SU481868A1 - Acoustic Isolator for Acoustic Logging Tool - Google Patents

Description

one

I The invention relates to geophysical instruments for the investigation of boreholes by the acoustic logging method of elastic waves. To obtain reliable data for well logging wells in the device, it is necessary to separate the emitter and receiver of elastic waves. Acoustic isolators serve this purpose.

In order to meet the requirements imposed on them, in the insulators there must be the necessary attenuation (attenuation) of the signal and the low velocity of propagation of sound waves.

The known constructions of insulators are not always suitable for operation due to their large dimensions, low rigidity and low tensile strength.

Such is the isolator for the sonic logging probe, the element is -. the holder of which is made in the form of a steel pipe, in which holes are made in a certain way to extend the wave path.

However, to obtain the required elongation, considerable dimensions are required, and the holes in the pipe significantly reduce its strength and rigidity.

The purpose of the invention is to increase stiffness and increase the efficiency of the insulator. This is achieved by the fact that the alimentation of the acoustic insulator delay is made in the form of series-connected rods and; w plates of arbitrary cross-section of the rectangular KOHTjrpa framework, rotated one relative to each other at a certain angle and located in a sound absorber, for example rubber.

This type of isolator is a delay line. Due to the special arrangement of the rods of the framework, the front of an elastic oscillation propagating along the insulator must be traveled a longer way than along an ordinary pipe. The propagation of the front of elastic oscillations in this construction is subject to laws similar to those of geometric optics, primarily on the principle of least time (the Fermat principle /.

Based on this principle, it is necessary to calculate the sizes of the rods and. their location, i.e. so that for longitudinal waves, shorter time takes the way along the forming cylinder.

In this way, the longitudinal waves experience a significant attenuation due to their account;

multiple reflections on the grasses i of the metal section from which the framework is made, and the substance filling the volume (e.g. rubber). Transverse waves propagate through the metal, since rubber is not, propagate; lem transverse waves. Thus, the dimensions and location of the rods must be calculated, assuming that only transverse waves actually propagate along the insulator, the speed of which is substantially less than the velocity of the longitudinal waves. The speed of longitudinal waves for steel is approximately equal to .5300 m / s, and the transverse - about 3200 m / s. The speed of sound in the drilling fluid located in the well) space, i.e. The speed to which the speed of oscillations passing through the insulator must be approached is approximately 1500 - ISOOi-m / s.

Thus in this design. a significant reduction in size is achieved, since the deceleration itself is carried out for the velocity of the transverse waves, which is significantly less than the velocity of the longitudinal waves.

The stiffness and strength of the structure are ensured by an upper frame that has stiffening ribs in all directions.

in fig. I shows a longitudinal section of the isolator in the vertical plane of FIG. 2 - the same in the horizontal plane; in fig. 3 ::: section aA. on aiir. i; in fig. 4 - section PoB-b;

1 to FIG. I; in fig. 5 is an axonometric image of an insulator delay element.

A backing element consists of two frames I of a rectangular contour, turned by one relative to another at a specific angle, for example, 90 °.

Pdmki one delay element, as well as successive elements are interconnected by a special way located rods or; plates 2 with an arbitrary cross-sectional shape. The delay elements form a rigid frame with stiffening ribs in all directions. At the ends of the frame, threaded plugs 3 are attached, which are connecting elements. The framework is filled with a material with a high attenuation coefficient, for example rubber.

PREED METIZOBE

Acoustic isolator for boreholes of an acoustic logging tool, having a cylindrical shape, containing audio delay elements, characterized in that, in order to increase rigidity and, to increase efficiency, the delay elements are made in the form of sequentially connected plates of arbitrary section of rectangular contours turned one relative to another, for example, 90.

Fig.Z

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FIG. five