JPH0468187A - Information measuring receiving antenna in case of well excavation - Google Patents

Abstract

PURPOSE:To improve S/N rario of a receiving signal from underground by burrying one electrode of an ultralong wave communication into the front end of a casing pipe, and burrying the other electrode into a vertical shaft provided at a certain distance from the pipe with approximately the same depth as that of one electrode. CONSTITUTION:One electrode 17a of an ultralong wave communication antenna 16 is mounted to the front end of a casing pipe 4 through an insulation case, and the other electrode 17b is burried into a vertical shaft 19 provided at a certain distance from the pipe 4 with approximately the same depth as that of the electrode 17a. By the receiving antenna 16 formed in such a way, an ultralong wave electromagnetic wave is received from underground at a position where an earth current generating from an electric equipment on a rib is damped to transmit it to an amplifier 12. According to the constitution, long distance signal transmission from the deeper depth can be ensured and, at the same time, reliability can be promoted.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a receiving antenna device used for transmitting underground information to the ground using extremely long wavelength electromagnetic waves when drilling wells for oil, natural gas, etc.

[Conventional technology]

When drilling wells for oil, natural gas, etc., what are the geological conditions at the drilling site? It is necessary to obtain underground information such as ML degree and pressure. Conventionally, a drilling pipe was raised above the ground, and then a measuring device for logging was lowered into the excavated well and measured by placing it underground. Mud logging methods have been adopted to examine the components of mud, which is circulated through mud. However, these methods require a long time for measurement;
It was not possible to measure underground information in real time during excavation. Therefore, recently, the information measurement method during excavation, MWD (Measurement While Dr.
Measurement technology aimed at real-time measurement called ``illing'' has been studied, and various methods have been proposed. Among these, methods that use electromagnetic waves are attracting particular attention. An example of a method using electromagnetic waves is shown in FIG. Koreba, US Literature Petroleum Engineers International (1'ETROLEUM IENGIN [
iER International) October 1988
[Status Report: MWD Tech
This is a state diagram when transmitting and receiving underground information using long wavelength electromagnetic waves, as shown in J. In the figure, a drilling rig 2 is being constructed on the ground 1.
Directly below this drilling rig 2, an excavated well 3 is formed. A steel casing pipe 4 is installed near the ground within this well 3 to prevent the wall of the well from collapsing. Further, a drill pipe 5 extends therein, and a drill collar 7 is connected to the tip of the drill pipe 5 via an insulating collar 6. A bit 8 for drilling is attached to the tip of the drill collar 7, and the ground 1 is excavated by rotating the drill pipe 5 with a motor 14 via a chain or gear. Inside the drill collar 7 is a detector that detects the temperature, pressure, etc. underground during excavation and converts it into an electrical signal, and the detection signal is used as a modulation signal to modulate the carrier frequency and send underground information to the ground as extremely long wavelength electromagnetic waves. It houses a transmitting device 9 for transmitting data to. A transmission output terminal (not shown) of the transmission bag W9 is connected to a drill pipe 5 and a drill collar 7 that are connected with an insulating collar 6 in between, and the drill pipe 5 and drill collar 7 function as a transmission dipole antenna. It then transmits modulated extremely long wavelength electromagnetic waves to the ground. On the other hand, at the base of the drilling rig 2 on the ground, in order to receive extremely long wavelength electromagnetic waves transmitted from the ground, the - pole is taken out from the casing pipe 4, and the other pole is an electrode 10 buried in the ground at a predetermined distance. A dipole antenna 11 is installed. The signal received by the dipole antenna 11 is input to an amplifier 12, and the amplified signal is input to a signal processing unit 13 for demodulating (detecting) the signal to obtain underground information. Note that depending on the strata, geology, depth, etc., extremely long wavelength electromagnetic waves with a frequency of several tens of tlz are used. The current i shown in the figure indicates the distribution of current flowing underground when the transmitting device 9 radiates electromagnetic waves underground. Also,
E is an equipotential line formed by the current i5. The receiving antenna 11 detects this potential difference. This signal is amplified by the amplifier I2 and recognized by the signal processing section 13 as information from underground. By the way, in order to drill by turning the bit 8, the drill pipe 5 is directly rotated by the motor 14 on the floor of the rig 2. When this motor 14 is driven, as shown in FIG.
Earth current In++inz to earth via C2+c3
+Ins flows. This earth current is iI in Figure 6,
Drill pipe as shown in 5. Muddy water15. It flows out into the earth 1 through the casing pipe 4 and is connected to the receiving antenna 11.
is mixed in the same way as the transmitted signal i, and the S/ of the transmitted signal i,
This will lower N'tc. This current ifi is called noise.

[Problem to be solved by the invention]

The MWD receiving antenna that uses conventional electromagnetic wave communication is
With the above configuration, when electrical equipment installed on the rig floor, especially the motor, starts operating, ground current flows and enters the receiving antenna through the ground, reducing the S/N of the received signal from underground. did. The transmission efficiency of electromagnetic waves within the earth is not as good as that in the atmosphere, so S/
This affected N, making it impossible to transmit information from deeper depths. Additionally, there were problems such as a decrease in the reliability of information. One way to solve the above problem is to increase the transmission power of the transmitting device 9, but in order to increase the transmission power, the shape of the device needs to be thicker. Therefore, it was difficult to accommodate it within the drill pipe 5 due to the size limit. This invention was made to solve the above-mentioned problems, and aims to improve the S/N of a received signal and to obtain a receiving antenna that increases the reliability of information from underground.

[Means to solve the problem]

The present invention is a receiving antenna device for ultra-long wavelength electromagnetic wave communication that transmits underground information to the ground during well drilling, and the earth current generated from electrical equipment on the rig is substantially reduced underground or under the sea. One electrode of the receiving antenna is installed on or near the casing pipe or near the drill pipe at a depth position of It is characterized by the fact that it is equipped with electrodes. As a specific form, the present invention has one electrode of a receiving antenna fixed to the tip of a casing pipe via an insulating case, or one electrode of a receiving antenna installed in a shaft near a casing pipe or a drill pipe. It is characterized by the fact that it was installed in Another feature is that both electrodes of the receiving antenna are installed on the ocean floor.

[For use]

According to the receiving antenna device of the present invention, extremely long wavelength electromagnetic waves from underground are received at a position where the earth current generated from equipment on the rig is attenuated. As a result, it is possible to extremely reduce the amount of noise mixed into the received signal. The type in which one side of the antenna electrode is provided at the tip of the casing pipe is easy to construct because it is an integrated type. Further, a method in which one of the electrodes is installed in a shaft near the casing pipe or drill pipe is advantageous in that the installation depth can be changed depending on the degree of attenuation of the earth current. Furthermore, in the type where both electrodes are installed on the seabed, installation work is extremely simple.

【Example】

An embodiment of the present invention will be described below with reference to the drawings. In addition, in the figure, the same or similar parts as in FIG. 6 are indicated by the same reference numerals. In FIG. 1, I6 is a receiving antenna buried deep underground, and 17a is an electrode having the same shape and two dimensions as the casing pipe 4 in cross section. An insulating case 18 electrically isolates and insulates the electrode 17a and the casing pipe 4, and is mechanically supported by the casing pipe 4. 17b is an electrode similar to the electrode shown in FIG. 6, 10, and 19 is a vertical shaft for installing the electrode 17b deep underground, which is provided at a certain distance from the casing pipe 4, for example, about 100 m. The electrode 17b is buried at approximately the same depth Z as the electrode 17a. 2Qa, 20
b is an insulated wire that transmits the signals detected by the electrodes 17a and 17b to the amplifier 12. FIG. 2 shows the shape of the electrode 17a installed directly below the drill pipe 5 of the receiving antenna 16. (A) The figure is a top view of the drill pipe 5, (B) The figure is (A)
The AA' cross-sectional view in the figure, and the side view in (c). 2j is a groove for embedding the insulated electric wire 20a in the side surface of the drill pipe 5. The terminal of the insulated wire 20a is the electrode 17
It is electrically connected to a. Next, the operation according to an embodiment of the present invention will be explained. Transmission method and operation of extremely long wavelength electromagnetic waves, and Rig 2
The method for drilling a well is the same as the conventional operation described above, so the explanation will be omitted. Here, a configuration of a receiving antenna that reduces the influence of noise i generated in the rig, which is the subject of the present invention, will be described. The current flowing through the drill pipe 5 buried in a damping medium such as the earth is described in the literature SPE Drilling Engineering.
earing) June 1987 [Propagating of Electromagnetic Waves Alonga Drillstring of Finite Conductivity (Propagating of Elec
tromagnetie Waves Along a
Drillstring of Finite Co
nductivity) It is known that as shown by J, the attenuation decreases according to the distance. That-
An example is shown in Figure 3, which represents the current distribution on a pipe in seawater. Experimental equipment: - 40 m steel pipe equipped with a transmitter - Electrode length 1 m - Outer radius of the pipe 1.27 am - Inner radius of the pipe 1.05 cm Constants of the medium: Pipe... Conductivity 4.2 x IO' s/m, relative permeability 27 Sea Water...Conductivity 4-5 s/m (15℃) Experimental method...Measuring pipe current using frequency as a parameter. Theoretical values are shown by curves and experimental values by marked points. Further, the attenuation amount α of electromagnetic waves can be approximately expressed by the following equation. α=e−2πfμσ·2 Here, f: frequency (Hz) μ: magnetic permeability of the medium σ: electrical conductivity of the medium (s/m) 2: depth (m). For example, when the conductivity σ of the medium is 0.1 and 4.0, the frequency f
The attenuation amount α when is 10 Hz and 20 tlz is estimated as shown in the table below. Table 1 According to the results of both studies, it can be seen that the trends of current attenuation are almost the same. As shown in Table 1, a similar attenuation phenomenon can be considered underground. That is, as the depth of the drill pipe 5 or the casing pipe 4 becomes deeper, the noise current i,,1 flowing out from the pipe becomes smaller. That is, ir++>i,, □. Therefore,
If the installation depth of the receiving antenna 16 is increased, the noise current i, generated in the rig 2. A transmission signal j5 with a good S/N ratio can be obtained with little influence from the above. From the above, as shown in FIGS. 1 and 2, one pole 7a of the receiving antenna 16 is attached to the tip of the casing pipe 4, and the other electrode 17b is provided at a certain distance from the casing pipe 4. Electrode 17a in shaft 19
According to the receiving antenna 16 configured to be buried at approximately the same depth Z, the noise generated by the rig is attenuated, and a signal with a good S/N ratio can be received. FIG. 4 shows another embodiment of the invention. Here, a shaft 19b is dug near the casing pipe 4, and one pole 7c of the receiving antenna 16 is buried in the same manner as the electrode 17b. In this way, a vertical shaft can be arbitrarily provided without machining the casing pipe 4 and after setting the casing pipe 4, and the antenna can have the same function as the antenna of the embodiment shown in FIG. I can do it. FIG. 5 shows a third embodiment of the present invention, which concerns installation of an antenna during excavation in the ocean. In the case of drilling in the ocean, as shown in Table 1 above, it can be seen that the effect of the amount of attenuation of the noise current 10 is large, and the effect of S/N improvement is significant. Therefore, in the case of the ocean, there is a receiving antenna 16 on the ocean floor.
If the electrodes 17d and 17e are installed, a similar effect on S/N improvement can be obtained.

【Effect of the invention】

As described above, according to the present invention, the receiving antenna is installed at a deep depth, and the influence of noise caused by the earth current generated on the rig is reduced, so that the S/N of the received signal is improved. As a result, the transmission distance of the transmitted signal becomes longer,
Furthermore, there are effects such as improved transmission reliability.

[Brief explanation of drawings]

FIG. 1 shows a schematic configuration diagram of a large-scale depth receiving antenna arrangement for MWD using electromagnetic wave communication according to an embodiment of the present invention. Fig. 2 is a partially enlarged view of one pole of the same receiving antenna, Fig. 3 is a diagram of the attenuation characteristics of the current flowing through the pipe, and Figs. 4 and 5 are schematic configuration diagrams showing other embodiments of the present invention. , FIG. 6 is a schematic configuration diagram showing the arrangement of a conventional receiving antenna, and FIG. 7 is a circuit diagram illustrating the generation path of noise current, which is taken up as a problem in the present invention. DESCRIPTION OF SYMBOLS 1... Earth, 4... Casing pipe, 5... Drill pipe, 12... Amplifier, 13... Signal processing device, 16... Receiving antenna, 17... Electrode of receiving antenna, 18...Insulation case, 19...Shaft, 2
0...Insulated wire.

Claims (4)

[Claims] (1) In a receiving antenna device for ultra-long wavelength electromagnetic wave communication that transmits underground information to the ground during well drilling, the depth position where the earth current generated from electrical equipment on the rig is substantially attenuated underground or under the sea. One electrode of the receiving antenna is installed on or near the casing pipe or near the drill pipe, and the other electrode of the receiving antenna is installed at a predetermined distance from this electrode and at approximately the same depth as the electrode. A receiving antenna device for measuring information during well drilling. (2) The receiving antenna device for measuring information during well drilling according to claim 1, wherein one electrode of the receiving antenna is fixed to the tip of the casing pipe via an insulating case. (3) The receiving antenna device for measuring information during well drilling according to claim 1, wherein one electrode of the receiving antenna is installed in a shaft provided near a casing pipe or a drill pipe. (4) The receiving antenna device for measuring information during well drilling according to claim (1), wherein both electrodes of the receiving antenna are installed on the seabed.