Title:
PROTECTIVE STRUCTURE FOR SUBMERGED WELLS
United States Patent 3866676
Abstract:
A hydrocarbon producing well located at an offshore site, completely submerged beneath the water. The well includes a flow line extending from a reservoir in the substrate, which flow line passes along the floor of the body of water, and thence to a collection point. Flow control mechanism at the well head regulates fluid flow through said line. A casing extending into the substrate and terminating at the floor of the latter, substantially surrounds and forms a protective barrier about the upper portion of the flow line. The casing is provided with means for actuating the flow control mechanism whereby to discontinue fluid flow through the line under emergency conditions at such time as the actuating means is tripped.
US Patent References:
Underwater christmas tree protector
Logan - November 1962 - 3063500
Subsea production system
McIntosh - January 1968 - 3366173
Surface condition responsive subsurface safety valve system
Sizer - December 1968 - 3419076
FAIL-SAFE SUBSEA FLUID TRANSPORTATION SYSTEM
Brooks - July 1969 - 3454083
REMOTE-CONTROLLED OIL WELL PIPE SHEAR AND SHUTOFF APPARATUS
Orund et al. - July 1971 - 3590920
Underwater christmas tree protector
Logan - November 1962 - 3063500
Subsea production system
McIntosh - January 1968 - 3366173
Surface condition responsive subsurface safety valve system
Sizer - December 1968 - 3419076
FAIL-SAFE SUBSEA FLUID TRANSPORTATION SYSTEM
Brooks - July 1969 - 3454083
REMOTE-CONTROLLED OIL WELL PIPE SHEAR AND SHUTOFF APPARATUS
Orund et al. - July 1971 - 3590920
Application Number:
05/363289
Publication Date:
02/18/1975
Filing Date:
05/23/1973
View Patent Images:
Export Citation:
Assignee:
Texaco Development Corporation (New York, NY)
Primary Class:
Other Classes:
166/53, 166/375, 166/72, 166/364
International Classes:
E21B33/037; E21B34/04; E21B43/01; E21B43/12; E21B33/03; E21B34/00; E21B43/00; E21B43/01
Field of Search:
166/.5,.6,53,55,72,315 137/236
US Patent References:
Primary Examiner:
Abbott, Frank L.
Assistant Examiner:
Favreau, Richard E.
Attorney, Agent or Firm:
Whaley, Ries T. H. C. G.
Claims:
1. Well structure for a hydrocarbon fluid producing well submerged beneath a body of water subject to moving ice masses and other floating objects which might scour the substrate, said well including;
2. In a well structure as defined in claim 1, wherein said caisson includes; cylindrical upper and lower sections, said upper section extending from the substrate surface to said flow control means, and including a plurality of horizontally positioned caisson segments being
3. In a well structure as defined in claim 1, wherein said caisson includes; an upper end having a lip extending upward beyond the substrate surface, and said trigger mechanism being operably connected to said
4. In a well structure as defined in claim 1, wherein said flow control means includes; a power source disposed adjacent to the flow control means
5. In a well structure as defined in claim 1, including; a reservoir of pressurized actuating fluid and valve means communicated therewith, said valve means being connected to said trigger mechanism whereby to be operated in response to displacement of the trigger mechanism when said
6. In a well structure as defined in claim 1, wherein said flow control means includes; a quick acting valve communicated with a reservoir holding a pressurized actuating fluid, said quick acting valve being normally maintained in fully open position, and said trigger mechanism being operably connected to said pressurized actuating fluid whereby to regulate the same and thereby adjust said quick acting valve to a closed position.
7. In a well structure as defined in claim 1, wherein said caisson includes; at least a portion thereof being formed of horizonally disposed segmented sections adjacent of said sections being connected at
8. In a well structure as defined in claim 7, wherein said well flow line extends longitudinally of said caisson upper end, and said trigger mechanism includes cable means operably connected to the respective horizontally positioned caisson segments to adjust said flow control means to a closed position when the relative disposition of a caisson segment is
9. In a well structure as defined in claim 7, wherein said flow line extends longitudinally of said caisson upper end, said trigger means includes at least one bracket connected to the flow line, and cable means connected at one end thereof to said at least one bracket engaging the respective horizontally disposed caisson segments, whereby to adjust said
10. In a well structure as defined in claim 9, wherein said at least one bracket includes; a collar carried on said flow line, a plurality of arms extending radially from said collar, and said trigger mechanism including a plurality of cables, each connected at one end thereof to said flow line bracket and to the respective caisson horizontal segments, whereby to adjust said flow control means to a closed position when said flow line is vertically displaced with respect to said caisson.
2. In a well structure as defined in claim 1, wherein said caisson includes; cylindrical upper and lower sections, said upper section extending from the substrate surface to said flow control means, and including a plurality of horizontally positioned caisson segments being
3. In a well structure as defined in claim 1, wherein said caisson includes; an upper end having a lip extending upward beyond the substrate surface, and said trigger mechanism being operably connected to said
4. In a well structure as defined in claim 1, wherein said flow control means includes; a power source disposed adjacent to the flow control means
5. In a well structure as defined in claim 1, including; a reservoir of pressurized actuating fluid and valve means communicated therewith, said valve means being connected to said trigger mechanism whereby to be operated in response to displacement of the trigger mechanism when said
6. In a well structure as defined in claim 1, wherein said flow control means includes; a quick acting valve communicated with a reservoir holding a pressurized actuating fluid, said quick acting valve being normally maintained in fully open position, and said trigger mechanism being operably connected to said pressurized actuating fluid whereby to regulate the same and thereby adjust said quick acting valve to a closed position.
7. In a well structure as defined in claim 1, wherein said caisson includes; at least a portion thereof being formed of horizonally disposed segmented sections adjacent of said sections being connected at
8. In a well structure as defined in claim 7, wherein said well flow line extends longitudinally of said caisson upper end, and said trigger mechanism includes cable means operably connected to the respective horizontally positioned caisson segments to adjust said flow control means to a closed position when the relative disposition of a caisson segment is
9. In a well structure as defined in claim 7, wherein said flow line extends longitudinally of said caisson upper end, said trigger means includes at least one bracket connected to the flow line, and cable means connected at one end thereof to said at least one bracket engaging the respective horizontally disposed caisson segments, whereby to adjust said
10. In a well structure as defined in claim 9, wherein said at least one bracket includes; a collar carried on said flow line, a plurality of arms extending radially from said collar, and said trigger mechanism including a plurality of cables, each connected at one end thereof to said flow line bracket and to the respective caisson horizontal segments, whereby to adjust said flow control means to a closed position when said flow line is vertically displaced with respect to said caisson.
Description:
BACKGROUND OF THE INVENTION
In relatively shallow waters, such as those prevalent in the Beaufort Sea area of Alaska, a constant hazard to offshore, submerged hydrocarbon producing wells exists. This hazard resides primarily in floating ice which, although normally at the water's surface, tends at times to accumulate. Over a period of time and in certain seasons, the floating ice will develop into ice ridges which not only accumulate above the water but also develop a substantial submerged section.
As in the instance of icebergs, such ice masses will tend to drift when urged by the wind or tidal conditions. In the instance of relatively shallow waters characterized by the Beaufort Sea area, as these large ice ridges or ice masses are driven toward the shore, they are of such bulk that they scour the ocean floor. In effect they will excavate a trench in the ocean floor as they move until the depth of the water prohibits further progress of the mass.
To submerged wells, or a pipeline extending from the well, such scouring action could be devastating on either the well or the pipeline. In the instance of the latter it would tend to deform and bend the pipe until a breaking point is reached. In the instance of a well, should direct contact be made between the ice mass and the well, the latter could be substantially demolished. The consequent breaking of the flow line or the well proper would be in either instance cause an unrestricted flow of fluid, either gas or crude oil, from the well to the water's surface.
Were such a well break to occur, it would be virtually impossible to cut off the crude flow or to plug the well using standard methods presently employed by the industry. The presence of the ice mass directly over and adjacent to the damaged well would effectively prevent further drilling or other operation to cut off the uncontrolled well with the result that a major pollution occurrence would be imminent.
For remotely controlled offshore wells, particularly in deeper waters, means is provided for actuating the well flow control system to regulate fluid flow therethrough. Such means can include the normal blow-out preventer type mechanism utilized during the drilling period, down hole chokes, or similar valving inserted in either the well structure or in the flow line, to be remotely actuated at any time that the flow requires regulation.
However, the control lines to such equipment, whether electrical, hydraulic or otherwise, are always exposed and susceptible to damage or breakage. Under such circumstances the equipment could be designed such that the well would be automatically closed in. The chance exists though that the control lines will be damaged such as to maintain the well uncontrollable.
In the present arrangement, and toward overcoming the stated problem, emergency flow control means is provided within the submerged well at a point substantially below the floor of the substrate. By so embedding emergency flow control valves beneath the surface, they will be beyond the normal reach of icebergs, ice ridges and other floating masses, thus free from damage. Therefore, even though the latter tend to scour the ocean floor and damage parts of the well and pipeline, the emergency control means would remain relatively safe.
The actual flow control means, such as blow-out preventers or similar emergency valve mechanisms, are positioned within the well main flow line. An actuating media, normally fluid or gas powered, is connected to the flow control means whereby to actuate the latter to a closed position whereby to shut off fluid flow. Said actuating mechanism or system is likewise positioned sufficiently low in the substrate to be safe from damage.
A triggering means is connected to the actuating mechanism or powering system, and to the well structure upper end such that when the latter is damaged by an ice mass, the triggering means will automatically come into operation to adjust the flow controllers to a closed position.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is an elevation view in cross section of the submerged well contemplated.
FIG. 2 is a top view of FIG. 1.
FIG. 3 is a segmentary view on an enlarged scale and in cross section of a portion of the structure shown in FIG. 1.
FIG. 4 is an elevation view in partial cross section illustrating the present system schematically.
Referring to FIG. 1, the present well structure is shown embedded into the substrate S beneath a body of water W, the depth D of which can vary from several, to several hundred feet. It has been determined that over a period of time, the scouring action of ice masses and the like at the Alaskan North Slope, has been limited to a depth of approximately 50 feet into the sea floor. Further, in the Beaufort Sea area much of the substrate beneath the water is comprised primarily of sand and gravel, and is susceptible to being scoured and gouged.
The present well 10 follows to a large extent the standard construction, comprising a plurality of concentrically disposed casing members 11, 12 and 13 which extend downwardly and are cemented together and into the substrate S. A string of production tubing 15 extends downwardly through the respective casing lengths, terminating at its lower end within the hydrocarbon reservoir area. The upper end of said production tubing 15 is supported at a pad 18 which rests on the substrate surface. Flow control means 14 is positioned at the upper end of the production line 15 to regulate and control the passage of fluids therethrough. Said flow control means 14 as shown, is embedded a sufficient distance D' below the ocean floor F to put the flow control means beyond the reach of damaging ice that might contact the well.
The flow control means 14 can include the usual Christmas tree type regulating valve or valves which are manually adjusted. Preferably, said valves are remotely adjusted through a suitable mechanism to afford a desired fluid flow rate from the well. Supplemental to the flow control valves 14, emergency shut off means 17 comprises a shut off valve of the kind peculiar to a drilling or producing operation such as a blow-out preventer arrangement. The latter is normally connected directly into the flow line to discontinue flow in the event of a runaway or out of control well.
Said blow-out preventer includes in effect valve means positioned in, and movable transversely of the flow line, being normally retained in the fully opened position. With the advent of an uncontrollable flow condition arising within the well, the emergency valve mechanism is actuated to fully close, whereby to discontinue further flow from the well.
The lower end of flow line 16 communicates with the emergency valving 17 to define the fluid path. The upper end of said line 16 is communicated with a pipeline 19 which is supported along the surface of substrate S. Said pipeline in the usual manner carries a stream of hydrocarbon fluid from the well. It normally connects with or is manifolded with adjacent offshore wells to lead the entire produced product to a storage or refining facility 20.
As previously noted, the pipeline complex which connects the respective submerged satellite wells, is susceptible because of its being normally positioned at the sea floor, to ice scouring and damage. Breaking of the line could therefore quickly result in a water polluting saturation, even though to a minor degree. The industry has for many years utilized caissons about offshore wells. It is also known to submerge a well head into a caisson and beneath the ocean floor. Such a well head is shown in U.S. Pat. No. 3,461,957.
In accordance with the invention, well 10 is provided with an elongated, two sectioned caisson comprising a lower end 21 and an upper end 22. The caisson is embedded into the substrate S such that lower end 22 is at a depth below which ice scouring can be expected. As herein noted, said depth is determined to be approximately 50 to 60 feet.
Lower caisson 21 can be embedded by the usual methods such as driving, jetting or a combination of the two. The caisson lower end is a relatively heavy walled cylindrical member adapted to be urged into the substratum thereby to form a foundation for the upper end 22.
Caisson upper end 22 comprises a plurality of horizontally connected circular segments such as 24 and 25 which are joined one to the other solely at a plurality of welded or bolted breakaway joints 20, 20a and 20b. Said upper end is so arranged that in the event of contact with an ice mass the entire caisson will not be damaged or deformed. Rather, only particular segments will be effected so as to break from the remaining lower part of the caisson at the respective breakaway joints.
Caisson upper end 22 comprises a plurality of substantially cylindrical steel members. The latter are constructed with sufficient structural strength to serve the function of defining a water filled well in the substrate from the surface of the latter. While the walls of the respective segments need not be as heavy as the wall thickness of the caisson lower end 21, they are of sufficient structural capability to withstand the inward lateral forces provided by the substrate. Since the interior of caisson upper end 22 will be evacuated, the cavity so formed will remain substantially filled with water at all times.
Emergency flow shut off equipment exemplified by flow control means 17, is powered preferably by a hydraulic or pneumatic system positioned immediately adjacent to the well head. In such a position said system is beyond the reach of scouring ice which might cause damage thereto. While it is noted above that the system can embody a hydraulic or pneumatic medium, for the purpose of the present invention a pneumatic system will be specifically delineated.
It is appreciated that emergency actuated systems are presently incorporated on drilling vessels, platforms and the like, and connected to blow-out preventers at a well head particularly during the drilling of an exploratory well. The powering system normally functions in a manner to provide a quick power source for closing blow-out preventers at the well head at such time as an emergency blow-out is anticipated or occurs.
Referring to FIG. 4, the present arrangement provides a bank of pressurized gas cylinders 26 which are suitably connected through manifold means 27 and pressure regulators 28 to provide the necessary force for actuating the flow control member 17 to closed position, thus blocking the passage of fluid upwardly through line 15 and into line 16. The flow of gaseous actuating medium is controlled through a line valve 29 positioned in main line 31-32 connecting said manifold to emergency shut off valve 17. Valve 29 embodies no particular structure with the exception that it is quick acting. Said valve is sufficiently heavy to accommodate the high pressure normally maintained in gas cylinders 26 to provide the necessary closing force to discontinue fluid flow from the well.
The entire pressure system for shut off means 17 can be enclosed within a suitable closure member 33 to protect it from the environment. Said closure 33 further can be extended to enclose or communicate with a portion of the well to provide a degree of heating to the system by virtue of heat transfer from the hot crude product.
Thus, although upper caisson 22 is substantially filled with water, the closure member 33 surrounding the power system may likewise be water filled and yet surround a portion of the heated flow line such as control valve 14. The upward flowing, normally warm crude product will therefore continuously transfer sufficient heat to the surrounding water to prevent the system from being unduly affected by the normally cold water.
The means for actuating the powering system and thus valve 17, includes a triggering mechanism connected to flow line valve 29. Said triggering mechanism can include a number of embodiments susceptible to adjustment at such time as one or more of the caisson segments 24-25 is deformed due to being laterally impinged on by a body of ice scouring the substrate. The action of the moving ice mass will tend to deform one or more of the caisson segments in accordance with the bulk of the ice mass. However, with the breakaway joints 20, 20a and 20b, the upper segment such as 24, will tend to separate from the next lower segment thereby in effect leaving the entire lower part of the caisson intact.
The power system triggering mechanism includes a plurality of tensioned cables 36, 37 and 38 which extend longitudinally of the caisson 22, being slidably guided at each segment through loop guides 39 and 41. The latter depend inwardly from the caisson wall and are positioned adjacent one to the other.
Thus, as an upper caisson segment is deformed inwardly, it will tend to pull or displace at least one triggering cable depending on the direction from which ice approaches the well caisson. The lower end of each of said cables is connected to operating arm 42 of line control valve 29. Said cable, when thus adjusted from its normal tensioned condition by virtue of a deforming of the caisson segments, displaces the operating arm 40 thereby permitting the valve 29 to immediately move to fully open position.
The respective triggering cables 36, 37 and 39 are disposed at spaced intervals about the periphery of the caisson 22 to be in position to be tripped or adjusted, regardless of the direction from which scouring ice approaches the caisson. The upper ends of the respective cables are anchored to the outwardly radiating arms 42, 43 and 44 of a spider bracket 46, which is in turn connected to the upper end of flow line 16.
Said bracket 46 includes a split center collar 47 which encircles and is affixed to the vertical portion of said line 16 at a point beyond the upper edge of caisson segment 24. The respective outwardly radiating bracket arms in turn extend beyond the said segment upper lip of the caisson segment, either resting on the latter or merely spaced therefrom to permit movement therebetween.
With the shown structure, the crude carrying line 16 in effect is in a quasi-floating position with the spider bracket 46 rigidly mounted thereto. Thus, any appreciable displacement of pipeline 19 as a result of being displaced by a moving ice mass, will cause the line 16 to be offset. Consequently one or more of the triggering cables 36, 37 and 38 will be similarly displaced as to operate control valve arm. Said action will close valve 29 and discontinue flow through the pipeline 19.
In brief, whether the ice mass contacts and deforms a portion of well caisson, or the flow line 19, the effect will be the same. That is, the triggering mechanism at the caisson will be set into motion such that one or more of the triggering cables will displace the control arm to fully open control valve 29.
While the foregoing powering system is described as automatically introducing the pressurized medium to controller valve 17, a like result can be achieved through other means. Preferably, controller 17 is maintained open by virtue of valve 29 being open to apply pressure to said valve 17. Thereafter, with release of pressure under emergency conditions, valve 17 will automatically adjust to the closed position.
With the shown and described arrangement a producing well and operating pipeline communicated therewith can realize year round operation. Since the emergency flow control system is self operating, even though primary flow control source may be inoperable, the opportunity for a runaway or water polluting condition at the well is obviated.
While not shown in detail, means may be further provided on the well head to permit the vertical pipe segment 16 to rapidly disconnect from the well head. Thus, should a section be displaced due to contact with a scouring ice mass, it will permit the triggering mechanism to function and yet leave the well head intact.
With respect to restoring crude flow after the emergency condition has been removed or overcome, the powering system need only be recharged and the triggering means reset. are indicated
Other modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof, and therefore, only such limitations should be imposed as areindicated in the appended claims.
In relatively shallow waters, such as those prevalent in the Beaufort Sea area of Alaska, a constant hazard to offshore, submerged hydrocarbon producing wells exists. This hazard resides primarily in floating ice which, although normally at the water's surface, tends at times to accumulate. Over a period of time and in certain seasons, the floating ice will develop into ice ridges which not only accumulate above the water but also develop a substantial submerged section.
As in the instance of icebergs, such ice masses will tend to drift when urged by the wind or tidal conditions. In the instance of relatively shallow waters characterized by the Beaufort Sea area, as these large ice ridges or ice masses are driven toward the shore, they are of such bulk that they scour the ocean floor. In effect they will excavate a trench in the ocean floor as they move until the depth of the water prohibits further progress of the mass.
To submerged wells, or a pipeline extending from the well, such scouring action could be devastating on either the well or the pipeline. In the instance of the latter it would tend to deform and bend the pipe until a breaking point is reached. In the instance of a well, should direct contact be made between the ice mass and the well, the latter could be substantially demolished. The consequent breaking of the flow line or the well proper would be in either instance cause an unrestricted flow of fluid, either gas or crude oil, from the well to the water's surface.
Were such a well break to occur, it would be virtually impossible to cut off the crude flow or to plug the well using standard methods presently employed by the industry. The presence of the ice mass directly over and adjacent to the damaged well would effectively prevent further drilling or other operation to cut off the uncontrolled well with the result that a major pollution occurrence would be imminent.
For remotely controlled offshore wells, particularly in deeper waters, means is provided for actuating the well flow control system to regulate fluid flow therethrough. Such means can include the normal blow-out preventer type mechanism utilized during the drilling period, down hole chokes, or similar valving inserted in either the well structure or in the flow line, to be remotely actuated at any time that the flow requires regulation.
However, the control lines to such equipment, whether electrical, hydraulic or otherwise, are always exposed and susceptible to damage or breakage. Under such circumstances the equipment could be designed such that the well would be automatically closed in. The chance exists though that the control lines will be damaged such as to maintain the well uncontrollable.
In the present arrangement, and toward overcoming the stated problem, emergency flow control means is provided within the submerged well at a point substantially below the floor of the substrate. By so embedding emergency flow control valves beneath the surface, they will be beyond the normal reach of icebergs, ice ridges and other floating masses, thus free from damage. Therefore, even though the latter tend to scour the ocean floor and damage parts of the well and pipeline, the emergency control means would remain relatively safe.
The actual flow control means, such as blow-out preventers or similar emergency valve mechanisms, are positioned within the well main flow line. An actuating media, normally fluid or gas powered, is connected to the flow control means whereby to actuate the latter to a closed position whereby to shut off fluid flow. Said actuating mechanism or system is likewise positioned sufficiently low in the substrate to be safe from damage.
A triggering means is connected to the actuating mechanism or powering system, and to the well structure upper end such that when the latter is damaged by an ice mass, the triggering means will automatically come into operation to adjust the flow controllers to a closed position.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is an elevation view in cross section of the submerged well contemplated.
FIG. 2 is a top view of FIG. 1.
FIG. 3 is a segmentary view on an enlarged scale and in cross section of a portion of the structure shown in FIG. 1.
FIG. 4 is an elevation view in partial cross section illustrating the present system schematically.
Referring to FIG. 1, the present well structure is shown embedded into the substrate S beneath a body of water W, the depth D of which can vary from several, to several hundred feet. It has been determined that over a period of time, the scouring action of ice masses and the like at the Alaskan North Slope, has been limited to a depth of approximately 50 feet into the sea floor. Further, in the Beaufort Sea area much of the substrate beneath the water is comprised primarily of sand and gravel, and is susceptible to being scoured and gouged.
The present well 10 follows to a large extent the standard construction, comprising a plurality of concentrically disposed casing members 11, 12 and 13 which extend downwardly and are cemented together and into the substrate S. A string of production tubing 15 extends downwardly through the respective casing lengths, terminating at its lower end within the hydrocarbon reservoir area. The upper end of said production tubing 15 is supported at a pad 18 which rests on the substrate surface. Flow control means 14 is positioned at the upper end of the production line 15 to regulate and control the passage of fluids therethrough. Said flow control means 14 as shown, is embedded a sufficient distance D' below the ocean floor F to put the flow control means beyond the reach of damaging ice that might contact the well.
The flow control means 14 can include the usual Christmas tree type regulating valve or valves which are manually adjusted. Preferably, said valves are remotely adjusted through a suitable mechanism to afford a desired fluid flow rate from the well. Supplemental to the flow control valves 14, emergency shut off means 17 comprises a shut off valve of the kind peculiar to a drilling or producing operation such as a blow-out preventer arrangement. The latter is normally connected directly into the flow line to discontinue flow in the event of a runaway or out of control well.
Said blow-out preventer includes in effect valve means positioned in, and movable transversely of the flow line, being normally retained in the fully opened position. With the advent of an uncontrollable flow condition arising within the well, the emergency valve mechanism is actuated to fully close, whereby to discontinue further flow from the well.
The lower end of flow line 16 communicates with the emergency valving 17 to define the fluid path. The upper end of said line 16 is communicated with a pipeline 19 which is supported along the surface of substrate S. Said pipeline in the usual manner carries a stream of hydrocarbon fluid from the well. It normally connects with or is manifolded with adjacent offshore wells to lead the entire produced product to a storage or refining facility 20.
As previously noted, the pipeline complex which connects the respective submerged satellite wells, is susceptible because of its being normally positioned at the sea floor, to ice scouring and damage. Breaking of the line could therefore quickly result in a water polluting saturation, even though to a minor degree. The industry has for many years utilized caissons about offshore wells. It is also known to submerge a well head into a caisson and beneath the ocean floor. Such a well head is shown in U.S. Pat. No. 3,461,957.
In accordance with the invention, well 10 is provided with an elongated, two sectioned caisson comprising a lower end 21 and an upper end 22. The caisson is embedded into the substrate S such that lower end 22 is at a depth below which ice scouring can be expected. As herein noted, said depth is determined to be approximately 50 to 60 feet.
Lower caisson 21 can be embedded by the usual methods such as driving, jetting or a combination of the two. The caisson lower end is a relatively heavy walled cylindrical member adapted to be urged into the substratum thereby to form a foundation for the upper end 22.
Caisson upper end 22 comprises a plurality of horizontally connected circular segments such as 24 and 25 which are joined one to the other solely at a plurality of welded or bolted breakaway joints 20, 20a and 20b. Said upper end is so arranged that in the event of contact with an ice mass the entire caisson will not be damaged or deformed. Rather, only particular segments will be effected so as to break from the remaining lower part of the caisson at the respective breakaway joints.
Caisson upper end 22 comprises a plurality of substantially cylindrical steel members. The latter are constructed with sufficient structural strength to serve the function of defining a water filled well in the substrate from the surface of the latter. While the walls of the respective segments need not be as heavy as the wall thickness of the caisson lower end 21, they are of sufficient structural capability to withstand the inward lateral forces provided by the substrate. Since the interior of caisson upper end 22 will be evacuated, the cavity so formed will remain substantially filled with water at all times.
Emergency flow shut off equipment exemplified by flow control means 17, is powered preferably by a hydraulic or pneumatic system positioned immediately adjacent to the well head. In such a position said system is beyond the reach of scouring ice which might cause damage thereto. While it is noted above that the system can embody a hydraulic or pneumatic medium, for the purpose of the present invention a pneumatic system will be specifically delineated.
It is appreciated that emergency actuated systems are presently incorporated on drilling vessels, platforms and the like, and connected to blow-out preventers at a well head particularly during the drilling of an exploratory well. The powering system normally functions in a manner to provide a quick power source for closing blow-out preventers at the well head at such time as an emergency blow-out is anticipated or occurs.
Referring to FIG. 4, the present arrangement provides a bank of pressurized gas cylinders 26 which are suitably connected through manifold means 27 and pressure regulators 28 to provide the necessary force for actuating the flow control member 17 to closed position, thus blocking the passage of fluid upwardly through line 15 and into line 16. The flow of gaseous actuating medium is controlled through a line valve 29 positioned in main line 31-32 connecting said manifold to emergency shut off valve 17. Valve 29 embodies no particular structure with the exception that it is quick acting. Said valve is sufficiently heavy to accommodate the high pressure normally maintained in gas cylinders 26 to provide the necessary closing force to discontinue fluid flow from the well.
The entire pressure system for shut off means 17 can be enclosed within a suitable closure member 33 to protect it from the environment. Said closure 33 further can be extended to enclose or communicate with a portion of the well to provide a degree of heating to the system by virtue of heat transfer from the hot crude product.
Thus, although upper caisson 22 is substantially filled with water, the closure member 33 surrounding the power system may likewise be water filled and yet surround a portion of the heated flow line such as control valve 14. The upward flowing, normally warm crude product will therefore continuously transfer sufficient heat to the surrounding water to prevent the system from being unduly affected by the normally cold water.
The means for actuating the powering system and thus valve 17, includes a triggering mechanism connected to flow line valve 29. Said triggering mechanism can include a number of embodiments susceptible to adjustment at such time as one or more of the caisson segments 24-25 is deformed due to being laterally impinged on by a body of ice scouring the substrate. The action of the moving ice mass will tend to deform one or more of the caisson segments in accordance with the bulk of the ice mass. However, with the breakaway joints 20, 20a and 20b, the upper segment such as 24, will tend to separate from the next lower segment thereby in effect leaving the entire lower part of the caisson intact.
The power system triggering mechanism includes a plurality of tensioned cables 36, 37 and 38 which extend longitudinally of the caisson 22, being slidably guided at each segment through loop guides 39 and 41. The latter depend inwardly from the caisson wall and are positioned adjacent one to the other.
Thus, as an upper caisson segment is deformed inwardly, it will tend to pull or displace at least one triggering cable depending on the direction from which ice approaches the well caisson. The lower end of each of said cables is connected to operating arm 42 of line control valve 29. Said cable, when thus adjusted from its normal tensioned condition by virtue of a deforming of the caisson segments, displaces the operating arm 40 thereby permitting the valve 29 to immediately move to fully open position.
The respective triggering cables 36, 37 and 39 are disposed at spaced intervals about the periphery of the caisson 22 to be in position to be tripped or adjusted, regardless of the direction from which scouring ice approaches the caisson. The upper ends of the respective cables are anchored to the outwardly radiating arms 42, 43 and 44 of a spider bracket 46, which is in turn connected to the upper end of flow line 16.
Said bracket 46 includes a split center collar 47 which encircles and is affixed to the vertical portion of said line 16 at a point beyond the upper edge of caisson segment 24. The respective outwardly radiating bracket arms in turn extend beyond the said segment upper lip of the caisson segment, either resting on the latter or merely spaced therefrom to permit movement therebetween.
With the shown structure, the crude carrying line 16 in effect is in a quasi-floating position with the spider bracket 46 rigidly mounted thereto. Thus, any appreciable displacement of pipeline 19 as a result of being displaced by a moving ice mass, will cause the line 16 to be offset. Consequently one or more of the triggering cables 36, 37 and 38 will be similarly displaced as to operate control valve arm. Said action will close valve 29 and discontinue flow through the pipeline 19.
In brief, whether the ice mass contacts and deforms a portion of well caisson, or the flow line 19, the effect will be the same. That is, the triggering mechanism at the caisson will be set into motion such that one or more of the triggering cables will displace the control arm to fully open control valve 29.
While the foregoing powering system is described as automatically introducing the pressurized medium to controller valve 17, a like result can be achieved through other means. Preferably, controller 17 is maintained open by virtue of valve 29 being open to apply pressure to said valve 17. Thereafter, with release of pressure under emergency conditions, valve 17 will automatically adjust to the closed position.
With the shown and described arrangement a producing well and operating pipeline communicated therewith can realize year round operation. Since the emergency flow control system is self operating, even though primary flow control source may be inoperable, the opportunity for a runaway or water polluting condition at the well is obviated.
While not shown in detail, means may be further provided on the well head to permit the vertical pipe segment 16 to rapidly disconnect from the well head. Thus, should a section be displaced due to contact with a scouring ice mass, it will permit the triggering mechanism to function and yet leave the well head intact.
With respect to restoring crude flow after the emergency condition has been removed or overcome, the powering system need only be recharged and the triggering means reset. are indicated
Other modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof, and therefore, only such limitations should be imposed as areindicated in the appended claims.