METHOD AND APPARATUS FOR ENTRENCHING SUBMERGED ELONGATE STRUCTURES

• US 3,786,642 A
• Filed: 05/16/1972
• Issued: 01/22/1974
• Est. Priority Date: 05/16/1972
• Status: Expired due to Term

• Current Assignee: Alan E. Good, Delbert R. Ward
• Original Assignee: Alan E. Good, Delbert R. Ward
• Inventors: Ward, Delbert R., Good, Alan E.
• Primary Examiner(s): Shapiro, Jacob
• Application Number:
  US05/253,895
• Time in Patent Office: 616 Days
• Field of Search: 61/72.4,72.1,72.3 37/62,63
• US Class Current: 405/163
• CPC Class Codes: E02F 5/104 for burying conduits or cables in trenches under water floating substructures per se E02F9/06
• CPC Class Codes: E02F 5/107 using blowing-effect devices, e.g. jets digging devices using a blowing effect per se E02F3/9206
• CPC Class Codes: E02F 9/067 with arrangements for heave compensation for drilling structures E21B19/09; for lifting devices B66C13/02

Abstract

A method and apparatus for entrenching submerged elongate structures within the bed of a body of water including a floating vessel, and at least one submergible vehicle connected to the floating vessel and operable to be lowered adjacent to a submerged elongate structure to be entrenched. The submergible vehicle includes a frame having a fore end and an aft end with a first primary and a first alternate cutting means connected to the frame and generally operably directed toward the fore end thereof for cutting a trench within the water bed beneath the submerged elongate structure. Additionally, the submergible vehicle may be provided with a second primary and a second alternate cutting means connected to the frame and generally operably directed toward the aft end thereof for forming a trench within the water bed beneath the submerged elongate structure to be entrenched. In one embodiment of the invention a motion compensation system is connected between the floating vessel and at least one submergible vehicle in order to minimize relative, sea induced, motion between the floating vessel and the submergible vehicle.

Claims

1. An apparatus for entrenching a submerged elongate means within the bed of a body of water comprising:

a frame having a fore end and an aft end operable to be lowered adjacent to and transported along a submerged elongate means to be entrenched;

primary fluid jet cutting means connected to said frame and directed toward the free end thereof for forming a trench within the water bed generally beneath the submerged elongate means to be entrenched, said primary fluid jet cutting means including, a pair of tubular conduits operable to extend with one of said pair of conduits on one side of a vertical plane extending longitudinally through the submerged elongate means to be entrenched and with the other one of said pair of conduits on an opposite side of the vertical plane extending longitudinally through the submerged elongate means to be entrenched with said pair of tubular conduits having a plurality of apertures therein for directing a plurality of fluid jets generally toward the fore end of said frame and into the water bed on generally opposite sides of the vertical plane extending longitudinally through the submerged elongate means to be entrenched;

alternate fluid jet cutting means connected to said frame and directed toward the fore end thereof for forming a trench within the water bed generally beneath the submerged elongate means to be entrenched, said alternate fluid jet cutting means including, a pair of tubular conduits operable to extend with one of said pair of conduits on one side of the vertical plane extending longitudinally through the submerged elongate means to be entrenched and with the other one of said pair of conduits on an opposite side of the vertical plane extending longitudinally through the submerged elongate means to be entrenched with each of said tubular conduits having at least one but less than the total number of apertures in a corresponding conduit of said primary fluid jet cutting means for directing one or more fluid jets generally toward the fore end of said frame and said pair of tubular conduits being operable to direct fluid jets into the water bed on generally opposite sides of the vertical plane extending longitudinally through the submerged elongate means to be entrenched; and

means connected to said primary and said alternate cutting means for selectively actuating one or the other of said priMary or said alternate cutting means.

2. An apparatus for entrenching a submerged elongate means as defined in claim 1 wherein:

each of said pair of tubular conduits comprising said alternate fluid jet cutting means is provided with a single aperture therein for directing a unitary fluid jet therefrom generally toward the forward end of said frame and into the water bed.

3. An apparatus for entrenching a submerged elongate means as defined in claim 2 wherein:

said apertures in said pair of tubular conduits comprising said alternate fluid jet cutting means are fashioned at a mutually convergent angle such that unitary fluid jets emanating from said apertures will each intersect the vertical plane extending longitudinally through the submerged elongate means at approximately the intersection of said plane and a second vertical plane lying normal to said plane and extending through the fore end of said frame.

4. An apparatus for entrenching a submerged elongate means as defined in claim 1 wherein said means for selectively actuating comprises:

a valve positioned in each conduit of said pair of primary fluid jet tubular conduits; and

a valve positioned in each conduit of said pair of alternate fluid jet tubular conduits.

5. An apparatus for entrenching a submerged elongate means within the bed of a body of water comprising:

a frame having a fore end and an aft end operable to be lowered adjacent to and transported along a submerged elongate means to be entrenched;

primary fluid jet cutting means connected to said frame and directed toward the fore end thereof for forming a trench within the water bed generally beneath the submerged elongate means to be entrenched;

first alternate fluid jet cutting means connected to said frame and directed toward the fore end thereof for forming a trench within the water bed generally beneath the submerged elongate means to be entrenched;

second alternate fluid jet cutting means connected to said frame and directed toward the aft end thereof for forming a trench within the water bed generally beneath the submerged elongate means to be entrenched; and

means connected to said primary cutting means, said first alternate cutting means and said second alternate cutting means for selectively actuating one of said primary cutting means, said first alternate cutting means, or said second alternate cutting means.

6. An apparatus for entrenching a sumberged elongate means within the bed of a body of water comprising:

a frame having a fore end and an aft end operable to be lowered adjacent to and transported along a submerged elongate means to be entrenched;

first primary fluid jet emitting means connected to said frame and directed toward the fore end thereof for forming a trench within the water bed generally beneath the submerged elongate means to be entrenched;

second primary fluid jet cutting means connected to said frame and directed toward the aft end thereof for forming a trench within the water bed generally beneath the submerged elongate means to be entrenched;

first alternate fluid jet means connected to said frame and directed toward the fore end thereof for forming a trench within the water bed generally beneath the submerged elongate means to be entrenched;

second alternate fluid jet cutting means connected to said frame and directed toward the aft end thereof for forming a trench within the water bed generally beneath the submerged elongate means to be entrenched; and

means connected to said first primary cutting means, said secondary primary cutting means, said first alternate cutting means and second alternate cutting means for selectively actuating one of said first primary cutting means, said second primary cutting means, said first alternate cutting means, or said second alternate cutting means.

7. An apparatus for entrenching a submerged elongate means as defined in claim 6 wherein said first primary fluid jet cutting means each cOmprise:

a pair of tubular conduits operable to extend with one of said pair of conduits on one side of a vertical plane extending longitudinally through the submerged elongate means to be entrenched and with the other one of said pair of conduits on an opposite side of the vertical plane extending longitudinally through the submerged elongate means to be entrenched with said pair of tubular conduits of said first and second primary fluid jet cutting means having a plurality of apertures therein for directing a plurality of fluid jets generally toward the fore and aft ends respectively of said frame and into the water bed on generally opposite sides of the vertical plane extending longitudinally through the submerged elongate means.

8. An apparatus for entrenching a submerged elongate means as defined in claim 7 wherein said first and second alternate fluid jet cutting means each comprise:

a pair of tubular conduits operable to extend with one of said pair of conduits on one side of the vertical plane extending longitudinally through the submerged elongate means to be entrenched and with the other one of said pair of conduits on an opposite side of the vertical plane extending longitudinally through the submerged elongate means to be entrenched with each of said tubular conduits having at least one but less than the total number of apertures in a corresponding conduit of said first and second primary fluid jet cutting means for directing one or more fluid jets generally toward the fore and aft ends respectively of said frame and said pair of tubular conduits being operable to direct fluid jets into the water bed on generally opposite sides of the vertical plane extending longitudinally through the submerged elongate means to be entrenched.

9. An apparatus for entrenching a submerged elongate means as defined in claim 8 wherein:

each of said tubular conduits comprising said first and second alternate fluid jet cutting means is provided with a single aperture therein for directing a unitary fluid jet therefrom generally toward and into the water bed.

10. An apparatus for entrenching a submerged elongate means as defined in claim 9 wherein:

said apertures in said pair of tubular conduits comprising said first alternate fluid jet cutting means are fashioned at a mutually convergent angle such that unitary fluid jets emanating from said apertures will each intersect the vertical plane extending longitudinally through the submerged elongate means at approximately the intersection of said plane and a second vertical plane lying normal to said plane and extending through the fore end of said frame; and

said apertures in said pair of tubular conduits comprising said second alternate fluid jet cutting means are fashioned at a mutually convergent angle such that unitary fluid jets emanating from said apertures will each intersect the vertical plane extending longitudinally through the submerged elongate means at approximately the intersection of said plane and a second vertical plane lying normal to said plane and extending through the aft end of said frame.

11. An apparatus for entrenching a submerged elongate means as defined in claim 6 wherein said means for selectively actuating comprises:

a valve positioned in each of said first and second primary and said first and second alternate cutting means for selectively actuating any one of said first and second primary and said first and second alternate cutting means.

12. An apparatus for entrenching a submerged elongate means within the bed of a body of water comprising:

a floating vessel;

a submergible vehicle operable to be lowered adjacent to a submerged elongate means to be entrenched, said submergible vehicle including, a frame having a fore end and an aft end;

primary fluid jet cutting means connected to said frame and directed toward the fore end thereof for forming a trench within the water bed generally beneath the submerged elongate means to be entrenched;

first aLternate fluid jet cutting means connected to said frame and directed toward the fore end thereof for forming a trench within the water bed generally beneath the submerged elongate means to be entrenched;

second alternate fluid jet cutting means connected to said frame and directed toward the aft end thereof for forming a trench within the water bed generally beneath the submerged elongate means to be entrenched;

means connecting said fore end of said submergible vehicle with said floating vessel for inducing movement of said submergible vehicle in response to movement of said floating vessel;

means connected to said floating vessel for pressurizing fluid;

means for connecting in fluid communication said means for pressurizing fluid and said primary fluid jet cutting means, said first alternate fluid jet cutting means and said second alternate fluid jet cutting means; and

means connected to said primary, said first alternate and said second alternate fluid jet cutting means for selectively controlling the flow of fluid from said means for pressurizing fluid to said primary, said first alternate and said second alternate fluid jet cutting means.

13. An apparatus for entrenching a submerged elongate means as defined in claim 12 wherein:

said primary fluid jet cutting means comprises, a pair of tubular conduits operable to extend with one of said pair of conduits on one side of a vertical plane extending longitudinally through the submerged elongate means to be entrenched and with the other one of said pair of conduits on an opposite side of the vertical plane extending longitudinally through the submerged elongate means to be entrenched with said tubular conduits having a plurality of apertures therein or directing a plurality of fluid jets generally toward the fore end of said frame and into the body of water on generally opposite sides of the vertical plane extending longitudinally through the submerged elongate means to be entrenched; and

said first and second alternate fluid jet cutting means each comprise, a pair of tubular conduits operable to extend with one of said pair of conduits on one side of the vertical plane extending longitudinally through the submerged elongate means to be entrenched and with the other one of said pair of conduits on an opposite side of the vertical plane extending longitudinally through the submerged elongate means to be entrenched with each of said tubular conduits having at least one but less than the total number of apertures in a conduit of said primary fluid jet cutting means for directing one or more fluid jets generally toward the fore and aft ends respectively of said frame and said pair of tubular conduits being operable to direct fluid jets into the water bed on generally opposite sides of the vertical plane extending longitudinally through the submerged elongate means to be entrenched.

14. An apparatus for entrenching a submerged elongate means as defined in claim 13 wherein each of said tubular conduits of said first and second alternate fluid jet cutting means is provided with:

a single aperture therein for directing a unitary fluid jet generally toward the water bed.

15. An apparatus for entrenching a submerged elongate means as defined in claim 14 wherein:

said means connecting said fore end of said submergible vehicle with said floating vessel is connected to said floating vessel at a fore end thereof.

16. An apparatus for entrenching a submerged elongate means as defined in claim 14 wherein:

said means connecting said fore end of said submerged vehicle with said floating vessel is connected to an aft end of said floating vessel.

17. A method for entrenching a submerged elongate means within the bed of a body of water utilizing a floating vessel, a submergible vehicle operable to be lowered adjacent to a submerged elongate means to be entrenched, said submerged vehicle including a frame having a fore end and an aft end;

a primary fluid jet cutting means connecTed to said frame and directed toward the fore end thereof; and

an alternate fluid jet cutting means connected to said frame and directed toward the end thereof, comprising the steps of;

lowering the submergible vehicle adjacent to a submerged elongate means to be entrenched; and

selectively actuating at one time only one or the other of the primary or the alternate cutting means for eroding away a portion of the water bed positioned beneath the submerged elongate means including the step of, selectively directing a flow of high pressure fluid into the primary fluid jet cutting means comprising a pair of tubular conduits having a plurality of jetting apertures therein or, in the event a tough or hard water bed formation is encountered, into the alternate fluid jet cutting means comprising a pair of tubular conduits having a lesser number of jetting apertures therein than the primary fluid jet cutting means.

18. A method for entrenching a submerged elongate means within the bed of a body of water utilizing a floating vessel;

a submergible vehicle operable to be lowered adjacent to a submerged elongate means to be entrenched, said submerged vehicle including a frame having a fore end and an aft end;

a primary cutting means connected to said frame and directed toward the fore end thereof; and

an alternate cutting means connected to said frame and directed toward the fore end thereof, comprising the steps of;

lowering the submergible vehicle adjacent to a submerged elongate means to be entrenched;

actuating the primary cutting means for removing a portion of the water bed lying beneath the submerged elongate means;

towing the submergible vehicle along the submerged elongate means to form a trench beneath the submerged elongate means within the water bed;

deactuating the primary cutting means upon encountering a tough or hard formation of the water bed;

actuating the alternate cutting means for eroding away the tough or hard formation of the water bed; and

towing a submergible vehicle along the submerged elongate means to form a trench beneath the submerged elongate means within the tough or hard portion of the bed of the body of water.

19. A method for entrenching a submerged elongate means as defined in claim 18 and further comprising the step of:

deactuating the alternate cutting means upon passing through the tough or hard portion of the bed of the body of water; and

reactuating the primary cutting means for forming a trench beneath the submerged elongate means within the bed of the body of water.

20. A method for entrenching a submerged elongate means as defined in claim 19 wherein said steps of actuating and deactuating the primary and alternate cutting means comprises:

controlling the flow of high pressure fluid into the primary cutting means comprising a pair of conduits having a plurality of jetting apertures therein or into the alternate cutting means comprising a pair of conduits having a lesser number of jetting apertures therein than the primary cutting means.

21. A method of entrenching a submerged elongate means resting upon the bed of a body of water at an obstruction, such as a valve section, pipeline cross over, or the like, utilizing a floating vessel;

a submergible vehicle operated to be lowered adjacent to a submerged elongate means to be entrenched, said submerged vehicle including a frame having a fore end and an aft end;

a primary cutting means connected to said frame and directed toward the fore end thereof;

a first alternate cutting means connected to said frame and directed toward the fore end thereof; and

a second alternate cutting means connected to said frame and directed toward the aft end thereof;

comprising the steps of;

lowering the submergible vehicle adjacent to a submerged elongate means to be entrenched;

actuating the primary fluid jet cutting means for eroding away a portion of the water bed lying beneath the submerged elongate means;

towing the submergiblE vehicle along the submerged elongate means to form a trench beneath the submerged elongate means within the water bed;

upon reaching an obstruction, deactuating the primary fluid jet cutting means;

actuating the first alternate fluid jet cutting means for removing a portion of the water bed beneath the obstruction;

deactuating the first alternate fluid jet cutting means;

transporting the submergible vehicle over the obstruction to a location adjacent to but downstream from the obstruction;

actuating the second alternate cutting means for removing the remaining portion of the water bed beneath the obstruction to form a trench within the seabed beneath the submerged elongate means at the obstruction.

22. A method for entrenching a submerged elongate means as defined in claim 21 and further comprising the steps of:

subsequent for forming a trench beneath said obstruction actuating said second alternate cutting means;

actuating said primary fluid jet cutting means; and

towing the submergible vehicle along the submerged elongate means to be entrenched to form a trench beneath the submerged elongate means within the bed of the body of water.

23. A method for entrenching a submerged elongate means as defined in claim 22 wherein said steps of actuating and deactuating the primary, first and second alternate cutting means comprises:

controlling the flow of high pressure fluid into the primary cutting means comprising a pair of conduits having a plurality of jetting apertures therein or into the first alternate cutting means comprising a pair of conduits having a lesser number of jetting apertures therein than the primary cutting means or into the second alternate cutting means comprising a pair of conduits having a lesser number of jetting apertures therein than the primary cutting means.

24. A method for entrenching a pipeline riser within the bed of a body of water utilizing a floating vessel;

a submergible vehicle operable to be lowered adjacent to the bottom bend to be entrenched, said submerged vehicle including a frame having a fore end and an aft end;

first primary cutting means connected to said frame and directed toward the fore end thereof;

second primary cutting means connected to said frame and directed toward the aft end thereof;

first alternate cutting means connected to said frame and directed toward the fore end thereof;

second alternate cutting means connected to said frame and directed toward the aft end thereof, comprising the steps of;

lowering the submergible elongate means from a bow portion of the floating vessel to a position adjacent a bend in the pipeline riser with the aft end of the submerged vehicle in a position adjacent the pipeline riser;

selectively actuating the second primary or the second alternate cutting means for forming a trench beneath the bend section of the pipeline riser within the bed of the body of water;

selectively actuating the first primary cutting means or the first alternate cutting means for forming a trench beneath a submerged elongate means connected to the riser; and

towing said submergible vehicle along the submerged elongate means to entrench the submerged elongate means within the bed of the body of water.

25. A method for entrenching a pipeline riser as defined in claim 24 wherein said steps of actuating and deactuating the first and second primary and the first and second alternate cutting means comprises:

controlling the flow of high pressure fluid into the first or second primary cutting means each comprising a pair of conduits having a plurality of jetting apertures therein or into the first or second alternate cutting means each comprising a pair of conduits having a lesser number of jetting apertures therein than the first or second primary cutting means.