respectively, and the power supply frequency selects 800kHz to transmit signals. The included angles of the antenna structure and the stratum are respectively 5 degrees, 15 degrees, 30 degrees, 45 degrees, 60 degrees, 75 degrees and 90 degrees. And (5) extracting the difference signals by adopting the method in the step (I), and analyzing the detection characteristics under different inclination angles, thereby determining the relation between the edge detection capability and the inclination angle. As shown in fig. 6, when the instrument is perpendicular to the formation, the receiving antenna differential signal amplitude is the largest, and as the included angle is reduced, both the signal amplitude and the edge-finding distance (the distance from the formation interface to the transmitting antenna) are significantly reduced. Thus, adding a pair of tilted antennas enhances the measurement of radial signals.
Step three
And (5) simulating according to the optimal parameters of the well-periphery interface detection obtained in the step (II), and establishing a well-periphery interface identification rendezvous graph under different inclination angles by adopting a single-transmitting four-receiving antenna structure. The simulation conditions are that the resistivity of the medium I is 100 omega.m, the resistivity of the medium II is 10 omega.m, the source distance of the inclined antenna is 1m, the source distance of the coaxial antenna is 0.8m, and the transmitting frequency is 800 kHz. In order to obtain the interface position, the induced electromotive forces in the four receiving antennas are measured respectively, and the difference signals in the two groups of receiving coils are obtained to form a cross map, wherein the cross map takes the difference signal intensity of the coaxial antennas as an abscissa and the difference signal intensity of the inclined antennas as an ordinate. When the relative position of the well periphery interface is identified, only the signal difference of the coaxial coil and the inclined coil needs to be measured, and the included angle and the vertical distance between the interface and the antenna structure are determined according to the position of the data falling point of the intersection of the difference signals.
The boundary detection is carried out by using the well-periphery interface detection method, the relative position of the interface can be accurately determined, and the exploration and development efficiency is improved.
The above-mentioned embodiments are merely provided for the convenience of illustration of the present invention, and do not limit the scope of the present invention, and various simple modifications and modifications made by those skilled in the art within the technical scope of the present invention should be included in the above-mentioned claims.
Claims (2)
1. A method for detecting a well-periphery interface based on electromagnetic scattering is characterized by comprising the following steps: the method comprises the following steps:
(1) establishing a stratum model and an interface information extraction mode;
the antenna structure is composed of a transmitting antenna and two groups of receiving antennas, wherein one group of receiving antennas are obliquely arranged, each group of receiving antennas comprises two receiving antennas, and the two receiving antennas are symmetrically distributed on two sides of the transmitting antenna and have equal distances to the transmitting antenna; solving the signal difference strength of two groups of receiving antennas, and taking the signal difference strength as an identification mark of a well-periphery interface; the transmitting frequency of the transmitting antenna is 400kHz, the source distance from the transmitting antenna to the inclined receiving antenna is 1m, the stratum model comprises a medium I and a medium II, the resistivity of the medium I is 100 omega.m, and the resistivity of the medium II is 10 omega.m; the method for obtaining the signal difference strength of the receiving antenna comprises the following steps: the vector potential method is utilized to carry out the study of the forward modeling algorithm of the one-dimensional layered medium, the coil is equivalent to a magnetic dipole source, the interface is at the coordinate origin, and the spatial distribution of the electromagnetic field can be regarded as the superposition of the fields generated by a horizontal magnetic dipole source and a vertical magnetic dipole source independently;
in the formula (1), FiIs the vector potential of the i-th layer,
the component of the horizontal magnetic dipole in the ith layer in the vertical direction,
the component of the perpendicular magnetic dipole in the ith layer in the perpendicular direction,
is the component of the horizontal magnetic dipole in the i-th layer in the horizontal direction, ex、ezAre all unit vectors;
and (3) solving the following conditions according to the relation between the induced electromotive force and the vector potential:
in the formula (2), E is induced electromotive force and ^ is a Hamiltonian;
(2) optimizing antenna parameters;
according to the method for detecting the interface by calculating the signal difference of the receiving antennas in the step (1), the influence of different factors on the edge detection capability of the method is researched, wherein the factors comprise the transmitting frequency, the source distance and the inclination angle; analyzing numerical simulation results under different factors, and finding out optimal parameters for detecting the well-periphery interface;
the frequency optimization method comprises the following steps: the single-transmitting and double-receiving antenna structure with the source distance of 1m is used, the antenna structure is vertical to an interface, and the edge detection characteristic of an antenna system under multiple frequencies is discussed aiming at an isotropic stratum; the resistivity of the medium I, II is respectively 100 omega m and 10 omega m, the power supply frequency is respectively 200kHz, 400kHz, 800kHz and 1MHz, the difference signal is extracted by adopting the method in the step (1), the detection characteristics under different frequency conditions are analyzed, the relation between the edge detection capability and the emission frequency is determined, and therefore the optimal detection frequency is found;
the optimization method of the source distance comprises the following steps: selecting 0.5m, 1m, 1.2m and 2m from the source distances of the single-transmitting and double-receiving antenna structure respectively, enabling the antenna structure to be vertical to an interface, and discussing the edge detection characteristics of the antenna system under different source distances aiming at the isotropic stratum; the resistivity of the medium I, II is 100 omega m and 10 omega m respectively, and the power supply frequency selects 800kHz to transmit signals; extracting difference signals by adopting the method in the step (1), analyzing detection characteristics under different source distances, and determining the relation between the edge detection capability and the source distance so as to find out the optimal source distance;
the optimization method of the inclination angle comprises the following steps: the method comprises the following steps of using a single-transmitting double-receiving antenna structure with a source distance of 1m, changing an included angle between the antenna structure and an interface, and discussing the edge detection characteristics of an antenna system under different dip angles aiming at an isotropic stratum; the resistivity of the medium I, II is 100 omega m and 10 omega m respectively, 800kHz emission signals are selected as power supply frequency, difference signals are extracted by adopting the method in the step (1), the detection characteristics under different inclination angles are analyzed, the relation between the edge detection capability and the inclination angle is determined, and therefore the optimal inclination angle is found;
(3) simulating according to the optimal parameters of the well-periphery interface detection obtained in the step (2), carrying out numerical simulation aiming at stratum models under different inclination angles and distances, and establishing an intersection graph of a coaxial antenna and an inclined antenna, wherein the abscissa is the signal difference strength of the coaxial antenna, and the ordinate is the signal difference strength of the inclined antenna; and determining the relative position of the interface according to the position of the meeting data drop point.
2. The method for detecting the well-peripheral interface based on the electromagnetic scattering according to the claim 1, characterized in that in the step (3): and connecting the difference signal data points of the same depth point under different inclination angles, and dividing the intersection map into a plurality of regions, wherein each region represents different positions of the well-periphery interface.
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| CN201710371300.4A CN107191181B (en) | 2017-05-24 | 2017-05-24 | Well periphery interface detection method based on electromagnetic scattering |
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| CN107742015B (en) * | 2017-09-30 | 2021-04-23 | 中南大学 | DC induced polarization method three-dimensional numerical simulation method based on arbitrary dipole-dipole device |
| CN108005646B (en) * | 2017-12-14 | 2021-03-02 | 中国石油大学(华东) | Stratum anisotropic resistivity extraction method based on electromagnetic wave logging while drilling data |
| CN109057781B (en) * | 2018-07-26 | 2022-05-10 | 中国石油天然气集团有限公司 | Multi-component multi-detection-depth electromagnetic wave antenna system while drilling and measurement method |
| CN109209354B (en) * | 2018-10-15 | 2019-11-22 | 中国石油大学(华东) | A kind of remote detection method in time-domain transient electrical magnetic wave well logging boundary |
| CN113156526B (en) * | 2021-04-26 | 2023-06-27 | 中国地质科学院地球物理地球化学勘查研究所 | Full-region multi-source electromagnetic sounding method and multi-field source multi-component data joint inversion technology |
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