JPH02501561A - Offshore oil well floating production system and drilling vessel - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Floating production system for offshore oil well pressure and drilling ship The present invention is a simplified production system for offshore oil well pressure. Floating production systems, especially those intended to minimize costs for underwater equipment. Regarding tem. The invention also provides for semi-submersible drilling vessels for use with such systems. related.

As oil prices decline, extraction of forked seabed oil reserves becomes increasingly difficult. In recent years, it has become important to reduce extraction costs as much as possible in order to prevent rice fields from becoming unprofitable. ing. In particular, in recent years, installation, inspection, and maintenance of equipment has become expensive on the seabed. Minimize equipment costs and install as many facilities as possible at or near the sea surface. Attempts are being made to establish one.

− According to the proposal, piping would be routed straight from the subsea well to a fixed platform on the sea surface. The oil well head is installed on the main deck. and moored a floating production ship to the side. , thereby reducing the size of the platform and therefore lower cost. . Nevertheless, the cost of such fixed platforms is high.

Another factor that increases the cost of known systems of this type is that the drilling vessels used are Based on codes developed for mobile semi-submersible drilling vessels and their design, construction and operations. This is the foundation. Significant savings can be achieved using fixed floating structures. .

Conventional mobile semi-submersible drilling vessels are of the so-called catamaran type, with four rods extending below the sea surface. It has a superstructure supported by floating legs. Each of these legs has Strong reinforcement is required at the upper end of each leg due to severe bending stresses. this Therefore, such structures significantly increase weight and cost, and tend to be bulky. Ru.

G B-A-2159468 has four legs that support the platform. A cotton body structure is disclosed that is connected at its lower end by an elongated cylindrical box-shaped structure. deer Traditionally, these legs had a rounded cross section due to the effects of waves and ocean currents on the structure. It was always thought that it had to be of shape. G B-A-21 59468, the legs and the elongated bottom connecting structure are cylindrical in cross section. , which requires complex connections at the bottom corners of the ship to obtain the required stiffness. It means that.

The present inventors constructed a drilling ship with legs having a square or rectangular cross-sectional shape. It is possible to obtain a simple structure with superior hydrodynamic properties. I found out.

Therefore, the present invention supports the upper structure by the legs, and connects the lower ends of the legs to each other to provide rigidity. In a semi-submersible drilling vessel with a floating oil production system that has a floating structure, the legs has a square or rectangular horizontal cross-sectional shape, and the ship is made up of multiple box-like butt welded To provide a semi-submersible drilling vessel with a floating oil production system characterized by the following configuration: It is something.

Preferably, the bottom connection between the legs also has a square or rectangular cross-sectional shape to simplify construction. The overall structure consists of multiple square or rectangular steel boxes, with butt welding between the boxes. It is desirable to provide a tangential connection to form a continuous straight wall.

Known floating production systems use a composite flexible hose to transport rock from an offshore oil well. In addition to pumping oil, it is also used for transportation, choke and suppression lines, and water injection. This is used for commercial and gas lifts. This flexibility allows for “fixed” floating above the sea surface. Even in formula structures, this is necessary because considerable movement is forced by wind, waves, and currents. This is what is said to be. However, such hoses are expensive and the cost of the entire equipment will significantly increase. These flexible hoses prevent hose buckling and In order to avoid blockages caused by It is laid with sufficient tension.

The present invention also reduces subsea equipment costs (and allows relatively rigid vibes to be Floating type generator configured to be used not only as a riser but also for other purposes. The purpose is to provide a production system.

According to another aspect of the invention, one or more fixed buoys, usually moored below the sea surface, can be used. connected to the well by a relatively rigid catenary riser of - or multiple Provides a floating production system connected to a semi-submersible drilling vessel by flexible risers be done. This semi-submersible drilling vessel is equipped with processing equipment. Oil on drilling ship or buoy A well head can be provided.

A fixed buoy is located below sea level (preferably about 50 meters below sea level) at its point of action. Because it is moored to It's just that the movement is large. Its position relative to the oil well remains fairly constant. Therefore, pipes made of relatively rigid and inexpensive materials, such as steel, should be used to connect the oil well. can continue. On the other hand, semi-submersible drilling vessels have flexible connections to the buoy. Therefore, there is some freedom of movement relative to the buoy.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a perspective view of a floating production system according to the present invention.

FIG. 2 is a side view of the system shown in FIG.

FIG. 3 is a side view taken in the direction of the arrow ■ in FIG. 2.

Figures 4 through 8 illustrate the stages in the installation of the systems of Figures 1 through 3. .

FIG. 9 shows the structure of an embodiment of a semi-submersible drilling vessel of the present invention.

Fig. 1θ shows a semi-submersible drilling ship according to another embodiment, and Fig. 11 shows Fig. 9 or Fig. 1O. Schematic diagram of the onboard power generation system of the drilling ship, Figure 12 shows the underwater cable for power transmission from the drilling ship. Figure 13 diagrammatically shows the assembly status of the drilling ship part in Figure 9. FIG. 4 is a cross-sectional view of the shape of the box constituting the leg of FIG. 13.

Referring to FIG. 1, a number of risers 12, preferably made of steel, are mounted above the seabed. A set of oil wellheads lO is connected to a submersible buoy 18. Each oil well head 10 on the seabed simply consists of a master valve and an annular valve. The riser 12 is A 18 to the seabed, and then tangentially along the seabed to each wellhead 10. It is curved to .

The buoy 18 is equipped with multiple buoyancy tanks 26 and is anchored to the seabed by four anchor chains. It is tethered and is thus held against large movements. tank is filled Alternatively, the depth of the buoy can be adjusted by ejection.

Buoy 18 also has a steel pipe that transfers oil or gas to pipeline 16 leading to land. 14 is connected, and this steel pipe is also curved tangentially to the sea bed.

Crude oil from riser 12 is routed from buoy 18 via flexible hose 22 to semi-submersible bar. Sent to Ji 24. Hose 22 is connected to riser 1 by a corresponding valve 28 on the buoy. Connected to 2. These hoses are connected to inlets on the barge 24 to pump crude oil transport to each process facility on the stage 24. Oil and gas separated from crude oil are e.g. For example, it is transported to land via pipelines 14,16.

Not all of the catenary steel pipes 12 are necessarily used for oil or gas transportation. There isn't. Some are used for choke or suppression lines.

FIGS. 3 to 8 illustrate the installation status of the system.

In FIG. 4, the steel riser 12 is transported to the site and moored adjacent to the buoy 18. The pipe is laid in a fixed position by the pipe laying barge 34. At this stage, the buoy is The upper end of the riser, which is above sea level, is then transferred to the crane 22, as shown in FIG. It will be hoisted onto buoy 18 as shown below.

The upper end of the riser is fixed to the buoy. A flexible lamp with one end connected to the crane 32 The iser 22 is then secured to the buoy 18 by its ends. Other end (see Figure 6) The lower end shown) is connected to the barge 24 by a cable 36. This end is then Hoisted by derrick 30 and connected to the required processing equipment on the barge at 31 be done.

As shown, the adjacent ends of the flexible riser 26 and the steel riser 12 are now Connected on buoy 18. Finally, as shown in Figure 8, buoy 18 is placed in its final position. and lowered to a location, preferably 50 meters below sea level. At this depth position, the buoy does not undergo large movements due to wind, waves, or currents, so the riser 12 is held securely against the wellhead at the lower end of the wellhead. On the other hand, barge 24 to the buoy via the flexible riser 26 without breaking or interrupting the connection. virtually free of relative movement.

The flexible riser 26 is a flow line or choke that connects equipment on the sea surface to the seabed. ・Made of polytetrafluoroethylene, the type conventionally used for suppression lines, etc. An ordinary composite structure made of stainless steel or the like may be used. Such hoses are relatively rigid are significantly more expensive than standard steel risers, and therefore require both surface equipment and subsea wellheads. Use steel risers for the majority of the distance between the cables and for a small portion of said distance. Significant cost savings can be realized by using flexible risers only when I can do it. Further, both buoy 18 and riser 12 can be operated under virtually any weather conditions. It can be left in place even under the It can be easily attached to and removed from the page 24. This flexible riser can be removed from the barge and left in the hand from the buoy when not needed. , its free end is attached to a marker buoy.

The steel riser 12 is tensioned to form a depending portion between the buoy 18 and the sea bed. Ocean At the bottom, pipes (and control cables) descend tangentially to the seabed to the mooring point. and then lift up from the seabed to reach the corresponding wellhead and Avoid the arches and enter the oil well vertically.

Oil well security generally begins with purge 24. For small renovations, the tool (as normally done on land) via a swab valve on the stage.

The tool is lowered through a line to the ocean floor and into the oil well. For major renovations, separate The method of Purge is moored to the side of the buoy 18 on the opposite side. Then, pilot the boat to each section of the oil well. position on the interconnect line and use a workover rig to install the tubing. It is possible to pull.

Figure 9 shows in more detail the semi-submersible purge shown schematically in Figure 1. Ru. This purge is composed of a large number of hollow boxes 50 made of mild steel or the like. this The boxes are constructed into the desired structure by simply butt welding them together. typically A ship is constructed using 200 to 300 of these boxes.

Unlike traditional semi-submersible platforms where the lower ends of the legs are free, the parts of the present invention The table has a rectangular base 58 from which four upright legs 60 protrude upwards to form a platform. I support Ki62. As can be seen from FIG. 9, each leg 60 is made up of four welded boxes. It has a cross-section that is shaped like this, giving it considerable strength and rigidity.

The base 58 is formed by welding the sides of multiple pairs of box bodies, and the decks are It is composed of a single layer of box body.

The legs of the ship are connected to each other at the lower end, so they are not affected by bending movements caused by wind, waves or currents. I rarely receive it.

Stresses on the ship are distributed more evenly throughout the ship and are therefore normally The required heavy reinforcement of the upper part of the leg under the deck can be omitted. this This reduces the overall cost of the ship and also lowers the center of gravity, making the ship safer in the water. The accuracy can be improved. Furthermore, the deck can support a larger load. Can be done.

The base may be equipped with additional pontoons on the bow and stern sides, which It is possible to more easily tow a ship between sites.

The deck includes a deck crane 52, a storage section 54, a helicopter landing pad 56, and a winch 63, as well as the usual equipment for semi-submersible vessels of this type. It is being

The steel boxes that make up a drilling vessel usually have a length of 5 to 10 meters on each edge, typically 7. ．． A portion of the 5 meter cube 0 box may also be in the form of a buoyancy tank or storage tank. It's okay.

A drilling vessel according to the invention is relatively inexpensive and easy to construct and launch.

Also, the cost savings that can be achieved will help reduce costs that have previously been considered marginal. This will be part of making the oil field profitable.

To explain Fig. 10, the upper shape is similar to that shown in Fig. 9, and 9 shows a semi-submersible purge with an upper deck 70 which can be installed similar to that of FIG. It is. Therefore, there is no need to explain the equipment again. It is supported on four struts or legs 71 that project upwardly from a ring 73.

The housing 73 is mostly hollow to provide the required buoyancy and is buoyant. power tank and an oil or liquefied gas storage tank 75. The latter tank is a support It is accessible via a lip which is accessible through 71.

A delivery and pumping system 76 is also provided at the lower end of the tank.

Furthermore, according to the present invention, the semi-submersible purge as shown in FIGS. For example, by bolting or welding, larger platforms can be fixed together, for example by bolting or welding. Intended to form a form.

Figure 11 schematically shows the onboard gas-fired power generation system; It can be installed in the drilling ships shown in Figures 0 and 11. The gas from the riser - is supplied via the balcony to a treatment plant 81 where it is made suitable for combustion. The gas to be processed is then fed to a gas turbine 80, which has a reduction gear. A generator 86 is driven via system 84 .

The generator 86 supplies power to the ship's main switchboard 88, which supplies power for heating and certification. , the necessary power for the ship, such as for pumps, etc., is supplied. The power is also shown in section in Figure 12. Power will also be distributed to land areas via the Una submarine cable. This cable must be made of suitable non-corrosive material. a protective sheath 99 of the helical winding made of or coated with an edible alloy; It consists of an insulated cable 98.

The system uses heat from the exhaust gas of a gas turbine to generate steam. The heating boiler 92 generates steam and drives the steam turbine 94, and the main switchboard is connected to the It is equipped with a generator 96 that supplies power.

The semi-submersible drilling ship of the present invention can handle crude oil, condensates, gas/oil mixtures, and natural gas. For various liquefied gases such as gas (methane), propane, and butane, as well as for oil well heads. storage facilities for all components normally found in offshore oil and gas produced in can be provided.

Drillships can contain crude oil and gas processing equipment, so the generators mentioned above can be Instead of using a gas bottle, it is also possible to use an oil-fired type.

The present invention is intended to include within its scope the above embodiments as well as other aspects. Ru. For example, the platform should be triangular instead of square, and there should be three platforms instead of the ileum. It is possible to support it with the legs. In this case, the base also usually has a triangular shape in plan view. The shape of the box body can also be connected by simple butt welding without the need for complicated connections. It is possible to form a wall surface with a rough shape.

Referring to FIG. 13, the four legs 60 supporting the platform 62 are - consists of a steel box that is welded to form multiple layers of four boxes each. There is. Platform 62 and base 104 are also square, with simple butt connections. is formed between the legs, the platform, and the base, and the cylindrical column-shaped excavation of the prior art is A continuous flat structural surface can be created without the need for complex connecting structures like those used in ship drilling. I'm configuring it.

As shown in FIG. 14, each box 15 has an open vertical side on one side, and each of its edges is in contact with and welded to the vertical side of the adjacent box. This provides high rigidity. A simple structure is formed with a strong central connection, especially in the middle part of the leg.

The base 104 is made up of a plurality of rectangular boxes that are butt-welded together like the box bodies 50 that constitute the legs. It is composed of a body 102.

These boxes may be provided with elongated reinforcing members 100, 101, etc. on the inner surface. can. These reinforcing members support the inner walls and provide -1 structural rigidity. be.

The inner surface of the box is determined depending on whether the box has one, two, or three open sides. to form individual compartments or continuous shafts or passageways. These shafts, Passages and compartments can be accessed, ducted, piped, cabled, accommodated, and stored as required. It can be used for other purposes.

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Claims (10)

[Claims] 1. The upper structure (62) is supported by legs (60), and the lower ends of the legs are connected to each other. A semi-submersible drilling vessel (24) with a floating oil production system that forms a rigid floating structure. In this case, the legs (60) have a square or rectangular horizontal cross-sectional shape, and A floating oil production system characterized by being constructed by butt welding several boxes (50). Stem's semi-submersible drilling vessel. 2. In the semi-submersible drilling ship according to claim 1, the legs are square or rectangular corners. It is characterized by having 4 pieces. 3. In the semi-submersible drilling ship according to claim 2, the lower end of the leg has a rectangular base (5 8). 4. In the semi-submersible drilling vessel according to any of the above claims, the bottom of the leg (60) The ends are connected by an elongated connecting structure (58) with a square or rectangular cross section. It is characterized by. 5. In the semi-submersible drilling ship according to claim 1 or 2, the legs (71) are rigid. It is characterized by protruding upward from the underwater housing (73). 6. In the semi-submersible drilling ship according to claim 5, the underwater housing contains petroleum and/or It is characterized by having a built-in gas storage tank. 7. The semi-submersible drilling vessel according to any of the above claims is provided with an oil well head. It is characterized by 8. At least one relatively rigid fixed buoy (18), usually moored below sea level connected to at least one subsea oil well by a catenary riser (12), and Semi-submersible excavation with processing equipment by at least one flexible riser (22) A floating oil production system characterized in that it is connected to a ship (24). 9. The oil production system of claim 8, wherein the rigid catenary riser (12 ) from the buoy to the seabed and then along the seabed to the corresponding well head (10). It is characterized by being curved in the linear direction. 10. Method of installation of a floating oil production system, characterized in that it includes the following stages: a) lower at least one rigid catenary riser (12) to the seabed; connecting one end to an oil wellhead (10) on the seabed; b) Fix the other end of the catenary riser (12) to the mooring buoy (18) on the sea surface step; c) Transfer the upper end of the catenary riser (12) on the buoy from the buoy to the semi-submersible production drilling vessel ( connecting to a flexible riser (22) extending to (24); and d) lowering the buoy (18) to which the riser is connected, effectively avoiding the movement of wind, waves and currents; The stage is to moor it at a depth that is not affected by the wind.