Offshore platform and method of construction

 

(57) Abstract:

Usage: in platforms that are installed in the open sea and operating in heavy ice conditions. The inventive platform 1 has a base 3, which relies on the protective structure consisting of the lower conical portion 4 and connected with it the upper cylindrical part 5. The protective structure is made hollow, and inside it are piles 8 separately from it and from each other. Pile 8 installed space 9 located above the upper part 5 of the protective structure and not in contact with it, and rig 11 is placed on the platform 9. Protective design with pre-assembled on the pile 8 is transported in a vertical position, is lowered to the seabed 2, hammer in the bottom 2 of 8 piles, then share the connection between the piles 8 and between them and the protective structure, and then install the pad 9 on top of the pile 8. 2 S. p. and 3 C.p f-crystals, 4 Il.

The present invention relates to marine structures, installed in the open sea, and the method of its construction, and in particular, to an offshore platform.

Currently, the only major area of application of offshore structures for oil or Gah structures. Practice the operation of these structures is discussed in the report OTS 5929 presented at the 21st conference of the OTC, Houston, pc. Texas, USA in 1989, But in the area of cook inlet ice conditions are relatively mild and for calculations it is assumed that the thickness of the ice is equal to 1.5 meters. In this case, it is quite acceptable standard pile design.

Standard gravity platforms are used in the area of the North slope of Alaska in the Beaufort sea. Typically, gravity platforms sit on a firm seabed, although sometimes they are placed on the seabed with a weak ground. This type of platform are based directly on the seabed. In the case of weak soils may provide additional support in the form of a peripheral wall or skirt, protruding down from the platform plate in the bottom of the sea and bury in the ground. Practically they play a role in piles. An example of this type of platform is described in the journal "Offchore", August 1984, pages 99-100, for structures which on the seabed of its containment structure is transported in a vertical position at a desired location and then install it on the seabed.

Other known designs for ice conditions can be called a marine platform that sod is lower conical part and connected to it the upper cylindrical part, the space and submerged in the seabed piles (USSR Author's certificate N 1184905, 1985).

None of the known constructions, neither of pile construction, nor the gravity of the platform, artificial island or structure with a movable bottom, you can't effectively carry out constant drilling and mining at depths greater than 25 metres in terms of drifting ice in seismically active areas.

According to the present invention offers a design that is installed in the open sea and resting on the seabed through piles and directly on the bottom. This design is a hybrid gravity and pile structures and is designed to operate in harsh environmental conditions, including the impact of sea ice, and seismic loads.

In the new offshore platform cylindrical portion of the protective structure partially protrudes above the surface of the sea, piles placed inside protective structures separately from it and from each other, and the site is located on the top of the pile.

When this protective design perform with two plates and at least a portion of the space between the casings is filled with mortar.

In addition, according to the safety design is mounted pile and deliver them together with a protective structure at the installation site, then the pile hammer pile in the seabed inside protective structures, share the connection between the piles and between them and the protective structure, and establish a platform on top of the pile.

Fig. 1 is a schematic side view of an offshore platform according to the invention; Fig. 2 a cross section on line l-l of a support platform of Fig. 1; Fig. 3 is a partial side view of the platform illustrating the means of pile driving; Fig. 4

schematic side view of the platform showing the mounting pad, forming the upper part of the platform.

As shown in Fig. 1 platform 1 according to the invention is installed on the seabed 2 base 3, on which rests the protective design of the platform.

The protective structure comprises a lower conical portion 4 and connected with it the upper cylindrical part 5. Cylindrical part 5 protective structures partially protrudes above the surface of the sea 6.

This platform is designed to work in areas with drifting ice floes 7 and the outer surface of the lower 4 and upper 5 parts protective design protects the platform from the effects of drifting ice.

Protective design of the platform is made hollow, and inside it are piles 8, cotrugli and substrate 3. On top of the pile 8 establish a platform 9, which in its lower part 10 is connected with piles, and is located above the upper part 5 of the protective structure of the platform and separated from it. The pad 9 is mounted drilling rig 11.

Option platform according to the invention, shown in Fig. 1 and 2, has the geometry of a typical gravitational platform with a single Radome, namely, the large size in terms of /to the base 3/, choose from the conditions for optimal pressure on the base on the ground taking into account the soil properties. Another feature of this design sustainable buoyancy previously gathered design that allows you to build the design in the dock, and then tow the proposed location offshore drilling and, having loaded ballast, lower directly on the seabed with a minimum amount of work away from the coast. This is a very important feature for working at sea in remote areas.

The lower part of the platform, including the base 3 and part 4, 5 protective structures, can be made of concrete or steel, or using both materials.

The concrete structure has considerable mass, which increases its resistance to sliding along the sandy Foundation and ristici concrete structures can be improved, if you use steel construction with double hull, filled with a solution after a descent design for water.

Steel construction suitable for weaker soils, because its mass is less concrete structures of the same size. In addition, the design with a smaller mass, apparently, structurally more efficient under the action of seismic effects. Steel construction has a shallower draft and simpler to manufacture. For example, the steel structure can be assembled in any dry dock and go down to the water from the place of manufacture in more shallow water than is possible in the case of concrete structures.

Choice of steel or concrete for the manufacture of construction depends on various economic factors, including the availability of local filling material in the desired installation location of the platform.

It is important that according to the invention, the pile 8 is located inside the protective structure at a distance from the outer periphery of the design /Fig. 1/. Pile 8 is designed to support platforms 9 and surface structures /for example, structures for drilling and production of oil or gas. After installation in the working conditions between the piles 8 and the base 3, and 4 parts, designs act solely as protection from exposure to ice and not transfer the load to the piles 8 site 9. In any case, protective design that extends up through the ice in the area, greatly enhanced, for example, is designed with double hull filled with mortar and withstand high local loads from hitting the ice.

In a variant of the construction according to the invention can include a peripheral skirt 12, if the design relies on weak ground. In addition, the skirt 12 can sense the portion of the lateral loads. Next, you can use peripheral piles instead of a skirt, if you want to provide support to the deeper layers of the soil. Such peripheral skirt 12 and /or peripheral piles/ intended mainly for the perception of environmental effects and have a completely different purpose compared to the piles 8 site 9.

The platform construction according to the invention is as follows.

The base 3 and part 4, 5 protective structures you can build a floating dock made of steel or concrete or using both materials.

After that, the base 3 and part 4, 5 of the protective structure can be towed to the site of the proposed oil or gas, where they are dipped /loading ballast/ on the seabed 2.

Once clogged piles 8, the mounting pad 9 with its lower part 10 can be made by well-known method using barges. For designs with a single cone, shown in Fig. 4, the said method comprises the use of the coupled barges 16, 17 for combining protective design with platform 9 and surface structures established by discharging ballast. This installation method eliminates the need for heavy floating cranes. Two other advantages are the following surface structures and Playground originally located on the ground level, and thus provides some flexibility, as surface-to-CLASS="ptx2">

Once mounted the platform, you can start drilling for oil or gas wells using oil rig 11. When the drilling is carried out within the protective structure of the platform.

In Fig. 1, 3, 4 shows a hybrid pile/gravity platform with a protective structure in the form of a simple cylindrical tower. In addition, you can use the design with multiple protective structures made according to the present invention.

1. Offshore platform containing installed on the seabed Foundation, the protective structure supported on the base and consisting of a lower conical part and connected to it the upper cylindrical part, the space and submerged in the seabed piles, characterized in that the cylindrical part of the protective structure partially protrudes above the surface of the sea, piles placed inside protective structures separately from it and from one another, and the site is located on the top of the pile.

2. Platform under item 1, characterized in that the protective structure is made with two coverings.

3. The method of construction of the offshore platform to the seabed, including transport of the protective structure in a vertically mounted pile and deliver them together with a protective structure at the installation site, then the pile hammer pile in the seabed inside protective structures, share the connection between the piles and between them and protective design and establish a platform on top of the pile.

4. The method according to p. 3, characterized in that the protective structure is carried out with two plates and at least a portion of the space between the casings is filled with mortar.

5. The method according to PP.3 and 4, characterized in that the piles have vertically inside the protective structure according to their layout, and Koper for pile driving are placed on a temporary work platform, which is mounted on the protective structure.

 

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