SU754344A1 - Well-logging piezoelectric geophone - Google Patents

Description

The invention relates to sound meters-geophones and can be used to record the manifestations of rock pressure in mine conditions.

In mining conditions have been used downhole sensors audiometric five- SHSHG ₅ Pa, comprising a cylindrical body approximately 40 mm in diameter, which is movable in the axial direction the massive body, acting on the piezometric cc [1].

In order to increase the sensitivity, it is proposed to use a package of plates bent under the action of a specified mass instead of a piezometric element working in compression and tension, [2].

Devices of this type differ from the disadvantage that with the greatest sensitivity ¹ NOSTA they perceive the vibrations directed along the borehole axis. This is due to the fact that the diameter of the instrument case is limited by the dimension of the well, the inertial mass in these sensors can have one degree of freedom — along the axis of the well. For reliable perception of sound waves in the mountain range, these devices must have good contact with the walls of the well. This requires spe2

Special measures involving wedging of the sensor body in the wells increases the cost and complexity of the sound-measuring equipment.

The closest in technical essence to the invention is a downhole piezoelectric geophone containing a cylindrical sensor body with a piezoelectric element placed at one of its ends and recording equipment. Such a sensor does not require special wedging in the well and can simply be lowered into an inclined well, and then, if necessary, removed and used again [3].

The disadvantage of this sound pressure transducer is its one-sided orientation. This sensor has the greatest sensitivity in the direction perpendicular to the plane of the piezoelectric plate, which makes it necessary to orient it in the well. In hard-to-reach places, the orientation of the sensor in the well, as a rule, is excluded, therefore the effectiveness of using such devices is greatly reduced.

The purpose of the invention is to increase the sensitivity of the geophone and the expansion of the diagram3

754344

We are the directivity of the piezoelectric sensor device.

This goal is achieved by the fact that a second piezoelectric element, detecting links and a signal adder are inserted into a downhole piezoelectric geophon, the second piezoelectric element, detecting links and a signal adder, with the second piezoelectric element placed at the second end of the body in a plane perpendicular to the plane of the first piezoelectric elements and the piezoelectric elements. the detection units and the adder are connected to the recording equipment.

FIG. 1 is a block diagram of a downhole piezoelectric geophone; in fig. 2 - sensor design; in fig. 3-5 shows the signal on the piezoelectric elements, after detection and after the summation link, respectively.

The geophone includes a case of a cylindrical sensor 1, inside of which and along its axis two rectangular piezoelectric elements 2 and 3 are placed. Piezo elements 2 and 3 in case 1 are fixed to the console. The planes of the piezoelectric elements are mutually perpendicular.

The working surfaces of the piezoelectric elements are electrically connected with the links 4 of detection. Detectors 4 are connected to a signal adder 5, which in turn is connected to recording equipment 6, usually located outside the well.

The sensor (see Fig. 2) includes a cylindrical body 1 in the form of a pipe, closed at the ends with threaded covers 7 and 8 through sealing gaskets 9. The covers are pressed to the special flanges of the holders 10 of the piezoelectric elements 2 and 3. The holders are made in the form of forks, in the slots of which plates 2 and 3 are cantilevered with gland screws I. From the holders 10 and screws 11, plates 2 are electrically insulated. The angular position of the holders is fixed by pins 12. To transmit the signal from the sensor, there is a cable 13, passed through the cover 8. The cable is fixed in the housing with a screw plug 14 with sealing gaskets 15 and 16.

The device works as follows.

A sound wave is applied to a sensor located in a specially drilled well, causing the cantilever-mounted piezoelectric elements 2 and 3 to vibrate. On the working surfaces of the piezoelectric elements, a time-varying electric charge occurs. Piezo elements can oscillate with some phase shift, like

this is shown in FIG. 3 diagrams of change of charge on two piezoelements (positions 17 and 18). The currents caused by these charges are detected in the links 4. The current diagram after the detectors is shown in FIG. 4. After summing up the currents (or voltages) in the adder 5, the signal entering the recording equipment has the form shown in FIG. five.

In comparison with the known ones, the proposed downhole piezoelectric geophone has a wider radiation pattern. Theoretically, only the waves driving the sensor exactly along the axis of the well will not be perceived. But since sound sources create both longitudinal and transverse waves, the sensor will react to the sound source located anywhere in relation to it. The known device will not react also to the waves acting on the piezo-plate in the direction of its plane. This advantage allows not to worry about how the sensor is oriented in the well, which greatly simplifies its operation.

In addition, the proposed geophone has a higher sensitivity than the known one, since the signal to the recording equipment is supplied from two piezoplates.

Claims (1)

Claim A downhole piezoelectric geophone containing a cylindrical sensor body with a piezoelectric element located at one of the ends and recording equipment, "characterized in that, in order to increase the sensitivity and expansion of the radiation pattern, a second piezoelement unit and a signal adder are introduced into it, the second The piezoelectric element is placed at the second end of the housing in a plane perpendicular to the plane of the first piezoelectric element, and both piezoelectric elements are connected to the recording equipment.