RU2573372C2 - Jack-up drilling offshore unit of ice class with gas mixing and ice-reinforced screens for support legs - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention is related to the sphere of drilling equipment. The jack-up drilling offshore unit of ice class with gas mixing comprises a floating hull, an area of ice deflector, support legs of truss structure, jack-up mechanism, ice-reinforced screens for support legs and gas system for water mixing. The floating hull has smooth deck in the upper part and ice-deflecting pattern in the lower part. The area of ice deflector passes along perimeter of the hull bottom. Support legs are designed for recovery from the bottom. Jack-up mechanism my recover support legs from the bottom in order to push the hull from water. Gas system is designed to mix water in order to reduce ice-related problems close to the support legs.

EFFECT: prolongation of drilling season is ensured in shallow water near the Arctic shore or at placed subject to ice formation.

20 cl, 6 dwg

Description

This invention relates to mobile offshore drilling bases, often referred to as "self-lifting" drilling bases or drilling rigs that are used in shallow water, typically at depths less than 400 feet (122 m), for drilling oil and gas wells.

In the never-ending search for hydrocarbons, many oil and gas reservoirs have been discovered over the past more than one hundred and fifty years. Many technologies have been developed to search for new reservoirs and reserves, and in many areas in the world exploration work has been carried out, giving new discoveries. The discovery of new unexplored reserves near populated areas and in accessible places is unlikely. Instead, large new reserves are opening up in problematic and elusive areas.

One promising area is the coastal zone of the Arctic. At the same time, the Arctic is remote and cold, where ice on water creates significant difficulties for the exploration and production of hydrocarbons. For many years, in general, it is believed that six unprofitable wells should be drilled for each profitable well. If this is actually true, it is necessary to make the construction of unprofitable wells inexpensive. However, in the Arctic there is practically nothing inexpensive.

Currently, in shallow water in places with cold weather, such as the Arctic, self-elevating or mobile offshore drilling bases can be used for about 45-90 days in a short period of open water in the summer season. Prediction of the beginning and end of the drilling season depends on random factors, and a lot of effort is spent on determining the moment of safe towing of the self-lifting base to the drilling site and the beginning of drilling. After the start of construction, it is critical that the well be completed on time to prevent involuntary disconnection and retreat in the event ice arrives before the well completes. Even during several weeks of open water, floating ice floes pose a significant risk to self-elevating drilling rigs, when the drilling rig is on site and the legs of the self-elevating drilling rig are exposed and highly vulnerable to damage.

Self-elevating drilling rigs are mobile, independently rising offshore drilling and overhaul platforms and are equipped with supports made with the ability to descend to the seabed and then raise the body above the water. Self-elevating drilling rigs usually include drilling equipment and / or overhaul equipment, a support lifting system, residential compartments, cargo handling facilities, storage areas for bulk and liquid materials, a helipad and other necessary facilities and equipment.

The self-elevating drilling rig is structurally designed to be towed to the drilling site and lifted on supports above the water so that sea waves act only on supports that have a very small cross-section, thus ensuring the passage of waves without communicating significant movement of the self-lifting drilling rig. At the same time, the supports of the self-elevating rig are poorly protected from collision with floating ice floes, and a floating ice floe of any significant size can cause structural damage to one or more supports and / or push the rig from the site. If such an event occurs before the completion of drilling and completion with the installation of appropriate protection, a hydrocarbon leak may occur. Even a slight risk of such a leak is completely unacceptable in the oil and gas industry, for supervisors and the public.

Thus, after determining that a potentially cost-effective well has been drilled during this short season, a very large-sized, self-supporting system or similar structure can be delivered and installed on the seabed for a long-term drilling and hydrocarbon production process. Data held by its own weight is very large and very expensive, but able to withstand the forces of ice throughout the year.

The invention relates to a self-elevating ice class drilling rig for drilling for oil and gas in potentially ice conditions on coastal sea areas, including a floating hull having a relatively smooth deck in its upper part. The floating hull additionally includes a mold for bending ice in its lower part, passing around the perimeter of the hull, while the mold for bending ice passes from the hull area near the deck level and extends down to the bottom of the hull along with an ice deflector section passing around the bottom perimeter casing, for directing ice around the casing and not under the casing. The drilling rig includes at least three truss supports installed in the perimeter of the bottom of the hull, while the supports are capable of being lifted from the seabed to allow towing of the rig through shallow water and also extension to the seabed and additional extension for lifting the hull partially or completely out of the water. A self-lifting device is connected to each support and serves both to lift the support from the seabed, giving the ice-class self-lifting rig an opportunity to swim due to the buoyancy of the hull, and pushing the supports down to the seabed and pushing the hull up with partial exit from the water when floating ice floes threaten drilling rig, and with the exit completely out of the water when ice is absent. The drilling rig includes ice supports screens to protect the truss supports from ice and a gas mixing system to mix water near the supports and reduce problems from ice near the supports.

The invention further relates to a method for drilling wells in waters prone to ice. The method includes creating a floating hull with a relatively smooth deck in its upper part and with a shape for ice bending in its lower part, the shape for ice bending passing from the hull area near the deck level and going down to the area near the bottom of the hull, and a section of ice a deflector passing around the perimeter of the bottom of the body to direct ice around the body and not under the body. At least three truss supports are installed in the perimeter of the bottom of the housing, each support containing a plurality of vertical posts connected by transverse elements, and ice screens are installed between the posts to protect the transverse elements from ice. Each support extends downward so that the shoes from the bottom of the supports come into contact with the seabed and lift the body up and out of the water when ice does not threaten the rig, when the rig drills a well at the rig site. The casing is additionally lowered into the ice protection configuration so that the ice caving mold extends above and below the sea surface to cave in the ice going to the rig to allow the ice to sink into the water and apply bending forces breaking the ice, while the ice bypasses drilling rig. Water is mixed near the supports, while problems from ice near the supports are reduced.

A more complete understanding of the present invention and its advantages gives the following description with the accompanying drawings, which show the following.

Figure 1 shows a side view of a first embodiment of the present invention, where the drilling rig is afloat and ready to be towed to the drilling site.

Figure 2 shows a side view of a first embodiment of the present invention, where the drilling rig is raised above the water for drilling in open water through the drilling shaft.

Figure 3 shows a side view of an embodiment of the present invention, where the drilling rig is partially lowered into the ice-water interface, but continues to be supported by supports, in a protective configuration for drilling in potentially ice conditions.

Figure 4 shows a side view with an enlarged fragment of the configuration of one end of the first embodiment of the present invention of figure 3 with ice moving to the drilling rig.

Figure 5 shows a top view of the support of the rig with the first embodiment of the ice screens of the supports in place.

Figure 6 shows a top view of the support of the drilling rig with a second embodiment of the ice screens of the supports in place.

When considering the detailed description of the preferred device or devices of the present invention, it should be understood that the features of the invention and concepts may appear in other devices and that the scope of the invention is not limited to the described or shown embodiments. The scope of the invention is limited only by the scope of the claims below.

Figure 1 shows a self-elevating drilling rig of ice class, generally indicated by arrow 10. In Figure 1, a self-lifting drilling rig 10 is shown with a hull 20 afloat at sea, and supports 25 in a raised position, where most of the length of the supports 25 rises above deck 21 of hull 20. On deck 21 there is a tower 30 used for drilling wells. In the configuration shown in FIG. 1, a jack-up drilling rig 10 may be towed from one prospected field to another and to or from the base on shore for maintenance and other onshore operations.

When the self-elevating drilling rig 10 is towed to the drilling site, generally in shallow water, the supports 25 are lowered through openings 27 in the housing 20 until the shoes 26 at the lower ends of the supports 25 come into contact with the seabed 15, as shown in FIG. 2. In a preferred embodiment, the shoes 26 are connected to the support caissons 28 to secure the drilling rig 10 to the seabed. After connecting the shoes 26 to the seabed 15, the lifting devices in the openings 27 raise the housing 20 from the water on the supports 25. When the housing 20 is completely raised from the water, any impact of the waves and the stormy sea bypasses the supports 25, creating a reduced load in comparison with the impact of the waves on a large a floating object, such as hull 20. Well drilling operations can take place in the usual manner, while there is no ice in the work area.

Ice class self-elevating drilling rig 10 is designed to withstand ice floes due to ice protection created by the hull in a displacement position, as shown in FIG. Figure 3 shows that ice usually dampens waves and waves of the sea, so that the sea surface 12 seems less threatening, however, the dangers of the marine environment only change and do not decrease. When the ice class self-elevating drilling rig 10 adopts an ice-protective configuration with the housing in the displacement position, the housing 20 is brought into contact with water, but not so much that the housing 20 floats. A significant portion of the weight of the drilling rig 10 preferably continues to act on the supports 25 to secure the drilling rig 10 to the drilling site, in a position of resistance to any pressure that the ice field may exert. As shown in FIG. 4, the rig 10 is lowered so that an inwardly sloping ice curving surface 41 overlaps the sea surface 12 or the ice-water interface to come into contact with any floating ice that may be suitable for the rig 10.

The inclined ice-bending surface 41 extends from a ledge 42 located on the edge of the deck 26 to the neckline 44. The ice deflector 45 extends downward from the neckline 44. Thus, when a floating ice floe, such as shown at 51, approaches the rig 10, the ice-bending surface 41 submerges the leading edge of the floating ice 51 under the sea surface 12 and exerts a significant bending force, breaking large ice floes into smaller, less destructive and less dangerous pieces of ice. For example, it can be assumed that an ice field of hundreds of feet and possibly miles across can go to rig 10. If a floating ice breaks into pieces less than twenty feet (6 m) long, such pieces can bypass rig 10, causing much less concerns.

As shown in FIGS. 2, 3 and 4, the present invention provides a first additional aspect of ice protection, where the blower 35 is configured to supply air down through the hoses 36 to the support coffers 28. The support coffers 28 include openings or diffusers for discharge air bubbles to mix the water around the supports 25. The stirred water moves to prevent the formation of ice on the supports and creates a natural flow away from the supports. With the gas mixing system, it is possible to operate the drilling rig 10 in the configuration shown in FIG. 2, when ice problems first occur, without immediately transferring the drilling rig 10 from the configuration shown in FIG. 2 to the ice protection configuration with the body in the displacement position shown in figure 3. This can be used if the weather forecast indicates the possibility of ice conditions for a period of time, followed by storms and a large wave (in this case, the configuration with the body raised above the water, shown in figure 2, is preferred).

In addition to gas mixing, the ice screens 32 of the supports are attached between the vertical struts 31 of the supports to create a second additional ice protection element of the present invention. The ice screens 32 of the towers shown in FIG. 5 are convex to create a rounded shape for directing any ice around the towers. 6, the ice screens 33 of the supports are relatively flat. As shown in FIGS. 2, 3 and 4, the ice screens 32 and 33 of the towers are preferably mounted on towers extending from a mark above to a mark below water line 12, but do not necessarily overlap each leg 25 in length.

Ice has a high compressive strength in the range of 4-12 MPa, but is much less flexural, usually having a flexural strength in the range of 0.3-0.5 MPa. As shown, the force from the floating ice floe 51 moving along the sea surface 12 causes the leading edge to creep under the sea surface 12 and the section 52 is torn off. When the floating ice floe 51 breaks into smaller ice floes, such as part 52 and piece 53, the smaller parts tend to float around the rig 10 without striking or exerting forces characteristic of a large ice floe. Preferably, ice is not crushed beneath the plane of the bottom of the hull 20, and the ice deflector 45 turns the ice to pass along the hull 20. If the ice is thick, the ice deflector 45 is formed to extend downward at a steeper angle than the ice-bending surface 41, and the deflector should increase the bending forces by floating ice floe. The ice deflector 45 is installed extending downward from the plane of the bottom of the hull 20. In the device used, if necessary, the cheekbone is flat below at the lower end of the ice deflector 45.

For additional resistance to the forces that the floating ice can transfer to the drilling rig 10, the shoes 26 of the supports can be made connecting with caissons 28 installed in the seabed, so that when the floating ice rests against the ice-bending surface 41, the supports 25 actually hold the body 20 on place and create the bending force of the floating ice, and counteract the lifting force from the floating ice, which in extreme cases can lift the near side of the drilling rig 10 and turn the drilling rig and the side shoes 26 with the use on the opposite side of the rig 10 as a rotary center points or hinge. Caissons in the seabed are known in other applications, and shoes 26 should include adequate compounds for both attaching to and releasing from caissons, if necessary.

Perhaps it should be noted that the transition from the conventional open water drilling configuration shown in FIG. 2 to the configuration with the displacement position of the ice casing shown in FIG. 3 may require significant planning and coordination depending on the drilling phase, passing at this time. Although some equipment may adapt to changing the height of deck 21, other equipment may require disconnection or readjustment to adapt to a new height above the seabed 15.

The ice class self-elevating drilling rig 10 is configured to operate as a conventional open-water self-elevating drilling rig, but is also configured to be ice protected and then returned to its normal position or configuration when the action of the waves is a concern. The shape of the hull 20 (as well as its strength) provides for the bending of ice and its breaking.

The housing 20 preferably has a multifaceted or multilateral shape, which gives the advantages of a round or oval shape and can reduce the cost of manufacture. The plates from which the body is assembled can then be flat, so that the entire structure can contain parts of a flat material, for example sheet steel, and becomes less complex. The ice-breaking surface preferably extends at least about five meters above the water or sea surface 12, taking into account that sea levels rise and fall under the influence of tides and storms and possibly other factors. The height above the sea surface is taken with the calculation of a significant thickness of the ice field and hummocks in it, rising above the sea surface 12, but with a sufficient height of the protrusion 42 above the sea surface 12, large ice floes are crushed down in contact with the drilling rig 10. At the same time, deck 21 on top of the hull 20 should be located high enough above the waterline so that the waves do not roll around the deck. In this case, deck 21 is preferably located at least 7-8 meters above the sea surface 12. On the contrary, the neckline 42 is preferably located at least 4-8 meters below the sea surface 12 to adequately bend the ice to break them into harmless parts. Thus, the hull 20 preferably has a height in the range of 5-16 meters from the plane of the bottom to deck 20, more preferably 8-16 meters or 11-16 meters.

It should also be noted that the supports 25 and the openings 27, in which the supports are connected to the body 20, are located around the perimeter of the ice deflector 45, while the possibility of ice contact with the supports decreases when the drilling rig 10 is in the ice protection configuration shown in FIG. 3 and sometimes referred to as a configuration with a housing in a displacement position. In addition, the drilling rig 10 should not respond to every threat from ice floes with a significant increase in the cost of production of oil and gas companies. If rig 10 can extend the drilling season by just a month, this could mean a fifty percent improvement in some ice-prone areas and therefore create significant cost savings in the industry.

In conclusion, it should be noted that the consideration of any link is not an assumption that it relates to a known technique for the present invention, in particular any link that may have a publication date after the priority date of this application. At the same time, all, without exception, paragraphs of the claims below are included in this description as an additional embodiment of the present invention.

Although systems and methods are described in detail herein, it should be understood that various changes, substitutions, and substitutions can be made without departing from the spirit and scope of the invention as defined by the claims below. A person skilled in the art can study preferred embodiments and identify other ways of implementing the invention that are not described herein. The inventors believe that the variations and equivalents of the invention are defined by the scope of the claims, while the description, nature and drawings should not limit the scope of the invention. The scope of the invention is specifically limited by the claims below and their equivalents.

Claims (20)

1. Self-elevating ice class drilling rig for drilling for oil and gas in potentially ice conditions on coastal sea areas, containing:
a floating hull having a relatively smooth deck in its upper part and an ice-bending shape in its lower part extending downward and inward around the perimeter of the hull, the ice-bending form extending from the hull area near the deck level and going down to the area near the bottom of the hull;
a section of an ice deflector passing around the perimeter of the bottom of the hull to direct ice around the hull and not under the hull;
at least three truss supports installed inside the perimeter of the bottom of the floating hull, while the supports are capable of being lifted from the seabed to tow the rig through shallow water and also extended to the seabed and further extended to lift the hull partially or completely out of the water ;
a self-lifting device connected to each support, both for lifting the support from the seabed, so that the ice-class self-lifting drilling rig can float due to the buoyancy of the hull, and pushing the supports down to the seabed and pushing the hull completely out of the water when there is no ice;
ice screens of supports made to protect the supports of the truss structure from ice; and
gas mixing system for mixing water near
supports and reduce problems from ice near the supports. 2. Self-elevating drilling rig according to claim 1, in which the truss supports include vertical posts and transverse elements connecting the posts, and ice screens are installed between the posts to protect the transverse elements. 3. A self-elevating drilling rig according to claim 1 or 2, wherein the ice-curving surface deviates upward and outward from a neckline of a reduced size to a ledge of an increased size. 4. A self-elevating drilling rig according to claim 1 or 2, wherein the ice-curving surface extends vertically at least 8-10 or more meters. 5. A self-elevating drilling rig according to claim 1 or 2, wherein the ice-curving surface extends vertically at least 8-10 meters or more. 6. The self-elevating drilling rig according to claim 4, in which the angle of the surface curving the ice has a value in the range of 30-60 degrees from the vertical. 7. Self-elevating drilling rig according to claim 5, in which the angle of the surface curving the ice has a value in the range of 30-60 degrees from the vertical. 8. The self-elevating drilling rig according to claim 1 or 2, wherein the ice-curving surface comprises a plurality of relatively smooth inclined sections extending around the periphery of the drilling rig. 9. The self-elevating drilling rig of claim 3, wherein the ice-curving surface comprises a plurality of relatively smooth inclined sections extending around the periphery of the drilling rig. 10. The self-elevating drilling rig of claim 4, wherein the ice-curving surface comprises a plurality of relatively smooth inclined sections extending around the periphery of the drilling rig. 11. The self-elevating drilling rig of claim 5, wherein the ice-curving surface comprises a plurality of relatively smooth inclined sections extending around the periphery of the drilling rig. 12. The self-elevating drilling rig of claim 6, wherein the ice-curving surface comprises a plurality of relatively smooth inclined sections extending around the periphery of the drilling rig. 13. The self-elevating drilling rig of claim 7, wherein the ice-curving surface comprises a plurality of relatively smooth inclined sections extending around the periphery of the drilling rig. 14. A self-elevating drilling rig according to claim 1 or 2, wherein the ice-curving surface is a reinforced surface. 15. A method of drilling in waters prone to ice, in which:
provide a drilling rig with a floating hull having a relatively smooth deck in its upper part and an ice-bending form in its lower part, the ice-bending form extending from the hull area near the deck level and extending down to the area near the bottom, and an ice deflector section passing around the perimeter of the bottom of the body for directing ice around the body and not under the body;
provide at least three truss supports installed in the perimeter of the bottom of the housing, each support contains many vertically oriented racks connected by transverse elements, and ice screens are made between the racks to protect the transverse elements from ice;
lower each support so that the shoes at the bottom of the supports come into contact with the seabed and lift the body up and out of the water when ice does not threaten the rig, when the rig drills a well at the drilling site;
the body is lowered into the ice protection configuration, with the ice bending form passing above and below the sea surface to bend the ice entering the rig, to ensure that the ice is submerged under water and applying bending forces breaking the ice, while the ice bypasses the drilling installation; and
mix water near the supports to reduce problems from ice near the supports. 16. The method according to p. 15, further comprising the stage of fixing the support on the seabed for additional resistance to the forces of floating ice floes. 17. The method according to p. 15 or 16, in which the curving surface of the ice extends from the ledge to the neckline, and the step of lowering the hull into the water, in particular, includes lowering the hull into the water so that the neckline is at least 4 meters below the sea surface, and the ledge is at least 7 meters above the sea surface. 18. The method according to p. 15 or 16, further comprising the step of lifting the hull from the water when the threat from floating ice is reduced. 19. The method according to p. 17, further comprising the step of lifting the hull from the water when the threat from floating ice floes is reduced. 20. A method of drilling in waters prone to ice, comprising using a drilling rig according to any one of paragraphs. 1-14.

Images