A signal excitation device for TE11 mode of microwave communication while drilling

Abstract

The present invention discloses a signal excitation device for the TE11 mode of microwave communication while drilling downhole, which includes a communication relay metal mount (1) and an E-type excitation mechanism (2). The E-type excitation mechanism (2) includes a bottom metal column (5) and multiple connecting metal columns. The bottom metal column (5) is connected to the communication relay metal mount (1) through the connecting metal columns and is parallel to the surface of the communication relay metal mount (1). The communication signal line (4) inside the communication relay metal mount (1) is connected to the bottom metal column (5) through one of the connecting metal columns. Compared with the traditional excitation structure, the present invention has a smaller cross-sectional area, thereby reducing air resistance. In addition, the present invention has three fulcrums with the waveguide wall, improving mechanical strength and being more suitable for application in the downhole communication system while drilling in gas drilling.

Description

Technical Field

[0001] The present invention relates to the technical field of microwave communication while drilling downhole, and particularly to a signal excitation device for the TE11 mode of microwave communication while drilling downhole. Background Art

[0002] Gas drilling has the advantages of improving the drilling speed, reducing the damage of drilling fluid to oil and gas reservoirs, and reducing the drilling cost, and has been widely studied in recent years. Measurement While Drilling (MWD) is essential for drilling, which can measure and feedback information to the ground during the drilling process. For MWD technology, one of the key technologies is to achieve real-time communication between downhole and the surface. However, since there is only gas inside the drill pipe, traditional mud pulses are difficult to apply to gas drilling, and other methods such as acoustic measurement while drilling and electromagnetic measurement while drilling have low stability and are easily affected by the environment.

[0003] In recent years, the proposed microwave communication while drilling downhole technology (MCDWD) realizes communication between downhole and the ground in a relay form. Since the depth of gas drilling can reach more than 3000 meters, and the signal propagation distance in the drilling channel is about 200 meters, it is impossible to directly achieve communication between downhole and the ground. Therefore, the signal between the ground and downhole is transmitted in a relay manner by multiple communication relays placed inside the drill pipe. Each communication relay consists of a metal cylinder mount, a signal excitation structure, an internal communication module, and a battery. Among them, the metal cylinder mount is fixed to the drill pipe in a certain way, the communication module and the battery are sealed inside the sleeve, and the communication module and the excitation structure are connected by a radio frequency coaxial cable. Compared with traditional downhole data communication methods, MCDWD has a faster data transmission speed and is not sensitive to the environment. This technology uses the space inside the drill string to transmit electromagnetic wave signals. MCDWD transmits signals through the main mode of the circular waveguide. Although the excitation of the TE11 mode in the circular waveguide has been studied for decades, due to the very high air flow velocity (200 - 300 KM / h) inside the drill pipe and the very limited space, traditional excitation structures are difficult to apply. Summary of the Invention

[0004] The purpose of the present invention is to provide a signal excitation device for the TE11 mode of microwave communication while drilling downhole to solve the technical problem that traditional excitation structures are difficult to apply to drill pipes with a relatively high air flow velocity.

[0005] The present invention is implemented by the following technical solutions: A signal excitation device for the TE11 mode of microwave communication while drilling downhole includes a communication relay metal mount and an E-type excitation mechanism. The E-type excitation mechanism includes a bottom metal column and multiple connecting metal columns. The bottom metal column is connected to the communication relay metal mount through the connecting metal columns and is parallel to the surface of the communication relay metal mount. The communication signal line inside the communication relay metal mount is connected to the bottom metal column through one of the connecting metal columns.

[0006] Further, the communication relay metal mount is fixed inside the drill pipe and is responsible for loading the communication circuit and the battery.

[0007] Further, the connecting metal columns include a first connecting metal column and a third connecting metal column. The first connecting metal column and the third connecting metal column are respectively arranged at both ends of the bottom metal column. The bottom metal column is connected to the surface of the communication relay metal mount through the first connecting metal column and the third connecting metal column.

[0008] Further, the connecting metal columns further include a second connecting metal column. The second connecting metal column is arranged at the middle position of the bottom metal column. The bottom metal column is connected to the communication signal line inside the communication relay metal mount through the second connecting metal column.

[0009] Further, a communication signal feed opening for placing the communication signal line is provided on the communication relay metal mount.

[0010] Further, the bottom metal column and the connecting metal columns are in the shape of a cylinder or a square column.

[0011] Further, the length range of the bottom metal column is: 3D to 6D, where D is the inner diameter of the drill pipe.

[0012] Further, the cross-sectional area of the bottom metal column is 0.0001D 2 ~0.01D 2 , where D is the inner diameter of the drill pipe.

[0013] Further, the length range of each of the first connecting metal column, the second connecting metal column, and the third connecting metal column is: 0.15D to 0.4D, where D is the inner diameter of the drill pipe.

[0014] Further, the cross-sectional area of each of the first connecting metal column, the second connecting metal column, and the third connecting metal column is 0.0001D 2 ~0.01D 2 , where D is the inner diameter of the drill pipe.

[0015] The beneficial effects of the present invention are as follows: Compared with the traditional excitation structure, the present invention has a smaller cross-sectional area, thereby reducing the air resistance. In addition, the present invention has three fulcrums with the waveguide wall, improving the mechanical strength and being more suitable for application in the downhole communication system while drilling in gas drilling. Description of the Drawings

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0017] Figure 1 It is the top view of the present invention;

[0018] Figure 2 It is the side view of the present invention;

[0019] Figure 3 It is the S-parameter diagram of E-shaped excitation;

[0020] Figure 4 It is the equivalent circuit diagram;

[0021] Figure 5 It is the comparison diagram of the reflection coefficients of the circuit model and the simulation model;

[0022] In the figure, 1 - communication relay metal mount, 2 - E-shaped excitation mechanism, 3 - communication signal feeding opening, 4 - communication signal line, 5 - bottom metal column, 6 - first connection metal column, 7 - second connection metal column, 8 - third connection metal column. Specific embodiments

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and illustrated in the drawings here can be arranged and designed in various different configurations.

[0024] It should be noted that: similar reference numerals and letters represent similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0025] The following will, with reference to the drawings, elaborate on some embodiments of the present invention. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0026] Embodiment 1

[0027] See Figure 1 、 Figure 2, a signal excitation device for TE11 mode of microwave communication while drilling, comprising a communication relay metal mount 1 and an E-type excitation mechanism 2. The E-type excitation mechanism 2 includes a bottom metal column 5 and multiple connecting metal columns. The bottom metal column 5 is connected to the communication relay metal mount 1 through the connecting metal columns and is parallel to the surface of the communication relay metal mount 1. The communication signal line 4 inside the communication relay metal mount 1 is connected to the bottom metal column 5 through one of the connecting metal columns.

[0028] In this embodiment, the communication relay metal mount 1 is fixed inside the drill pipe and is responsible for loading devices such as communication circuits and batteries. The communication relay metal mount 1 is provided with a communication signal feed opening 3 for placing the communication signal line 4. Further, the communication relay metal mount 1 is a partially hollowed metal cylinder. The hollowed part is used to place the communication circuit and the supporting power supply, and the hollowed part is sealed with a cover plate to ensure that the circuit is not affected by the external environment. The drill pipe is fixed, and the signal is connected between the communication circuit and the excitation structure through a coaxial cable and fed by the coaxial cable.

[0029] In this embodiment, the connecting metal columns include a first connecting metal column 6 and a third connecting metal column 8. The first connecting metal column 6 and the third connecting metal column 8 are respectively arranged at both ends of the bottom metal column (5). The bottom metal column 5 is connected to the surface of the communication relay metal mount 1 through the first connecting metal column 6 and the third connecting metal column 8. Further, the connecting metal column also includes a second connecting metal column 7. The second connecting metal column 7 is arranged at the middle position of the bottom metal column 5. The bottom metal column 5 is connected to the communication signal line 4 inside the communication relay metal mount 1 through the second connecting metal column 7.

[0030] In this embodiment, the material of the E-type excitation mechanism 2 is copper or other metals with high conductivity. Among them, the shapes of the bottom metal column 5 and the connecting metal columns can be cylindrical or square columns with the same length and similar cross-sectional areas. One end of the first connecting metal column 6, the second connecting metal column 7, and the third connecting metal column 8 are all connected to the bottom metal column 5, and can be connected by welding, conductive adhesive bonding, etc. Further, if the inner diameter of the drill pipe is D and the working frequency is 2.2 to 2.5 GHz, the length range of the bottom metal column 5 is 3D to 6D; the lengths of the three metal columns (the first connecting metal column 6, the second connecting metal column 7, and the third connecting metal column 8) perpendicular to the surface of the communication relay metal mount 1 are 0.15D to 0.4D, and the cross-sectional areas of each cylinder (the bottom metal column 5, the first connecting metal column 6, the second connecting metal column 7, and the third connecting metal column 8) are 0.0001D 2 to 0.01D 2 .

[0031] The principle of the E-type excitation mechanism 2 is as follows: The communication signal current generates resonance on the surface of the E-type excitation structure 2. The resonant current serves as a source, exciting a time-varying electromagnetic field around it, and finally forming an electromagnetic wave inside the drill pipe, which propagates inside the drill pipe. Among them, during resonance, the current amplitude is distributed in the form of a standing wave on the surface of the E-type excitation structure 2, and the current reaches its maximum at the connection between the two side excitation structures and the surface of the communication relay metal mount 1.

[0032] To verify the performance of the present invention, an excitation structure suitable for 5-inch API drill pipes was designed, and the operating frequency was selected to be 2.4 GHz to 2.5 GHz. The simulated S parameters are as Figure 3 shown. The insertion losses are all higher than -3.2 dB, and the return losses within the operating frequency range are all less than -15 dB, which can meet the requirements of signal excitation. In addition, according to the reciprocity theorem, the excitation structure can also be used as a receiving device. Therefore, only one excitation structure is required for the entire communication relay to achieve signal communication with adjacent relays.

[0033] Three-dimensional electromagnetic simulations were carried out to further analyze the working mechanism of the proposed excitation structure. The results show that the current reaches its maximum at two parts, one is the joint of the ring and the circular waveguide, and the other is the joint of the ring and the coaxial cable. According to the field distribution, an equivalent circuit was established as Figure 4 to explain the working principle. This transformer represents the impedance transformation from the coaxial cable to the waveguide, and the capacitor Ca is responsible for the capacitance between the inner and outer conductors at the waveguide aperture. The inductor L represents the inductance effect introduced by the current into the loop. The capacitance effect introduced by the electric field around the loop is represented by C. The parameter values were obtained by simulating the S11 of the excitation structure, and the corresponding values are: L1 = 17.1 nH, L2 = 9.9 nH, C1 = 0.66 pF, Ca = 0.07 pF, T = 1.96. The comparison of the reflection coefficients between the circuit model and the simulation model is as Figure 5 , and the two have good approximations, which proves the correctness of the analysis of the excitation.

[0034] The mechanical reliability of the excitation structure was studied through fluid-structure interaction simulations. The simulation mainly studied its reliability by calculating the strain of the excitation structure when high-speed air flow passes through. At the same time, the strain of the probe structure with the same electrical performance was compared, and the air flow velocity was 50 m / s to simulate the real downhole environment of air drilling. The results show that: The maximum strain of both structures occurs near the coaxial cable joint. The maximum strain of the E-shaped excitation is 0.047 MPa, and the maximum strain of the probe is 0.31 MPa. This shows that the proposed structure has lower strain and stronger mechanical reliability because the cross-sectional area of this structure is smaller and more fulcrums bear the external force together.

[0035] Generally speaking, the performance of the present invention is verified through electromagnetic simulation, and the working principle is introduced in detail. The mechanical reliability is verified through fluid-structure interaction. The electromagnetic simulation results show that from 2.4 GHz to 2.5 GHz, the insertion loss is greater than -3.2 dB, and the return loss is less than -15 dB. At the same time, under the same air flow conditions, the structure has less strain and is more suitable for application in the downhole communication system while drilling in gas drilling.

[0036] It should be noted that the terms "connection" and "setting" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "connection" and "setting" may explicitly or implicitly include one or more of such features. Moreover, the terms "connection", "setting", etc. are used to distinguish similar objects and do not necessarily have to be used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. And for the foregoing embodiments, for simplicity of description, they are all expressed as a series of action combinations. However, those skilled in the art should know that the present application is not limited by the described action sequence, because according to the present application, some steps can be performed in other sequences or simultaneously. Secondly, those skilled in the art should also know that the embodiments described in the specification are preferred embodiments, and the actions involved are not necessarily essential to the present application.

[0037] In the above embodiments, the basic principles, main features and advantages of the present invention are described. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, any modifications and changes made by those skilled in the art that do not depart from the spirit and scope of the present invention shall fall within the protection scope of the appended claims of the present invention.

Claims

1. A signal excitation device for TE11 mode of microwave communication while drilling downhole, characterized in that, It includes a communication relay metal mount (1) and an E-type excitation mechanism (2). The E-type excitation mechanism (2) includes a bottom metal column (5) and multiple connecting metal columns. The bottom metal column (5) is connected to the communication relay metal mount (1) through the connecting metal columns and is parallel to the surface of the communication relay metal mount (1). The communication signal line (4) inside the communication relay metal mount (1) is connected to the bottom metal column (5) through one of the connecting metal columns. The communication relay metal mount (1) is fixed inside the drill pipe and is responsible for loading the communication circuit and the battery. The connecting metal columns include a first connecting metal column (6) and a third connecting metal column (8). The first connecting metal column (6) and the third connecting metal column (8) are respectively arranged at both ends of the bottom metal column (5). The bottom metal column (5) is connected to the surface of the communication relay metal mount (1) through the first connecting metal column (6) and the third connecting metal column (8). The connecting metal columns further include a second connecting metal column (7). The second connecting metal column (7) is arranged at the middle position of the bottom metal column (5). The bottom metal column (5) is connected to the communication signal line (4) inside the communication relay metal mount (1) through the second connecting metal column (7). A communication signal feed opening (3) for placing the communication signal line (4) is provided on the communication relay metal mount (1).

2. The signal excitation device for TE11 mode of microwave communication while drilling downhole according to claim 1, characterized in that, The bottom metal column (5) and the connecting metal columns are in the shape of a cylinder or a square column.

3. The signal excitation device for TE11 mode of microwave communication while drilling downhole according to claim 1, characterized in that, The length range of the bottom metal column (5) is: 3D~6D, where D is the inner diameter of the drill pipe.

4. The signal excitation device for TE11 mode of microwave communication while drilling downhole according to claim 3, characterized in that, The cross-sectional area of the bottom metal column (5) is 0.0001D 2 ~0.01D 2 , where D is the inner diameter of the drill pipe.

5. The signal excitation device for TE11 mode of microwave communication while drilling downhole according to claim 1, characterized in that, The length ranges of the first connecting metal column (6), the second connecting metal column (7), and the third connecting metal column (8) are all: 0.15D~0.4D, where D is the inner diameter of the drill pipe.

6. The signal excitation device for TE11 mode of microwave communication while drilling downhole according to claim 5, characterized in that, The cross-sectional areas of the first connecting metal column (6), the second connecting metal column (7), and the third connecting metal column (8) are all 0.0001D 2 ~0.01D 2 , where D is the inner diameter of the drill pipe.

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