A equiangular spiral antenna for seismic logging

Abstract

The present invention proposes an equiangular spiral antenna for seismic logging, comprising a dielectric substrate and a metal patch located on the upper surface of the dielectric substrate. The metal patch constitutes the two arms of the novel equiangular spiral antenna, and the two arms are centrosymmetrical around the center point of the dielectric substrate, and their shapes and boundaries are composed of spiral lines and circular arcs. Unlike traditional equiangular spiral antennas, which usually have feeding points at the inner ends of the two arms, the feeding points of the present equiangular spiral antenna are at the outer ends of the two arms. Both arms of the antenna are above the dielectric substrate and are centrosymmetrically distributed at the center of the circular dielectric substrate. The novel equiangular spiral antenna proposed in the present invention utilizes the characteristics of the wider bandwidth of the equiangular spiral antenna and is made of flexible materials to better fit the well wall environment during logging, thereby realizing the reception of seismic signals and having a high signal-to-noise ratio, and has broad application prospects.

Description

Technical Field

[0001] The present invention relates to the field of radio theory and technology, and in particular to an equiangular spiral antenna for seismic logging and a preparation method thereof. Background Art

[0002] Seismic electrical logging is a geophysical technique that uses the coupling effect between seismic waves and electric fields to study underground geological structures and fluid properties. First proposed in the 1960s, it has continued to develop with advances in geophysical theory, measurement techniques, and computer simulation technology. The basic principle of seismic electrical logging is that when elastic waves pass through a porous medium, the pore fluid and the solid matrix undergo relative displacement, generating oscillations and displacement currents in the double electrical layer between the solid and liquid phases, thereby generating seismic electrical signals. These signals are related to the acoustic and electrical properties of the medium and can be used to estimate various properties, such as porosity, permeability, and fluid saturation.

[0003] Research on seismic electrical logging has mainly focused on two aspects: theory and experiment. On the theoretical side, researchers have studied and improved the mathematical models that describe the coupling process between seismic waves and electric fields. They have also developed numerical simulation methods to analyze the response characteristics of different geological media and parameters. On the experimental side, indoor experiments and field tests have been carried out to verify and optimize seismic electrical logging technology and examine its feasibility and effectiveness under different geological conditions. The current status of seismic electrical logging research shows that it has the potential to become an important supplement to traditional geophysical technologies such as seismic, electromagnetic, and well logging. However, the technology still faces challenges, such as the need to further improve the signal-to-noise ratio, investigation depth, and spatial resolution of measurements.

[0004] One of the key components of seismic logging is the antenna used to detect seismic signals. These antennas must exhibit high sensitivity and a high signal-to-noise ratio. Current antennas used for seismic logging have limitations in sensitivity and signal-to-noise ratio, potentially compromising the accuracy and reliability of measurement results. Therefore, a new antenna design is needed to improve the performance of seismic logging. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an equiangular spiral antenna for receiving seismoelectric signals in seismoelectric logging.

[0006] The technical solution adopted by the present invention to solve the above technical problems is a equiangular spiral antenna, comprising a circular dielectric substrate and two metal patches of the same shape located on the upper surface of the dielectric substrate, wherein the two metal patches are centrally symmetrical about the center point of the dielectric substrate to form two arms of the antenna;

[0007] The shape of the metal patch is defined by the area enclosed by two equiangular spirals and the arc of a quarter-circular dielectric substrate. The center point of the dielectric substrate serves as the starting point for the equiangular spirals in the metal patch, and the quarter-circular arc 6 aligns with a quarter-circular arc of a concentric circle whose diameter is slightly smaller than the outer contour of the circular dielectric substrate.

[0008] The feeding points of the equiangular helical antenna are arranged at the outer ends of the two arms of the antenna, and the feeding points at the outer ends of the two arms are connected to the receiving circuit.

[0009] The beneficial effects of the present invention are: while achieving a good signal-to-noise ratio and directivity, it has a wider bandwidth, ensuring that weak seismoelectric signals can be well received. In practical applications, the diameter and spiral angle of the antenna can be flexibly selected according to needs. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 Schematic diagram of the three-dimensional structure of the equiangular helical antenna in the embodiment;

[0011] Figure 2 A schematic top view of a conformal helical antenna in an embodiment;

[0012] Figure 3 The helical line equation and endpoint diagram of the equiangular helical antenna in the embodiment; DETAILED DESCRIPTION

[0013] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings, but the protection scope of the present invention is not limited to the following.

[0014] like Figure 1 The equiangular helical antenna shown in the figure consists of a dielectric substrate 1 and metal patches 2 and 3 located on its upper surface. Dielectric substrate 1 is a perfect circle with a radius of 53 mm and a thickness of 0.25 mm. Made of polytetrafluoroethylene (PTFE), it has a relative dielectric constant of 2.65. The substrate is flexible enough to conform to the wellbore environment.

[0015] The two arms of the antenna are composed of metal patches 2 and 3.

[0016] like Figure 2 As shown, the metal patch 2 is shaped like a portion surrounded by two equiangular spirals 4 and 5 and a quarter-circular dielectric substrate arc 6. The center point of the dielectric substrate serves as the starting point for the equiangular spirals in the metal patch, and the final quarter-circle arc 6 aligns with a quarter-circle arc of a concentric circle whose diameter is slightly smaller than the outer contour of the circular dielectric substrate.

[0017] The shape of metal patch 3 is the same as that of metal patch 2, which is rotated 180 degrees around the center of the dielectric substrate with metal patch 2 as the reference. Therefore, metal patch 2 and metal patch 3 are symmetrically distributed at the center of the circular dielectric substrate 1.

[0018] Metal patches 2 and 3 are etched out of the metal portion of the dielectric substrate, thereby completing the manufacture of the two arms of the antenna.

[0019] like Figure 3 As shown, the center point of the dielectric substrate is the origin of the two-dimensional rectangular coordinate system. The horizontal direction of the plane formed by the dielectric substrate surface is the x-axis, the vertical direction is the y-axis, and the angle formed with the x-axis on the two-dimensional rectangular coordinate plane is θ. The expression of the equiangular helix 4 is: x = 0.831 × e 0.2185θ ×cos(θ),y=0.831×e 0.2185θ ×sin(θ),θ∈[0,6π]. Specifically, when θ=6π, it is the outer endpoint, and the expression of the equiangular helix 4 is: x=0.831×e 0.2185θ ×cos(θ-π / 2),y=0.831×e 0.2185θ ×sin(θ-π / 2).

[0020] Different from the traditional antenna, the inner end points of the two arms are used as feeding points, such as Figure 2 、 Figure 3 As shown, the applicant has positioned the feed point of the equiangular helical antenna at the outer endpoints 7 and 8 of the antenna's two arms, achieving optimal signal reception at this location. The feed point is connected to a receiving circuit, which includes amplification and filtering circuits for processing the seismoelectric signals received by the antenna.

[0021] Parameters such as the spiral angle and number of periods of the helical line of the equiangular spiral antenna can be designed and adjusted according to actual conditions. In this specific embodiment, the central operating frequency f0 of the novel periodic leaky-wave antenna is 25 kHz, and its operating frequency can be appropriately adjusted by changing the size and shape of the helical line of the antenna.

[0022] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention's description and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A equiangular spiral receiving antenna for seismic logging, characterized in that: The antenna comprises a circular dielectric substrate and two metal patches located on the upper surface of the dielectric substrate. The two metal patches of the same shape are centrally symmetrical with respect to the center point of the dielectric substrate to form two arms of the antenna. The substrate has the flexibility to conform to the well wall environment. The shape of the metal patch is determined by the portion enclosed by two equiangular spirals and the arc of a quarter-circular dielectric substrate. The center point of the dielectric substrate is used as the starting point of the equiangular spiral of the metal patch, and the quarter-circular arc is aligned with the quarter-circular arc of a concentric circle whose diameter is smaller than the outer contour of the circular dielectric substrate. The feeding points of the equiangular spiral antenna are set at the outer ends of the two arms of the antenna to ensure the best signal reception effect of the antenna; the feeding points at the outer ends of the two arms are connected to the receiving circuit; the receiving circuit includes an amplification and filtering circuit for processing the seismoelectric signals received by the antenna.

2. The equiangular helical receiving antenna according to claim 1, wherein: The center point of the circular dielectric substrate is taken as the origin of the two-dimensional rectangular coordinate system. The horizontal direction of the plane formed by the dielectric substrate surface is the x-axis, the vertical direction is the y-axis, and the angle formed with the x-axis on the two-dimensional rectangular coordinate plane is θ. The expression of the equiangular helix is: x = 0.831 × e 0.2185θ ×cos(θ),y=0.831×e 0.2185θ ×sin(θ),θ∈[0,6π].

3. The equiangular spiral receiving antenna according to claim 1, characterized in that: The circular dielectric substrate has a radius of 53 mm and a thickness of 0.25 mm. The material is polytetrafluoroethylene and the relative dielectric constant is 2.65.

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