US3111692A

US3111692A - Floating production platform

Info

Publication number: US3111692A
Application number: US75709A
Authority: US
Inventors: Harold D Cox
Original assignee: Shell Oil Co
Current assignee: Shell USA Inc
Priority date: 1960-12-14
Filing date: 1960-12-14
Publication date: 1963-11-26
Anticipated expiration: 1980-11-26
Also published as: GB923576A

Description

Nov. 26, 1963 H. D. cox 3,111,692 FLOATING PRODUCTION PLATFORM Filed D80- 14, 1960 2 Sheets-Sheet l IIIIIIIIII.

47 INVENTORI 53 FIG. 4 H. D. cox

HIS AGENT Nov. 26, 1963 I H. D. cox 3,111,692

FLOATING PRODUCTION PLATFORM Filed D90- 14, 1960 2 Sheets-Sheet 2 INVENTOR H.'D. COX B H341.

IS AGENT United States Patent 3,111,692 FLUATHNG FROIDUQHQN PLATFORM Harold 1). Cox, Houston, Tex, assignor to flhell Gil Cornpany, New York, N.Y., a corporation of Delaware Filed Dec. 14, 1960, Ser. No. 75,7419 Qlahns. (Cl. 9-3) This invention relates to production platforms of the type used in oil and gas fields and pertains more particularly to a releasable floating production platform having a releasable portion and adapted to handle. production fluid from oil and gas fields in Water-covered areas.

In many areas wells have been drilled to produce oil and gas from oil fields located many miles offshore in water-covered areas. it is necessary in many cases to run the production fluid flowlines from individual wells along the ocean floor to a collection and treating station positioned either onshore or on a permanent platform positioned offshore among a number of wells which are some distance from the production platform. ln general, production platforms which are positioned on permanent piles driven in the ocean floor cannot be located in waters deeper than 200 feet.

it is therefore a primary object of the present invention to provide a floating production platform which may be employed in waters of any depth to produce one or more wells of an offshore oil field.

Presently known floating platforms, adapted to beanchored to the ocean floor in deep Water for serving as a production platform for adjacent oil and gas wells, cannot be used in areas subject to violent storms as there is always the danger of the anchored production platform dragging its anchors and rupturing the oil and gas flowlines connected thereto, thus necessitating the replacement of thousands or millions of dollars worth of well flow and control lines.

It is therefore a further object of the present invention to provide a floating production platform adapted to be operatively connected to a number of oil and gas well flowlines duringnormal operations and yet being readily disconnectable from the flowlines in the event of a storm.

Another object of the present invention is to provide apparatus for disconnecting a plurality of fluid floWiin-es rom a production platform and positioning the disconnected ends of the flowlines at a predetermined depth below the surface of the body of water from which location they may readily be recovered after a storm has passed.

These and other objects of this invention will be understood from the following description taken with reference to the drawing, wherein:

FIGURE 1 is a schematic view, taken in partial longitudinal cross-section, of a floating production platform in accordance with the present invention when a plurality of flowlines from individual wells are connected to the platform;

FIGURE 2 is a schematic view illustrating the position of a floating production platform in accordance with the present invention with relation to a plurality of well flowlines which have been disconnected from the platform;

FIGURE 3 is a diagrammatic view, taken in partial cross-section, of a releasable connector for a pipe line which is movably connected to an auxiliary float carried by the production platform of the present invention; and,

FIGURE. 4 is a cross-sectional view of a flexible joint on the float.

Referring to FIGURE 1 of the drawing, the offshore platform 11 of the present invention comprises a buoyant hull 12 having a vertical opening 1-3 therethrough. Thehull 12 may be of any suitable shape and size and the vertical opening 13 therethrough may be positioned at any desired location. A doughnut-shaped hull is illustrated "ice in FIGURE 1, although a rectangilar hull or a hull of any other desired shape and/ or design may be employed with the opening 13 extending vertically therethrough at any point. If desired, the vertical opening 13 may extend in from one edge of the hull, similar to a slotin a drilling barge.

A support frame. or platform 14 is rigidly secured to the hull 12 on vertical structural members or legs 15 at a height that is normally above the wave action of the body of Water 16. Various types of oil and gas handling and treating equipment may be positioned on the platform 14 depending upon the operations that it is desired to carry out on the platform. The platform is normally provided with suitable manifolding means 1'7 which is employed to direct or combine the flow from one or more of the wells and channel it to the proper equipment. In FlGURE yl the manifold 17 on the platform 14 is shown as being provided with a number of pipes 26 extending downwardly from a manifold 17, there being at least one pipe 29 for each well connected to the production platform. Each of the pipes 21 is provided with valves 21 therein for closing the pipes. The valves 21 may be of any suitable type and are preferably power-actuated valves which may be controlled from a remote position on the platform 14. 'In some well systems there are two flowiines running to each well.

The lower end of each pipe 26 is provided with a pipe.

connector Zflby which the pipe 211 is connected in fluid communication with a flexible fluid flowline 26. Each of the flexible fluid flowlines 23 extends down through the vertical opening 13 in the hull d2 of the offshore platform 11 and generally bends down in a gentle curve to the ocean floor where it runs along the floor to the well. The upper ends of the flexible fluid flowlines 223 are preferably provided with valves 24 for closing the flowlines. The valves 24 are preferably of the remotely-operable power-actuated type similar to valves 21. The upper end of each flexible fiowline 23 is secured by means of any suitable flexible device, such as a swivel joint 25' having a pivot .pin 26,.to an auxiliary float which, for ease of description, will be termed a fiowline float 27. One or more of the flowlines 2-3 may be of the same or larger diameter for transporting oil from the offshore platform to onshore storage facilities or to tanker loading facilities (not shown).

The-fiowline float 27 is of a size so that it can pass through the opening 13 in the hull 12 of the offshore platform. The float 2 7 is designed to have a buoyancy suflicient to support the upper ends of all of the flexible flovvlines 23 when the fiowline float 27 is disconnected from the offshore platform 11. Any suitable means may shore platform 11 illustrated in FIGURE 1, the fiowline float 27 is held at a predetermined height below the operating platform 14 by means of a pair of

lines

30 and 31 which connect the

suitable hoists

32 and 33. Although the

hoists

32 and 33 could be positioned on the operating platform 14, they are shown as being positioned on a higher platform 34 in order to get them out of the way of the operating equipment on platform 14. The hoist lines 353 and 31 are shown as extending downwardly through

tubes

36 and 37 in the fiowline float 27. The lower ends of the hoist lines 361 and 31 are connected to an anchor ll) which is lowerable through the vertical opening 13 inthe hull 12 of the offshore platform. Preferably, the offshore platform is anchored at all times by means of

anchor lines

41 and 42, and as many others are necessary, which extend outwardly from the hull 12 at an angle and direction so that they do not inter fere with the flexible flowlines 23.

In FIGURE 3, the float anchor line 36 extending downwardly through the vertical tube in the hull ofthe flowline float 27 is shown as having a stop member 43 fixedly secured thereto at a predetermined point so as to secure the anchor 4% to the flowline float 2'7. A second stop member 44 is preferably employed when a float 27 is used that is normally suspended above the water. Although a pull-out type of pipe connector 22 is illustrated in FIGURE 3, any suitable type of releasable pipe connector may be employed. Any type of swivel joints may be employed in connecting the flowlines 23 to the float 27 in a manner to assure Zero moment under all conditions of service and loading.

During routine operation of the offshore platform of the present invention, the hull 12 floats on the surface of the water as illustrated in FIGURE 1 of the drawing and the flowline float 27 is secured to the offshore platform 11 together with the flexible flowlines 23. Although the flowline float 27 is illustrated as being secured well above the water level 16 and just below the operating platform 14 of the apparatus, it is realized that the flowline float may be at any desired level and may even ride in or under the water within the vertical opening 13 of the hull 12. If desired the manifold 17 may be positioned on the float 27 instead of on the platform 14 with a single pipe running up to the operating platform.

When operations on the offshore platform must be suspended, for example, in case of a storm which might rupture the flowlines 23, the valves 21 and 24 in the pipes 20 and the flowlines 23, respectively, are closed and the pipe connectors 22 are disconnected. With the flexible flowlines 23 disconnected from the pipes 25), the winches or

hoists

32 and 33 are set in motion to lower the anchor 40 and the flowline float 2.7 through the vertical opening 13 and the hull 12 of the offshore platform 11. When the anchor 40 is at a predetermined height above the ocean floor, stop members 43 and 44 (FIGURE 3) are connected to the

hoist lines

30 and 31 to prevent further movement of the hoist lines 3i and 31 through the flowline float 27. The lowering of the

hoist lines

30 and 31 is continued causing the flowline float 27 to be pulled downwardly with the anchor 43 until the anchor 40 rests on the ocean floor, in a position illustrated in FIGURE 2 of the drawing wherein the float 27 is, for example, 100 feet below the surface of the body of water 16. The

hoist lines

30 and 31 are then disconnected at or between the float and platform or dropped from the hoists so that the flowline float 27 is entirely free from the offshore platform 11. If, during the storm, the offshore platform 11 (FIGURE 2) should pull or drag the anchors (not shown) secured to the ends of the

anchor lines

41 and 42, the flowline float 27 and the flexible flowlines 23 connected thereto will not be affected. After the storm the ofshore platform 11 is re-positioned over the flowline float 27 and divers pick up or re-attach the

hoist lines

30 and 31 to the device from which they were disconnected so that the flowline float 27 and its flexible flowlines 23 can be raised to its original position, as shown in FIGURE 1, and the flowlines 23 are again connected to the pipe manifold 17.

The flowline float 27 is designed so as to have a calculated positive buoyancy in excess of the weight of the flowlines 23 attached to it when it is in its anchored position, as shown in FIGURE 2. The float anchor 40 is of sufficient Weight to prevent the flowline float from dragging the anchor 40 when the anchor is resting on the ocean floor and the flowline float 27 is submerged and subjected to wave forces generated by a maximum storm. While the flowlines 23 have been described hereinabove as being flexible flowlines, it is apparent from the operation of the present invention that most of each flowline which extends from the well along the ocean floor can be a normal metallic flowline which is connected to a portion of flexible flowline of suflicient length to bend upwardly from the ocean floor and be raised to its connected position as illustrated in FIGURE 1. The size of the flowlines depends generally upon the amount of production fluid being handled from each well. The design of the flowlines 23 is such that they do not become overstressed or fail due to (1) stresses due to horizontal and vertical movement of the offshore platform 11 and wave forces on the lines produced by weather conditions in which wave heights are predicted not to exceed 30 feet, or (2) stresses due to the horizontal and vertical movement of the flowline float 27 during a storm in its submerged position, or during the lowering of the float and anchor together with all flowlines to its submerged position. Another feature of the present invention is that the offshore platform 11, without its flexible flowlines 23 and flowline float 27, may be readily moved to shore or to dry dock for repairs or inspection.

A preferred type of swivel joint for connecting the flowlines 23 to the flowline float 27 is shown in FIGURE 4. The joint consists of a short section of pipe 46 extending through a ball 47 of a ball-and-socket joint having one body portion 48 secured in a rigid manner to the flowline float 2'7. An upper body portion 49 is fixedly secured, as by bolts 5%, to the lower portion 48. One or more G-ring seals 51 may be used to hold a lubricant such as grease between the ball 47 and the

body portions

48 and 49. The upper and lower ends of the pipe section 45 are secured by suitable pipe connectors or

couplings

52 and 53 to flexible sections of the flowlines 259 and 23, respectively, above and below the flexible joint.

I claim as my invention:

1. An offshore production platform for handling production fluid from oil and gas fields in water-covered areas, said offshore platform comprising a buoyant hull adapted to float on a body of water, said hull having a vertical opening therethrough, support means rigidly secured to said hull and positioned above the normal wave level of said body of water, flowline float means releasably secured to said support means in vertical alignment with the opening in the hull, said flowline float means being of a size to pass through said opening in said hull, flexible flowline means extending up from the ocean floor to said flowline float means, flexible joint means securing the upper ends of said flexible flowline means to the flowline float means, fluid conduit means carried by said offshore platform, releasable pipe connector means carried between and connecting said flowline means to said fluid conduit means, and anchor means adapted to be connected to said flowline float means and including anchor line means of a length to position said flowline float means below the surface of said body of water when the float means are positioned therein.

2. An oflshore production platform for handling production fluid from oil and gas fields in water-covered areas, said oifshore platform comprising a buoyant hull adapted to float on a body of water, said hull having a vertical opening therethrough, support means rigidly secured to said hull and positioned above the normal wave level of said body of Water, flowline float means releasably secured to said support means in vertical alignment with the opening in the hull, said flowline float means being of a size to pass through said opening in said hull, flexible flowline means including a plurality of flexible fluid flowlines extending up from the ocean floor to said flowline float means, flexible joint means securing the upper ends of said flexible flowline means to the flowline float means, fluid conduit means carried by said offshore platform, releasable pipe connector means carried between and connecting the upper end of said flowline means to the lower end of said fluid conduit means, anchor means adapted to be connected to said flowline float means and including anchor line means of a length to position said flowline float means below the surface of said body of water, when the float means are positioned therein, and hoist means mounted on said support means and releasably connected to said anchor line means for raising and lowering said flowline float means.

3. An offshore production platform for handling production fluid from oil and gas fields in water-covered areas, said offshore platform comprising a buoyant hull adapted to float on a body of water, said hull having a vertical opening therethrough, platform means rigidly secured to said hull and positioned above the normal wave level of said body of water, flowline float means releasably secured to said offshore platform means in vertical alignment with the opening in the hull, said flowline float means being of a size to pass through said opening in said hull, flowline means including a plurality of flexible fluid flowlines bending up from the ocean floor to said flowline float means, flexible joint means securing the upper ends of said flexible flowlines to the flowline float means, fluid conduit means carried by said offshore platform, releasable pipe connector means carried between and connecting the upper end of said flowline means to the lower end of said fluid conduit means, anchor means releasably carried by said offshore platform and adapted to be connected to said flowline float means, anchor line means secured to said anchor means, means for connecting said anchor line means to said flowline float means, and hoist means mounted on said offshore platform means releasably connected to said anchor line means for raising and lowering said fiowline float means.

4. An offshore production platform for handling production fluid from oil and gas fields in water-covered areas, said offshore platform comprising a buoyant hull adapted to float on a body of Water, said hull having a vertical opening therethrough, platform means rigidly secured to the top of said hull and positioned above the normal wave level of said body of water, fluid manifold means carried on said platform means, flowline fioat means releasably secured to said offshore platform means in vertical alignment with the opening in the hull, said flowline float means being of a size to pass through said opening in said hull, flowline means including a plurality of flexible fluid flowlines bending up from the ocean floor to said flowline float means, flexible-joint swivel means securing the upper ends of said flexible flowlines to the flowline float means, fluid conduit means carried by said offshore platform in communication with said manifold means carried thereon, releasable pipe connector means carried between and connecting the upper end of said flowline means to the lower end of said fluid conduit means, anchor means releasably carried by said offshore platform and adapted to be secured to said flowline float means, anchor line means secured to said anchor means and extending upwardly through said flowline float means, means for connecting said anchor line means to said flowline float means, and hoist means mounted on said oflshore platform means and releasably connected to said anchor line means for raising and lowering said anchor means and said flowline float means.

5. An offshore production platform for handling production fluid from oil and gas fields in water-covered areas, said offshore platform comprising a buoyant hull adapted to float on a body of water, said hull having a vertical opening therethrough, support means rigidly secured to said hull and positioned above the normal wave level of said body of water, flowline float means releasably secured to said support means in vertical alignment with the opening in the hull, said flowline float means being of a size to pass through said opening in said hull, flowline means having a flexible portion therein and extending up from the ocean floor to said flowline float means, means securing the upper ends of said flexible flowline means to the flowline float means, fluid conduit means carried by said offshore platform, and releasable pipe connector means carried between and connecting said flowline means to said fluid conduit means.

References Cited in the file of this patent UNITED STATES PATENTS 604,235 Jordan May 17, 1898 2,614,803 Wiggins Oct. 21, 1952 2,650,558 Nizery Sept, 1, 1953 2,748,739 Monti June 5, 1956 2,894,268 Grebe July 14, 1959 2,907,172 Crake Oct. 6, 1959 2,981,347 Bauer Apr. 25, 1961