RU2510051C1 - Bottom station for marine geophysical survey - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: disclosed is a bottom station for marine geophysical survey, having a housing which accommodates a unit of buoys, a signal recorder, movable bars with non-polarisable electrodes, sensors, including induction sensors, an opening switch, an antenna, a power supply unit and an anchor. The bottom station further includes a three-component ferroprobe. At least two devices from a group which includes a sensor, a recorder, a power supply unit and an acoustic system, are placed in separate sealed housings, lying at a distance of 2-5 m from the station and connected to the housing by cantilevers. Induction sensors lying inside the housing of the station are arranged such that the centres of induction coils are maximally close to each other.

EFFECT: high accuracy of exploration data.

4 cl, 2 dwg

Description

The invention relates to the field of exploration geophysics, in particular to equipment complexes for geoelectrical exploration using apparent resistivity and magnetotelluric methods, and is intended for predicting hydrocarbon deposits under the seabed and studying the deep structure of the earth's crust.

Currently, marine stations of various designs and purposes are widely used for marine geophysical studies.

Thus, a self-floating electromagnetic station is known (US 5770945, 2010), which has two mutually orthogonal induction magnetic field sensors located in the station’s body, and a system for measuring the horizontal components of the electric field, consisting of horizontal semi-rigid rods (“arms”) attached to the station’s body five meters each with electrodes at the ends.

The disadvantage of the station is the ability to measure only two components, as well as the fact that the main structural elements - a recorder, a power source, a speaker circuit breaker are located inside the station housing near the primary field sensors - induction converters and affect them, increasing the noise level, and also affect on the readings of the magnetic compass in the sensor for determining the angles, which leads to significant errors in determining the orientation of the station. In addition, this design of the station requires free space on the deck with an area of at least 100 square meters. meters and special equipment for hoisting operations.

Closest to the technical nature of the claimed design is a self-floating station for electromagnetic measurements (US 6842006, 2002). The station has a hull, a block of glass buoyancy, a signal recorder, sensors, a breaker, an antenna, a power supply and an anchor. Rods with a length of five meters and a diameter of about five centimeters with electrodes forming two mutually perpendicular dipoles can freely move in a vertical plane, which simplifies the hoisting operations. Induction sensors (from one to four) are located within the length of the rods, usually closer to their end to reduce the influence of the station's magnetic masses on the results of magnetic field measurements. The station is brought overboard with booms directed vertically downward, which, although it simplifies the descent of the station, requires a special crane with a high lifting height and, in addition, increases the likelihood of damage to the electrodes and induction sensors when the water flow during descent does not have time to translate rods in a vertical position or bends one or more rods under the load.

The disadvantage of the station is the ability to measure only two components, as well as the incompletely eliminated negative impact associated with the interference caused by operating devices. Another disadvantage of this and other existing stations is the use of predominantly induction magnetic field sensors in existing stations, which have a high noise level at low frequencies.

The problem solved by the authors is to create a station design that allows to reduce the impact of interference and to carry out more reliable geophysical measurements.

The proposed solution is based on the use of a three-component flux-probe sensor (FZD) at the station, which provides registration of three orthogonal components of the magnetic field, whose strong influence on other measuring channels did not allow their previous use in bottom stations, as well as the creation of a design that minimizes such an effect.

The technical result was achieved by creating a design in which, along with the use of FZD, equipment that can affect the measured signals is placed in separate sealed cases, 2-5 meters away from the station case. The nomenclature of such equipment includes at least two elements from the group that includes the sensor, recorder, power supply and speaker system. However, it is possible to remove additional elements from the station building

An additional improvement in the operation of the station is achieved by arranging the magnetic sensors inside the station housing so that the centers of the induction coils are as close to each other as possible. Such an arrangement, unlike the analogs, where they are placed on the rods, provides the measurement of three components of the magnetic field (and not two, as in the analogue), which makes it possible to have a complete vector. Through the use of FZD, three components are also measured, but in the low-frequency range (0-1000 Hz).

Remote devices are connected to the body, as a rule, using consoles made of non-magnetic material, such as plastic or aluminum-magnesium alloy.

Figure 1 shows the station, a top view; figure 2 shows the station, side view. The following notation is used:

1. The station building.

2. The buoyancy unit.

3. Consoles of blocks 9, 10, 11, 12.

4. Rods with non-polarizing electrodes.

5. Induction sensors.

6. Breakers.

7. Acoustic antenna.

8. Anchor.

9. Fluxgate sensor in a sealed housing.

10. Signal recorder in a sealed enclosure.

11. The power supply in a sealed enclosure.

12. The acoustic system of the circuit breaker with a pressure sensor in a sealed enclosure.

13. The angle sensor in a sealed enclosure.

14. The lock of temporary fastening of consoles in a quasi-vertical position.

Station building 1, as a rule, is made of non-wettable material, such as fluoroplastic, to prevent the station building from sticking to the ground.

Inside the housing 1 there are a buoyancy unit 2 made of syntactics or glass spheres, an orthogonal rod system with electrodes 4, which provides measurement of three components of the electric field, an orthogonal system 5 of induction sensors, which measures three components of the magnetic field in the frequency range 0.001-500 Hz, electrochemical breakers 6, an acoustic antenna 7 and an angle sensor 13.

Elements that can influence the measured signals are a fluxgate sensor 9, which provides registration of three cortogonal components of the magnetic field in the range 0-0.003 Hz, a recorder 10, a power supply 11, and an acoustic system 12, are placed in sealed enclosures and placed from the station a distance of 2-5 meters using consoles 3 made of non-magnetic material, such as polyethylene, or an aluminum-magnesium alloy.

The power supply 11 (battery or battery), as a rule, is placed in a pressure housing on a separate console. This option is preferable for long-term productions, since it allows you to completely replace the module when using any type of source and does not require additional costs of ship time. At the same time, it is possible that the power sources are located in the recorder module 10 and / or the disconnector module 6, and the fluxgate sensor 9 is powered from one of the sources, for example, from the recorder. Such a scheme is especially attractive when working with an active source, where a fluxgate sensor is not required and can be limited to two consoles. But in this case, it is preferable to use batteries in the power supply 11, since they can be charged without opening the case through the connector.

Induction sensors 5, FZD 9, electrodes on the rods 4, as a rule, are connected to the registrar 10; antenna 7, angle sensor 13, circuit breaker 6 - to the circuit breaker module. For ease of connection and reducing the number of connectors on the pressurized enclosures of the modules, the connection can be carried out through an additionally installed switching unit, which is powered up during operation according to the first embodiment.

Consoles 3 can be fixed in a horizontal position or rotate freely around a horizontal axis to simplify hoisting operations.

The number of consoles 3, depending on the features of the equipment used, is, as a rule, from 2 to 6. So, when working with artificial fields in the higher frequency range, where a flux-probe sensor is not required, 2 or 3 consoles are used. In this case, the power sources can be located directly in the pressurized housing of the recorder 10 and acoustics 12. The angle sensor 13 can be connected to the speaker system 12 to transmit information about the orientation of the station at the bottom through the acoustic channel to the ship.

Sealed enclosures of modules 9-13 and induction sensors 5, as a rule, are equipped with vacuum ports (not shown) to exclude moisture formation inside the enclosures and exclude leaks.

Depending on the number of consoles and the features of the hoisting device used, the shape of the station building 1 can have a circle or polygon shape in horizontal section.

The station operates as follows. Consoles 3 before descent using the temporary lock 14, as a rule, are fixed in a quasi-vertical position with an angle of inclination of 10-15 degrees. After lowering the station overboard, the locks 14 are automatically activated under the weight of the station after it has been separated from the launching and lifting device. Consoles 3 maintain a quasi-vertical position during descent due to the flow of water, and when the station reaches the bottom they are moved to a horizontal position under the influence of the weight of modules 9-12 and the initial angle of the consoles. On command from the vessel, the station begins to take measurements, and then, after receiving the corresponding signal, the breakers 6 and the armature are released 8. The cantilevers 3 are ascended in a quasi-vertical position when ascending, which provides a minimum of three times the station ascent speed compared to the design, in which consoles are fixed horizontally.

The inventive design has passed successful field trials, which showed the possibility of obtaining with its help more accurate data on the structure of the seabed. Compared with other stations, the claimed design is more compact and convenient to use.

Claims (4)

1. The bottom station for marine geophysical exploration, comprising a housing in which a buoyancy unit, a signal recorder, movable rods with non-polarizing electrodes, sensors, including induction, a disconnector, an antenna, a power supply and an armature, characterized in that it is additionally used as sensors contains a three-component flux-probe, and at least two devices from the group including a sensor, a recorder, a power supply and an acoustic system are placed in separate sealed enclosures assigned to t of the station building at a distance of 2-5 meters and connected to the case by means of consoles, and the induction sensors located inside the station case are located so that the centers of the induction coils are as close to each other as possible. 2. The bottom station for marine geophysical exploration according to claim 1, characterized in that it has from 2 to 6 consoles. 3. The bottom station for marine geophysical exploration according to claim 4, characterized in that the consoles are fixed in a horizontal position. 4. The bottom station for marine geophysical exploration according to claim 4, characterized in that the consoles rotate freely around a horizontal axis

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