SU972442A1 - Method of acoustic well-logging - Google Patents

Description

(54) SPEAKING METHOD

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The invention relates to field and geophysical well testing using multiprobe acoustic logging and can be used to isolate and measure parameters of various types of elastic waves from a full acoustic signal using the two-dimensional spatial-temporal filtering method when processing recorded signals on a computer.

There is a method of acoustic carriage based on continuous movement of the downhole tool, excitation in the well and receiving elastic, oscillations at probe distances using several acoustic transducers, processing received signals by summing and accumulating in the random access memory for several cycles and registering the total signal on magnetic media.

Due to the accumulation of signals over several radiation cycles, the noise immunity and measurement accuracy of digital processing t1 is increased.

However, this method can be used only to obtain a longitudinal

waves and at low speed of the downhole tool.

There is also known a method of acoustic logging, according to which, due to the .cy imimage of received signals from two transducers along the transverse-wave hodograph line, an increase in the accuracy of its entry 2 is improved.

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However, since the distance between the receivers is inconsistent with the wavelengths excited in the applied acoustic signals, as well as due to the influence of the inhomogeneity of the hole cut, significant errors occur.

Closest to the invention is an acoustic logging method based on continuous displacement of a downhole tool, excitation and reception of elastic oscillations at the wellbore at the probe distances using several acoustic transducers, processing the received 25 signals by amplitude equalization and summing up with the direction taken hodograph lines of the selected and measured type of 3J waves.

Due to the accumulation by means of a satellite along the hodograph line, it is possible to provide a separation and measurement of a certain type of wave from a full acoustic signal. However, when measuring in an inhomogeneous section of a well, both the excitation and the receiving acoustic transducers simultaneously change their position. Consequently, the accuracy of measurements is influenced by the inhomogeneity of the well sections both in the area of the exciting and in the area of the receiving transmitter. The purpose of the invention is to increase the accuracy and speed of logging. . This goal is achieved in that, according to the method of acoustic logging, consisting in the continuous movement of the downhole tool, the excitation and reception in the well of elastic oscillations at probe distances using several acoustic transducers, the processing of received signals by amplitude equalization and summation taking into account the direction hodograph of the selected and measured wave type, synchronous excitation of the radiating acoustic transducer and switching of the receiving acoustic transducers ovateley carried out at a speed equal to the speed of the device-wells, but oppositely directed, the step located acoustic receivers of transducers leu equal to half the minimum wavelength. waves in the spectrum of the elastic oscillations being excited and received in the borehole, and the distance between the extreme receiving acoustic transducers is equal to the maximum wavelength in the spectrum of the excited and received acoustic oscillations. FIG. 1 (a, 6, Bj given devices that implements the proposed method; Fig. 2 (a, b, c) shows time diagrams of the explanatory method. The device contains a borehole acoustic device 1 connected by line 2 of communication with ground equipment and including an acoustic radiator 3, block 4 of acoustic receivers containing 16 receivers (P1-P16; located at a constant pitch, probe distance 5–7, fixed depth value 8. The ground part includes block 9 of matching and controlling parameters of the downhole probe and data processing units analog-digital conversion The user 10 is a random access memory (RAM) 11 and a magnetic tape drive 12. The method is as follows: With broadband acoustic logging, the prevailing frequencies in the spectrum of the excited and recorded signals for the main types of P, S, LJ waves and the ranges of the elastic wave velocity in the rocks correspond to the following wavelengths: for the longitudinal wave (P) VP 2500-8000 m / s; f 12.5-30 kHz; -yr (W1,083 m; Ltah m; for the transverse wave (SV 1600-4500 m / s; f 8-20 kHz; d, 0.08 m; for the Lamb wave i, L) V. 1450 m / s; f 3-12.5 kHz; l. 0.116 m; cf 0.48 m. Therefore, to implement the spatial-temporal filtering when processing signals, the spacing between the receiving transducers can be chosen to be Li,; receivers, i.e., the distance between the extreme transducers, is chosen to be 0.64 m, while it can consist of 16 transducers (nl-ni6J. With a continuous movement of the downhole tool with the speed and the acoustic emitter is chosen so that during the time between the excitation cycles, the downhole tool covered a distance equal to the step of the receiving transducers in the acoustic receiver unit 4. For example, at the emitter start frequency of 12.5 Hz, the logging speed should be chosen as in the time between the moment of excitation of the radiator, the probe travels a distance equal to the pitch (0.04 m) between the receiving transducer / W. The logging speed can be reduced, but at the same time, accordingly, the frequency of starting the emitter should be reduced. Acoustic signals are received by the transducer, which is located at a fixed value of the depth of the borehole 8 (Fig. 1). To position the borehole probe in, the x-to-b signals shown in FIG. 2, (a-b) are respectively adopted by transducers P1, Pv and P16 over probe distances x 5-7. Thus, the reception of acoustic signals is always carried out at a constant fixed value of the depth of the well, thus eliminating the influence of the heterogeneity of rocks in the area of receiving transducers. The heterogeneities of the section in the region of the acoustic radiator, which are in the deviation of the hodograph lines of the extracted types of longitudinal waves 13, transverse 14, etc., from the linear ones can be taken into account when processing signals on a computer.

Claims (3)

Claim The method of acoustic logging based on the continuous movement of the downhole tool, the excitation and reception of elastic vibrations in the well 1 at probe distances using several acoustic transducers using Yu, processing the received signals by amplitude equalization and summing, taking into account the direction of the hodograph line of the extracted and measured 15 of the type of waves, characterized in that, in order to increase the accuracy and speed of logging, synchronous excitation of the emitting acoustic transducer and switching acoustic transducers are carried out at a speed equal to the velocity of the downhole tool, but oppositely directed, while the step of the location of the receiving acoustic transducers is equal to half the minimum wavelength in the spectrum of elastic vibrations excited and received in the well, and the distance between the extreme receiving acoustic transducers is equal to the maximum wavelength in the spectrum of ⁴ excited and received vibrations. sources of information taken into account during the examination 1. USSR copyright certificate No. 416651, cl. G 01 V 1/40, 1972. 2. US Patent No. 3390377, cl. 340-18, published. 1968. 3. French patent No. 2312784, cl. G 01 V 1/40, published. 1978.