US3493074A - Marine seismographic prospecting - Google Patents

Marine seismographic prospecting Download PDF

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US3493074A
US3493074A US710616A US3493074DA US3493074A US 3493074 A US3493074 A US 3493074A US 710616 A US710616 A US 710616A US 3493074D A US3493074D A US 3493074DA US 3493074 A US3493074 A US 3493074A
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explosive
cord
charge
drag
charges
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US710616A
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Frank Mcdonald Murray
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Imperial Chemical Industries Ltd
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Imperial Chemical Industries Ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V1/00—Seismology; Seismic or acoustic prospecting or detecting
    • G01V1/38—Seismology; Seismic or acoustic prospecting or detecting specially adapted for water-covered areas
    • G01V1/393—Means for loading explosive underwater charges, e.g. combined with ignition devices
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63G—OFFENSIVE OR DEFENSIVE ARRANGEMENTS ON VESSELS; MINE-LAYING; MINE-SWEEPING; SUBMARINES; AIRCRAFT CARRIERS
    • B63G8/00—Underwater vessels, e.g. submarines; Equipment specially adapted therefor
    • B63G8/42—Towed underwater vessels
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V1/00—Seismology; Seismic or acoustic prospecting or detecting
    • G01V1/02—Generating seismic energy
    • G01V1/104—Generating seismic energy using explosive charges
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V1/00—Seismology; Seismic or acoustic prospecting or detecting
    • G01V1/38—Seismology; Seismic or acoustic prospecting or detecting specially adapted for water-covered areas

Definitions

  • An assembly for marine seismographic prospecting comprises a plurality of lengths of fuse cord and a plurality of lengths of non-explosive cord, each of the latter being connected between two of the lengths of fuse cord.
  • drag elements are attached to the non-explosive cords so that sequential lengths of fuse cord will be dragged into the water after the initial drag element is thrown into the water from a moving boat.
  • This invention relates to a method of laying elongated explosive charges underwater in marine seismographic prospecting operations and to an assemblyof explosive charges for use therein.
  • elongated explosive charges for marine seismographic prospecting in order to diminish the effect on the seismographic record of the expanding and contracting gas bubble produced by the explosion.
  • One form of elongated explosive charge which is favoured for this purpose is detonating fuse-cord in lengths of at least 15 metres comprising a core of a granular high explosive such as pentaerythritoltetranitrate (PETN) or cyclotrimethylenetrinitramine, surrounded by textile wrappings and encased in a flexible waterproof envelope of synthetic plastic material.
  • PETN pentaerythritoltetranitrate
  • cyclotrimethylenetrinitramine surrounded by textile wrappings and encased in a flexible waterproof envelope of synthetic plastic material.
  • the elongated explosive is stored as a bulk supply on reels on a boat and each individual charge in withdrawn as required from the reel, cut from the supply, fitted with detonation initiating means and fed into the water behind the moving boat. At least the initial portion of the elongated charge must be positively fed from the boat into the water until sufficient length is immersed for the drag of the water to pull the remainder from the boat.
  • a method of laying elongated explosive charges consecutively in position for firing in marine seismographic prospecting comprises immersing in the water at a prospect area a first drag elesufficient length to prevent communication of detonation from one charge to the next.
  • Each drag element may be in the form of a non-explosive cord which may be joined at its ends to consecutive explosive charges.
  • a vane which may be in the form of a disc or funnel, is attached to the cord to present a resistance area perpendicular to the cord.
  • the elongated explosive charges may conveniently be lengths of detonating fuse-cord, and in this case the charges are conveniently joined together by intermediate lengths of non-explosive cord or string which are preferably joined to the fuse-cord by crimped metal sleeve Joints.
  • the arrangement of charges may advantageously be stored on reels which may be mounted for rotation on an axle to permit the charges to be withdrawn as required.
  • the charges are conveniently fired by means of detonating initiating means comprising an electric detonator and for this purpose a long firing cable terminating in an uninsulated hook may be trailed behind the boat so as to sink the charge to the required firing depth.
  • a metal slipring on the cable is attached to one terminal wire of the electric detonator and is also attached by a tie member to an explosive charge, the tie member being arranged to prevent strain on the terminal wire.
  • the other terminal wire of the detonator is left free.
  • the drag element When the first explosive charge is fired the drag element is left trailing in the water and the drag may be used to pull the next charge into the water.
  • the invention also includes a method of producing a seismic record of underwater rock formations which comprises laying an elongated explosive charge at a pros ect area by the aforedescribed method, detonating the explosive charge and receiving and recording the resulting seismic waves reflected or refracted from the underwater rock layer interfaces.
  • FIG. 2 shows diagrammatically. an explosive charge being towed behind a boat in position for firing.
  • the assembly of elongated explosive charges for use in the invention comprises two or more elongated explosive charges joined one end of one to one end of another by means of one or more intermediate drag elements of
  • the charge assembly shown in FIG. 1 comprises lengths of detonating fuse-cord 11 and lengths of cotton string 12 arranged alternately with their ends joined by a crimped aluminium sleeve 13.
  • the assembly is stored on a reel 14.
  • the reel 14 In using the assembled charge for seismographic prospecting the reel 14 is mounted for free rotation around its axis on a boat 15 (shown in FIG. 2) from which an insulated firing cable 16 terminating in a bare metal book 17 is towed as the boat is moved over the prospect sea area.
  • a funnel-shaped metal drag member 18 is crimped on the end length of string 12 to augment the drag on the string 12, and this end length of string 12 is thrown into the sea.
  • the first length of detonating fuse-cord is thereby pulled into the sea, but before it leaves the boat it is temporarily stopped and an electric detonator 19 is crimped to it by means of a deformable metal clip 20.
  • a metal slip-ring 21 which is around the firing cable 16 is joined to the length of detonating fuse-cord 11 by means of a cotton string 22 and a crimped metal sleeve 13 and is also joined to a bared end portion of one of the terminal wires 2-4 of the detonator 19.
  • a further drag member 18 is crimped on the next length of string 12 and the assembly is released.
  • the slip-ring 21 slides along the cable 16 until it reaches the hook 17 Where it is arrested.
  • the string 22 becomes taut and the immersed charge is dragged at a fixed distance behind the boat as shown in FIG.
  • the second terminal wire 25 has a bared end portion which lies in the water to provide an earth return for the firing circuit.
  • the charge in this position is fired by applying a high voltage between the cable and the boat.
  • the length of detonating fuse-cord 11 is destroyed and the next length of string 12 is free to be pulled away from the boat thereby to draw a further length of detonating fuse-cord 11 into the Water.
  • Slip-rings 21 from fired charges are pushed off the end of the hook 17 into the water by subsequent rings 21 being moved into the firing position.
  • the lengths of detonating fuse-cord may be varied over a wide range as desired but lengths of 15 to 150 metres of a detonating fuse commercially available as Cordtex (registered trademark) containing -20 g. of PETN per metre have been found convenient.
  • the lengths of string 12 may also vary widely but lengths of to 50 metres are usually sufficient to separate the detonating fuse-cord charges sufiiciently to enable one charge to be fired without any portion of the next charge being in the water.
  • a method of laying elongated explosive charges consecutively in position for firing in marine seismographlc prospecting which comprises immersing in the water at a prospect area a first drag element attached to one end of an elongated explosive charge on a moving boat, permitting said explosive charge to be drawn into the water by the pull of the drag element, attaching detonation initiating means and a second drag element to the other end of said explosive charge, and permitting the second drag element to be drawn into the water by the pull of the first drag element, said second drag element being also joined to one end of a next consecutive explosive charge and being of sufficient length to separate the ends of consecutive explosive charges sufiiciently to prevent communication of detonation from one charge to the next.
  • each drag element comprises a non-explosive cord.
  • An assembly of elongated explosive charges for use in marine seismographic prospecting comprising at least two elongated explosive charges, each including a length of detonating fuse cord, joined one end of one to one end of another by means of intermediate drag elements of sufficient length to prevent communication of detonation from one charge to the next, each of said drag elements including a length of non-explosive cord joined to the fuse cord by crimped metal sleeve joints.
  • a method of producing a record of underwater rock formations which comprises laying an elongated explosive charge at a prospect area by a method as claimed in claim 1, detonating said explosive charge and receiving and recording the resulting seismic waves reflected or refracted from the underwater rock layer interfaces.
  • An assembly of elongated explosive charges for use in marine seismographic prospecting comprising a pinrality of distinct elongated explosive charges and a plurality of elongated distinct intermediate drag elements of sufiicient length to prevent communication of detonation from one explosive charge to the next, the opposite ends of each drag element being connected to one end of a different explosive charge.
  • each drag element comprises a non-explosive cord.
  • An assembly as in claim 8 including a vane attached to the non-explosive cord to present a resistance area perpendicular to the non-explosive cord.
  • each of the explosive charges comprises a detonating fuse cord.

Description

1970 FR ANK M DONALD MURRAY 3,493,074
' MARINE SEISMOGRAPHIC PRQSPECTING V Fi1ed March 5. 1968 United States Patent 3,493,074 MARINE SEISMOGRAPHIC PROSPECTING Frank McDonald Murray, Kilmarnock, Scotland, assignor to Imperial Chemical Industries Limited, London, England, a corporation of Great Britain Filed Mar. 5, 1968, Ser. No. 710,616 Claims priority, application Great Britain, Mar. 10, 1967, 11,316/ 67 Int. Cl. G01v l/38 US. Cl. 181-5 11 Claims ABSTRACT OF THE DISCLOSURE An assembly for marine seismographic prospecting comprises a plurality of lengths of fuse cord and a plurality of lengths of non-explosive cord, each of the latter being connected between two of the lengths of fuse cord. In use drag elements are attached to the non-explosive cords so that sequential lengths of fuse cord will be dragged into the water after the initial drag element is thrown into the water from a moving boat.
This invention relates to a method of laying elongated explosive charges underwater in marine seismographic prospecting operations and to an assemblyof explosive charges for use therein.
It has recently been proposed to use elongated explosive charges for marine seismographic prospecting in order to diminish the effect on the seismographic record of the expanding and contracting gas bubble produced by the explosion. One form of elongated explosive charge which is favoured for this purpose is detonating fuse-cord in lengths of at least 15 metres comprising a core of a granular high explosive such as pentaerythritoltetranitrate (PETN) or cyclotrimethylenetrinitramine, surrounded by textile wrappings and encased in a flexible waterproof envelope of synthetic plastic material. In the marine seismographic prospecting operations the elongated explosive is stored as a bulk supply on reels on a boat and each individual charge in withdrawn as required from the reel, cut from the supply, fitted with detonation initiating means and fed into the water behind the moving boat. At least the initial portion of the elongated charge must be positively fed from the boat into the water until sufficient length is immersed for the drag of the water to pull the remainder from the boat.
It is an object of this invention to provide a method of laying elongated charges underwater for seismographic prospecting wherein all the charge is pulled from the boat by the drag of the water and to provide an assembly of charges whereby this may be achieved.
In accordance with this invention a method of laying elongated explosive charges consecutively in position for firing in marine seismographic prospecting comprises immersing in the water at a prospect area a first drag elesufficient length to prevent communication of detonation from one charge to the next.
Each drag element may be in the form of a non-explosive cord which may be joined at its ends to consecutive explosive charges. In a preferred form having improved drag, a vane, which may be in the form of a disc or funnel, is attached to the cord to present a resistance area perpendicular to the cord.
The elongated explosive charges may conveniently be lengths of detonating fuse-cord, and in this case the charges are conveniently joined together by intermediate lengths of non-explosive cord or string which are preferably joined to the fuse-cord by crimped metal sleeve Joints.
The arrangement of charges may advantageously be stored on reels which may be mounted for rotation on an axle to permit the charges to be withdrawn as required.
The charges are conveniently fired by means of detonating initiating means comprising an electric detonator and for this purpose a long firing cable terminating in an uninsulated hook may be trailed behind the boat so as to sink the charge to the required firing depth. A metal slipring on the cable is attached to one terminal wire of the electric detonator and is also attached by a tie member to an explosive charge, the tie member being arranged to prevent strain on the terminal wire. The other terminal wire of the detonator is left free. When the explosive charge is pulled from the boat the metal slip-ring slides down the cable to contact and to engage and be held by the hook. The free terminal wire trails in the sea to pro vide an earth return for the firing circuit. The charge is thus held in position for firing and the firing circuit through the detonator is ready for firing and may be fired by applying an appropriate voltage to the cable.
When the first explosive charge is fired the drag element is left trailing in the water and the drag may be used to pull the next charge into the water.
The invention also includes a method of producing a seismic record of underwater rock formations which comprises laying an elongated explosive charge at a pros ect area by the aforedescribed method, detonating the explosive charge and receiving and recording the resulting seismic waves reflected or refracted from the underwater rock layer interfaces.
Further features of the invention are included in the preferred embodiment which is hereinafter described, by
way of example only, with reference to the accompanying drawings wherein FIG. 2 shows diagrammatically. an explosive charge being towed behind a boat in position for firing.
ment attached to one end of an elongated explosive charge v.
on a moving boat, permitting said explosive charge to be drawn into the water by the pull of the drag element, attaching to the other end of said explosive charge detonation initiating means and a second drag element, and permitting the second drag element to be drawn into the water by the pull of the first drag element, said second drag element being also joined to one end of the next consecutive explosive charge and being of sufficient length to separate the ends of the consecutive explosive charges sufliciently to prevent communication of detonation from one charge to the next.
The assembly of elongated explosive charges for use in the invention comprises two or more elongated explosive charges joined one end of one to one end of another by means of one or more intermediate drag elements of The charge assembly shown in FIG. 1 comprises lengths of detonating fuse-cord 11 and lengths of cotton string 12 arranged alternately with their ends joined by a crimped aluminium sleeve 13. The assembly is stored on a reel 14.
In using the assembled charge for seismographic prospecting the reel 14 is mounted for free rotation around its axis on a boat 15 (shown in FIG. 2) from which an insulated firing cable 16 terminating in a bare metal book 17 is towed as the boat is moved over the prospect sea area. A funnel-shaped metal drag member 18 is crimped on the end length of string 12 to augment the drag on the string 12, and this end length of string 12 is thrown into the sea. The first length of detonating fuse-cord is thereby pulled into the sea, but before it leaves the boat it is temporarily stopped and an electric detonator 19 is crimped to it by means of a deformable metal clip 20. A metal slip-ring 21 which is around the firing cable 16 is joined to the length of detonating fuse-cord 11 by means of a cotton string 22 and a crimped metal sleeve 13 and is also joined to a bared end portion of one of the terminal wires 2-4 of the detonator 19. A further drag member 18 is crimped on the next length of string 12 and the assembly is released. The slip-ring 21 slides along the cable 16 until it reaches the hook 17 Where it is arrested. On further movement of the boat 15 the string 22 becomes taut and the immersed charge is dragged at a fixed distance behind the boat as shown in FIG. 2 so that the terminal wire 24 is not tensioned The second terminal wire 25 has a bared end portion which lies in the water to provide an earth return for the firing circuit. The charge in this position is fired by applying a high voltage between the cable and the boat. On firing the length of detonating fuse-cord 11 is destroyed and the next length of string 12 is free to be pulled away from the boat thereby to draw a further length of detonating fuse-cord 11 into the Water. Slip-rings 21 from fired charges are pushed off the end of the hook 17 into the water by subsequent rings 21 being moved into the firing position.
The lengths of detonating fuse-cord may be varied over a wide range as desired but lengths of 15 to 150 metres of a detonating fuse commercially available as Cordtex (registered trademark) containing -20 g. of PETN per metre have been found convenient. The lengths of string 12 may also vary widely but lengths of to 50 metres are usually sufficient to separate the detonating fuse-cord charges sufiiciently to enable one charge to be fired without any portion of the next charge being in the water.
What I claim is:
1. A method of laying elongated explosive charges consecutively in position for firing in marine seismographlc prospecting which comprises immersing in the water at a prospect area a first drag element attached to one end of an elongated explosive charge on a moving boat, permitting said explosive charge to be drawn into the water by the pull of the drag element, attaching detonation initiating means and a second drag element to the other end of said explosive charge, and permitting the second drag element to be drawn into the water by the pull of the first drag element, said second drag element being also joined to one end of a next consecutive explosive charge and being of sufficient length to separate the ends of consecutive explosive charges sufiiciently to prevent communication of detonation from one charge to the next.
2. A method as claimed in claim 1 wherein each drag element comprises a non-explosive cord.
3. A method as claimed in claim 2 wherein a vane is attached to the cord to present a resistance area perpendicular to the cord.
4. A method as claimed in claim 1 wherein the explosive charge comprises detonating fuse-cord.
5. An assembly of elongated explosive charges for use in marine seismographic prospecting comprising at least two elongated explosive charges, each including a length of detonating fuse cord, joined one end of one to one end of another by means of intermediate drag elements of sufficient length to prevent communication of detonation from one charge to the next, each of said drag elements including a length of non-explosive cord joined to the fuse cord by crimped metal sleeve joints.
6. A method of producing a record of underwater rock formations which comprises laying an elongated explosive charge at a prospect area by a method as claimed in claim 1, detonating said explosive charge and receiving and recording the resulting seismic waves reflected or refracted from the underwater rock layer interfaces.
7. An assembly of elongated explosive charges for use in marine seismographic prospecting comprising a pinrality of distinct elongated explosive charges and a plurality of elongated distinct intermediate drag elements of sufiicient length to prevent communication of detonation from one explosive charge to the next, the opposite ends of each drag element being connected to one end of a different explosive charge.
8. An assembly as in claim 7 wherein each drag element comprises a non-explosive cord.
9. An assembly as in claim 8 including a vane attached to the non-explosive cord to present a resistance area perpendicular to the non-explosive cord.
' 10. An assembly as in claim 9 wherein said vane is in the form of a disc or funnel.
11. An assembly as in claim 8 wherein each of the explosive charges comprises a detonating fuse cord.
References Cited UNITED STATES PATENTS 2,609,885 9/1952 Silverman.
2,729,300 1/1956 Paslay et al.
2,790,388 4/1957 MacLeod 10221.8 X 3,064,568 11/1962 Ainslie et al. 102-9 3,118,374 1/1964 Karpovich 102-216 X 3,125,859 3/1964 Dilbey 102-13 X 3,354,826 11/1967 Axelson et al. 10210 X VERLIN R. PENDEGRASS, Primary Examiner US. Cl. X.R. 102 1, 13, 27
US710616A 1967-03-10 1968-03-05 Marine seismographic prospecting Expired - Lifetime US3493074A (en)

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GB01316/67A GB1168095A (en) 1967-03-10 1967-03-10 Marine Seismographic Prospecting

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FR (1) FR1556117A (en)
GB (1) GB1168095A (en)
MY (1) MY7000091A (en)
NL (1) NL158940B (en)
OA (1) OA02757A (en)
SE (1) SE333698B (en)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3908789A (en) * 1972-03-30 1975-09-30 Texaco Inc Methods for generating and shaping a seismic energy pulse
US4034672A (en) * 1976-01-02 1977-07-12 Eckels Robert E Linear explosive
CN110609316A (en) * 2019-10-22 2019-12-24 辽宁科技大学 Protection device for microseismic monitoring sensor in tunnel and use method thereof
WO2023222327A1 (en) * 2022-05-19 2023-11-23 Thales Towed submarine device

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2609885A (en) * 1950-12-29 1952-09-09 Stanolind Oil & Gas Co Seismic-wave generation
US2729300A (en) * 1949-11-29 1956-01-03 Marine Instr Company Water borne means for making seismic surveys
US2790388A (en) * 1949-04-21 1957-04-30 Norman A Macleod Means and method for stimulating the flow of well fluids and for declogging well bore walls and well casing perforations
US3064568A (en) * 1956-08-15 1962-11-20 Robert E Ainslie Stabilized line dispensing device
US3118374A (en) * 1964-01-21 Agent
US3125859A (en) * 1964-03-24 Cable laying apparatus
US3354826A (en) * 1966-10-24 1967-11-28 Carl A Axelson Multiple explosive, line charge, package

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3118374A (en) * 1964-01-21 Agent
US3125859A (en) * 1964-03-24 Cable laying apparatus
US2790388A (en) * 1949-04-21 1957-04-30 Norman A Macleod Means and method for stimulating the flow of well fluids and for declogging well bore walls and well casing perforations
US2729300A (en) * 1949-11-29 1956-01-03 Marine Instr Company Water borne means for making seismic surveys
US2609885A (en) * 1950-12-29 1952-09-09 Stanolind Oil & Gas Co Seismic-wave generation
US3064568A (en) * 1956-08-15 1962-11-20 Robert E Ainslie Stabilized line dispensing device
US3354826A (en) * 1966-10-24 1967-11-28 Carl A Axelson Multiple explosive, line charge, package

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3908789A (en) * 1972-03-30 1975-09-30 Texaco Inc Methods for generating and shaping a seismic energy pulse
US4034672A (en) * 1976-01-02 1977-07-12 Eckels Robert E Linear explosive
CN110609316A (en) * 2019-10-22 2019-12-24 辽宁科技大学 Protection device for microseismic monitoring sensor in tunnel and use method thereof
WO2023222327A1 (en) * 2022-05-19 2023-11-23 Thales Towed submarine device
FR3135695A1 (en) * 2022-05-19 2023-11-24 Thales Towed underwater device

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NL158940B (en) 1978-12-15
GB1168095A (en) 1969-10-22
SE333698B (en) 1971-03-22
DE1673917B2 (en) 1976-06-16
OA02757A (en) 1970-12-15
MY7000091A (en) 1970-12-31
DE1673917A1 (en) 1971-08-12
FR1556117A (en) 1969-01-31
NL6803282A (en) 1968-09-11

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