SU913303A1 - Method and device for acoustic well-logging - Google Patents

Description

The invention relates to the geophysical studies of wells and can be used to determine the properties of rocks in the near-wellbore space.

An acoustic logging method has been learned, in which two high-frequency signals are excited, and a difference low-frequency signal is formed from them, which is used to probe the near-borehole space. To implement this method, a highly directional acoustic source is used, containing two high-frequency generators, a cavity with a liquid, an emitter and a reflector. In this method, high-frequency oscillations excited by two generators are directed into a cavity with a liquid having known properties. When these oscillations interact, a differential low-frequency signal is formed in the cavity, which is used to

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studies of the near-wellbore [11.

The disadvantage of this method is that the time parameters recorded in it are executed by the influence of the structural elements of the well and require the introduction of corrections for their influence.

There is also known a method of sound location (acoustic logging), in which two high-frequency signals are excited, these signals interact in a fluid with known properties, receive a low-frequency difference frequency signal and record its parameters [2 3.

The disadvantage of this method is its low resolution, since it uses the temporal parameters of a predetermined signal of a certain frequency (or wavelength) as information. Therefore, he is not allowed3 91 '

not detect irregularities whose dimensions are smaller than the wavelength of the specified signal.

A device for implementing the method is known, which comprises a borehole projectile with two high-frequency generators, a radiator and a low-frequency receiver, a cable and ground equipment, including an amplifier, a filter and a recording device Ϊ23.

"A disadvantage of this device is that it allows you to emit a probe signal of only one frequency, due to other things being equal to the size of the vessel with the liquid in which this signal is formed, and the parameters of the liquid itself.

The purpose of the invention is to increase the resolution of the method.

This goal is achieved by the fact that in the method of acoustic logging, consisting in the excitation of two high-frequency acoustic signals, their interaction and receiving a low-frequency signal of the difference frequency, the interaction of high-frequency signals is carried out in the test medium and the amplitude of the received signal is judged on the nonlinear parameters of the medium. The method is based on the fact that the amplitude of the signal of the difference frequency arising under the influence of medium inhomogeneity is proportional to the coefficient of its nonlinearity.

In the device for implementing the method consisting of a borehole projectile containing two high-frequency oscillator, emitter, low-frequency generator, emitter, low-frequency receiver and amplifier, cable and ground equipment containing an amplifier, filter and “recording device, the borehole projectile is equipped with a second high-frequency emitter in ground detector equipment is introduced.

The drawing shows the block diagram of the device.

The device consists of a downhole tool 1 containing generators 2 and 3 "emitters 4 and 5" receivers 6 and 7, amplifier 8, cable 9 and ground equipment 10 containing filter 11, amplifier 12, detector 13 and recording device 14.

The method is implemented as follows.

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High-frequency oscillators 2 and 3 excite two signals with similar frequencies of €, and which through radiators 4 and 5 are sent to the medium under study. As a result of the interaction of these signals in the medium under study, radiation of acoustic WAVE DIFFICULT

frequency, the amplitude of which depends on the degree of nonlinearity (heterogeneity) of the interaction zone. This wave is received by receivers 6 and 7 and transmitted through amplifier 9 via cable 9 to ground equipment 10. Here, the signal is free from interference by filter 11 and through amplifier 12 and detector 13 is fed to recording device 14. The amplitude of the received signal is determined and its properties are judged the study environment.

This method allows you to more accurately determine the properties of the environment outside the disturbed zone.

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Claims (2)

Claim 1. The method of acoustic logging, including the excitation of two high-frequency acoustic signals, , their interaction and reception of a low-frequency signal of a difference frequency, characterized in that, in order to increase the resolution of the method, the interaction of high-frequency signals is carried out in the medium under study and the amplitude of the received signal is judged on the nonlinear parameters of the medium. 2. A device for implementing the method according to claim. and a detector is introduced into the ground equipment.