SU510681A1 - Borehole acoustic receiver - Google Patents

Description

one

The invention is intended for use in acoustic logging equipment and may find use in the exploration of mineral deposits.

A borehole acoustic receiver is known, in which two independent receiving elements are installed, which are connected in antiphase to the input of one information transmission channel. The acoustic receiver is provided with a sound screen separating one of the two receiving elements from the fill, and the well of the liquid or gaseous medium through which the useful signals propagate. Thus, one of the receiving elements perceives both useful signals and interferences propagating through the structural elements, and the second receiving element perceives only interferences. Since the receiving elements are connected in antiphase, the noise is subtracted, which helps to improve the signal to the noise.

A disadvantage of the known borehole acoustic receiver is that the two receiving elements are not identical in it: one of them is connected to the body and the well fluid through a thin flexible membrane, which can be affected by the hydrostatic pressure of the well fluid and the other is connected only to the body thick inflexible membrane and hydrostat9

Tical pressure does not affect it. As a result, the sensitivity of receiving elements to interference and the dependence of this sensitivity on frequency turn out to be significantly different. Compensation of this disadvantage in signal processing in the receiving equipment causes considerable difficulties. To reduce the effect of sound interference in the proposed downhole active receiver, both receiving elements have the same sensitivity with respect to interference propagating through the design elements of the downhole tool; Both receiving elements are installed in the receiver housing in exactly the same way and equally experiencing the hydrostatic effect of the fluid filling the borehole. For this, in the sound screen separating one of the receiving elements from the well fluid, there is an orifice whose diameter is much smaller (normal or more) long waves of useful signals coming to a borehole acoustic receiver through a filling fluid. Such an orifice freely transfers the hydrostatic pressure of the borehole fluid onto the prism element without disturbing the sound-insulating properties of the sound screen with respect to the bottom sound process, which takes place during the propagation of useful waves through the fluid. FIG. 1 shows a downhole acoustic receiver section; pas figs. 2 (a and b) examples of recording with |) azocorrel cyoiii. signal diagrams without subtracting the will-pod.x (Fig. 2a) and with subtraction (Fig. 26), and tracing in the well and using the layout of the proposed receiver. The proposed borehole acoustically ii receiver (Fig. 1) consists of a cylindrical body 1, in the cross hole of which, at the same time, 2 identical glasses 3 and 4 are connected by a threaded connection. Inside the stacks, two identical piezoelectric elements 5 and 6 are tightly fixed on the bottom of the stacks and help of rubber gaskets 7 and cylindrical nuts 8. The cups 3 and 4 and the joints 5 and 6 comprise two receiving elements. Glass 3 with a zeo-element 5 is closed with a metal lid 9, covered with edges and a corius 1 and touching glass 3. Above Cornus 1 and Lid 9 there is an elastic rubber cover 10. The cover 9 and cover 10 constitute a sound screen, and a plastic shield and a pair of covers and sound cover, and a shield that comes with a sound shield and cover and a sound shield, and a cover and a sound shield, and a cover of 10 Inelement 5. In the cover 10 and the cover 9 and against Stack: Ana 3 there is a hole 11, the diameter of which is much smaller than the length of the will and the heavy metal. Hole And spontaneously transmits to the glass 3 the hydrostatic pressure of the well of liquid; At the same time, the small diameter of the hole will not practically degrade the sound-shielding properties of the screen. The outer and upper surface of the bottom of the glass 4 is the working surface of the rim and the reception of iolian sigals and eleozoeleite 6, therefore, against the glass 4, there is no sound screen. The dimensions of the hole in the corus 1 and the coating 10 and against the glass 4 are comparable with the lengths of the useful waves or they are 1 1 1 1. Thus, the piezoelectric element 6 seamlessly adheres the useful waves that are propagated by the borehole fluid. Wires 12 from both receiving units are brought out through the central axial hole of an S3 and are connected in opposite to the opposite direction to the common input of the amplifier in the transmission channel and information sigia.uv. Thus, out of two gi of ezoelements 5 and 6, only piezoelement 6 doesn’t have useful sigals, spreads over the well liquid, piezoelemite 5 is shielded from them by a lid 9 and gapping 10. At the same time, both izoezoelement 5 and 6 have the same sensitivity and oyoshy 10 to wave interference spreading to the structural elements of the downhole tool, since they are installed in the housing 1 and experience the same rise of the hydrostatic pressure of the civBa / KHHiA liquid. As a result, by subtracting the signals, which are 5 5 n by the Ezozelemites, good mutual computation of the wave-rooms and the release of the radio waves is achieved. FIG. Figure 2a shows an example of the recording of the phase-correlation diagram, which was obtained from the model of the well logging tool in the well, without subtracting interference. At times of 320-420 μs, the useful waves will be distorted by the current system; no-iomeha extending through the wellbore body. FIG. 26 shows the phase correlation of the zioin diagram, found in the same well and in the same depth interval, with the subtraction of the digits spawned by the two receiving elements. The Volia-Iomeha recording is absent, half of the waves are fixed without distortion. Ph o mma l and 3 o b e p e n i s Weades A first acoustic transceiver containing at least one pair of independent and second elements installed in the same diametral section and connected to the same channel ne | 1 peda) P1 (|) ormai, ai, and sound screen, a division of the young of the useful elements from the borehole environment, with the fact that, in order to reduce the influence of the home screen, the sound screen has a hole, the diameter of which many useful waves.

7h

eight

P

but

OP 300 00 500 600 700

200 300 t $ 00 600

 .2