JP2641375B2 - Underground communication receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an underground communication receiving apparatus for receiving a signal of an extremely long wavelength electromagnetic wave used for transmitting and receiving underground information to and from the ground when drilling a well such as oil and natural gas. It is about.

[0002]

2. Description of the Related Art FIG.
Engineer International (Status Report MWD Technology) October 1988 "
(PETROLEUM ENGINEER International, OCTOBER 1988
It is a state diagram when conventional underground information shown in “Status-report: MWD Technology”) is transmitted and received by an extremely long wavelength electromagnetic wave.

Conventionally, when excavating a well such as oil or natural gas, it is necessary to obtain underground information such as the geology, temperature, and pressure at the excavation part. As a method, a drilling pipe is pulled up to the ground. A method of measuring by placing a measuring device for logging from underground from the drilled well to underground, or a mud called mud that circulates between the ground and the ground through a drilling pipe during drilling A logging method was employed.

[0004] However, these methods require a long time for measurement and cannot measure underground information during excavation in real time. Therefore, recently MWD (Measurem
Measurement techniques for real-time measurement called ontWhile Drelling (measurement during excavation) have been studied, and various methods have been proposed. Among them, the method using electromagnetic waves is the method shown in FIG.

[0005] In FIG. 4, a drilling rig 2 is constructed on the ground 1, and a drilled well 3 is formed immediately below the drilling rig 2, and a well is formed in the well 3 near the ground. A steel casing pipe 4 is provided so that the wall of the drill pipe does not collapse. A drill pipe 5 extends into the casing pipe 4, and a drill collar 7 is provided at an end of the drill pipe 5 through an insulating collar 6. Are linked. In addition, a spout prevention device (BO) is provided above the drill pipe 5.
P) 5a is provided.

A bit 8 for drilling is attached to the tip of the drill collar 7, and the ground 1 is drilled by rotating the drill pipe 5 with a motor 14 via a chain or gear. In the drill collar 7, a transmitting device 9 for detecting underground temperature, pressure and the like during excavation and transmitting underground information to the ground by a modulated signal converted into an electric signal is housed.

A transmitting output terminal (not shown) of the transmitting device 9 is connected to a drill pipe 5 and a drill collar 7 connected with an insulating collar 6 interposed therebetween, and the drill pipe 5 and the drill collar 7 are connected to a transmitting dipole. An extremely long wavelength electromagnetic wave modulated as an antenna is transmitted to the ground.

On the other hand, at the base of the drilling rig 2 on the ground, one pole is taken out of the casing pipe 4 and the other pole is taken from the electrode 10 embedded in the ground in order to detect a very long wavelength electromagnetic wave transmitted from underground. A receiving antenna 11 of a dipole antenna type is installed to receive an extremely long wavelength electromagnetic wave from underground. The signal received by the receiving 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 and obtaining underground information. Note that an extremely long wavelength electromagnetic wave having a frequency of several tens of Hz is used depending on the formation, geology, depth, and the like.

[0009] As shown in FIG. 4, the current i _s (solid line) indicates that when the transmitting device 9 radiates an electromagnetic wave into the ground,
This is a current flowing through the drill pipe 5 and the underground. E is the equipotential lines formed by the current i _s. The receiving antenna 11 detects this potential difference. This signal is amplified by the amplifier 12 and recognized by the signal processing unit 13 as information from underground.

In the rig 2, the drill pipe 5 is directly rotated by the motor 14 for drilling through the bit 8. When this motor 14 is driven, as shown in FIG. 5, stray capacitances C ₁ , C ₂ , C ₂ between the lead wire from the drive circuit 15 of the motor 14 to the motor 14 and the ground, and between the winding of the motor 14 and the rig 2. ₃ and ground currents i _n1 , i
_n2 and i _n3 flow. This ground current is the current i _{n in} FIG.
Drill pipe 5 as shown in (broken line), mud (hatched portion in the drawing) and through the casing pipe 4 flows into the ground 1, similarly mixed transmission signal i _s to the receiving antenna 11, transmitting signal i _s Are lowered. The current i _n referred to as artificial noise current.

Furthermore, variations in the ionosphere and geomagnetic the earth 1, further (in the figure, dashed line) natural current (ground current) i _e that is to be induced due to the impact of mantle convection magma is flowing. This current i _e is distributed in band lower than said artificial noise i _n, transmission signal i
_Since the band is the same as the low band of _s , the S of the transmission signal is
This is a factor that lowers the N ratio.

[0012]

Since the conventional receiving apparatus is constructed as described above, when the electric equipment installed on the rig 2, especially the motor 14, operates, the ground currents _in1 , _in2 , and _ground2 are generated. i _n3 flows out and enters the receiving antenna 11 via the ground 1, so that the SN ratio of the received signal from underground decreases. Also, in order to improve the SN ratio of the received signal,
Be transmitted the received signal with less low frequency attenuation amount of the transmission path, increases the noise component of the natural current i _e, the effect of improving the SN ratio of the received signal is not improved, therefore the information from deeper depths Transmission becomes impossible, and the reliability of information is reduced. Further, as a countermeasure against this problem, the transmission power of the transmission device 9 may be increased. However, in order to increase the transmission power, the shape of the transmission device 9 becomes large. There was a problem that it could not be realized from.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has been made to improve the SN ratio of a received signal,
An object of the present invention is to obtain an underground communication receiving device that enhances the reliability of information from underground.

[0014]

According to a first aspect of the present invention, there is provided an underground communication receiving apparatus comprising: an artificial noise reference signal detector for detecting artificial noise mixed in a transmission signal received by a receiving antenna; A natural noise reference signal detector that detects natural noise mixed into the signal, a noise canceller circuit that adds and subtracts artificial noise and natural noise from a transmission signal received by the receiving antenna, and removes a noise component included in the transmission signal. It is provided with.

According to a second aspect of the present invention, there is provided a receiving device for underground communication, wherein one pole is an electrode buried in the ground, and the other pole is a receiving antenna electrically connected to a casing pipe or a drill pipe. An artificial noise reference signal detector consisting of a toroidal coil provided around the casing pipe or drill pipe and an amplifier for amplifying the detected current; an asymmetric casing pipe or drill pipe and one pole connected to the casing pipe; Or a natural noise reference signal detector consisting of a dipole antenna buried at the same position as the direction from the drill pipe to the electrode of the receiving antenna and an amplifier for amplifying the potential difference, and an artificial signal derived from the transmission signal received by the receiving antenna. Adds and subtracts noise and natural noise, and noise components included in the transmitted signal It is obtained by a noise canceller circuit for removing.

An underground communication receiving apparatus according to a third aspect of the present invention is an adaptive filter for adjusting a transfer function provided corresponding to each of the artificial noise reference signal detector and the natural noise reference signal detector, and an adaptive filter thereof. The noise canceller circuit includes an adder for obtaining the sum of output signals from the filter, and a subtractor for subtracting the sum of output signals obtained by the adder from a transmission signal received by the receiving antenna.

[0017]

The underground communication receiver according to the first aspect of the present invention adds the artificial noise detected by the artificial noise reference signal detector and the natural noise detected by the natural noise reference signal detector, and adds the added results. The noise component contained in the transmission signal is removed by subtracting the noise component from the transmission signal received by the receiving antenna.

In the underground communication receiver according to the second aspect of the present invention, by providing a toroidal coil around a casing pipe or a drill pipe, a current that flows through the casing pipe or the drill pipe and becomes an artificial noise of a transmission signal is detected. I do. In addition, one pole of the dipole antenna is embedded in the same position as the direction from the casing pipe or the drill pipe to the electrode of the receiving antenna, so that the sensitivity of the dipole antenna and the receiving antenna to natural noise is the same. Further, by embedding the dipole antenna axially symmetrically with the casing pipe or the drill pipe, the differential detection value of the transmission signal from underground is reduced to zero.

According to a third aspect of the present invention, in the underground communication receiver, the adaptive filter adjusts a transfer function corresponding to the artificial noise and the natural noise of the artificial noise reference signal detector and the natural noise reference signal detector, The output value of this noise canceller circuit is minimized. At this time, the output of the noise canceller circuit does not include a noise component.

[0020]

[Embodiment 1] An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, 16 is a toroidal coil for detecting a current flowing through the casing pipe 4, 17 is an iron core wound with the toroidal coil 16, 18 is an amplifier for amplifying an output signal of the toroidal coil 16, and 19 is a toroidal coil 16 and an amplifier. Reference numeral 18 denotes an artificial noise reference signal detector. Reference numeral 20 denotes a dipole antenna that embeds two electrodes 20a and 20b in the ground with the well 3 as a symmetric axis and detects a natural current. Reference numeral 21 amplifies an output signal of the dipole antenna 20. The amplifier 22 is a dipole antenna 20
And a natural noise reference signal detector comprising an amplifier and an amplifier.

Reference numeral 23 denotes an adaptive filter for adjusting the amplitude and phase characteristics of the output signal of the amplifier 18, reference numeral 24 denotes an adaptive filter for adjusting the amplitude and phase characteristics of the output signal of the amplifier 21, and reference numeral 25 denotes an adaptive filter from the output signal of the amplifier 12.
And an adder / subtractor 26 for removing components of the output signal, and a noise canceller circuit 26 comprising adaptive filters 23 and 24 and an adder / subtractor 25.

FIG. 2 is a configuration diagram of a noise canceller circuit 26 using a parallel adaptive filter. FIG. 3 is a plan view of the receiving antenna 11, the toroidal coil 16 for detecting a noise reference signal, and the dipole antenna 20. .

Next, the operation will be described. The transmission operation of the electromagnetic wave and the excavation operation of the well by the rig 2 are the same as the above-described conventional operation, and therefore the description thereof is omitted.

[0024] As mentioned in the description of the conventional operation, when receiving a transmission signal from Anasoko while drilling the wellbore, as shown in FIG. 1, the ground current i _n2 generated by electric devices rig 2
Flows out from the drill pipe 5 and from the drill pipe 5 to the ground 1 via the muddy water slanting part and the casing pipe 4 as shown by a broken-line arrow _in1 and enters the receiving antenna 11. Also, the natural current i _e flows in a band of the current as shown in FIG. 1 or FIG. 3, is mixed into the receiving antenna 11.

Meanwhile, transmission signal IS _0, as shown by the solid line arrow i _s1, propagates to the ground surface receiving antenna 11 while propagating through the drill pipe 5 and the ground 1 is installed. In addition, as shown by a solid line arrow _is2 , a part of the drill pipe 5
Above the ground surface and to the rig 2 where the motor 14 is installed.

[0026] Here, the frequency of the transmission signal i _s0 and f _0, when the frequency band of the noise current to a ground current i _n1, i _n2, i _n3 natural current i _e and f ₁ ~f ₂ = Δf, The relationship between the frequencies can be expressed as follows. f ₁ <f ₀ <f ₂ (1) That is, the transmission frequency f ₀ is within a range of the noise current band f ₁ to f ₁ .
It is included in the f _2. Therefore, noise cannot be removed by the conventional filter.

Therefore, a reference signal correlated with a noise current, which is a noise component of the transmission signal, is detected by a method different from that of the reception antenna 11 for receiving the transmission signal, and the noise component is detected by taking the difference between the two. Then, only the transmission signal component is extracted. The principle will be described below. In this description, all signals are represented by scalar quantities to simplify the description.

On the ground surface, the transmission signal _is1 and the earth current _in1
Flows in the same direction with respect to the receiving antenna 11, the transmission signal _is1 and the ground current _in1 are in-phase signals. Also, the natural current i _e, as shown in FIG. 3, mixed with the flow receiving antenna 11 in one direction. Therefore, the signal that can be received by the receiving antenna 11, that is, the output e of the amplifier 12
₁₂ can be expressed by the following equation. _{e 12 = a 12 (i s1} + i n1 + i e) ····· (2) where, a ₁₂ current of the amplifier 12 - the voltage conversion factor.

On the other hand, the transmission signal i flowing through the drill pipe 5
_s2 and the ground current _in2 flow in opposite directions at the place where the toroidal coil 16 is installed. Therefore, the current that can be detected by the toroidal coil 16, that is, the output e of the amplifier 18,
₁₈ becomes like the following formula. _{e 18 = a 18 (i s2} -i n2) ····· (3) where, a ₁₈ current amplifiers 18 - a voltage conversion factor. The direction of flow of the current, relative to the transmission signal i _s.

Furthermore, as shown in FIG. 3, with respect to ground current i _n1 generated by the transmission signal i _s1 and rig 2 has equipotential lines concentrically around the well 3, the noise reference signals natural currents i _e Dipole antenna 20 has electrodes 20a and 20b equidistant from the well 3 as an axis of symmetry.
It has a function of differentially detecting the transmission signal _is1 and the ground current _in1 . Therefore, the signal can be detected by the dipole antenna 20, only a component of its natural current i _e,
The output e ₂₁ of the amplifier 21 is expressed by the following equation. _{e 21 = a 21 · i e} ····· (4) where, a ₂₁ current amplifiers 21 - a voltage conversion factor.

Next, the adaptive filters 23 and 24 shown in FIG.
The output signal e ₁₈ output by the amplifiers 18 and 21
And adjusts the amplitude and phase of e _21, the noise canceller circuit 2
When the output value of 6 is minimized, the relationship of equation (5) is obtained. a ₁₂ (i _n1 + i _e ) = K · {−a ₁₈ (−i _n2 ) + a ₂₁ i _e } (5) The output e ₀ of the noise canceller circuit 26 at this time can be expressed as follows. _{e 0 = e 12 - (-} e 18 + e 21) = a 12 (i s1 + i n1 + i e) - {K · [-a 18 (i s2 -i n2) + a 21 · i e] ···· ( _{6) = a 12 i s1 +} K · a 18 · i s2 ······ (7) as can be seen from equation 7, the output signal e ₀ of the noise canceller circuit, components of the noise current i _n1 and i _e is removed Is done. By performing the above-described noise cancellation processing, a received signal having a good SN ratio can be obtained, so that the reliability of demodulation by the demodulator 13 is improved.

[0032]

As described above, according to the first aspect of the present invention, an artificial noise reference signal detector for detecting artificial noise mixed in a transmission signal received by a receiving antenna, and a natural noise reference signal detector mixed in the transmission signal A natural noise reference signal detector that detects noise, and adds and subtracts artificial noise and natural noise from a transmission signal received by the receiving antenna,
Since it is configured to include a noise canceller circuit that removes a noise component included in the transmission signal, the noise component included in the transmission signal received by the receiving antenna can be removed, the SN ratio can be improved, and the underground information can be improved. Reliability can be improved.

According to the second aspect of the present invention, one pole is an electrode buried in the ground, the other pole is a receiving antenna electrically connected to a casing pipe or a drill pipe, and the casing pipe or the drill pipe. An artificial noise reference signal detector consisting of a toroidal coil and an amplifier for amplifying the detected current provided around the casing pipe and the casing pipe or drill pipe being axially symmetrical and having one pole receiving from the casing pipe or drill pipe. A dipole antenna buried at the same position as the direction of the antenna electrode and an amplifier that amplifies the potential difference, a natural noise reference signal detector, and addition and subtraction of artificial noise and natural noise from the transmission signal received by the receiving antenna And removes noise components contained in the transmitted signal. Since the toroidal coil is provided around the casing pipe or the drill pipe, it is possible to detect a current that becomes artificial noise of a transmission signal flowing through the casing pipe or the drill pipe, By burying one pole of the dipole antenna at the same position as the direction from its casing pipe or drill pipe to the electrode of the receiving antenna, the sensitivity of the dipole antenna and the receiving antenna to natural noise can be made the same, By burying the dipole antenna symmetrically with the casing pipe or drill pipe, it is possible to reduce the differential detection value of the transmission signal from the ground to zero, further improve the SN ratio and increase the reliability of underground information Can be.

According to the third aspect of the present invention, there is provided an adaptive filter provided for the artificial noise reference signal detector and the natural noise reference signal detector for adjusting the transfer function, respectively.
A configuration including a noise canceller circuit having an adder for obtaining the sum of output signals from the adaptive filter and a subtractor for subtracting the sum of output signals obtained by the adder from a transmission signal received by the reception antenna. Therefore, the adaptive filter adjusts the transfer function corresponding to the artificial noise and the natural noise of the artificial noise reference signal detector and the natural noise reference signal detector, and sets the output of the noise canceller circuit to the minimum value that does not include the noise component. To Therefore, even if the transfer function of the noise component and the noise reference signal mixed into the receiving antenna becomes equal or different from each other and is not known, the output value is automatically set to the minimum value.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a receiving device for underground communication according to an embodiment of the present invention.

FIG. 2 is a configuration diagram illustrating a noise canceller circuit of FIG. 1;

FIG. 3 is a plan view showing the antenna unit of FIG. 1;

FIG. 4 is a state diagram when conventional underground information is transmitted and received by an extremely long wavelength electromagnetic wave.

FIG. 5 is a configuration diagram illustrating a motor unit of FIG. 4;

[Explanation of symbols]

 Reference Signs List 4 casing pipe 5 drill pipe 10 electrode 11 receiving antenna 16 toroidal coil 18, 21 amplifier 19 artificial noise reference signal detector 20 dipole antenna 22 natural noise reference signal detector 23, 24 adaptive filter 25 adder, subtractor 26 noise canceller circuit

Claims (3)

(57) [Claims] 1. A receiving antenna for receiving a transmission signal from the ground, an artificial noise reference signal detector for detecting artificial noise mixed in the transmission signal, and a natural noise detecting natural noise mixed in the transmission signal An underground communication receiver comprising: a reference signal detector; and a noise canceller circuit that adds and subtracts artificial noise and natural noise from a transmission signal received by the reception antenna and removes a noise component included in the transmission signal. 2. One electrode is an electrode buried in the ground, and the other electrode is electrically connected to a casing pipe or a drill pipe, and a receiving antenna for receiving a transmission signal from the ground is provided. consists amplifier for amplifying the toroidal coil and the detected current detecting a current flowing through the casing pipe or drill pipe provided around the drill pipe, said receiving antenna
Signal of artificial noise mixed into the transmitted signal received from
And artificial noise reference signal detector for detecting the item, the earth and embedded in one pole is the same position and orientation from the casing pipe or drill pipe to the electrodes of the receiving antenna with an axis of symmetry of the casing pipe or drill pipe dipole consists antenna and amplifier for amplifying the potential difference, received from the receiving antenna to detect the potential difference
Natural noise reference signal detector and artificial noise reference signal Contact <br/> preliminary natural noise of the reference signal from the transmission signal received by said receiving antenna for detecting the reference signal of the natural noise mixed in Shin transmission signal And a noise canceller circuit for removing a noise component included in the transmission signal. 3. An adaptive filter provided for each of the artificial noise reference signal detector and the natural noise reference signal detector for adjusting a transfer function, an adder for obtaining a sum of output signals from the adaptive filters, and a receiving unit. 3. The underground communication according to claim 1, further comprising: a noise canceller circuit having a subtractor for subtracting a sum of output signals obtained by the adder from a transmission signal received by the antenna. For receiving device.