CA1248870A - System for installing subsea wellhead protective silo - Google Patents
System for installing subsea wellhead protective siloInfo
- Publication number
- CA1248870A CA1248870A CA000479171A CA479171A CA1248870A CA 1248870 A CA1248870 A CA 1248870A CA 000479171 A CA000479171 A CA 000479171A CA 479171 A CA479171 A CA 479171A CA 1248870 A CA1248870 A CA 1248870A
- Authority
- CA
- Canada
- Prior art keywords
- silo
- excavating
- seabed
- module
- excavating module
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 230000001681 protective effect Effects 0.000 title claims abstract description 15
- 238000009412 basement excavation Methods 0.000 claims abstract description 18
- 239000000463 material Substances 0.000 claims description 27
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 15
- 238000005520 cutting process Methods 0.000 claims description 14
- 239000012528 membrane Substances 0.000 claims description 6
- 238000000034 method Methods 0.000 claims description 6
- 230000000284 resting effect Effects 0.000 claims description 4
- 239000004744 fabric Substances 0.000 claims description 3
- 238000007599 discharging Methods 0.000 claims 1
- 230000002706 hydrostatic effect Effects 0.000 abstract description 4
- 238000009434 installation Methods 0.000 abstract 2
- 230000035515 penetration Effects 0.000 abstract 1
- 210000004379 membrane Anatomy 0.000 description 3
- 229910000831 Steel Inorganic materials 0.000 description 2
- 238000005086 pumping Methods 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- NSMXQKNUPPXBRG-SECBINFHSA-N (R)-lisofylline Chemical compound O=C1N(CCCC[C@H](O)C)C(=O)N(C)C2=C1N(C)C=N2 NSMXQKNUPPXBRG-SECBINFHSA-N 0.000 description 1
- 238000003780 insertion Methods 0.000 description 1
- 230000037431 insertion Effects 0.000 description 1
- 230000001050 lubricating effect Effects 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 238000009991 scouring Methods 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 239000003566 sealing material Substances 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 239000002689 soil Substances 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
Classifications
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B7/00—Special methods or apparatus for drilling
- E21B7/18—Drilling by liquid or gas jets, with or without entrained pellets
- E21B7/185—Drilling by liquid or gas jets, with or without entrained pellets underwater
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B33/00—Sealing or packing boreholes or wells
- E21B33/02—Surface sealing or packing
- E21B33/03—Well heads; Setting-up thereof
- E21B33/035—Well heads; Setting-up thereof specially adapted for underwater installations
- E21B33/037—Protective housings therefor
Landscapes
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Geology (AREA)
- Mining & Mineral Resources (AREA)
- Physics & Mathematics (AREA)
- Environmental & Geological Engineering (AREA)
- Fluid Mechanics (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Earth Drilling (AREA)
Abstract
Abstract:
A subsea wellhead protective silo and excavating module therefor is described. For installation of the protective silo in the sea floor, an excavating module is mounted within the silo. This excavating module has an excavating member within the base of the silo such as to simultaneously excavate a hole in the sea floor and position the silo therein. The silo and excavating module are designed to make use of hydrostatic pressure to aid penetration of the silo into the excavation. When the silo is in position, the excavating module is removed through the top of the silo for use in another installation.
A subsea wellhead protective silo and excavating module therefor is described. For installation of the protective silo in the sea floor, an excavating module is mounted within the silo. This excavating module has an excavating member within the base of the silo such as to simultaneously excavate a hole in the sea floor and position the silo therein. The silo and excavating module are designed to make use of hydrostatic pressure to aid penetration of the silo into the excavation. When the silo is in position, the excavating module is removed through the top of the silo for use in another installation.
Description
7~
System for installing subsea_wellhead protec~ive silo ~ This invention relates to a subsea wellhead protective silo and excavating module there$or.
It has now become a widespread practice to drill oil producing wells in shallow offshore sea areas. In the Beaufort Sea there is a serious hazard in the form of floating ice which tends to accumulate. This floating ice may develop into ice ridges which not only accumulate above the water but also develop a substantial submerged section.
These ice ridges and icebergs tend to drift and as they are driven into shallow areas, they may scour the sea floQr. Thus, it has become necessary for all companies operating in the Beaufort Sea to provide means of protect-in~ the subsea wellhead equipment, known as the blow outpreventor (BOP), from the risk of ice damage by these moving ice ridges. This has been accomplished by placing the BOP stack beneath the point in the sea 100r of known ice ridge scour. The required depth was achieved by dredging a large area of the seabed to a depth below known iceberg or ice ridge scouring and settin~ the~OP in this depression on the sea floor.
The above method is extremely costly and requires the dredging of large quanti~ties;~o~material with a~seagoing dredger of high capacity,~or~operating a dredgehead airlift combined on a drill ship, or by a large~ diameter drill bit and airlift arrangement~from a drill ship~.
': . ,~ . . :
An example of a prior system is described in Canadian Patent 995,583, issued August 24, 1976. That system included a caisson embedded in the sea floor by methods ~such as driving, ~etting or a combination of the two. The upper region of this caisson included a plurality of hori-zontally connected circular segments joined by breakaway join~s. In this manner, when an upper portion of ~he caisson comes into contact with an ice mass, the entire caisson is not damaged or deformed but only a particular segment may be broken away.
It is the object of the present invention to provide an improved and less expensive system for excavating the seabed and sinking a silo or caisson thereinO ThUs, the present invention in its broadest aspect relates to a combination subsea wellhead protective silo and excavating module therefor. The silo comprises a substantially cylindrical retainer wall assembly having a hollow interior, the retainer wall having an upper rim portion forming a top opening and a lower rim portion forming a bottom opening. Vertical guideways are fixed to the inner surface of the retaining wall and an abutment member or members are fixed to the retaining wall inner face in the region of the lower ends of the guideways. Attachment means are provided for attaching the upper end of the retainer wall to a suitable crane on a floating vessel for lowering the silo to the sea floor.
The excavating module comprises a cylindrical shell positioned within the silo and being adapted to move verti-cally within the guideways and to rest on the abutment member or members. This cylindrical shell has a closed top and bottom to provide an interior compartment, a power source within the compartment, a rotatable seabed excavat-ing means extending downwardly from the bottom Gf the shell and operatively connected to the power source and attach~
ment means for attaching the top of the module to a crane , , . , }~37~
on the floating vessel. This excavating means is adapted to loosen seabed material from the beneath the silo and excavating module.
A conduit means is provided for removing loosened sea-bed material from the excavating means to the sea floor and a power source and control means is provided for the excavating module which is connectable to the floating vessel. With this system, operation of the excavating module while resting within the silo forms an excavation in the seabed within which both the siLo and excavating module sink to a desired depth. Thereafter~ the excavating module is lifted out of the silo and recovered by the floating vessel for use in another location.
This system greatly reduces the cost o installing a protective silo in the seabed. Thus, it does not use expensive dredges or drillships, does not require the support of other equipment other than supply vessels and greatly reduces the quantity of material to be handled.
In the drawings which illustrate certain preferred embodiments of this invention:
Figure 1 is a schematic elevation view of the system of the invention in use;
Figure 2 is an elevation view in cross section of a protective silo and excavating module;
Figure 3 i5 a side elevation of a crosshead guide unit;
Figure 4 is a detailed view of a swivel hook support;
Figure S is a elevation view in cross section of a second embodiment of excavating module;
Figure 6 is a an elevation view in cross section of the excavating module of Figure 5 mounted within a protective silo.
Figure 7 is an elevation view in cross section of a further embodiment of a protective silo and excavating module; and 37~
Figure 8 is an elevation view in cross section of a still further embodiment of a protective silo and excavating module.
~ Referring to Figure 1, a seagoing barge B has a flat working surface capable of supporting machinery such as heavy lift cranes, generators, compressors, winches, crew cabins, helicopter pad, etc. The barge includes one or more winches 10 for lowering by way of ropes or cables 11 a silo or caisson C to the mud line and into an excavation 16 in the sea floor F. A separate rope or cable 12 , supports an excavating module 15. These ropes or cables 11 and 12 are guided through a crosshead 14. A separate line 13 provides power, control and other services between the barge B and excavating module 15.
One embodiment of the silo and excavating module is shown in Figure 2. The ~ilo C has a cylindrical wall 17 constructed of steel or concrete. The size and dimensions of a particular silo are based on the duty in which it is to perform. A typical silo has an internal diameter of about 5.5 m and a height of 20 m. The typical working depth of the water is about 20 to 70 m or deeper. The function of the silo C is to prevent the sides of the hole 16 from collapsing into the excavation and to provide a housing for the BOP. As described in Canadian Patent 995,583, the silo is preferably constructed in several pieces or rings.
The interior of the shell 17 includes two or more vertical guideways 18 for guiding the excavating module 15 therein~ The upper end of shell 17 also has bracket members 19 for connection to ropes or cables 11 by way of swivel hooks 40. The lower edge of the silo is provided with a cutting shoe 20 which extends around the base. The cutting shoe is constructed in a manner which creakes an annulus around the outside of the silo as the shoe is of larger diameter than the silo, This annu1us can be , 7~
passively employed or may be used to pass water, or lubri-cating muds upwards around the silos exterior to reduce friction acting on the exterior o~ the silo. The shoe is ~also provided with a plurality oE slurry ports 21 to allow excavated materials to pass through the silo and upwards on the ou~side of the silo for disposal on the seabed.
Moun~ed for vertical movement within the silo is the excavating module 15. This excavating module also includes a cylindrical steel shell portion 22 typically having a diameter of about 5.3 m. A series of rollers 23 are con-nected to the outer surface of the shell 22 and travel on the guideways 18 thereby permitting only vertical, axial movement between the excavating module 15 and the silo C.
The excavating module 15 also includes support cables 29 connected to a support ring 30 which is in turn connected to swivel hook of rope or cable 12. In this manner, the module may be lifted by the barge winch 10.
The lower end of the excavating module shell 22 has an outwardly projecting thrust ring 24 which abuts on a matching support ring 25 on the inner face of silo C. A
sealing material is placed between the thrust and support rings to seal the excavation work area from the remainder of the system. Thus it will be seen from Figure 2 that the excavating module can rest on and be supported by the silo C. Since the excavating module is quite heavy, i~
acts together with the weight of the silo to overcome skin ~riction between the silo and the excavation.
The excavating module 15 includes a top wall 39, a bottom deck 26, a middle deck 27 and an upper deck 28.
Supported by the upper deck 28 is a high pressure pump 31 for pumping water. This pump may be electrically or hydraulically powered and is pre~erably submersible. The pump connects to a discharge line 32 which continues into a main down pipe 33 and in turn operatively connects via a thrust hearing 41 to a rotatab1e down pire 35. This . _ ~: , .
~ ' :
7~3 rotatable down pipe passes through a seal 42 in middle deck 27 and through a seal 43 in bottom deck 26. The rotational motion of pipe 35 is provided by a drive and gearbox 34.
Connected to the bottom end of rotatable pipe 35 are a vertical jet 36 and lateral jets 37 and 38. High pressure water is pumped through these jets from pump 310 Optionally, a separate pipe 39 may be provided which delivers compressed air to the cutting chamber beneath bottom deck 26. The purpose of this is to provide additional lift for water and cuttings as they exi~ the cutting zone and pass through the outlet ports 21 and up through the annular space between the silo C and the edge of the excavation 16. It is important to provide an excess of water pressure, or combined water and air pressure in order to ensure that the annular clearance is maintained during silo insertion. This eliminates the risk of ground pressure in the form of skin friction causing the silo to stick in the excavation. The upper end of pipe 39 is connected to a manifold (not shown) which distributes air through a number of nozzles into the excavating zone. The compressed air is supplied from the surface vessel using an air supply hose via conduit 13.
The crosshead 14 is described in greater detail in Figure 3. It will be seen that it includes a bottom beam 50, a top beam 51, vertical beams 52 and angle braces 53.
Sleeves 54 and 55 are provided for the ropes or cables Ll and 12 to pass through without damage. The crosshead allows the withdrawal and replacement of the excavating equipment when required, as the crosshead controls the movement of the equipment when descending or rising on cables 11.
A second embodiment o~ the excavating module is shown in Figures 5 and 6. It includes an outer shell S9 which is similar to the shell 22 of excavatlng module 15. This . ~
: '.
' : .
shell includes a bottom wall 60 below which is mounted an annular bracket 61. This bracket 61 supports a rotatable base member 62, this base member being rotatable via a motor and gear drive 63.
~ Mounted above the floor 60 is a pump and motor 64 having a suction conduit 65 extending downwardly and con-necting to a dredge arm 66 which is pivotally mounted on a bracket 67 fixed to rotatable base 62. The lower end of dredge arm 66 includes a dredge head 6~ and the vertical positioning of the dredge head is controlled by way of a hydraulic cylinder 71. The discharge of pump 64 is connected to an ejector pipe 69 and this is arranged to discharge material above the top rim of the silo C.
This excavating module may also be provided with a down pipe 70. This is a static device which equalizes any pressure difference in the cutting zone caused when the dredge head is running, e.g. as water is pumped from the cutting zone, water is introduced to the cutting zone from the down pipe or pipes 70.
The silo C is similar to the one shown in Figure 2 and is provided with an inwardly projecting support ring 58 on the inner face thereof, on which abuts an outwardly pro-jecting thrust ring on the excavating module. The lower edqe of the silo is provided with a shoe having a cutting edge 57.
According to another embodiment of the invention, the excavating module of Figure 5 may include a feature to make use of natural hydrostatic pressure present to increase the downward thrust of the cutting edge 57. It is well under-stood that hydrostatic pressure acts on a vessel when sub-merged and that this pressure is a function of depth and surface area of the vessel According to a modi~ication, the excavating module makes use o hydrostatic pressure bearing on the excavating module when water is ejected from within the module by the pump 54. When this happens, a downward thrust on the silo i5 Lnduced as hydraulic , .
~4 ~
pressure at~empts to equalize the pressures wi~hin the excavating module. This may continually be achieved by providing a domed top on the excavating module and the ;sides may be strengthened to carry the hydrualic thrus~
transferred to the silo cutting edge 57.
Another preferred embodiment comprises a fabric mem-brane fixed to the upper edge of the cutting shoe thereby forming a tube which surrounds and covers the exterior surface of the silo. This membane is particularly useful ~ in soil conditions that are soft and of poor strength. The membrane provides an annulus between the side of the silo and the excavation and protects the soft sides of the excavation thereby reducing the risk of cavities forming in the excavation as material is pumped up the side of the silo. The membrane tube remains with the silo when the excavation is complete and pumping stopped. The fabric tube then collapses and forms itself against the silo walls thereby closing off and sealing the ports in the base of the silo from any running materials.
Two further embodiments of the protective silo and excavating module are shown in Figures 7 and 8. Both of these embodiments use a rotatable jet nozzle array 44 in the excavating zone, the rotation being provided by a hydraulic motor 46 and drive system.
In the embodiment of Figure 7, water is pumped to the jet no2~1e array by way of jet pump 31 and the excavated material is drawn off by way of dredge pump 45 and ejection pipe 48. On the other hand, in Figure 8, water is pumped to the jet nozzle array by way of jet pumps 31 and the excavated material is forced out through ejection ports 47 and up through an annular space between the silo and the excavation.
~ : .
-
System for installing subsea_wellhead protec~ive silo ~ This invention relates to a subsea wellhead protective silo and excavating module there$or.
It has now become a widespread practice to drill oil producing wells in shallow offshore sea areas. In the Beaufort Sea there is a serious hazard in the form of floating ice which tends to accumulate. This floating ice may develop into ice ridges which not only accumulate above the water but also develop a substantial submerged section.
These ice ridges and icebergs tend to drift and as they are driven into shallow areas, they may scour the sea floQr. Thus, it has become necessary for all companies operating in the Beaufort Sea to provide means of protect-in~ the subsea wellhead equipment, known as the blow outpreventor (BOP), from the risk of ice damage by these moving ice ridges. This has been accomplished by placing the BOP stack beneath the point in the sea 100r of known ice ridge scour. The required depth was achieved by dredging a large area of the seabed to a depth below known iceberg or ice ridge scouring and settin~ the~OP in this depression on the sea floor.
The above method is extremely costly and requires the dredging of large quanti~ties;~o~material with a~seagoing dredger of high capacity,~or~operating a dredgehead airlift combined on a drill ship, or by a large~ diameter drill bit and airlift arrangement~from a drill ship~.
': . ,~ . . :
An example of a prior system is described in Canadian Patent 995,583, issued August 24, 1976. That system included a caisson embedded in the sea floor by methods ~such as driving, ~etting or a combination of the two. The upper region of this caisson included a plurality of hori-zontally connected circular segments joined by breakaway join~s. In this manner, when an upper portion of ~he caisson comes into contact with an ice mass, the entire caisson is not damaged or deformed but only a particular segment may be broken away.
It is the object of the present invention to provide an improved and less expensive system for excavating the seabed and sinking a silo or caisson thereinO ThUs, the present invention in its broadest aspect relates to a combination subsea wellhead protective silo and excavating module therefor. The silo comprises a substantially cylindrical retainer wall assembly having a hollow interior, the retainer wall having an upper rim portion forming a top opening and a lower rim portion forming a bottom opening. Vertical guideways are fixed to the inner surface of the retaining wall and an abutment member or members are fixed to the retaining wall inner face in the region of the lower ends of the guideways. Attachment means are provided for attaching the upper end of the retainer wall to a suitable crane on a floating vessel for lowering the silo to the sea floor.
The excavating module comprises a cylindrical shell positioned within the silo and being adapted to move verti-cally within the guideways and to rest on the abutment member or members. This cylindrical shell has a closed top and bottom to provide an interior compartment, a power source within the compartment, a rotatable seabed excavat-ing means extending downwardly from the bottom Gf the shell and operatively connected to the power source and attach~
ment means for attaching the top of the module to a crane , , . , }~37~
on the floating vessel. This excavating means is adapted to loosen seabed material from the beneath the silo and excavating module.
A conduit means is provided for removing loosened sea-bed material from the excavating means to the sea floor and a power source and control means is provided for the excavating module which is connectable to the floating vessel. With this system, operation of the excavating module while resting within the silo forms an excavation in the seabed within which both the siLo and excavating module sink to a desired depth. Thereafter~ the excavating module is lifted out of the silo and recovered by the floating vessel for use in another location.
This system greatly reduces the cost o installing a protective silo in the seabed. Thus, it does not use expensive dredges or drillships, does not require the support of other equipment other than supply vessels and greatly reduces the quantity of material to be handled.
In the drawings which illustrate certain preferred embodiments of this invention:
Figure 1 is a schematic elevation view of the system of the invention in use;
Figure 2 is an elevation view in cross section of a protective silo and excavating module;
Figure 3 i5 a side elevation of a crosshead guide unit;
Figure 4 is a detailed view of a swivel hook support;
Figure S is a elevation view in cross section of a second embodiment of excavating module;
Figure 6 is a an elevation view in cross section of the excavating module of Figure 5 mounted within a protective silo.
Figure 7 is an elevation view in cross section of a further embodiment of a protective silo and excavating module; and 37~
Figure 8 is an elevation view in cross section of a still further embodiment of a protective silo and excavating module.
~ Referring to Figure 1, a seagoing barge B has a flat working surface capable of supporting machinery such as heavy lift cranes, generators, compressors, winches, crew cabins, helicopter pad, etc. The barge includes one or more winches 10 for lowering by way of ropes or cables 11 a silo or caisson C to the mud line and into an excavation 16 in the sea floor F. A separate rope or cable 12 , supports an excavating module 15. These ropes or cables 11 and 12 are guided through a crosshead 14. A separate line 13 provides power, control and other services between the barge B and excavating module 15.
One embodiment of the silo and excavating module is shown in Figure 2. The ~ilo C has a cylindrical wall 17 constructed of steel or concrete. The size and dimensions of a particular silo are based on the duty in which it is to perform. A typical silo has an internal diameter of about 5.5 m and a height of 20 m. The typical working depth of the water is about 20 to 70 m or deeper. The function of the silo C is to prevent the sides of the hole 16 from collapsing into the excavation and to provide a housing for the BOP. As described in Canadian Patent 995,583, the silo is preferably constructed in several pieces or rings.
The interior of the shell 17 includes two or more vertical guideways 18 for guiding the excavating module 15 therein~ The upper end of shell 17 also has bracket members 19 for connection to ropes or cables 11 by way of swivel hooks 40. The lower edge of the silo is provided with a cutting shoe 20 which extends around the base. The cutting shoe is constructed in a manner which creakes an annulus around the outside of the silo as the shoe is of larger diameter than the silo, This annu1us can be , 7~
passively employed or may be used to pass water, or lubri-cating muds upwards around the silos exterior to reduce friction acting on the exterior o~ the silo. The shoe is ~also provided with a plurality oE slurry ports 21 to allow excavated materials to pass through the silo and upwards on the ou~side of the silo for disposal on the seabed.
Moun~ed for vertical movement within the silo is the excavating module 15. This excavating module also includes a cylindrical steel shell portion 22 typically having a diameter of about 5.3 m. A series of rollers 23 are con-nected to the outer surface of the shell 22 and travel on the guideways 18 thereby permitting only vertical, axial movement between the excavating module 15 and the silo C.
The excavating module 15 also includes support cables 29 connected to a support ring 30 which is in turn connected to swivel hook of rope or cable 12. In this manner, the module may be lifted by the barge winch 10.
The lower end of the excavating module shell 22 has an outwardly projecting thrust ring 24 which abuts on a matching support ring 25 on the inner face of silo C. A
sealing material is placed between the thrust and support rings to seal the excavation work area from the remainder of the system. Thus it will be seen from Figure 2 that the excavating module can rest on and be supported by the silo C. Since the excavating module is quite heavy, i~
acts together with the weight of the silo to overcome skin ~riction between the silo and the excavation.
The excavating module 15 includes a top wall 39, a bottom deck 26, a middle deck 27 and an upper deck 28.
Supported by the upper deck 28 is a high pressure pump 31 for pumping water. This pump may be electrically or hydraulically powered and is pre~erably submersible. The pump connects to a discharge line 32 which continues into a main down pipe 33 and in turn operatively connects via a thrust hearing 41 to a rotatab1e down pire 35. This . _ ~: , .
~ ' :
7~3 rotatable down pipe passes through a seal 42 in middle deck 27 and through a seal 43 in bottom deck 26. The rotational motion of pipe 35 is provided by a drive and gearbox 34.
Connected to the bottom end of rotatable pipe 35 are a vertical jet 36 and lateral jets 37 and 38. High pressure water is pumped through these jets from pump 310 Optionally, a separate pipe 39 may be provided which delivers compressed air to the cutting chamber beneath bottom deck 26. The purpose of this is to provide additional lift for water and cuttings as they exi~ the cutting zone and pass through the outlet ports 21 and up through the annular space between the silo C and the edge of the excavation 16. It is important to provide an excess of water pressure, or combined water and air pressure in order to ensure that the annular clearance is maintained during silo insertion. This eliminates the risk of ground pressure in the form of skin friction causing the silo to stick in the excavation. The upper end of pipe 39 is connected to a manifold (not shown) which distributes air through a number of nozzles into the excavating zone. The compressed air is supplied from the surface vessel using an air supply hose via conduit 13.
The crosshead 14 is described in greater detail in Figure 3. It will be seen that it includes a bottom beam 50, a top beam 51, vertical beams 52 and angle braces 53.
Sleeves 54 and 55 are provided for the ropes or cables Ll and 12 to pass through without damage. The crosshead allows the withdrawal and replacement of the excavating equipment when required, as the crosshead controls the movement of the equipment when descending or rising on cables 11.
A second embodiment o~ the excavating module is shown in Figures 5 and 6. It includes an outer shell S9 which is similar to the shell 22 of excavatlng module 15. This . ~
: '.
' : .
shell includes a bottom wall 60 below which is mounted an annular bracket 61. This bracket 61 supports a rotatable base member 62, this base member being rotatable via a motor and gear drive 63.
~ Mounted above the floor 60 is a pump and motor 64 having a suction conduit 65 extending downwardly and con-necting to a dredge arm 66 which is pivotally mounted on a bracket 67 fixed to rotatable base 62. The lower end of dredge arm 66 includes a dredge head 6~ and the vertical positioning of the dredge head is controlled by way of a hydraulic cylinder 71. The discharge of pump 64 is connected to an ejector pipe 69 and this is arranged to discharge material above the top rim of the silo C.
This excavating module may also be provided with a down pipe 70. This is a static device which equalizes any pressure difference in the cutting zone caused when the dredge head is running, e.g. as water is pumped from the cutting zone, water is introduced to the cutting zone from the down pipe or pipes 70.
The silo C is similar to the one shown in Figure 2 and is provided with an inwardly projecting support ring 58 on the inner face thereof, on which abuts an outwardly pro-jecting thrust ring on the excavating module. The lower edqe of the silo is provided with a shoe having a cutting edge 57.
According to another embodiment of the invention, the excavating module of Figure 5 may include a feature to make use of natural hydrostatic pressure present to increase the downward thrust of the cutting edge 57. It is well under-stood that hydrostatic pressure acts on a vessel when sub-merged and that this pressure is a function of depth and surface area of the vessel According to a modi~ication, the excavating module makes use o hydrostatic pressure bearing on the excavating module when water is ejected from within the module by the pump 54. When this happens, a downward thrust on the silo i5 Lnduced as hydraulic , .
~4 ~
pressure at~empts to equalize the pressures wi~hin the excavating module. This may continually be achieved by providing a domed top on the excavating module and the ;sides may be strengthened to carry the hydrualic thrus~
transferred to the silo cutting edge 57.
Another preferred embodiment comprises a fabric mem-brane fixed to the upper edge of the cutting shoe thereby forming a tube which surrounds and covers the exterior surface of the silo. This membane is particularly useful ~ in soil conditions that are soft and of poor strength. The membrane provides an annulus between the side of the silo and the excavation and protects the soft sides of the excavation thereby reducing the risk of cavities forming in the excavation as material is pumped up the side of the silo. The membrane tube remains with the silo when the excavation is complete and pumping stopped. The fabric tube then collapses and forms itself against the silo walls thereby closing off and sealing the ports in the base of the silo from any running materials.
Two further embodiments of the protective silo and excavating module are shown in Figures 7 and 8. Both of these embodiments use a rotatable jet nozzle array 44 in the excavating zone, the rotation being provided by a hydraulic motor 46 and drive system.
In the embodiment of Figure 7, water is pumped to the jet no2~1e array by way of jet pump 31 and the excavated material is drawn off by way of dredge pump 45 and ejection pipe 48. On the other hand, in Figure 8, water is pumped to the jet nozzle array by way of jet pumps 31 and the excavated material is forced out through ejection ports 47 and up through an annular space between the silo and the excavation.
~ : .
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Claims (14)
1. A combination subsea wellhead protective silo and excavating module therefor; said silo comprising a substan-tially cylindrical retainer wall assembly having a hollow interior, said retainer wall having an upper rim portion forming a top opening and a lower rim portion forming a bottom opening, vertical guideways fixed to the inner face of said retainer wall, abutment member fixed to said retainer wall inner face in the region of the lower ends of said guideways, and attachment means for attaching the upper end of said retainer wall to a suitable winch on a floating vessel for lowering the silo to the sea floor;
said excavating module comprising a cylindrical shell positioned within said silo and being adapted to move vertically within said guideways and to rest on said abutment member, said cylindrical shell having a closed top and bottom to provide an interior compartment, a power source within said compartment, a rotatable seabed excavating means extending downwardly from the bottom of said shell and operatively connected to said power source and attachment means for attaching the top of said module to a crane on said floating vessel, said excavating means being adapted to loosen seabed material from beneath said silo and excavating module;
conduit means for removing loosened seabed material from said excavating means to the sea floor; and power source and control means for said excavating module connectable to said floating vessel;
whereby operation of said excavating module while resting within said silo forms an excavation in the seabed within which both the silo and excavating module sink to a desired depth, after which the excavating module is lifted out of the silo and recovered by said floating vessel.
said excavating module comprising a cylindrical shell positioned within said silo and being adapted to move vertically within said guideways and to rest on said abutment member, said cylindrical shell having a closed top and bottom to provide an interior compartment, a power source within said compartment, a rotatable seabed excavating means extending downwardly from the bottom of said shell and operatively connected to said power source and attachment means for attaching the top of said module to a crane on said floating vessel, said excavating means being adapted to loosen seabed material from beneath said silo and excavating module;
conduit means for removing loosened seabed material from said excavating means to the sea floor; and power source and control means for said excavating module connectable to said floating vessel;
whereby operation of said excavating module while resting within said silo forms an excavation in the seabed within which both the silo and excavating module sink to a desired depth, after which the excavating module is lifted out of the silo and recovered by said floating vessel.
2. The device according to claim 1 wherein the excavating means comprises rotatable high pressure water jets connected to high pressure pump means.
3. The device according to claim 2 wherein the high pressure pump is mounted within said cyclindrical shell.
4. The device according to claim 3 wherein the high pressure pump is a submersible hydraulic pump.
5. The device according to claim 2 wherein the conduit means for removing loosened seabed material comprises opening in the cylindrical wall of the silo adjacent said water jets.
6. The device according to claim 2 wherein the lower rim portion of the silo comprises a sharp cutting edge.
7. The device according to claim 1 wherein the excavating means comprises at least one rotatable dredging arm with a dredging head, said dredging head having associated therewith the intake of a conduit which is connected to the inlet of a pump within said cylindrical shell, said pump serving to pump the dredged material outside the silo and excavating module.
8. The device according to claim 7 wherein the pump connects to an ejector pipe for discharging dredged material above the top of the silo.
9. A combination subsea wellhead protection silo and excavating module therefore; said silo comprising a retainer wall assembly having a hollow interior, said retainer wall having an upper rim portion forming a top opening and a lower rim portion forming a bottom opening, abutment means defined within said retainer wall adjacent said lower rim portion, and means for lowering the silo to the sea floor;
said excavating module being positionable within said silo and being adapted to move vertically within said re-tainer wall and to rest on said abutment member, excavating module having a power source, seabed excavating said means extending downwardly from the bottom of said excavating module and operatively connected to said power source, said excavating means being adapted to loosen seabed material from beneath said silo and excavating module;
means for removing loosened seabed material from said excavating means and conducting said loosended seabed material to the surface of the seabed; and power source and control means for said excavating module; whereby operation of said excavating module while resting within said silo forms an excavation in the seabed within which both the silo and excavating module sink to a desired depth, after which the excavating module is removed from within the sunken silo and recovered for subsequent use.
said excavating module being positionable within said silo and being adapted to move vertically within said re-tainer wall and to rest on said abutment member, excavating module having a power source, seabed excavating said means extending downwardly from the bottom of said excavating module and operatively connected to said power source, said excavating means being adapted to loosen seabed material from beneath said silo and excavating module;
means for removing loosened seabed material from said excavating means and conducting said loosended seabed material to the surface of the seabed; and power source and control means for said excavating module; whereby operation of said excavating module while resting within said silo forms an excavation in the seabed within which both the silo and excavating module sink to a desired depth, after which the excavating module is removed from within the sunken silo and recovered for subsequent use.
10. An excavating module for sinking subsea wall head protective silos to a desired depth within a seabed, wherein said silos comprise a retainer wall assembly forming a hollow interior, said retainer wall assembly having an upper rim portion forming a top opening and a lower rim portion forming a bottom opening, abutment means defined within said retainer wall in the region of the lower rim portion, the excavating module comprising;
a module structure adapted to be positioned within said silo and adapted to move vertically within said silo and to rest on said abutment means, said module structure forming an interior compartment, a power source within said compart-ment, seabed excavating means extending downwardly from the bottom of said excavating module and operatively connected to said power source, said excavating means being adapted to loosen seabed material from beneath said silo and excavating module;
means for removing loosened seabed material from said excavating means and conducting said loosened seabed material to the surface of the seabed; and power source and control means for said excavating module whereby operation of said excavating module while resting within said silo forms an excavation in the seabed within which both the silo and excavating module sink to a desired depth, after which the excavating module is removed from the sunken silo and recovered for subsequent use.
a module structure adapted to be positioned within said silo and adapted to move vertically within said silo and to rest on said abutment means, said module structure forming an interior compartment, a power source within said compart-ment, seabed excavating means extending downwardly from the bottom of said excavating module and operatively connected to said power source, said excavating means being adapted to loosen seabed material from beneath said silo and excavating module;
means for removing loosened seabed material from said excavating means and conducting said loosened seabed material to the surface of the seabed; and power source and control means for said excavating module whereby operation of said excavating module while resting within said silo forms an excavation in the seabed within which both the silo and excavating module sink to a desired depth, after which the excavating module is removed from the sunken silo and recovered for subsequent use.
11. A method of sinking an open ended subsea wellhead protective silo to a desired depth within the seabed, comprising:
positioning said silo with the lower end thereof in contact with the seabed;
positioning excavating means within said silo and near the material of said seabed;
energizing said excavating means, causing loosening of the material of said seabed;
ejecting said loosened seabed material from said silo thus simultaneously causing sinking of said silo to a desired level within said seabed and forming a protective chamber beneath the surface of the seabed for positioning a wellhead therein; and removing said excavating means from said silo and recovering said excavating means for subsequent use.
positioning said silo with the lower end thereof in contact with the seabed;
positioning excavating means within said silo and near the material of said seabed;
energizing said excavating means, causing loosening of the material of said seabed;
ejecting said loosened seabed material from said silo thus simultaneously causing sinking of said silo to a desired level within said seabed and forming a protective chamber beneath the surface of the seabed for positioning a wellhead therein; and removing said excavating means from said silo and recovering said excavating means for subsequent use.
12. A method as recited in claim 11 wherein said loosened seabed material is ejected from the open upper end of said silo.
13. A method as recited in claim 11 wherein the loosened seabed material is ejected through the lower end of said silo and is conducted upwardly to the surface of the seabed along the exterior of said silo.
14. A method as recited in claim 11 wherein a fabric membrane in the form of a tube surrounds and covers the exterior surface of said silo, said membrane being attached at its lower end to a cutting shoe forming part of the lower end of said silo and providing an annulus between the side of the silo and the excavation during ejection of loosened seabed material and said membrane remaining with the silo after the excavation is completed and forming a seal against the exterior surface of said silo.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000479171A CA1248870A (en) | 1985-04-15 | 1985-04-15 | System for installing subsea wellhead protective silo |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000479171A CA1248870A (en) | 1985-04-15 | 1985-04-15 | System for installing subsea wellhead protective silo |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1248870A true CA1248870A (en) | 1989-01-17 |
Family
ID=4130275
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000479171A Expired CA1248870A (en) | 1985-04-15 | 1985-04-15 | System for installing subsea wellhead protective silo |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1248870A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2001065050A1 (en) * | 2000-02-29 | 2001-09-07 | Harald Strand | Foundation for suction in installation of conductor casing |
| US20150197907A1 (en) * | 2014-01-14 | 2015-07-16 | Conocophillips Company | Method of forming a mudline cellar for offshore arctic drilling |
| WO2017048941A1 (en) | 2015-09-15 | 2017-03-23 | Noble Drilling Services Inc. | Method for excavating a mud line cellar for subsea well drilling |
-
1985
- 1985-04-15 CA CA000479171A patent/CA1248870A/en not_active Expired
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2001065050A1 (en) * | 2000-02-29 | 2001-09-07 | Harald Strand | Foundation for suction in installation of conductor casing |
| US6692194B2 (en) | 2000-02-29 | 2004-02-17 | Harald Strand | Method for installing a conductor casing through a suction substructure |
| US20150197907A1 (en) * | 2014-01-14 | 2015-07-16 | Conocophillips Company | Method of forming a mudline cellar for offshore arctic drilling |
| US10267009B2 (en) * | 2014-01-14 | 2019-04-23 | Conocophillips Company | Method of forming a mudline cellar for offshore arctic drilling |
| WO2017048941A1 (en) | 2015-09-15 | 2017-03-23 | Noble Drilling Services Inc. | Method for excavating a mud line cellar for subsea well drilling |
| EP3353368A4 (en) * | 2015-09-15 | 2019-05-01 | Noble Drilling Services, Inc. | Method for excavating a mud line cellar for subsea well drilling |
| US10364609B2 (en) | 2015-09-15 | 2019-07-30 | Noble Drilling Services Inc. | Method for excavating mud line cellar for subsea well drilling |
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