RU1805425C - Receiver for seismic prospecting of water areas - Google Patents

Abstract

Usage: the method is used in electrical exploration studies in shallow pools (depths of up to 200 m) with a monotonous relief: bottom. SUMMARY OF THE INVENTION: A multi-electrode installation consisting of supply and receiving electrodes is towed in the bottom layer, the distances between them increase exponentially. The minimum and maximum spacings are selected depending on the distance from the electrical prospecting installation to the bottom of the pool and the power of the studied thickness. In this case, the distance to the bottom is measured continuously using depth sensors. The depth of the electrodes is used in the processing of electrometric measurement data. 1 ill.

Description

The invention relates to the field of marine engineering geophysics, and in particular to marine electrical exploration.

The aim of the invention is to improve the quality of measurements.

The drawing shows a diagram of the observations and the design of the receiving device.

When solving engineering and geological problems in conditions of shallow water, electric profiling and electric sensing are carried out by multi-electrode devices of the ABMiNi (i 1-n) type, in which the electrode of the previous measuring device IMi, remote from the vessel, is closest to the vessel in the subsequent measuring unit. Mi-1. The distance BMi is selected age-; exponentially with coefficient V2-2. The length of the IAB supply line is not less than the magnitude of vmp. The number n 9 is established from experience. The parameters of the electrical exploration spit 1 are determined by the conditions of work - the depth of the sea and the depth

research; The minimum and maximum spacing are determined by condition (1): the minimum spacing is equal to half the distance at which the spit is towed from the seabed, the maximum spacing is equal to twice the sum of this distance and the thickness of the studied sediment thickness.

In order to provide towing of the electric cable in the bottom layer in the receiving device for marine electrical exploration, including a multicore cable with receiving electrodes distributed along its length along a successively increasing distance from the supply electrodes, and connected to the recording equipment on the carrier vessel with a flexible cable-rope, in the upper part of the receiving line there are supporting buoys in the form of sectionally distributed tubes filled with air, the length of which is established by the condition of hydrostatic equilibrium, and in

ate

with

00

about eating

Nь N5

ate

The initial and tail portions of the receiving line are respectively equipped with a depth sensor and a stabilizer. .

When moving along the profile, the electrodes of the receiving line should be at a distance of 0.5-1.0 m from the bottom when working on sites with a change in the size of the bottom by no more than 0.3-0.5 m.

The BMP receiving line is assembled from three lashes of different KTSh-03 logging cable lengths (3 electrodes on each lash). The supply line AB is made of a cable of the GPMP brand, the cable with the electrode B being rigidly connected to the cables of the receiving line, and the cable with the electrode A being released separately, at a fixed distance at the selected speed of the vessel. The supply lines provide a current strength of 1 to 20 A. Non-polarizing Mi-Mn electrodes are used in the receiving line, the housing is made of plexiglass, the electrodes are copper, the electrode is fixed to the housing and isolated from water when connected. cable is produced by epoxy resin. The space between the casing and the electrode is filled with a helium filler (sulphurous-copper on a gelatinous base). Through which the electrodes come into contact with the medium, the supply electrodes are lead or carbon. Insulation of the junction points of the electrodes with the cable is carried out, for example, with epoxy resin. . ..

Supporting buoys 1-1 are made of polyvinyl chloride tubes, sec-: c ionically distributed along the receiving line, the VM line and attached to the receiving cable; da, lines;.: -. .:,: The total length of the sections of the supporting bu 1 should ensure zero buoyancy of the receiving line under the condition of its hydrostatic equilibrium (the settlement speed is low 3-5 knots, then the hydrodynamic characteristics of the braid can be ignored). For the conditions of a particular water area (for a given salinity of water), the total mass of the portion of the receiving line of the line is taken; with two or one lashes of a logging cable D, the masses in water and the lifting force per unit length are calculated. From the condition of hydrostatic equilibrium, the total length of the support buoy is determined. After that, sections of 5-10 m are distributed along the receiving line Proportional to the mass of its sections, pipe sections filled with air.

The position of the receiving line of the PMP is monitored using depth sensors 2 (for example, pressure or acoustic sensors), as indicated

which continuously measure the installation distance from

 - the seabed for subsequent correction of the measurement results.

A stabilizer 3 (for example, of the type of a parachute) is placed in the rear part of the BMP receiving line, which ensures the constant tension of the receiving line.

The design of the electrical exploration receiver provides zero

buoyancy at a given depth with a measurement of towing parameters (distance 1

from bottom) according to depth sensors

2 and adjusting the distance by means of 5. the slack of the cable and the speed of the carrier ship. Retention at a given towing depth ensures that the reception conditions are identical for all the electrodes of the receiving line distributed along its length, which allows you to confidently enter the correction for the depth of the water layer and ensure the necessary, quality of measurements ..

Such conditions of towing and the choice of spacing according to condition (1) significantly approximate the conditions of work to the bottom towing, which is necessary to solve engineering and geological problems, and at the same time have the advantage that they meet environmental requirements and are not compatible 0 create additional electrical noise during the movement of the braid and the danger of clipping the braid from uneven terrain. . SUMMARY OF THE INVENTION A method for offshore electrical exploration of offshore zones 5, which consists in towing a multi-electrode installation consisting of supply and receiving electrodes. of genera located at distances growing exponentially, 0 measure the current strength and the potential difference and determine the values of electrical resistivity, which are used to judge the parameters of the geoelectric section, characterized in that, for the purpose of improving the quality of measurements during geotechnical investigations by eliminating the influence of the water layer on the measurement results,. Towing the multi-electrode installation 0 is carried out in the bottom layer with continuous measurement of the distance to the seabed, while the minimum Gmin and maximum Gmax plant spacing are set by the condition

5Gmin 1 / 2h0,,: -. Gmax 1 (H + ho), -

where h0 is the distance from the electrical exploration

 installation to the seabed;

 - N - power of the studied soil strata.

about

&

Ј