RU2478222C1 - Seismic wave source for marine seismic survey - Google Patents

Abstract

FIELD: mining.

SUBSTANCE: device includes a pneumatic chamber with a cylindrical housing, an upper cover plate and a lower cover plate made on its inner side in the form of steps, a card arranged in upper part of pneumatic chamber and provided with possibility of interacting at its lower end face and forming a pilot-operated check valve with an upper end face of cylindrical waveguide, which is equipped with an O-ring. The above card is rigidly fixed on inner surface of upper cover plate of pneumatic chamber, and waveguide forms on some end part of the working stroke with inner surface of lower cover plate of pneumatic chamber a damper cavity that is connected to the pneumatic chamber through an annular channel formed with inner cylindrical surface of the step of larger diameter of lower cover plate of pneumatic chamber and outer surface of step of larger diameter of waveguide.

EFFECT: avoiding repeated pulsations of the emitting card during the source working cycle.

2 dwg

Description

The proposed device relates to the field of seismic exploration of mineral deposits, and more specifically to the excitation of seismic waves during seismic surveys in the waters.

A device for exciting seismic waves (see "Marine seismic survey. Under the editorship of Telegin AN - M .: LLC" Geoinformmark ", 2004, Fig. 5.11), including a high-pressure pneumatic chamber, a cylindrical body with exhaust windows and piston rod. Excitation of seismic waves is realized in the process of exhausting through exhaust windows a portion of compressed air from a pneumatic chamber into the environment (water) up to a pressure of 10-15 MPa. The disadvantage of this device is the repeated pulsation of the air bubble in the water, which significantly reduces the resolution of seismic exploration. The practical use of this device requires special complex measures to suppress ripple. In addition, the release of compressed air into the water through windows of a limited (due to design restrictions) size leads to a decrease in the loading rate of the liquid, and therefore to a limitation of the frequency of the generated waves, which also reduces the efficiency of the device.

These disadvantages are partially eliminated in the device for the excitation of seismic waves (see AS SU No. 1728820 A1, 04/23/1992), which can be adopted as a prototype. The device includes a pneumatic chamber with a cylindrical body, upper and lower, made on its inner side in a stepped form, with covers, a board located on the upper part of the pneumatic chamber and configured to interact with its lower end and form a pneumatic lock with the upper end of the cylindrical stepwise waveguide provided with a sealing ring while its upper larger step is placed in the pneumatic chamber, and the lower one is passed through the bottom cover of the pneumatic chamber ery and equipped at its lower end with a radiating stove.

The high loading speed of the medium with this device is ensured by the fact that during depressurization of the pneumatic lock, compressed air acts almost simultaneously on the entire surface of the upper end of the waveguide, the area of which is comparable with the area of the emitting plate. However, this device is not excluded the main disadvantage. During its operation in the aquatic environment, repeated pulsations are also formed due to the reciprocating movements of the radiating plate. This is due to the fact that the damper cavity, isolated from the pneumatic chamber, acts as a pneumatic spring. With the expansion of compressed air in the pneumatic chamber during the displacement of the waveguide from it, air is compressed in the damper cavity. At the end of the forward travel of the waveguide, the force acting on it from the side of the damper cavity significantly exceeds the force acting on the air from the side of the pneumatic chamber. As a result, the waveguide returns inside the pneumatic chamber, accompanied by an increase in pressure in it and a drop in pressure in the damper cavity. And this process of reciprocating motion of the waveguide, generating ripples in the aquatic environment, with a certain attenuation coefficient lasts for some time.

The aim of the invention is to increase the efficiency of the device for the excitation of seismic waves in the water by eliminating repeated pulsations in the process of the working cycle.

The goal is achieved by the fact that in the source of seismic waves for marine seismic exploration, the board is fixedly mounted on the inner surface of the upper cover of the pneumatic chamber, and the waveguide forms a damper cavity connected to the pneumatic chamber by an annular channel formed by an internal cylindrical part on the final part of the working path with the inner surface of the lower cover the surface of the step of a larger diameter of the lower cover and the outer surface of the step of a larger diameter of the waveguide.

The essence of the invention is illustrated by the drawing, where Fig. 1 shows a general view of the device before the production of the duty cycle, and Fig. 2 is a view of the device under dynamic loading of the medium.

The device includes a pneumatic chamber 1 formed by a cylindrical body 2, upper 3 and lower 4 covers, while the inner surface of the lower cover 4 is made stepwise, a board 5 located in the upper part of the pneumatic chamber 1, and a cylindrical waveguide 6 is stepwise shaped. The upper step of the larger diameter of the waveguide 6 is placed in the pneumatic chamber 1, and the lower step is passed through the lower cover 4 and is equipped with a radiating plate 7 at its lower end. The board 5 is installed with the possibility of interaction and the formation of a pneumatic lock with its lower end with the upper ring provided with a sealing ring 8 the end of the waveguide 6. On the upper cover 3 there is a control valve 9 with a pusher 10 and a sealing element 11, a relief valve 12 and an inlet valve 13 with a connecting tube 14. The device is equipped anal 15, 16, 17 and 18, and an elastic shock absorber 19.

The device operates as follows. Before doing the work, the source of seismic waves on a cable (not shown) is lowered into the water to the optimum depth. Using the control valve 9, the pusher 10 is lowered down and the sealing element 11 blocks the channel 16 (see figure 1). Through the inlet valve 13, the tube 14 and the channel 15, compressed air is supplied from the surface to the pneumatic chamber 1. At the same time, a small portion of air is pushed between the board 5 and the upper end of the waveguide 6 through the relief valve 12. At the same time, a pneumatic lock is formed that holds the waveguide in the upper position when filling the pneumatic chamber 1 with compressed air. After reaching the air pressure in the pneumatic chamber 1 of the working size (10-15 MPa), the inlet valve 13 is closed. A control signal is supplied to the control valve 9, the pusher 10 moves upward and air from the pneumatic chamber 1 enters the pneumatic lock through the channels 18 and 16. The pneumatic lock is depressurized, air under the working pressure acts on the entire area of the waveguide 6 end face and moves it with acceleration downward. In this case, the pneumatic chamber 1 moves upward. However, since the mass of the pneumatic chamber 1 significantly exceeds the mass of the waveguide 6 with the radiating board 7, the movement of the pneumatic chamber 1 is negligible. At the final part of the waveguide’s travel (see FIG. 2), the step of the larger diameter of the waveguide 6 interacts with the step of the larger diameter of the lower cover 4. Moreover, during the displacement of compressed air from the formed damper cavity through the annular channel between the inner cylindrical surface of the step of larger diameter the lower cover 4 and the outer surface of the larger diameter of the waveguide 6 into the pneumatic chamber 1 is the braking movement of the waveguide 6. The final braking of the waveguide 6 occurs when e it to an elastic shock absorber 19, which excludes the rigid collision of the waveguide 6 and the bottom cover 4. Such damping waveguide 6 practically eliminates its repeated shuttle movement relative to the air bag 1.

After completion of the working cycle and obtaining a seismic recording of signals, air from the pneumatic chamber 1 through the inlet valve 13 and the connecting pipe 14 is discharged into the atmosphere. Under the influence of hydrostatic pressure, the waveguide 6 moves inside the pneumatic chamber 1 and the device takes its initial position (see figure 1) and is ready to repeat the duty cycle.

Due to the influence of the working air pressure from the very beginning of the waveguide 6 travel with the radiating plate 7 on the entire surface of the waveguide end 6, a high loading rate of the medium is ensured and high-frequency signals are generated. The use of damping of the waveguide 6 at the final part of its working stroke eliminates repeated pulsations during the working cycle of the device, which significantly increases its seismic efficiency.

Claims (1)

A source of seismic waves for marine seismic exploration, including a pneumatic chamber with a cylindrical body, upper and lower, made on its inner side in a stepped form, with covers, a circuit board located at the top of the pneumatic chamber and configured to interact with its lower end and form a pneumatic lock with an equipped sealing ring the upper end of the cylindrical stepwise waveguide, while its upper larger diameter step is placed in the pneumatic chamber, and the lower It is passed through the bottom cover of the pneumatic chamber and is equipped with a radiating plate on its lower end, characterized in that the board is fixedly mounted on the inner surface of the top cover of the pneumatic chamber, and the waveguide forms a damper cavity at some final part of the travel with the inner surface of the bottom cover of the pneumatic chamber, connected to the pneumatic chamber by an annular channel formed by the inner cylindrical surface of the step of a larger diameter of the lower cover of the pneumatic tion chamber and the outer surface of the waveguide larger stage diameter.

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