US3557396A

US3557396A - Floating storage system with buoymounted separator

Info

Publication number: US3557396A
Application number: US775350A
Authority: US
Inventors: Lewis A Rupp
Original assignee: Mobil Oil Corp
Current assignee: ExxonMobil Oil Corp
Priority date: 1968-11-13
Filing date: 1968-11-13
Publication date: 1971-01-26
Anticipated expiration: 1988-01-26

Abstract

THE SPECIFICATION DISCLOSES A SYSTEM FOR PRODUCING, SEPARATING, AND STORING SUBMARINE OIL AND GAS. THE SYSTEM INCLUDES A FLOATING STORAGE VESSEL HAVING A SHIP-SHAPED HULL WHICH IS MOORED TO A BUOY SO THAT IT IS FREE TO PIVOT THROUGH 360* IN RESPONSE TO THE COMBINED FORCES OF WIND AND WATER. PRODUCED FLUIDS ARE DIRECTED FROM AN UNDERWATER LOCATION THROUGH A SWIVEL JOINT ON THE BUOY AND A FLOATING HOSE TO THE STORAGE TANKS OF THE FLOATING VESSEL. MOUNTED IN THE BUOY IS A UNIQUE OIL-GAS SEPARATOR WHICH COMPRISES A RIGID STANDPIPE SURROUNDED BY A MAIN PRESSURE VESSEL. AN INLET CONDUIT INTERSECTS THE RIGID STANDPIPE IN THE MAIN PRESSURE VESSEL AT TIGHT ANGLES, THUS PROVIDING A PAIR OF FLUID INLETS, ONE OF WHICH IS ALWAYS ABOVE THE SUMP FLUID. SEPARATED OIL IS DIRECTED THROUGH A SWIVEL JOINT CONCENTRIC WITH THE TOP OF THE STANDPIPE, WHILE SEPARATED GAS IS FLARED THROUGH AN UPWARD EXTENSION OF THE STANDPIPE.

Description

Jan. 26, 1971 1..v A. RUPP 3,557,396

FLOATING STORAGE SYSTEM WITH BUOYMOUNTED SEPARATOR Filed Nov. 13, 1968 2 Sheets-Sheet 2 .1971 L. A. RUPP FLOATING: STORAGE SYSTEM WITH BUOY-MOUNTED SEPARATOR Filed Nov. 15, 1968 2 Sheets-Sheet 1 United States Patent O 3 Claims ABSTRACT OF THE DISCLOSURE The specification discloses a system for producing, separating, and storing submarine oil and gas. The system includes a floating storage vessel having a ship-shaped hull which is moored to a buoy so that it is free to pivot through 360 in response to the combined forces of wind and water. Produced fluids are directed from an underwater location through a swivel joint on the buoy and a floating hose to the storage tanks of the floating vessel. Mounted in the buoy is a unique oil-gas separator which comprises a rigid standpipe surrounded by a main pressure vessel. An inlet conduit intersects the rigid standpipe in the main pressure vessel at tight angles, thus providing a pair of fluid inlets, one of which is always above the sump fluid. Separated oil is directed through a swivel joint concentric with the top of the standpipe, while separated gas is flared through an upward extension of the standpipe.

FIELD OF THE INVENTION The invention described herein relates to production and storage of fluid minerals, such as oil and gas, underlying a body of water.

SUMMARY OF THE INVENTION The present invention is a novel and improved floating storage system including a structure having a ship-shaped hull and a fluid storage tank. The floating storage structure is moored to a buoy in which is mounted a liquid-gas separator unit. A swivel joint is attached to the mooring buoy and is in fluid communication with the liquid outlet of the separator unit. A floating pipeline extends from the storage tank of the floating storage structure to the swivel joint.

By the present invention the need for high pressure swivel joints is eliminated because the fluid minerals are separated into liquid and gaseous components and reduced to atmospheric pressure in the mooring buoy before being directed through any swivel joints. No swivel connection is needed between the separator unit in the buoy and any subsurface points at which the fluid is applied. The gas separated out by the separator unit can be flared above the buoy, directed through a separate low pressure swivel joint to the floating storage structure where it is compressed and stored in separate storage tanks, pumped into subsurface formations, or piped to shore. If the gas is to be flared, it can be done on the mooring buoy away from the floating storage structure.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings, FIG. 1 is a schematic illustration of one form of the present invention used in conjunction with a submarine satellite gathering system; and

FIG. 2 is a side elevational view partially in cross section of one form of separator for use in the system of FIG. 2.

DETAILED DESCRIPTION OF FIG. 1

Referring to FIG. 1, a production system is shown utilizing a number of subsea satellite stations, one of which 3,557,396 Patented Jan. 26, 1971 is illustrated at 10, each station having a plurality of wells drilled through standing conductor pipe elements 12 of a template ring 14 resting on the marine bottom 15. The wells are all completed with subsea wellheads 16 mounted atop the conductor pipes 12 and in turn capped with connector units 18 for directing the produced fluid from the wellheads into the interior of satellite stations 10. The apparatus and method of installation of such a subsea satellite station are described in the copending application of William A. Talley, 11"., Ser. No. 740,520, filed June 27, 1968, and entitled Subsea Production Station.

The produced outputs of all of the satellite gathering stations 10 are connected through shipping lines 22 to a circular manifold 24 located on the marine bottom- 15 concentric with a tether pipe 26. Produced fluids are transported through tether pipe 26 from the marine bottom to an intermediate point several hundred feet below the water surface where the tether pipe 26 terminates in a buoyant chamber 38. A flexible connection 30 extends from the upper end of tether pipe 26 to a mooring buoy 106. Mooring lines 108 extend between anchor points 110 on the marine bottom to the mooring buoy 106. A separator unit 107 is mounted in the hollow interior of buoy 106. Separator unit 107 is designed to separate the production flow into its liquid and gaseous components, usually into its oil and gas components. A swivel 104 is mounted atop buoy 106. A floating storage structure 32, having a ship-shaped hull, is moored by means of mooring lines 102 to the swivel 104. A floating oil storage line 114 is shown connecting an oil outlet port of the swivel 104 with storage manifolds 116 on the floating storage structure 32. A central gas flare stack 11% extends upward concentrically through the swivel 104 for burning off the separated-out gas.

The liquid or oil separated out of the produced fluid is stored in the floating storage structure 32 until a transport tanker arrives. The transport tan ker will moor alongside storage structure 32 and oil will be pumped through large flexible hoses or Chicksan arms into the manifolds of the transport tanker. The transport tanker may be moored to the storage structure 32 so that the two, forming a single unit, may pivot about buoy 106 on mooring line 102. Alternatively, the transport tanker may be moored separately to the mooring line 102 by means of a yoke connection.

By mounting separator 107 in the buoy 106, a high pressure line is not required for the swivel 104. Swivel joints, designed to carry high pressure fluids, are more expensive, more complex, and more subject to defect and leakage than low pressure swivel joints.

The floating storage structure 32 is free to swivel about the buoy 106 on its mooring line 102 in response to wind and water forces.

DETAILED DESCRIPTION OF FIG. 2

FIG. 2 illustrates a specific separator unit 107 which is described in the copending application of William A. Talley, In, US. patent application Ser. No. 775,235, filed on Nov. 13, 1968, and entitled Marine Oil-Gas Separator.

As illustrated in FIG. 2, separator unit 107 includes a main pressure vessel 1.20 which is elongated or cigar shaped with its longest dimension extending horizontally. The main pressure vessel 120 rests on a lower bulkhead or deck 122 of the buoy 106 on integral legs 124. A rigid standpipe 126 extends fully through the pressure vessel 120, depending through the lower deck 122 from which it obtains its primary support. Standpipe 126 is rigidly connected to the lower deck 122 by means of angularly spaced diagonal struts 128. The lower end of standpipe 126 is welded directly to the lower face of deck 122 and to the upper face of a supporting plate 129, which rests on the deck 122. The standpipe 126 extends through the main pressure vessel 120 and the upper deck 130 of the buoy.

An inlet conduit 132 within the main pressure vessel 120 intersects the standpipe 126 at a perpendicular angle, thus providing a pair of fluid inlets. Conduit 132 is supported by straps 134 extending downward from the upper interior wall of the pressure vessel 120. Inlet deflectors 136 are mounted in the interior of pressure vessel 120 radially downward of each end of conduit 132. A circular secondary deflector 138 is mounted concentrically on the standpipe 126 between the conduit 132 and a mist extractor 140.

Radial ports 141 are formed through the standpipe 126 within mist extractor 140. A plate 142 closes off the standpipe 126 just below the mist extractor 140.

A gas pressure valve and float assembly 144 is mounted within the standpipe 126 above pressure vessel 120 but beneath the upper deck 130 of buoy 106. Stilling baffles 146 are mounted in the sump of pressure vessel 120 as is the inlet of a discharge line 148. The entrance of liquid into the discharge line 148 is controlled by a float-controlled valve arrangement 150 including a float 151 mounted in the lower end of discharge line 148. A valved drain 152 is connected to a depressed central portion of pressure vessel 120 to direct water and other impurities from the lower end of pressure vessel 120 directly into the water beneath buoy 106. A second valved drain 154 is provided for draining the fluid from the sump of pressure vessel 120 into the hollow interior of buoy 106.

The liquid discharge line 148 is connected at its upper end to a circular manifold 162 which is mounted concentrically around the gas flare stack 145. An oil swivel 158 is located concentrically about flare stack 145 just above manifold 156 with which the oil swivel is in fluid communication. Oil swivel 158 comprises an outer stationary pipe element 160 which nests concentrically in a necked down portion 162 of pipe element 126. The pipe element 160 has radial ports 163 providing fluid communication between the interior of pipe element 160 and the interior of an outer rotatable yoke portion 164 of the swivel 158. The outer end of the yoke portion 164 is coupled to the end of the floating hose 114 shown in FIG. 1.

At least one padeye 166 is mounted on the upper end of rotatable yoke portion 164 of the oil swivel 158 for connecting one end of the mooring line 102 which is used for mooring the floating storage structure 32 shown in FIG. 1 to buoy 106.

In use the separator unit of FIG. 2 is connected to a source of produced fluid such as through flexible connection 30 extending from the upper end of tether pipe 26 as described with respect to FIG. 1. The upper end of flexible hose 30 is connected to the lower end of the rigid standpipe 126 by means of a fluidtight connector 170.

The unique continuous design of standpipe 126 from under the buoy 106 to the flare stack 145 above buoy 106 provides for rigidity and eliminates the need for a supporting tower.

By means of the inlet conduit 132 the incoming oil-gas mixture is directed in two streams toward each end of the main pressure vessel 120, thus providing increased separation capacity per unit volume of the main pressure vessel 120, lower surge problems, and less problems with the unbalanced fluid levels due to wave action on the buoy. This permits the separator to function properly even when the buoy 106 is at a considerable angle to the horizontal. With a conventional low temperature separator mounted in buoy 106 when the buoy was inclined at an acute angle, oil would be forced through the mist extractor and out 4 through the flare stack. This cannot happen with the present invention, where at least one of the conduit 132 is always above the oil level in the sump.

The invention claimed is:

1. A system for producing and storing fluid minerals underlying a body of water comprising:

(a) a floating storage structure having a ship-shaped hull and at least one fluid storage tank;

(b) a mooring buoy;

(c) a liquid-gas separator unit mounted in the mooring buoy;

(d) a fluid flowline extending up through the body of water to the separator unit;

(e) anchor means connecting the mooring buoy to the floor of the body of water;

(f) a swivel joint attached to the mooring buoy and in fiuid communication with the liquid outlet of the separator unit;

(g) a liquid flowline in communication with the storage tank in the floating storage structure and coupled to the swivel joint for transporting liquid from the separator unit to the storage tank; and

(h) a mooring line linking the floating storage structure to the swivel joint whereby the floating storage structure may freely rotate about the mooring buoy in response to wind and water forces.

2. The system of claim 1 further comprising a flare stack mounted concentrically within the swivel joint and extending vertically for burning gas separated by the separator unit.

3. A system for producing and storing fluid minerals underlying a body of water comprising:

(a) at least one mineral producing well completed on the marine bottom of said body of water;

(b) a mooring buoy on the surface of said body of Water;

(0) a liquid-gas separator unit mounted in said buoy,

said separator unit having a liquid outlet;

(d) a fluid flowline connecting said well to said separator unit in said buoy;

(e) a swivel means attached to the mooring buoy and in fluid communication with said liquid outlet of said separator unit;

(f) a floating storage means on the surface of said body of water;

(g) a flowline in communication with said floating storage means and coupled to said swivel means for transporting liquid from the separator unit to said storage means; and

(h) mooring means for linking said floating storage means to said swivel means whereby said floating storage means may freely rotate about said mooring buoy in response to wind and. water forces.

References Cited UNITED STATES PATENTS 2,731,168 l/l956 Watts 98(O.PUX) 2,894,269 7/1959 Dodge 98.3 3,407,768 10/1968 Graham 98(OP)X 3,408,971 ll/l968 Mott 1140.5(T) 3,264,662 8/1966 Young 98(O.P.) 3,472,032 10/1969 Howard 98(O.P.)

TRYGVE M. BLIX, Primary Examiner US. Cl. X.R. 1l40.5