Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
  • G01V1/00—Seismology; Seismic or acoustic prospecting or detecting
  • G01V1/16—Receiving elements for seismic signals; Arrangements or adaptations of receiving elements

Definitions

• the present invention relates to a device arranged to be set down into the sea bed and comprising instruments for collecting and recording signals during seismic exploration of the substructures below a body of water, comprising a central main body having a substantially cylindrical shape, a pointed end portion and a head portion adapted for set ⁇ ting/pulling and other reguired handling of the device.
• the shear waves do not travel in water and cannot therefore be detected by a hydrophone cable. Moreover, with today's conventional hydrophone technology, it is not poss ⁇ ible to detect the directions of the measured signals, and this severely complicates possibilities for true three-dimen ⁇ sional data collection.
• the device shown in fig. 1 has a pole-like shape and compri ⁇ ses a cylindrical portion 1, a lower conically shaped or pointed end 2 and an upper portion 3.
• the upper portion 3 is compatible with equipment for inserting the pole down into, or pulling it out of the sea bed.
• the upper portion is designed with a narrowing part 4 and an upper flange 5.
• This design is chosen so that the flange 5 can be utilized as a striking organ for forcing the pole down into the sea bed, and the narrow part 4 is useful for when an engaging organ on a submarine vessel is to pull up the pole from the sea bed by making contact with the under side of the flange.
• the pointed end 2 of the pole is insulated from the rest of the pole by a vibration insulating spacer 6 made of an elastomer.
• the actual point has a completely conical shape which makes it easier for the pole to penetrate down into the sea bed.
• Other forms of embodiment are also applicable, for example a point divided into two with a lower cone shape ending in a shoulder and thereafter progressing into a new cone portion.
• the cylindrical part 1 of the pole constitutes the main volume of the pole and comprises a substantial part of all the equipment.
• the pointed end of the pole comprises three geophones 7- 9 arranged three-dimensionally in an x, y, and z direction.
• the geophones 7-9 which as such are of a type known per se are commercially available.
• the geophones are shown as being moulded into the pointed end by means of a polymer material.
• an electronic angle gauge 10a is also placed, which, based on the force of gravity gives the angle of the pole with the vertical axis.
• the end comprises further a compass 10b from which the rotation of the pole in the plane can be read.
• the cylindrical portion 1 of the pole contains the other equipment components.
• a processor 12 which at least processes signals from the geophones 7-9, from the electronic angle gauge lOa/the compass 10B and from a hydrophone which will be more closely described later.
• a memory unit 13 is placed. Seismic data, as well as background information about angle and direction is stored partly in the processor 12 and partly in the memory part 13.
• the pole comprises further a power supply unit 14 for supply of power to the various units.
• the uppermost unit in the pole comprises a hydrophone 17 which is a transducer for pressure waves. Pressure and shear waves (P and S waves) which are reflected from the sediments, are detected by the three-dimensional geophones placed in the lower pointed end 2 of the geopole, while the hydrophone 17 only detects pressure waves in the water layer.
• P and S waves Pressure and shear waves
• the object of the invention is to obtain an improved device to detect three-dimensional pressure and shear waves travelling through the substratum, and in particular to obtain a device which even when arranged in a soft sea bed portion is not brought into uncontrolled movements in rela ⁇ tion to the sea bed.
• the principle of the invention is to obtain an improved device to detect three-dimensional pressure and shear waves travelling through the substratum, and in particular to obtain a device which even when arranged in a soft sea bed portion is not brought into uncontrolled movements in rela ⁇ tion to the sea bed.
• the pole As with the earlier known geopoles it comprises a lower pointed end 2, an intermediate substantially cylindrical portion 1, and an upper handling portion 3. Along the outer surface of the cylindrical portion the pole is provided with a simple, continuous screw thread 21 running without interruptions from the pointed end of the pole up to the upper handling portion.
• the height of the thread h has to be adapted to the actual conditions on the bottom where the pole is to be used. However, it generally is desirable to use threads having a lower height when the bottom is firm.
• threads 21 having differenct cross-sectional shapes may be used. However, threads having a narrow section or profile are preferred so that the pole more easily may be screwed down into the bottom.
• the projec- ted area of the pole (in its length direction) is large and adapted to the nature (density) of the sea bed and the weight of the pole.
• threads having a pitch p typically in the range given by half of total dia- meter Ds of the threads.
• p typically in the range given by half of total dia- meter Ds of the threads.
• the number of times which the pole has been turned may be recorded by the integrated compass.
• the pole may be equiped with a small source (seis ⁇ mic source) .
• a small source such as a magnetomy source
• This evaluation may be undertaken for each pole or if a pole generates (a) somewhat stronger sig ⁇ nal(s) which closely arranged poles receive and calculate to decide the engagement.
• the handling portion of the pole is, according to a preferred embodiment, designed as a head shaped as a nut (not shown in the figure) to enlighten the handling with a tool when the pole is to be rotated.
• a manned or unmanned submarine vessel equiped with the required tool is used.
• the pole is first pressed towards the bottom so that at least the lower pointed end is partly penetrated into the sea bed.
• a rotating tool turns the pole a pre-determined number of times so that it is screwed down into the sea bed. In this position the pole stands stable and has a very good connection with the sea bed.
• the pole is in a similar way screwed out from the sea bed.

Landscapes

• Physics & Mathematics (AREA)
• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Acoustics & Sound (AREA)
• Environmental & Geological Engineering (AREA)
• Geology (AREA)
• Remote Sensing (AREA)
• General Life Sciences & Earth Sciences (AREA)
• General Physics & Mathematics (AREA)
• Geophysics (AREA)
• Geophysics And Detection Of Objects (AREA)
• Eye Examination Apparatus (AREA)
• Centrifugal Separators (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=19894100

Family Applications (1)

Country Status (3)

Cited By (8)

Citations (2)

• 1991
  • 1991-04-25 NO NO911639A patent/NO172823C/no not_active IP Right Cessation
• 1992
  • 1992-04-27 WO PCT/NO1992/000080 patent/WO1992019991A1/en active Application Filing
  • 1992-04-27 AU AU19827/92A patent/AU1982792A/en not_active Abandoned

Patent Citations (2)

Non-Patent Citations (2)

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