US2731168A

US2731168A - System for gathering and loading oil from underwater oil wells

Info

Publication number: US2731168A
Application number: US321028A
Authority: US
Inventors: Richard G Watts
Original assignee: Socony Mobil Oil Co Inc
Current assignee: ExxonMobil Oil Corp
Priority date: 1952-11-17
Filing date: 1952-11-17
Publication date: 1956-01-17
Anticipated expiration: 1973-01-17

Description

Jan. 17, 1956 R. G. WATTS 2,731,168

SYSTEM FOR GATHERING AND LOADING OIL FROM UNDERWATER OIL WELLS Filed NOV. 17, 1952 2 Sheets-Sheet 1 TTHNEY Jan. 17, 1956 R. G. WATTS 2.731,158

SYSTEM FOR GATHERING AND LOADING OIL FROM UNDERWATER OIL WELLS Filed NOV. 17. 1952 2 Sheets-Sheet 2 Erm-JARD E, WA T Ts I N V EN TOR.

TTHNEY United States Patent() SYSTEM FOR GATHERING AND LOADING OIL FROM UNDERWATER OIL WELLS Richard G. Watts, Dallas, Tex., assigner, by mesne assignments, to Socony Mobil Oil Company, Inc., a corporation of New York Application November 17, 1952, Serial No. 321,028

2 Claims. (Cl. 220-85) This invention relates to the production of oil from underwater oil wells and relates more particularly to the gathering and loading for transportation of oil produced from underwater wells.

ln the operation of oil wells located on dry land, the oil produced from the well may be passed directly from the weil through an appropriate valve and pipe arrangement to storage tanks to await transportation by pipe line or tank car to an oil refinery. Sufficient storage capacity compensates for the fluctuation in the rate at which oil may be transported by pipe line or loaded into tank cars and thus makes possible a continuous rate of production of oil from the well, which is highly `desirable from the standpoint of insuring maximum total' recovery of oil from the well, maximum utility of the pumps, valves, lines, etc., and stability of operation. The same reasons for desiring uniform rates of production exist in the case of underwater or offshore Wells where, as in the case of dry land wells, sufiicient storage capacity will compensate for the fiuctuation in the rate at which the oil may be transported to the refinery.

The peculiar nature of the location of underwater wells brings up particular problems in maintaining uniform rates of production. Due to the difficulty and expense involved in laying underwater pipe lines from the shore to the well, it is economically desirable to go to other means of transportation, such as oil tankers and barges. However, tankers and barges cannot be loaded during unfavorable weather conditions in the form of high winds and waves, and so production must stop or sufficient storage capacity must be provided to handle continuous production for whatever may be the maximum period of adverse weather conditions.

Tanks submerged in water have been used for the storage of oil, but with their use there has been the problem of the oil escaping into the surrounding water causing destruction of marine life and creating fire hazards duc to the oil oating on the surface' of the water. Another problem which has been encountered with the use of sub'- merged oil storage tanks has been the mixing of the waterwith the oil, which is not desirable.

it is an object of this invention to provide an underwater oil storage tank which may at. all times be maintained liquid full with oil, water, or oil and water and from which there will be no escaping of oil to the surrounding water. It is another object of this invention to provide an underwater oil storage tank which may be maintained liquid full at all times with oil, water, or oil and water without any mixing of the two liquids within the storage tank. It is another object of this invention to provide a method for gathering and loading oil from underwater oil wells. It is another object of this invention to provide an economical system for maintaining continuous production from underwater oil wells. It is another object of this invention to provide an apparatus .for gathering and loading oil from underwater oil wells.

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These and other objects of the invention will become apparent from the following description thereof.

ln accordance with the invention, oil from an underwater oil well is gathered from the well, stored in a storage tank positioned sufficiently below the surface of the water to be unaffected `by winds and surface waves, and drawn off from the storage tank to transport barges as desired. The storage tank is maintained liquid full at all times with either oil, water, or oil and water and is provided with suicient ballast, if necessary, to overcome the buoyancy etect of the surrounding water and to maintain the tank in its underwater position. A particular feature of the invention is that the storage tank may be liquid full at all times without any mixing of the oil and water and thus preventing any possibility of water getting into the transport barge from the storage tank. This is accomplished in accordance with this feature of the invention by providing a flexible membrane or a plurality of fiexible. membranes within the tank dividing the tank into a plurality of sections variable in volume as needed, due to the flexibility of the dividing membrane or membranes. The storage tank is provided in its oil storage section or sections with an oil inlet line and with an oil outlet line supported at a mooring dolphin, and provision is made to permit water to enter the water containing section or sections of the storage tank as defined by the flexible membrane or membranes.

Fig. 'l is a plan view schematically illustrating one embodiment of the invention. Fig. 2 is a view partially in elevation and partially in section of an underwater storage tank. Fig. 3 is a view taken along line 3-3 of Fig. 2

showing the position of the flexible membrane when the storage tank is substantially filled with oil. Fig. 4 is a View in section taken along the line 3 3 of Fig. 2 showing the position of the flexible membrane when the storage tank is substantially filled with water. Fig. 5 is an enlarged view in section showing the details of securing the flexible membrane to the interior of the storage tank.

The storage tank may be of any suitable type such as a cylindrical tank. The tank may be positioned at the bottom of the body of water where the bottom is hard, or it may be permitted to sink into the bottom where the bottom is soft. If desired, the tank may be positioned intermediate to the bottom and the surface of the water, although, in this case, it will be necessary to provide anchoring means to prevent the tank from rising to the surface where its overall specific gravity is less than the surrounding water, as where it is filled with oil, or hanging means, such as pilings sunk into the bottom, to prevent the tank from sinking to the bottom Where its overall specific gravity is greater than the surrounding water, as where it is filled with water. Ballast may be employed to maintain the overall specific gravity of the tank above the specific gravity of the water whereby the tank will maintain its position at the bottom or sink into the bottom, or be prevented from rising if positioned intermedate to the bottom and the surface.- Air tanks or the like may be provided to maintain the overall specific gravity of the storage tank below the surrounding water whereby the tank will be prevented from sinking where it is positioned intermediate to the bottom and the sur- In the embodiment of the invention shown in the drawings here, a cylindrical tank is used and it is com pletely buried in the bottom.

In operation, oil from the well s passed into the storage tank through the oil inlet line at a pressure in excess of the hydrostatic pressure of the surrounding water and v membrane assuming substantially the shape of the lower' half ofthe storage tank as thestorage tank becomes filled with oil. lf the pressure of the well is not in excess of the hydrostatic pressure within the storage tank, a pump may be employed to provide the necessary pressure. The displaced water leaves thestorage tank through a water line located at the bottom ofthe tank and ows .back to the surrounding water.

Oil is removed from the tank through an oil outlet line supported by a mooring dolphin to a transport barge. Since water has a higher specific gravity vthan oil and the oil in the tank is at the hydrostatic pressure of the surrounding water, the oil may flow to the barge without the assistance of pumps, where the tank is at a sufficient depth. However, the use of a pump is desirable, in any case, in order to lessen the .timerequired to load the transport barge. Water enters the tank. through the same line through which it leaves, or a separate line may be provided, thereby displacing the voil being loaded on the barge but remaining separated. from `the oil in the storage tank -by the flexible membrane which allows the tank to become substantially lled with water, at which time the membrane will have assumed the approximate form of the upper half of the tank.

Referring to the drawings, producing platform 10 is supported by a plurality'of piles 11 which are sunk deep into bottom 12 and are steadied by a plurality of braces 13. Extending from platform 10 downward into well 14 is casing 15. Platform 10 is at a sufficient height above water 2l) to protect it and the equipment mounted upon it from the effect of high waves during adverse weather conditions. Mounted on platform l are well head 21, heater 22. separator 23 and the usual lines and valves. Oil from well i4 passes through the various equipment just enumerated into separator 23. Line 24 provided with valve 2S, diaphragm valve 26, and brace 30 leads from .separator 23 to dome 31 mounted on storage tank 32, which is sunk into bottom 12, provided with ports 33 to allow flow of oil 'to and from dome 31. Oil flows from separator 23 through line 24, dome 31, and ports 33 into upper section 34 of tank 32. Water from that surrounding the storage tank ows to and fromplowrer section 3S of the storage tank through line 39, one end of which is open to the water and situated suciently below its surface that it will always be under hydrostatic pressure. Brace 44.9 is secured between .line 39 and tank 32. Oil is removed from the upper ,section of the tank by line 4l whichk leads from dome 31 to dolphin 42 which in this embodiment is supported on piles 43 which are sunk into vbottom 12. Dolphin 42 may, ofcourse, be a buoy anchored in position. Dolphin -42 is provided with means,

not shown, for mooring a ,transfer barge to it. Line 41 is provided with relief valve 44, valve 45 land means for connecting flexible .hose t) which supplies the oil to loading barge 5l., lDolphin k42 is placed at a suicient distance from platform to reduce re `hazards 4by preventing the spread of lire from the dolphin to the platform. Also, the dolphin is at a distance from the platform Ywhich will permit the mooring vof the loading barge to the dolphin at any position within .a circle around the dolphin without `the loadingbarge coming `in contact with the platform,

Cylindrical tank 32 is divided into upper section 34 and lower section 35 by ilexible membrane .52. Membrane S2 is secured :around its entire outer edge to the inside of the tank, thus lproviding a complete separation of `tank 32 into two separate compartments variable in volume. The line of contact of t-he edge ott-he membrane with the inside ofthe tank lies -vin a horizontal plane which divides the tank into approximately equal upper and lower sections. The membrane `,is heldin liquid tight contact with ythe inside of Ithe tank by bar 'S3 and. pipe S4, which are secured by a plurality of bolts ,55, nuts 6), lock washers 6l, .and contour washers Bolts 5 5' are welded to the .inside Aol? tank 3,2. At the Lpoints where vbolts .S5 pass through pipe 54 the 4pipe is provided with .ports 63 to allow access with a socket wrench. In addition to aiding bar 53' in maintaining Contact with membrane 52, pipe 54 prevents membrane 52 contacting bolts 55 which might tear or otherwise damage membrane 52. ln order to minimize corrosion, the above enumerated securing apparatus is positioned above membrane 52 within the oil containing upper section 34.

Flexible membrane 52 isl composed of a material, such as polyethylene or neoprene rubber, which will withstand contact -with oiland `sea water for long periods of time without deterioration and will be exiblc enough to conform to the inside shape of the upper and lower halves of tank 32. When the tank is substantially iilled with oil, the membrane will be in the position shown in Fig. 3 and when the tank is substantially filled with water, the membrane will be in the position shown in Fig. 4. The membrane must be of suficient size to allow it to assume the above described shapes without stress being put upon the membrane. The use of this iiexible mem brane provides the means whereby the storage .tank may be liquid full at all times with oil, water, or oil and water without any mixing of the two liquids. Therefore, `no water will be pumped with the oil into the loading barge and no oil will j low from. the tank into the surrounding water. As oil is pumped into the tank, water Ais displaced from it to the surrounding water. When the oil is re.- moved from the tank, waterflows from the surrounding water through line 39 into lower section 35 of the tank, replacing the Lvoil which is being removed to a loading barge. p

Having thus described my invention, it will be understood that such description has been given by .Way of illustration and example only and not by way lof limitation, reference for the latter purpose being had tothe appended claims.

'lclairnz l. In an underwater oil storage -tank having a flexible impervious membrane dividing said tank into an upper oil-containing section and ya lower water-containing section, means positioned above said membrane within said oil-containing section for securing lsaid membrane in liquid tight contact with the inside surface of said tank, said means comprising in combination a plurality o' bolts secured to the inside surface of said tank and projecting inwardly therefrom, said bolts passing through `said membrane near its lperiphery `to maintain said membrane in position in said tank, a bar fitted on said bolts adjacent to said membrane holding said membrane in liquid .tight contact with the inside surface .of said tank, and means secured on said bolts Ato maintain said bar in position and to prevent said membrane from contacting the inward endsof said bolts.

2. In an underwater oil storage tank having a exible impervious membrane .dividing said tank `into an upper oil-.containing section and a lower water-containing section, means positioned labove said membrane within said oil-containing section for securing said membrane in liquid tight contact with Vthe inside surface .of said tank, said means rcomprising in combination a plurality of bolts secured to the inside surface of Asaid tank Jand projecting inwardly therefrom, .said bolts passing through said membrane near -ts periphery to maintain said 4membrane in position in said stank, a bar fitted on said bolts adjacent to -said membrane holding said membrane in liquid tight contact with .the inside ,surface of said tank, a pipe tted on said bolts adjacent .to said bar to aid in .holding said b ar in `contact with 4said membrane and to prevent contact of said membrane rwith the inward ends of said bolts, a plurality of contour'washers `on said bolts adjacent to the inside surfacegofrsaid'pipe, ,a plurality of rlock washers Q11 :said bolts adjacent to said Ycontour washers, a P111- ralit-y of nuts ,iserewsthreaded on said bolts adjacent to saidA nuts.

References Cited inthe file of this patent UNITED STATES PATENTS Forster Ian. 3, 1888 6 Kirby Nov. 27, 1934 Guilford Mar. 10, 1936 Lippincott Mar. 20, 1945 Bast Oct. 30, 1951 Watts Apr. 22, 1952 Fino Jan. 6, 1953

Claims

1. IN AN UNDERWATER OIL STORAGE TANK HAVING A FLEXIBLE IMPERVIOUS MEMBRANE DIVIDING SAID TANK INTO AN UPPER OIL-CONTAINING SECTION AND A LOWER WATER-CONTAINING SECTION, MEANS POSITIONED ABOVE SAID MEMBRANE WITHIN SAID OIL-CONTAINING SECTION FOR SECURING SAID MEMBRANE IN LIQUID TIGHT CONTACT WITH THE INSIDE SURFACE OF SAID TANK, SAID MEANS COMPRISING IN COMBINATION A PLURALITY OF BOLTS SECURED TO THE INSIDE SURFACE OF SAID TANK AND PROJECTING INWARDLY THEREFROM, SAID BOLTS PASSING THROUGH SAID MEMBRANE NEAR ITS PERIPHERY TO MAINTAIN SAID MEMBRANE IN POSITION SAIDTANK, A BAR FITTED ON SAID BOLTS ADJACENT TO SAID MEMBRANE HOLDING SAID MEMBRANE IN LIQUID TIGHT CONTACT WITH THE INSIDE SURFACE OF SAID TANK, AND MEANS SECURED ON SAID BOLTS MAINTAIN SAID BAR IN POSITION AND TO PREVENT SAID MEMBRANE FROM CONTACTING THE INWARD ENDS OF SAID BOLTS.