US3738114A

US3738114A - Method and apparatus for forming ice island for drilling or the like

Info

Publication number: US3738114A
Application number: US00194125A
Authority: US
Inventors: G Bishop
Original assignee: Individual
Current assignee: Individual
Priority date: 1971-11-01
Filing date: 1971-11-01
Publication date: 1973-06-12
Anticipated expiration: 1990-06-12
Also published as: CA972975A

Abstract

A method and apparatus for forming an ice island in cold geographical regions to recover resources such as oil from areas normally covered with ice, frozen muskeg or the like in the winter. In one embodiment an oil drilling barge is moved to an offshore drill site during a thaw period and allowed to be frozen in at the onset of winter. Concentric, spaced apart walls are constructed about the barge and water is pumped into the area between the walls, frozen, and the cycle repeated a number of times until the weight of built-up ice causes the walls to sink gradually through the pack ice and eventually to the ocean bottom. The barge is next secured to the inner wall to serve as a drilling platform. Ice and water within the inner wall is removed and drilling proceeds. During seasonal thaws refrigeration equipment is utilized to keep the ice island in a frozen condition. When the ice island is to be moved to another drill site, air is introduced beneath the ice island, and the upper layers of ice are thawed, scraped away and dumped over the side during a thaw period unitl the lightened, buoyed island floats off the ocean bottom. It is towed to the new drill site, built up again, and sunk as before.

Description

ilnited States Patent 11 1 Bishop METHOD AND APPARATUS FOR FORMING ICE ISLAND FOR DRILLING OR THE LIKE [76] Inventor: Gilbert H. Bishop, 2140 Tulane j Avenue, Long Beach, Calif. 90815 22 Filed: Nov. 1, 1971 [21] Appl. No.: 194,125

OTHER PUBLICATIONS Oil and Gas Journal of Sept. 14, 1970, pages 60, 61.

Primary ExaminerJacob Shapiro Attorney-J.- F. McLellan, B. Edward Shlesinger,Jr., George A. Arkwright et a1. 1

[ June 112, 1973 [57] ABSTRACT A method and apparatus for forming an ice island in cold geographical regions to recover resources such as oil from areas normally covered with ice, frozen muskeg or the like in the winter. In one embodiment an oil drilling barge is moved to an offshore drill site during a thaw period and allowed to be frozen in at the onset of winter. Concentric, spaced apart walls are constructed about the barge and water is pumped into the area between the walls, frozen, and the cycle repeated a number of times until the weight of built-up ice causes the walls to sink gradually through the pack ice and eventually to the ocean bottom. The barge is next secured to the inner wall to serve as a drilling platform. Ice and water within the inner wall is removed and drilling proceeds. During seasonal thaws refrigeration equipment is utilized to keep the ice island in a frozen condition. When the ice island is to be moved to another drill site, air is introduced beneath the ice island, and the upper layers of ice are thawed, scraped away and dumped over the side during a thaw period unitl the lightened, buoyed island floats off the ocean bottom. It is towed to the new drill site, built up again, and sunk as before.

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METHOD AND APPARATUS FOR FORMING ICE ISLAND FOR DRILLING OR THE LIKE BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for forming an ice island, and particularly an ice island adapted to be utilized for recovering underwater resources such as oil or for impounding of hydrocarbons in liquid form in arctic and antarctic regions.

2. Description of the Prior Art The recovery of underwater resources, and particularly oil, from offshore areas in arctic and antarctic regions is extremely difficult. Areas such as the north slope of Alaska are covered with ice during 46-50 weeks of the year.

In one prior art method of drilling for oil in these areas a floating barge is used as the drilling platform, and the barge is allowed to become frozen in during the winter. This matters little so long as the position of the barge remains unchanged. However, the surrounding pack ice invariably shifts and changes with the tides and winds, moving the barge and often destroying and shearing away drilling equipment and drill pipe. Being trapped in the ice, it is impossible for the barge to be relocated to maintain its position over the drill site during the shifting of the pack ice.

Another drilling method of the prior art involves the formation of a permanent island of earth or other fill or the construction of permanent tubular steel platforms integral with the ocean bottom. Since these structures are an integral part of the ocean bottom, the integrity of the drilling rig and drill string were maintained during pack ice shifting. However, the island could not be moved to a new drill site once drilling was completed at the first site. The cost of constructing a new permanent island at each site is prohibitively expensive and construction work must be accomplished by divers.

All of the financially feasible drilling methods and apparatus of the prior art suffer from the extreme environmental conditions encountered in the arctic and antarctic, particularly in that the apparatus was incapable of resisting the tremendous forces exerted by shifting pack ice. There was an ever present risk of loss of a stable platform due to thaw conditions, such as underwater completions being sheared off by drifting icebergs in relatively shallow waters. The prior art structures also lack any means for making a completely subsurface well completion without some form of projection remaining above the natural ocean bottom.

SUMMARY OF THE INVENTION According to the present invention an ice island is formed, made integral with the ocean bottom, underwater strata, or permafrost, and maintained in a frozen state during thaw periods by refrigeration equipment. If located offshore or on a lake or the like, the ice island is adapted for transfer to a new location or drill site during a thaw period by warming the upper layers of the ice island, scraping off and dumping the thawed material, and introducing air to water beneath the island to separate it from the ocean bottom for towing to the new drilling site.

The particular method of the invention includes the steps of constructing spaced apart inner and outer walls on relatively thin fall season ice or on frozen muskeg or the like. In one embodiment the barge is towed to an offshore drill site, breaking through any ice which may exist. The barge is allowed to be frozen in as the cold weather sets in, with the inner and outer walls being constructed around the barge as soon as the surrounding ice will support the weight of construction equipment and wall structures.

The inner and outer walls are secured in spaced relation by bracing, and the barge is slidably mounted to the inner wall for upward movement as the island sinks under the weight of the accumulating ice. The ice is formed by introducing water from beneath and around the island to the upper surface of the ice between the inner and outer walls. This is done in stages, each layer of water being allowed to freeze until sufiicient ice is formed that its weight causes the complex to sink. This permits progressive refinement of grain structure of the ice through removal of surface concentrations of brine by mechanical means before the eutectic point for such impurities is reached. Upper extensions are constantly added to the inner and outer walls to accommodate the built up mass of accumulated ice and suitable bracing is added as it becomes necessary. The increasing weight of the island causes the lower edges of the inner and outer walls and the original ice shelf or crust to eventually sink into the ocean bottom. This grounds the original ice crust on the ocean bottom and compresses the subsurface to provide an excellent ice-to-earth bond.

The barge floats within the inner wall and may be rigidly fixed to the inner wall for service as a drilling platform. The ice and water within the inner wall is removed to expose the ocean bottom, and excavation and drilling is begun. After the drilling is completed, the excavation with the usual valving equipment is then covered over and the ice island readied for transfer to a new site.

The ice island could be maintained in the same position by utilizing refrigeration equipment to maintain the ice frozen during thaw periods. However, if the ice island is to be moved, this is done during a period of thaw. The thawed ice is removed from the surface of the island by suitable scraping equipment. Thaw water may be used to accelerate melting of the ice. Simultaneously, air or water is introduced beneath the ice island. This procedure is continued until the island is buoyed sufficiently to enable it to be towed by tugs or the like to the new drill site. The ice island is then sunk as before.

Because it is an integral part of the ocean bottom, the

ice island is not subject to shifting with the ice pack,

and the integrity of drilling equipment is preserved. The inner wall of the island serves as a caisson, allowing easy access to the ocean bottom for construction of a permanent subsurface work pit, which greatly facilitates recovery of resources such as oil from beneath the ocean bottom. Most importantly, the transferability of the ice island makes it possible to use the ice island at many different drill sites.

In another embodiment the ice island is formed on muskeg or the like in arctic regions such as Alaska. This permits drilling in an area which is a virtual quagmire during the'summer. The construction, of such an ice island is substantially identical to that just described, except that the inner and outer walls are constructed on the frozen muskeg during the winter season. Water is then pumped into the space between the walls through conduits extending to a source of water,

such as a nearby lake, river, or the ocean. The resulting mass of ice is preferably kept frozen by the refrigeration equipment during the following spring thaw.

Other objects and features of the invention will become apparent from consideration of the following description taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational view of the ice island formed by present apparatus, the island being illustrated in position on the ocean bottom;

FIG. 2 is a view taken along the line 2-2 of FIG. 1;

FIG. 3 is an enlarged detail view taken in the area designated by the numeral 3 in FIG. 1;

FIG. 4 is an enlarged detail view of one of the self purging conduits; and

FIGS. 5-9 illustrate in generally diagrammatic form the various stages in the formation and transfer of the ice island of FIG. 1, as follows: FIG. 5, the initial construction of the ice island walls; FIG. 6, partial formation of the ice island; FIG. 7, the completely formed ice island in position upon the ocean bottom; FIG. 8, removal of a portion of the ice and introduction of air or water beneath the island for initial separation from the ocean bottom with barge secured to and suspended from rails, water and ice removed from inner wall, and work pit constructed; and FIG. 9, separation of the ice island from the ocean bottom preparatory to transfer to a new drill site.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, and particularly to FIGS. 1-4, there is illustrated an apparatus for forming an ice island for use in exploiting substrata resources such as oil. The apparatus 10 comprises, generally, a central ship or drilling barge 12; a circular inner wall structure 14 surrounding the barge 12; and a circular outer wall structure 16 in concentric relation to the structure 14 and defining an annular space therewith.

The drilling barge 12 is made large enough to supply the needs of a working crew for extended periods of time. The barge 12 also supports usual oil drilling equipment and drilling rigs, a power supply, refrigeration and heating equipment, pumping equipment, a draw works house for pulling a string of pipe, and other necessary working tools and the like.

In constructing the ice island at a drill site in an arctic region, for example, the barge 12 is floated to the drill site during the summer thaw, being either selfpropelled or towed by a number of tugs. The barge is anchored and allowed to freeze in at the onset of winter. If there is any existing thin ice in the area when the barge is moved in, it refreezes and thickens as the winter nears.

Before the ice thickens, a plurality of dome-shaped containers, open at the bottom and constituting ballast tanks 24, are floated upon the water in circumferentially spaced apart relation about the barge 12. If thin ice is present, the tanks 24 are placed in openings cut in the thin ice crust. The tanks are kept pressurized to float on the water and are maintained in position by suitable securing lines (not shown) or by the flexible air lines 26 which extend radially inwardly and connect the tanks 24 to the pump equipment on the barge 12. Air pressure is also maintained to keep out as much water as possible to thereby prevent the formation of ice plugs in the tanks 24 as colder weather begins and the tanks freeze in.

When the ice is thick enough. to support construction equipment, such as about 2 feet thick, a pair of circular concentric grooves or cuts are formed in the ice about the barge 12. The structure 14 comprises a pair of concentric double walls, and these are set into the formed grooves or driven in by conventional pile driving equipment. The diameter of the structure 14 is approximately 300 feet.

The inner wall of the structure 14 is made of rigid material such as conventional dock facing sheet steel. as best seen in FIG. 3, approximately one-half to threefourths inches thick. Separate, generally rectangular sheets are interlocked at their side edges to form the peripherally continuous wall. The sheets are characterized by vertically oriented folds to improve their bending strength. As will be seen, the upper edges of the sheets are provided with suitable margins (not shown) to interfit with the lower margins of similar sheets so as to build up a higher structure 14 during the formation of the ice island. The lower edges of the sheets are wedge shaped to better cut through the subsurface when the ice island descends.

The inner face of the wall structure 14 is provided with vertically oriented I-beams or rails 18 upon which the barge 12 is slidably supported. For this purpose the bow and stern of the barge include suitable complemental fittings (not shown) and conventional jack equipment to jack up the barge relative to the rails 18. The reason for this arrangement will be explained subsequently. The sides of the barge also include similar fittings which slidably cooperate with rails 18 supported upon girders or bracing 20. The bracing 20 is attached to and projects radially inwardly of the wall structure 14, and is vertically oriented in coextensive relation with the rails 18.

The outer wall of the double wall structure 14 is preferably flexible to yield when water located between the

wall structures

14 and 16 freezes and expands. This flexibility can be provided in any suitable manner, such as by using overlapping wall sections which are slidable upon one another. These wall sections are supported by suitable bracing (not shown) extending between the spaced double walls. Except for a short distance from the bottom, the space between the walls is filled with heat insulating material such as compressible plastic foam material. The outer one of the double walls is thus essentially a retainer for the insulating material, but also provides structural strength.

The peripherally continuous double wall structure 16 is constructed and erected in a manner substantially identical to that just described for the structure 14, except that it is of considerably larger diameter, the innermost wall is flexible like the outer wall of the structure 14, and the outermost wall is rigid like the inner wall of the structure 14.

The diameter of the structure 16 is dictated by the mass of ice necessary to float the structure which is used to construct the island. It would be several hundred feet in diameter in the usual situation. The final height of the island is controlled by the depth of the water at the site and the weight of the island that is necessary to press against the ocean bottom sufficiently to achieve a good bond and resist lateral movement.

In all other respects the

structures

14 and 16 are constructed alike of double walls, interposed insulation, peripherally continuous, and adapted to be built up in height by adding successive sections. The lower edges of the walls of the structures 16 are set into circular grooves cut into the existing shelf ice, or are driven in with pile drivers, just as was the structure 14 to extend below the thickness of the natural shelf ice.

The walls of the

structures

14 and 16 are driven through the shelf ice with pile drivers until they extend below the ice approximately four feet. As the various wall sections are driven into position they freeze in almost immediately, as best seen in FIG. 5.

The lower portions of the

structures

14 and 16 do not include insulation since these portions preferably cut or bite into the bottom of the ocean for several feet. The void existing where the insulation is omitted is vented to atmosphere through one or more vent lines 19. This enables removal of any air or water entrapped upon engagement of the

structures

14 and 16 with the ocean bottom.

If the mass of the ice in the island is made great enough to bear heavily against the ocean bottom, and thereby of itself prevent water intrusion into the space within the inner wall structure 14, it will not be necessary to provide for embedment into the ocean bottom of the lower edges of the

structures

14 and 16. Instead, such edges need not project below the ice mass at all.

Since it will be important during the summer thaw to maintain the ice island in a frozen condition, an array of refrigerator coils 21 is arranged upon the confronting walls of the

wall structures

14 and 16, the conduits connecting the coils extending radially inwardly upon the surface of the existing shelf ice and through the structure 14 for connection to the refrigeration equipment located on the barge 12. The refrigeration coils extend about the periphery of the walls.

Elongated rods, pipes, bar or ice locks 22 are also laid upon the ice surface and attached to the confronting walls of the

structures

14 and 16, extending toward one another into the annular area between such structures. The locks 22 will later be surrounded with frozen layers of ice forming the island, and the locks 22 prevent relative vertical movement between the ice and the adjacent walls of the

structures

14 and 16.

A plurality of cables constituting wall braces 28 are also laid upon the existing ice shelf and attached at their opposite ends to the confronting walls of the

structures

14 and 16, the braces 28 extending like the spokes of a bicycle wheel and performing somewhat the same function. That is, the inner extremities of the braces 28 extend inwardly through the wall structure 14, and are provided with suitable means by which they can be tensioned. This prestresses the structures and preserves the circular'configuration under the stress of expanding ice in the space between them.

Several flexible water conduits 30 are also fanned out across the ice shelf surface, each extending from the pumping equipment on the barge 12, through wall structure 14, to the periphery of one of the ballast chambers 24, as seen in FIG. 2, and opening downwardly. Additional conduits 42 are similarly fanned out across the ice surface, extending through the

structures

14 and 16, and connected to the barge 12. The conduits 30 are utilized to pump out any water trapped beneath the ice island between the

wall structures

14 and 16 once the lower edges of such structures cut into the ocean bottom. This water is used for equipment coolant and for building up the mass of the ice island. Once the island descends to the ocean bottom, and the entrapped water is removed by the conduits 30, further water for equipment cooling and for ice build-up is obtained through the conduits 42.

Each conduit 30 and 42 is self purging. As best seen in FIG. 4, each conduit 30 comprises an outer rigid wall 32 of steel, a flexible inner wall 34 of rubber or the like, and a layer of insulating material 36 about the outer wall 32. The inner wall is joined to the outer wall at its ends, the end opening to the sea being conical in configuration. This opening forms the ice freezing in this area into a conical plug. An air line 38 opens into the annular space between the

walls

32 and 34. The conduits 42 are identically constricted. With this arrangement water may be pumped through the conduit formed by the inner wall 34 when it is expanded against the outer wall 32 by evacuation of air through the air line 38. When the conduit 30 or 42 is not being used, air is pumped through the line 38 into the space between the walls. No water is left in the conduit to freeze, except for the ice plug in the end. This can be blown out prior to pumping again by evacuating air from the annular space between the walls and pressurizing the inner conduit until the ice plug is blown out, or warm water can be pumped through the conduit to the area of the ice plug to melt it.

The formation of the ice forming the island is begun by pumping water from the sea through one or more conduits extending from the barge 12, through holes bored in the shelf ice, to the space beneath the barge. This water is sprayed onto the original shelf ice and covers the coils 21, locks 22, and braces 28 lying on the surface of the shelf ice. In the Arctic, sea water at l to 2C will freeze almost immediately on exposure to the ambient temperatures. Once the water has reached and frozen at a level above these coils, locks and braces, as best seen in FIG. 6, sweeper-scrapers (not shown) carried by the barge are placed on the ice and operated to scrape off the upper layer of ice and the impurities therein for discharge into the ocean, and for generally evening the surface of the ice. The freezing of ice is characteristically accompanied by upward migration of brine and impurities and concentrations of these are scraped away, thus reducing intercrystalline inclusions and refining the ice crystal structure. Such constant removal of impurities greatly improves the strength of the ice island.

The operation is repeated to add another layer of water, which is frozen, scraped, and so on. Additional sets of braces 28 are laid upon the freshly frozen surface at appropriate levels and connected to the

adjacent wall structures

14 and 16. Additional sets of ice locks 22, refrigeration coils 21, and wall extensions for the structures l4 and 16 are also added on as needed.

It is noted that sea water below 2C has undergone most of its liquid-to-ice crystal formation expansion so that further expansion, on freezing, is minimal, thereby reducing stresses on the

structures

14 and 16. Such expansion as does occur is taken up by the yieldable nature of the outer wall of the structure 14 and the inner wall of the structure 16. In addition, it will be understood that at all points where relative movement will occur because of such expansion, appropriate slip joints (not shown) are provided, particularly for the refrigeration coil conduits, locks 22 and braces 28 which pass through the

structures

14 and 16. Any conventional slip joint adapted for this purpose is suitable.

As the weight of the ice mass or island increases, the resistance to shear at the interface between the natural ice shelf and the adjacent walls is exceeded and the ice island begins to sink. The shelf ice within the inner wall structure 14 is next broken up and removed so that the barge 12 can float upwardly, sliding on the rails 18 as the ice island sinks. If necessary, the jacks cooperative with the rails 18 can be operated at this time to insure proper upward travel of the barge as the island descends.

As previously indicated, the descending of the island is accompanied by the construction of upper extensions of the

structures

14 and 16 to provide a continuous, vertically extending wall structure.

When the lower edges of the

structures

14 and 16 engage the ocean bottom, and bite deeper and deeper into the ocean substrata, air pressure in the ballast chambers 24 increases, indicating entrapment of water in the annular space under the island between the

structures

14 and 16. The lines 26 are now air pressurized to purge them of ice plugs, and lines 30.0perated to pump water out of the space between the

structures

14 and 16 to allow the ice island to sink completely to the ocean bottom at all points. Any small amount of water remaining tends to be frozen by the superjacent mass of the ice island thereby providing a strong earthto-ice seal, as seen in FIG. 7. In addition, the pumping of water from the space within the inner wall structure 14 is continued until it is dry. Preferably the barge 12 is clamped to the rails 18 as soon as the island touches bottom so that the barge will not float to the bottom as the water is pumped out of the structure 14.

The weight of the ice is such that water intrusion beneath it is unlikely. However, where coarse grained gravel structures or the like are encountered, water intrusion is prevented by such conventional means as hydraulic grouting through peripheral grouting openings drilled in the ice. Grout is discharged through these openings into such porous structures below the island to seal off the water intrusion. This is done in conjunction with removal of the ice and water from within the wall structure 14, the operation being continued until it is certain that water is not entering into this inner work area.

The ocean bottom must be relatively level. If it is not naturally level, it must be scraped or dredged during the thaw prior to location of the apparatus over the drill site.

The ocean bottom within the inner wall structure 14 is excavated to form the work pit within which the usual permanent valving and the like are installed below the natural sea bed surface. Once drilling is completed and the well is brought in and capped, it is connected to the valving equipment so that the oil can be drawn off in pipes going to shore, for example. The work pit is provided with a suitable cover and the island is made ready for transfer to another drill site.

However, if drilling operations are to continue for more than one season, at the onset of the spring and summer thaw the surface of the ice island between the

structures

14 and 16 is covered with a layer of insulat ing blankets (not shown), and the refrigeration equipment on the barge is operated to keep the temperature of the ice adjacent the

structures

14 and 16 at below freezing temperature.

If the ice island is to be moved to a new drill site this must be done during the summer thaw. Knowing the mass of ice which was required to sink the island, it is a comparatively straightforward procedure to determine the amount of ice which must be removed to again render the island buoyant.

The natural thawing of the upper ice layers is hastened by pumping sea water, preferably heated, onto the ice by means of the previously mentioned spray rig. The spray rig, indicated at 46 in FIG. 2, is conveniently movable on tracks attached to a circumferential platform 48 built on the top of the completed outer wall structure 16. This procedure softens the ice so that the previously mentioned power scrapers can remove the ice in an even, controlled manner so as to preserve the stability of the ice island. The coils 21, bracing 20, and ice locks 22 of each melting ice layer are preferably not employed in approximately the upper half of the thickness of ice forming the island. Consequently, they will not be in the way when the ice is being thawed. However, if the island is to be permanent, and used through many seasons of freeze and thaw, the coils 21, bracing 20 and ice locks 22 would preferably extend throughout the thickness of the ice.

All excess equipment and supplies are removed to reduce weight. As the weight of the ice island decreases, the natural buoyancy of ice in sea water tends to float the island off the ocean bottom, this tendency eventually being restrained primarily only by the suction of the ice-to-earth bond. At this time, and when all the towing tugs (not shown) are in position for towing and the tidal conditions are favorable, air or water is injected through the lines 30, and through the lines 26 into the ballast chambers 24. Air from the chambers 24 tends to pass between the ice and the bottom, breaking the bond, as seen in FIG. 8. The ballast chambers 24, being filled with air, further buoy the island and, when the lower edges of the

wall structures

14 and 16 separate from the ocean bottom, the barge 12 floats up with the rising water, as seen in FIG. 9. As soon as the

structures

14 and 16 are sufficiently clear of the bottom, the island is towed to its new location.

The stability and trim of the island during towing is regulated by adjusting the air pressure in the ballast chambers 24, by relocating scrapers, trucks, and other equipment on the surface of the island, and also by shifting the location of the spray rig on the perimeter of the wall structure 16. Operation of the refrigeration equipment, and use of insulating blankets over the surface of the island slow further melting and thawing of the ice mass.

When the island has reached its new location, air from the chambers 24 is exhausted through the lines 26, and the storage tanks and supplies of the barge 12 are replenished from supply ships to increase the islands weight. The barge 12 is jacked up on the l-beams 18 out of the water to further increase the weight of the island and help bring the lower edges of the

structures

14 and 16 into engagement with the ocean bottom. Once firm engagement is achieved, the island stays in position until it is frozen in during the following winter when the natural ice shelf is formed. In addition, the island is further weighted down by using the previously described method for building up a new mass of ice on the island to securely hold it in position.

The particular shape of the ice island is not critical and it can be changed simply by altering the configuration of the wall structures. If desired, such wall structures could be prefabricated and towed to the drill site by the attachment of suitable flotation equipment to such structures. In this regard, the insulation in the

wall structures

14 and 16 also has considerable buoyancy.

By utilizing the present method and apparatus for forming an ice island, it is possible to utilize extremely cold weather conditions to overcome the very problems which were created in the prior art by virtue of such conditions.

The ocean bottom within the innerwall structure 14 can be excavated without the use of pressure to prevent water intrusion and without any need for the services of underwater dives. Instead, the weight of the ice mass between the inner and outer wall structures is sufficient under most circumstances to provide the seal necessary to keep out water.

The strength and rigidity of the ice is such that it can be used in the same manner as a usual drilling platform. Simply by artificially increasing the thickness of the ice it can be made to sink to the ocean bottom to provide the fixed structure required for secure drilling. Conversely, by reducing the ice thickness, its natural buoyancy is utilized to float it for transfer and reuse at a new drill site.

The foregoing method and apparatus can also be utilized in the recovery of resources located beneath muskeg or the like in arctic or antarctic regions. During the thaw period of the year the muskeg becomes a quagmire or bog which is incapable of supporting the weight of equipment. The present ice island can be utilized under such circumstances to provide a stable yearround drilling platform.

The inner and outer walls are erected upon the muskeg during the winter when it is frozen. The water to build up the ice mass is piped from a nearby river, lake, or ocean and allowed to freeze between the walls. The mass is preferably kept frozen with the refrigerating coils previously described, and underlying muskeg will also be kept in a similarly frozen state during the following summer thaw. If the ice island is built up to a sufficient height, use of the refrigeration equipment may be unnecessary. The summer thaw results in thaw ing of only a predetermined number of feet of the upper portion of the ice island, leaving a thickness sufficient to preserve the integrity of the island until the following winter when the ice island can be built up again.

The ice island thus formed provides a solid and stable platform to support drilling equipment or the like for operations throughout the summer months.

The central area within the inner wall is preferably excavated to facilitate such drilling operations, as before.

In all of the embodiments the frozen mass of the ice island provides a reliable and fixed base of operations the year around for the recovery of substrata resources.

Various modifications and changes may be made with regard to the foregoing detailed description without departing from the spirit of the invention.

I claim:

1. Apparatus for forming an ice island comprising:

peripherally continuous, vertically oriented outer wall means;

peripherally continuous, vertically oriented inner wall means defining a space with said outer wall means; and

a drilling barge located within said inner wall means; means mounting said barge to said inner wall means for relative vertical movement; and means for introducing water in the space between the upper portions of said inner and outer wall means for freezing by the elements whereby the mass of frozen water builds up between the inner and outer wall means to urge the mass against the surface of the substrata. 2. Apparatus for forming an ice island comprising:- peripherally continuous, vertically oriented outer wall means; peripherally continuous, vertically oriented inner wall means defining a space with said outer wall means; means for introducing water in the space between the upper portions of said inner and outer wall means for freezing by the elements whereby the mass of frozen water builds up between the inner and outer wall means to urge the mass against the surface of the substrata, said inner and outer wall means each including lower portions projecting below the ice mass for cutting into said substrata; and ballast chambers located in said space between said lower portions of said inner and outer wall means for introducing fluid under pressure to separate said mass from the substrata and aid in trimming the island during flotation. 3. Apparatus for forming an ice island comprising: peripherally continuous, vertically oriented outer wall means; peripherally continuous, vertically oriented inner wall means defining a space with said outer wall means; means for introducing water in the space between the upper portions of said inner and outer wall means for freezing by the elements whereby the mass of frozen water builds up between the inner and outer wall means to urge the mass into engagement with the surface of the substrata, said inner and outer wall means each including lower portions projecting below the ice mass for cutting into said substrata; and means for pumping water from beneath said mass between said lower portions of said inner and outer wall means to facilitate said engagement between said mass and the substrata surface. 4i. Apparatus according to claim 3 wherein said conduit means comprises an elongated rigid pipe; a continuous, coextensive and flexible inner pipe within said rigid pipe and sealed at its ends to said rigid pipe to define an annular space; and means for evacuating and pressurizing said annular space to expand and collapse said inner pipe.

5. Apparatus for forming an ice island comprising: peripherally continuous, vertically oriented outer wall means; peripherally continuous, vertically oriented inner wall means defining a space with said outer wall means; means for introducing water in the space between the upper portions of said inner and outer wall means for freezing by the elements whereby the mass of frozen water builds up between the inner and outer wall means to urge the mass against the surface of the substrata; and

conduit means extending through said inner and outer wall means for pumping water from outside the outer wall means to form the frozen mass of the island, said conduit means comprising an elongated rigid pipe, a continuous, coextensive and flexible inner pipe within said rigid pipe and sealed at its ends to said rigid pipe within said rigid pipe and sealed at its ends to said rigid pipe to define an annular space, and means for venting and pressurizing said annular space to expand and collapse said inner pipe.

6. A method for forming an ice island in a geographical region having freezing winter temperatures, said method comprising the steps of:

floating a barge to said region and allowing said barge to freeze into said shelf ice; constructing a peripherally continuous, vertically oriented inner wall means on said shelf ice;

constructing a peripherally continuous, vertically oriented outer wall means on said shelf ice around said inner wall means;

allowing said inner and outer wall means to become frozen into said shelf ice, the upper extremities of said inner and outer wall means extending above said shelf ice;

pumping successive layers of water onto said shelf ice and allowing each layer to freeze to build up an ice mass having a weight sufficient to urge the lower extremities of said inner and outer wall means downwardly relative to said ice shelf and thereby sink said ice mass until said lower extremities cut into the sea bottom; and

utilizing the space within said inner wall means to gain access to the sea bottom.

7. A method for forming an ice island in a geographical region having freezing winter temperatures, said method comprising the steps of:

constructing a peripherally continuous, vertically oriented inner wall means;

constructing a peripherally continuous, vertically oriented outer wall means around said inner wall means; allowing said inner and outer wall means to become frozen into the offshore shelf ice in said region; and pumping successive layers of water onto said shelf ice between said inner and outer wall means and allowing each layer to freeze to build an ice mass having a weight sufficient to sink said ice mass, and contemporaneously adding upper extensions to said inner and outer wall means to provide upper extremities for said inner and outer wall means located above said shelf ice to contain said successive layers of water, until the lower extremities of said inner and outer wall means cut into the sea bottom. 8. A method for forming an ice island in a geographical region having freezing winter temperatures, said method comprising the steps of:

constructing a peripherally continuous, vertically oriented inner wall means;

constructing a peripherally continuous, vertically oriented outer wall means around said inner wall means; allowing said inner and outer wall means to become frozen into the offshore shelf ice in said region, the lower extremities of said inner and outer wall means extending below said shelf ice and the upper extremities thereof extending above said shelf ice;

pumping successive layers of water onto said shelf ice and allowing each layer to freeze to build an ice mass having a weight sufficient to sink said ice mass, and contemporaneously adding upper extensions to said inner and outer wall means to provide upper extremities for said inner and outer wall means located above said shelf ice to contain said successive layers of water, until said lower extremities cut into the sea bottom; and

9. The method according to claim 8 and including the step of laying bracing members on the ice between said inner and outer wall means and connecting the opposite extremities of said members thereto to brace said inner and outer wall means.

10. The method according to claim 8 and including the step of attaching a plurality of locking members to said inner and outer wall means to extend into the space between said inner and outer wall means whereby said locking members prevent relative vertical movement between said inner and outer wall means and said ice mass.

11. The method according to claim 8 and including the step of cooling said ice mass during a summer thaw period to prevent said ice mass from melting and becoming buoyant.

12. The method according to claim 8 and including the step of scraping away the upper portion of each said frozen layer prior to forming and freezing the next said layer whereby brine concentrations and other impurities are reduced to improve the strength of said ice mass.

13. The method according to claim 8 and including the further step of thawing the upper portion of said ice mass during warmer weather and introducing fluid under pressure to separate and float said ice mass from the sea bottom.

14. The method according to claim 13 including the further step of towing the floating said ice mass to a new site.

15. The method according to claim 14 including the further step of pumping successive layers of water onto said shelf ice and allowing each layer to freeze to build an ice mass having a weight sufficient to sink said ice mass until said lower extremities cut into the sea bottom.

Claims

1. Apparatus for forming an ice island comprising: peripherally continuous, vertically oriented outer wall means; peripherally continuous, vertically oriented inner wall means defining a space with said outer wall means; and a drilling barge located within said inner wall means; means mounting said barge to said inner wall means for relative vertical movement; and means for introducing water in the space between the upper portions of said inner and outer wall means for freezing by the elements whereby the mass of frozen water builds up between the inner and outer wall means to urge the mass against the surface of the substrata.

2. Apparatus for forming an ice island comprising: peripherally continuous, vertically oriented outer wall means; peripherally continuous, vertically oriented inner wall means defining a space with said outer wall means; means for introducing water in the space between the upper portions of said inner and outer wall means for freezing by the elements whereby the mass of frozen water builds up between the inner and outer wall means to urge the mass against the surface of the substrata, said inner and outer wall means each including lower portions projecting below the ice mass for cutting into said substrata; and ballast chambers located in said space between said lower portions of said inner and outer wall means for introducing fluid under pressure to separate said mass from the substrata and aid in trimming the island during flotation.

3. Apparatus for forming an ice island comprising: peripherally continuous, vertically oriented outer wall means; peripherally continuous, vertically oriented inner wall means defining a space with said outer wall means; means for introducing water in the space between the upper portions of said inner and outer wall means for freezing by the elements whereby the mass of frozen water builds up between the inner and outer wall means to urge the mass into engagement with the surface of the substrata, said inner and outer wall means each including lower portions projecting below the ice mass for cutting into said substrata; and means for pumping water from beneath said mass between said lower portions of said inner and outer wall means to facilitate said engagement between said mass and the substrata surface.

4. Apparatus according to claim 3 wherein said conduit means comprises an elongated rigid pipe; a continuous, coextensive and flexible inner pipe within said rigid pipe and sealed at its ends to said rigid pipe to define an annular space; and means for evacuating and pressurizing said annular space to expand and collapse said inner pipe.

5. Apparatus for forming an ice island comprising: peripherally continuous, vertically oriented outer wall means; peripherally continuous, vertically oriented inner wall means defining a space with said outer wall means; means for introducing water in the space between the upper portions of said inner and outer wall means for freezing by the elements whereby the mass of frozen water builds up between the inner and outer wall means to urge the mass against the surface of the substrata; and conduit means extending through said inner and outer wall means for pumping waTer from outside the outer wall means to form the frozen mass of the island, said conduit means comprising an elongated rigid pipe, a continuous, coextensive and flexible inner pipe within said rigid pipe and sealed at its ends to said rigid pipe within said rigid pipe and sealed at its ends to said rigid pipe to define an annular space, and means for venting and pressurizing said annular space to expand and collapse said inner pipe.

6. A method for forming an ice island in a geographical region having freezing winter temperatures, said method comprising the steps of: floating a barge to said region and allowing said barge to freeze into said shelf ice; constructing a peripherally continuous, vertically oriented inner wall means on said shelf ice; constructing a peripherally continuous, vertically oriented outer wall means on said shelf ice around said inner wall means; allowing said inner and outer wall means to become frozen into said shelf ice, the upper extremities of said inner and outer wall means extending above said shelf ice; pumping successive layers of water onto said shelf ice and allowing each layer to freeze to build up an ice mass having a weight sufficient to urge the lower extremities of said inner and outer wall means downwardly relative to said ice shelf and thereby sink said ice mass until said lower extremities cut into the sea bottom; and utilizing the space within said inner wall means to gain access to the sea bottom.

7. A method for forming an ice island in a geographical region having freezing winter temperatures, said method comprising the steps of: constructing a peripherally continuous, vertically oriented inner wall means; constructing a peripherally continuous, vertically oriented outer wall means around said inner wall means; allowing said inner and outer wall means to become frozen into the offshore shelf ice in said region; and pumping successive layers of water onto said shelf ice between said inner and outer wall means and allowing each layer to freeze to build an ice mass having a weight sufficient to sink said ice mass, and contemporaneously adding upper extensions to said inner and outer wall means to provide upper extremities for said inner and outer wall means located above said shelf ice to contain said successive layers of water, until the lower extremities of said inner and outer wall means cut into the sea bottom.

8. A method for forming an ice island in a geographical region having freezing winter temperatures, said method comprising the steps of: constructing a peripherally continuous, vertically oriented inner wall means; constructing a peripherally continuous, vertically oriented outer wall means around said inner wall means; allowing said inner and outer wall means to become frozen into the offshore shelf ice in said region, the lower extremities of said inner and outer wall means extending below said shelf ice and the upper extremities thereof extending above said shelf ice; pumping successive layers of water onto said shelf ice and allowing each layer to freeze to build an ice mass having a weight sufficient to sink said ice mass, and contemporaneously adding upper extensions to said inner and outer wall means to provide upper extremities for said inner and outer wall means located above said shelf ice to contain said successive layers of water, until said lower extremities cut into the sea bottom; and utilizing the space within said inner wall means to gain access to the sea bottom.