US3381481A

US3381481A - Offshore storage apparatus

Info

Publication number: US3381481A
Application number: US448947A
Authority: US
Inventors: Robert S Chamberlin; Donald C Stafford; Charles A Mcdonald
Original assignee: Chicago Bridge and Iron Co
Current assignee: Chicago Bridge and Iron Co
Priority date: 1965-04-19
Filing date: 1965-04-19
Publication date: 1968-05-07
Anticipated expiration: 1985-05-07
Also published as: NO117733B; BE679710A; SE327171B; GB1129960A; NL6605159A; DE1684606B2; DE1684606A1

Description

May 7, 1968 R. s. CHAMBERUN ET AL 3,381481 OFFSHORE STORAGE APPARATUS y Filed April 19, 1965 v 4 sheets-sheet 1 NW-ul May 7, 1968 R. s. CHAMBERUN ET AL 3,381,481

OFFSHORE STORAGE APPARATUS 4 Sheets-Sheet 2 Filed April 19. 1965 @amasar-:51,

May 7, 1968 VR. S. CHAMBERLIN ET AL OFFSHORE STORAGE APPARATUS 4 Sheets-Sheet 3 Filed April 19, 1965 May 7, 1968 R. s. CHAMBERLIN ET Al, 3,381,481

OFFSHORE STORAGE APPARATUS Filed April 19, 1965 4 Sheets-Sheet 4 fl/ y Q A y f @Awww I m/@nm-mnlm l//lll lll lll .IH

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@Wav/weg@ United States Patent O 3,381,481 OFFSHORE STRAGE APPARATUS Robert S. thamherlin, Western Springs, Donald C. Stafford, Homewood, and Charles A. McDonald, Palos Heights, lll., assignors to thieago Bridge d; lron Company, Galt Brook, lll., a corporation of illinois Filed Apr. 19, 1965, Ser. No. 448,947

ld Claims. (Cl. oli- 465) ABSTRACT F THE DTSCLSUREE An offshore storage system having interconnected Storage tanks, one of the tanks submerged in water and resting on the floor-of the water body, while the other tank is supported above the surface of the water. Liquid passageways transport water and a water-immiscible liquid between the tank for selectively filling the tanks and providing a ballast sufficient to anchor the system in a substantially fixed position.

This invention relates to apparatus for storing fluids in offshore locations.

At the present time oil is being recovered in many offshore locations and at various water depths. in many instances, the water-immiscible fluid is obtained in regions and areas which are of considerable distance from land. The water depths at which installations are established for recovering the water-immiscible oil vary greatly. Some present production is undertaken where the floor or bed of the water body is at depths even greater than 300 feet or more.

Economical production of the oil makes it essential that storage tank means should be provided in the general vicinity of the region where the oil drilling occurs. This drilling being through the floor or bed of the ocean or large lakes, places many demands upon the storage facility. Because of the distance from shore where quantiiies of oil are now being recovered in open-sea drilling locations totally submerged storage facilities have come into use. Generally speaking, such submerged storage facilities are calculated to lead to a more economical oil recovery procedure than would an equivalent size elevated or floating storage facility at the site of the offshore drilling. The submerged Storage facility in such location is much less subject to exposure to the effects of wind forces, wave currents or similar conditions.

Submerged storage `tank facilities appear, in many respects, to be a logical solution to the recovery problem. Such facilities are generally regarded as somewhat cheaper than elevated storage structures. However, they often require some auxiliary facilities. These are shown in the form of expensive support platforms upon which operation equipment is usually mounted. The platforms are supported by structures extending from beneath the ocean bed to a good many feet above the water surface. The submerged structures themselves introduce numerous and expensive new problems.

The recovered crude oil, being of lower specific gravity than water, is considerably lighter than the water in which the submerged storage facility is located. It is necessary, therefore, to provide ballast in one form or another to prevent the submerged storage tank from floating to the surface when filled with recovered oil. In some instances, the submerged storage tanks have been secured upon pilings driven into the floor of the body of the water, but this also is expensive. To position and anchor the storage facility onto the piling, particularly in deep-water locations, necessitates expensive installation operations which tend to make the cost of the storage facility extremely high. This inherently has some effect on the cost of the operation as a whole, and thus on the cost of the stored liquid.

Storage facilities, whether elevated, submerged or, float ing, in any event require substantial anchoring in order to resist wind or wave forces. It is also important that considerable thought and account be given to the maximum wind and wave forces that are apt to be effective. For this reason, much study has been given to the problern. Calculations for determining the forces of various types which the equipment must withstand have been made. Records which cover the experience of a substantial number of years relative to winds and wave are available. These records and data are used to predict the loads to which the structure is likely to be subjected The present invention embodies a combination of submerged -and elevated storage facilities arranged in novel association and cooperative relationship. The components under consideration are structurally connected in xed spaced relationship with respect to each other. There is, accordingly, a constant separation always maintained between the submerged and elevated bodies. The storage system to be described is operated upon a water-displacement principle. The storage tanks are so designed that no anchors or piles are required to hold the submerged tank in position. To the contrary, the weight of the elevated storage tank, together with its contents and structural bracing connections between it and the submer ed tank, as well as the fluid located in any connecting passages between the two components, is adequate to provide a permanent ballast suflicient to resist the buoyancy olf the submerged storage facility if filled with a water-immiscible product. rthe weight exceeds that of the submerged components to an extent necessary to resist also forces due to waves and wind. In this respect it is evident that the materials of the tank means and the supports have a specific gravity substantially greater than that of the water body in which it is submerged. Recognition can be given to this fact in the design of the elevated structure which can thus then be made smaller than would otherwiseV be possible.

In practicing the invention, the submerged tank or storage facility is so arranged that it is held and maintained at an internal pressure which will correspond to all or a selected part of the hydrostatic head of the elevated storage facility. The pressure provided is maintained in excess of any anticipated external pressure caused by wave action or any other externally applied force. For reasons of convenience and for efficiency of operation, it is usually desirable to so construct the submerged tank that it is compartmentalized to a substantial extent. No particular limitations as to shape or size of the submerged facility need be considered. Nevertheless, in one particularly useful form, the submerged tank structure may be a hexagonal configuration in plan and circular in cross section.

Fabricating the structure in this fashion makes it possible, generally, to erect the storage facility on or near land and then transport the components to the desired location for submerging them. By compartmentalizing the components the various sections can be selectively floated or emptied to assist in submerging, leveling, or even floating at a later time. Also, compartmentalizing generally makes possible easier assembly of the unit, as well as positioning it on the floor or bed of the water body without the assistance of a derrick barge. The costs are thus reduced and the use of marine equipment minimized.

By reducing the upper ballasting weight and then filling the lower tank with air, thus making the assembly sufficiently buoyant, the structure can be moved readily. Generally speaking, there is no rigid requirement as to the relative sizes of the submerged and elevated tanks. However, the type of bed, the wave action land the water depth should not be overlooked as imposing some limitations on the proportions. As above noted, it is important that the elevated tank means shall be of such size relative to the submerged tank that when the combination is in operation the weight of the elevated tank facility, plus its full contents added to the structural weight, together with the bracing and support elements which connect to the lower o1 submerged tank means, and, with this, the connections between the two units and the liquid filling the same, shall be adequate to balance any tendency of the submerged tank to rise, and provide stability against movement, if the submerged tank should be filled with water-immiscible liquid of the lower specific gravity than the water itself to overbalance the tank weight and accessories to an extent adequate to introduce buoyancy. As one gauge to calculating the relative sizes, the elevated tank means should be at least that volumetric fraction of the volume of the submerged tank means which is adequate to overcome any tendency to buoyancy resulting from the difference between the specific gravity of the water and the contained water-immiscible substance. Illustrative of one size example, the submerged tank might have a capacity of 24,000 barrels of oil. For this size, a 6,000-barrel capacity divided between the elevated tank structure and the columns will be adequate to anchor the submerged facility. It will also be adequate to satisfy cornmonly encountered wave forces and soil requirements.

For some operations the submerged storage facility may be provided with suitable flange or skirt means which generally extend downwardly in a plane substantially normal to the surface of the water. Such flange or skirt means then can settle into the soft or muddy surface of the water bed or oor to oppose lateral tank movement. The submerged tank facility is also normally expected to settle or seat itself into the water body floor. In some cases, the submerged tank structure may even `be embedded to some depth into the bed.

By the present invention, also, the operation is calculated upon maintaining each of the tanks or storage facilities full of liquid at all times. As the water-immiscible substance is forced into the storage facility, for instance, it floats and displaces water Through the connecting passage between the elevated and submerged tanks, a similar displacement of Water occurs in the elevated tank. With the withdrawal of stored oil from the system, the liquid volume of the oil is replaced by added water.

The invention provides components which serve automatically to maintain this changing character of the volumetric relationship.

With the foregoing structural features in mind, it is apparent that the invention has as one of its primary aims and objects that of providing an offshore storage system of high eficiency, substantial stability at relatively low cost, and yet a facility which can readily be transported to new locations should the need for making such shift arise.

The invention, while having been shown in preferred forms, is subject, of course, to wide variation in structure and it is contemplated that the accompanying drawings will be regarded as illustrative of the principle upon which the invention is based and not limiting to the particular structure represented.

By the drawings,

FIG. 1 represents a perspective view of one form of the apparatus and also, in schematic and partially phantorn form, auxiliary apparatus frequently desirable for use with the combination;

FIG. 2 shows the one form of the selected storage apparatus in elevation;

FIG. 3 is a section taken on the line 3 3 of FIG. 2, looking in the direction of the arrows;

FIG. 4 is a partial sectional view on the line 4 4 of FIGS. 2 and 3 through one of the tank compartment portions of FIG. 2, looking in the direction of the arrows and showing also a guide-rib structure tending to immobilize the unit when rested upon the bed of the body lof water in which it is located;

FIG. 5 is a schematic representation of one suitable control system for determining the inflow and outliow of both the water-immiscible liquid and the water into and out of the storage facility;

yFIG. 6 is also a section generally like that shown by FIG. 4 but showing a modification of the arrangement to locate and position the storage facility and to immobilize the same;

FIG. 7 is a View substantial in plan of a submerged storage tank structure modified from that shown by FIGS. 1, 2 and 3 (and showing a part in sectional detail) with the view taken generally looking in the direction of the arrows shown by line 7 7 of FIG. 2;

FIG. 8 is a sectional View of the modified form of submerged tank structure shfown by FIG, 7, taken along the line 8 8 of FIG. 7 looking in the direction of the arrows;

FIG. 9 is a sectional view taken from substantially the same plane as the showing of FIG. 7 but with a still further modification of the submerged tank structure; and

FIG. l0 is a section through the modied submerged tank structure of FIG. 9, taken along the line 1tl l0 of FIG. 9 looking in the direction of the arrows.

Reference may now be made to FIG. l of the drawings for a general understanding of the nature of the invention. In FIG. 1 the facility is depicted as comprising a submerged storage tank means, generally designated Il, connected with an elevated storage tank structure 13. Both the submerged and the elevated storage tank structures may have various shapes and sizes. One quite satisfactory form for the submerged tank structure in the particular operation depicted is, essentially, hexagonal in plan and circular in any cross section.

The invention will first be described herein with this form `of tank illustrative of a preferred structural form. Consequently, the designation hexagonal may be considered illustrative and not limiting. The submerged tank structure is connected rigidly with the elevated tank means by a selected number of support columns l5. In the form illustrated where three columns are used each is placed approximately 120 apart on both the submerged and elevated storage elements. The columns are braced laterally by an appropriate number of struts 19 which, for the chosen spaced location of the columns, are arranged in generally triangular form. Various other struts Z1 extend between different selected regions of the sup port columns 15 and the lower storage facility. Where necessary, although not shown, additional struts may be located both above and below those spacing struts shown at i9. The upper tank means is usually of the wellknown spherical or spheroidal form.

rl`he assembly including tank element 1l is adapted to be submerged with the connected elevated tank 13 supported above it. The unit is then located within a body of Water, such as the ocean (schematically represented at 22), with the larger lower tank structure 11 rested upon or embedded to any desired extent in the ocean bed or floor (schematically represented at 12). The surface 24- of the water body is likewise schematically reprepresented in FIG. 1 as being the mean high-water mark for average conditions. In the design of the submerged equipment, consideration should be given to the possible turbulence of the water body 22 and the calculated wave movement to be expected. For the elevated tank structu-re Wind forces are significant in the design. However, these matters are essentially design parameters and will not be considered further at this point in the description.

In order to obtain the water-immiscible substance, such as oil, from a drilling operation, it is desirable to have a service platform (schematically shown at 25) arranged and located generally near the tank units. The service platform per se is not a part of this invention. Suiice it,

therefore, to state that it obviously may contain certain pumping equipment, certain maintenance equipment, frequently small buildings and, if desired, even a landing platform 26 for helicopters. The service platform is usually carried upon heavy support members 27 which are secured and braced from the elevated platform 25. The supports extend beneath surface 24 to feet 31 which are anchored in the floor or bed 23 of the water body 22. The anchoring can be of any desired form, such as piles and suitable footings (not shown). Ship 147 can supply men and equipment by means of the dock adjacent thereto.

The cross bracings 2.9 for the support columns 27, as Well as the columns themselves, are designed to withstand any contemplated wind and water stresses, as well as to carry the weight of any equipment loaded upon the platform region Z5, while pumps or other equipment associated with oil drilling and pumping operations (not yspeoiticially shown) are carried upon the platform and supplied With oil from the supply located beneath the water bed or door. After pumping, the recovered oil is supplied, illustratively, through a pipe connection 36 into the submerged storage facility.

In the arrangement shown, it may be assumed, as will be apparent from the discussion of the remaining figures, that the columns 1S which carry the elevated tank structure 13 are of `such nature as to provide therein tubular passages of selected size through which oil may be transmitted from the pumping equipment to the storage tanks proper. The facility is also such that oil which is pumped through the tubular portions of the columns 15 first enters into the upper or elevated storage tank 13 and then passes down through this tank into the submerged storage facility in the form of the tank 11. Water, as will be seen particularly from the showing of FIG. 5 and the control system there depicted, likewise can pass through this common communicating facility.

In refinements, the support columns 15 are protected for a region above and below the average water level surface 24 by schematically represented bumper areas 35 secured to the outer surface of the column. The bumpers may be of any conventional type. They are designed to protect the columns'in the event that any marine equipment or barges may be tied to them. A landing platform 37 is usually arranged adjacent to one of the columns. From this landing platform a stairway 139 is normally arranged to spiral about the column to a service platform and Walkway (schematically designated at 41).

Suitable control equipment (not shown) is positioned on the service platform 141, as will be appa-rent from the discussion of FIG. 5 to follow. A loading boom 43 is usually pivotally attached to one of the support columns. This is connected through suitable conduit or hose elements to receive outiiowing oil from the storage facilities 13 and 11. A discharge-nozzle 145 is at the outer end of the boom, thereby to load vessels to transport the recovered oil to suitable onshore locations. The service platform 25 likewise is normally provided with a landing facility, such as that schematically represented at 26.

Reference may now be made to the more specific structural showing of FIG. 2. The tank structure, as above set out, is so designed that no permanent anchors or piles are required to hold the assembly in position on the door of the water body in which the oil is recovered. This factor permits moving and relocating the assembly should service requirements at any time change.

From what is to follow, it will likewise be apparent that the Weight of the structure, when coupled with the Weight of the contents lin the elevated tank means, as well as the Weight of the supporting columns and struts and the liquid in the columns, provides a permanent ballast that will resist any buoyancy introduced into the submerged storage tank 11 because of the introduction therein of oil all as above also noted. In addition, this weight is sufiicient to resist all force due to wind and waves and swells which might tend to cause the structure to move.

The installation operates on the principle of water displacement. Each of the tanks is at all times filled either vwith oil or with water, or the mixture of oil and water in selected proportions. As oil is removed following the yfilling of the tank, the tank volume previously occupied by oil is then filled with water. Conversely, at times when oil is added to the tanks, lWater is removed.

Generally Speaking, it is preferable to provide the submerged tank structure 11 as a compartmentalized unit. In the illustrated form the compartments are provided by forming the lower, generally hexagonal form, tank y11 with separating partitions or walls of any desired form represented by the diaphragm structures 4u (see particularly FIG. `3). Such partitions can be formed with or Without internal connections. The several compartments effectively divide the submerged tank (where it is hexagonal shape in plan) into six separate units. These connect With the elevated tank means. The formation of the separate compartmentalized structures permits selective ballasting and also insures controlled sinking, leveling and moving, thereby to assist in the general operation.

The submerged tank means 11 must be designed to resist any possible forces which may be experienced externally of the tank, as Well as internally thereof. To this end, in most instances, the tank structure 11 is designed to resist any internal pressure which is created by the hydrostatic head of the elevated tank and the liquid column within the connecting supports that can be considered effectively greater than the external pressure.

The elevated tank structure, as already suggested, is designed not only to carry liquid in the form of either, or both, oil and water, but is also designed with an adequate safety factor to withstand and resist any contemplated wind forces. The support columns 15 must be of adequate strength to carry the load of the elevated tank means and all forces due to wind and wave action.

At this point, reference may now be made to FIG. 5 as illustrative of the manner in which the recovered oil is introduced into the combined storage tank means and transferred between the elevated and submerged tanks. The storage tanks in operation should be full of either oil or water at all times. This is achieved by taking advantage of a water displacement principle of operation which is used for the oil/water transfer system. The oil filling system is provided through the connection 36, as in FIG. l. This serves to provide a transfer path for oil from the production platform 2S to the elevated and submerged storage tank means.

The filling system is substantially automatic, but under the conditions herein to be explained, the loading system by which oil is transferred from the nozzle outlet at the end of the loading boom 43 is described as utilizing manual attention to open and close the loading valve system. The specific arrangement described is purely optional and is illustrated only for the purpose of supplying an explanation of one form of arrangement by which an eiiicient and suitable operation may be achieved, rather than to set forth 'any limiting showing.

As depicted by FIG. 5, the system is generally designed to operate in such fashion -that oil supplied by the pump 39 which receives oil from the surge tank 41 is pumped through the connection inlet 36 to iiow through a valve structure, schematically represented as 43, and then through an inlet passage 44 extending partially through one of the supports 15 to enter internally of the elevated tank 13. At the inlet termination the incoming oil fiows over the upper edges of the schematically represented weir 45. It then can iiow into the storage tank 13 and, as will later be explained, also Iiow into the submerged tank structure 11 with the displacement of water therefrom.

Control of the system is established through the aid of suitable solenoid-operated iioat switches or relays 47, 48 and 49, respectively. These switches control the iilling and emptying of the tank structures. Each switch carries with it a suitable control element in the form of float elements, such as those shown at 50, 51 and 52, respectively. The association of the switch controls with particular valve mechanisms for determining ejection and entrance of water into the system will be pointed out at a later point. However, for simplication of illustration, the specic circuitry to operate the magnetically controlled valves is not shown. As will later be pointed out, the switch 48 has an additional oat element 51 which will also be described at a later point.

The filling of the tank 13 with oil, illustratively, now may be considered. First, it may be assumed that water within the system 'and in the elevated tank means 13 reaches to a level 53. At this time pump structure 39 is activated through control provided through switch 49 to force oil, as recovered by pumping mechanism (not shown) into the inlet Vpipe 36. The oil is then pumped through the valve 43 and connection 44 to flow over the weir 45, valve 71 then optionally either being open or closed. At this time the solenoid-operated valve 54 leading to an outlet to discharge water is opened. Under these circumstances, water which has been held within the tank system is discharged through valve 54 and outlet passage 55. Discharge continues until the water level within the tank 13 reaches a level 56 at which the lower oat element 51 beneath the solenoid switch or relay 48 is used to operate the switch. Connections (not shown) are provided in any desired fashion between the solenoid switch 48 and the valve 54 so that when the switch is operated through the lowering of the water level to the level position shown at 56, the valve 54 is closed. At this time oil introduced by the pumping action of pump 39 continues to flow into the upper tank 13 until it reaches the level 57 shown at the upper float 51 supported beneath the solenoid-operated switch 4S. At this point the switch 48 opens the valve 54 once more, and the cycle repeats.

Filling continues into the tank until the oil which is forced into the upper tank means 13 iows downwardly through the communicating support passage 161 into the lower tank and reaches a state where the oil to water interface level in the submerged tank is that schematically represented at 62. The zero level in the tank is schematically the tank bottom which is shown in FIG. 5 as 64.

When such condition happens, oil within the tank 13 is forced downwardly by the pumping action so as to ilow within the connections 60 thereby to cause the water which has been displaced by the oil to be discharged at the level indicated by the position of the valve 54 and its associated outlet passage 55. This level, as can be appreciated, is a function of the specific gravity of the oil. 1t is so located that the hydrostatic head `between the levels of the outlet tube 67 leading to valve 54 and passage 55 and the level of the oil to water interface, shown at 62, provides a hydrostatic head due to the water which equals the hydrostatic head due to the oil between the upper level 63 where the float 50 supported by the hydrostatic switch 47 is effective and the level 62 of the oil to water interface. With such relationship established, oil is prevented from being discharged out of the waterline 67, even when the oil level is at that height which is represented by the position of the float carried by the solenoid-operated switch 47.

With the upper tank 13 being so filled, in order to load the recovered fuel into carriers for transport to shore positions, a manually operated valve 71 is provided in a connecting relationship to the tubular passage leading between the supply connection 44 and the Weir 45. For such discharge of oil at the outlet terminal 72, which thus would be somewhat analogous to the nozzle 145 discharging water, the valve 71 is manually operated.

At the time valve 71 is opened the pump element 73 commences to pump water obtained from the connection 74 leading below the Waterline surface 24 into the system by way of the connection 76, the valve 77, and then into the communicating passage 60 through the support 15. The inlet of the water into the system occurs at the level 62 of the interface between oil and Water. The water in the system then rises. At the same time the oil which is displaced tlows over the weir 45 and through the tubular connection 44 and back through valve 71 to outlet 72 for discharge. This procedure then continues until the oil to Water interface rises to the level of the Weir 45 overflow at the level 53 represented by the position of the oat element 52 associated with the solenoid-operated switch 49. With the increase in level of 'water within the tank 13, the solenoid-operated switch 49 closes and through a suitable connection (not shown) shuts off the pump 73, thereby to prevent any discharge of water from the outlet connection 72 through valve '71.

Considering this showning, it will be observed that, for selected desired conditions, the valve 71 vmay be opened while oil is supplied through the pipe connection 36 and the valve 431. Under these circumstances, the pumped supplied oil in the pipe connection 36 may be supplied directly to a loading barge, or the like, through the outlet 72. At the same time, any excess so-supplied oil over and above that flowing through the valve 71 will be supplied through the inlet passage 44 in the fashion above described. At times, it is found that this method of connection tends to speed the loading operation and it makes unnecessary complete transfer as above described.

In the showing as in FIG. 5, it may now be appreciated that the solenoid-operated switch 47 With its suspended float 54 functions generally as a safety device when the oil level Within the tank 13 reaches that schematically represented level in which the float is positioned.

On contact it can be seen that the relays thus shut off either the pump 73, or the pump 39, as the case may be. The pump which is shut off is determined by the one which, at the signicant time, is in operation. The shut-off prevents either of the storage tanks from being overowed by either oil or water. With the cessation of an outlet flow of oil through the valve |mechanism 71, the valve can be manually closed by operating upon it from the service platform 141.

The broad operation of the device is set forth as stated above.

At this point reference may be made to FIG. 4, which represents a section through one arm of the assumed hexagonal submerged tank structure 11. The section is generally circular. Depending from the lower portion are one or more guide ange or skirt elements 81. These elements are adapted to force or wedge themselves into the soft or muddy bed or floor of the water body in which the submerged tank structure is located. Such anges or skirts extend substantially along the length of each tank section in a direction generally normal to the plane of the water surface. Where the tank structure is of generally hexagonal form, it is apparent that the submerged tank means, in reality, is located and protected against shifting due to ground swell, Waves, or wind effects on the elevated tank from several directions. It is thus possible to maintain a generally fixed position of the submerged tank 11 in the selected location. Further than this, the submerged tank, of itself, normally tends, by virtue of its own Weight and that of the support structure for the elevated tank which is rigidly secured to it, as well as the columns in which the oil and water passes, to embed itself, at least to some extent, in the bed or oor of the Water body. The flanges or skirts then extend further into the bed thereby to insure the stability of location.

Even in spite of this factor of a stable location it iS usually desirable to provide the connection through the feedline from the pumping mechanism 39 into the storage tank system sufciently exible to preclude any possibility of breakage in the event of minor location shifting.

It is, of course, evident that the submerged tank may also be immobilized by the use of projecting pins or piles extending beneath the submerged tank and into the bed as shown by pins 83 in FIG. 6. This usually is not quite as satisfactory as the skirt or fiange method of FIG. 4, but for some soil and bed conditions is preferable.

In a further modification of the submerged storage structure, as in FIG. 7, the submerged tank is formed as an annulus or single toroid 85. The columns and the struts 21 which connect to the elevated tank structure and which form the bracing are shown in the same relative positions as in FIGS. 2 and 3. The annular ring 85, in most instances, is formed from a number of generally straight plate segments. This is exemplified by the portion of FIG. 7 which is shown in section. The separate straight plate segments 87 are assembled in such fashion that the tank element 85 is circular in cross-section, as shown particularly at 89 in IFIG. 8. When the so-formed tank is embedded in the bed of the Water body, it may conveniently be held in position by a plurality of open-ended cylindrical elements 91 having downwardly extending side members 93 forming the lower end into a substantially tubular configuration. This shaping thus provides increased efficiency in the guiding members by avoiding the use of components acting in single shear, as are the downwardly depending skirts or flanges 81 or the piles 83. In other respects, the tank structure of FIG. 7 is essentially equivalent to the hexagonal-shaped tank of FIGS. 1 through 6, in particular.

The further modified submerged tank arrangement of FIG. 9 uses a substantially pad-like structure rather than the ring to support the submerged unit on the bed or floor of the water body. In this form, as can be seen particularly from FIG. 10, the pad is formed from a number of concentric intersecting toroidal rings of the type shown 'by FIG. 7. In this connection the toroidal rings which intersect are schematically designated as 95, 95', 95", etc., with dividing walls between them represented at 97, 98, 99, 100, etc., thereby to form the different toroidal sections into essentially separate compartments. The compartments may connect as desired and in accordance with the fashion explained in connection with FIG. 3.

The supply of Water and the Water-immiscible fluids in each of these modifications may follow the plan and pattern hereinbefore set out in connection with the showing of FIG. 3 and further exemplified by the diagram of FIG. 5.

While in the foregoing description the submerged and elevated tanks are generally shown as single units, or a single unit formed into various compartments or chambers, it is of course within the contemplation of this invention to provide interconnected multiple units each operating in conjunction with the other and supplied with liquid in accordance with the principles and means above outlined. Likewise, it is apparent that for many configurations of submerged structures relative to elevated tank structures, the number of supports and communicating columns establishing the rigid connection between the submerged and elevated means may vary in number from what is shown by the drawings accompanying this disclosure. Therefore, within the understanding of this description, reference to tank means either elevated or submerged, or support means, shall be broadly construed and not in any sense limited to the specific showing of the drawings for this description.

Various other modifications of the described arrangement of course may be made without departing in any respect from the spirit or scope of What is herein disclosed and, therefore, it is contemplated that the description and claim shall be construed in a scope which is equally as broad as permitted, in the light of the state of the art.

Having now described, the invention, what is claimed is:

1. A storage system for offshore storing of Water-immiscible liquids comprising the combination of a rst storage tank means adapted to be located and submerged on the bed beneath the surface of a body of water and adapted to receive water immiscible liquids and a second storage tank means adapted to be elevated above the surface of the body of water, supporting and communicating means connecting each of said first and second tank means for holding said rst and second tank means in permanently fixed spaced relationship relative to each other and for providing fluid passage therebetween, means to selectively lill said first and second tank means with water and water-immiscible liquid, and means for providing -a permanent ballast having a weight that is greater than the buoyant force which acts upon said combination when it is placed in a body of water to resist movement of said first storage tank means adapted to be positioned beneath the surface of the body of water thereby to insure anchoring of the combination.

2. An offshore system for storing Water-immiscible liquids comprising the combination of a first storage tank means adapted to be submerged beneath the surface of a body of water t-o rest upon the floor thereof and a second storage tank means adapted to be supported in elevated position above the surface of the body of Water, compression load bearing support means for fixedly connecting said first and second tank means in permanently fixed spaced `relationship relative to each other, means to supply and maintain in said first and second tank means a selected proportional relationship of Water and a waterimmiscible liquid, means to provide for .a flow of liquid in selected directions between said first and second storage tank means, said first tank means being of greater volume than said second tank means, and means for providing :a permanent ballast to resist movement of the submerged storage tank means thereby to insure anchoring of the combination free of pilings and external anchoring means.

3. An offshore system for storing water-immiscible liquids comprising the combination of a first storage tank means adapted to be submerged beneath the surface and to rest on the fioor of a body of water and a second storage tank means adapted to be elevated above the submerged storage tank means and the surface of the body of Water, tank supporting means adapted for supporting compression loads and for connecting said first and second storage tank means for holding said first and second tank means in permanently fixed spaced relationship relative to each other, means to selectively and controllably supply Water and water-immiscible liquid to said first and second tank means for storage and discharge, means for providing a permanent ballast to resist movement of the submerged storage tank means thereby to insure anchoring of the combination, and means t-o Withdraw waterimmiscible liquid from said second tank means and simultaneously maintain the liquid volume ywithin said first and second tank means substantially constant;

4. An offshore system for storing: water-immiscible liquids comprising the combination of a first storage tank means adapted t-o be submerged beneath the surface and to rest on the fioor of a body of water and a second storage tank means adapted to be elevated above the submerged storage tank means and the surface of the body of water, tank supporting and communicating means connecting said first and second storage tank means `for holding said rst and second separate tank means in permanently fixed spaced relationship relative to each other and providing for the passage of liquids between said first and second tank means in selected directions, means to selectively and controllably fill said first and second tank means -With water and water-immiscible liquid, means for providing a permanent ballast to resist movement of said first storage tank means thereby to insure anchoring of the -combination free of pilings and external anchoring means, and means to Withdraw Water-immiscible liquid from said second tank means `and simultaneously maintain the liquid volume within said first :and second tank means substantially constant.

`5. A storage system for offshore storing of water-iml 1 miscible liquids comprising a first storage tank means adapted to be located and fixed in a submerged position on the bed beneath the surface of a body of water and a second storage `tank means adapted to be elevated above the surface of the body of Water, both said first and second tank means being adapted to receive water and a water-immiscible liquid; supporting means adapted for supporting compression loads and for connecting said first and said second tank means for holding the first and second tank means in a permanently fixed spaced relationship relative to each other, means connected to said first and second tank means `for establishing `fluid passage between said first and said second tank means; means for supplying said first and said second tank means with Water and water-immiscible liquid; and means for providing a permanent ballast sufiicient to insure that said first storage tank means is prevented from movement and said system is anchored in a substantially fixed position.

6. The storage system as claimed in claim S wherein said first tank means is of hexagonal shape.

7. The system claimed in claim 5 comprising, in addition, a locating yfiange supported upon the lower surface of said first tank means and extending outwardly therefrom in a direction substantially perpendicular to the water surface for restricting tank movement.

8. The storage system as claimed in claim 5 wherein said first tank means comprises a plurality of substantially coplanar intersecting annular members.

9. The system claimed in claim 5 comprising, in addition, a fiange element extending outwardly from the lower surface of said first tank means in a direction substantially perpendicular to the surface of the water in which said first tank means is submerged, said flange extending substantially throughout the periphery of said first tank means.

10. In a tank system of the character claimed in claim 5, the additional components including means for supplying water-immiscible liquid to the tank comprising an inlet connection terminating in an over'fiow Weir within said second tank means, valve means for controlling the inlet, and switch means operating in accordance with the liquid introduced, thereby to control the quantity of waterimmiscible liquid introduced and the ejection of water concurrently therewith.

11. The storage system as claimed in claim S Wherein said first tank means is substantially of annular shape.

12. The system claimed in claim 11 comprising, in addition, -a plurality of cylindrical elements extending downwardly from said first tank means said cylindrical elements having their axes substantially perpendicular to l the surface of the water in which said first tank means is submerged.

13. Offshore storage apparatus comprising the cornbination of at least one first storage tank means adapted to be submerged within a body of water and to rest upon the door of the water body and at least one second tank means being adapted to be elevated above the surface of the body of water, substantially rigid support and communicating means between said first and second tank means for holding said first and second tank means in substantially lfixed spaced relationship relative to each other; each of said tank means being adapted to be lled with a combination of water and water immiscible liquid in chosen volumetric relationships; means to introduce water-immiscible liquid into said first and second tank means through said communicating means and simultaneously withdraw water from the combination; means to control the proportions of water and water-immiscible liquids in said first and second tank means; means to withdraw liquid from said second tank means of the combination; and, the said first and second tank means having relative volumes such that the loaded weight of the second tank means and the support and communicating means and water and water-immiscible liquid therein being a tall times sufficient to provide a ballast sufficient to resist the buoyant force caused 4by said first tank means when it is submerged and contains a water-immiscible liquid which has a lower specific gravity than that of the water in which the tank is submerged.

14. `Offshore storage apparatus comprising the combination of at least one first storage tank means adapted to be submerged within a body of water and to rest upon the floor of the water body;

at least one second tank means being adapted to be elevated above the surface of the body of water;

tripod support members which are adapted for supporting compression loads, said support members fixedly connecting said first and second tank means in permanently xed spaced relationship relative to each other;

liquid passage means connecting said first and second storage tank means for the transporting of water and water-immiscible liquid to said first and second storage tank means;

means for selectively filling said first and second storage tanks with water and water-immiscible liquid; and,

means for providing a ballast having a weight that is greater than the buoyant force which acts upon said apparatus when it is placed in a body of water thereby insuring the anchoring of the combination.

15. A storage system in accordance with claim 14 wherein said first storage tank means is 0f hexagonal shape.

16. A storage system in accordance with claim 14 wherein said second storage tank means is substantially spherically shaped.

17. A storage system in accordance with claim 14 wherein said liquid passage means are disposed within said support members.

18. Offshore storage apparatus comprising the combination of a first storage tank which is of hexagonal shape and adapted to be submerged within a body of water and to rest upon the fioor of the water body;

a second tank which is substantially spherically shaped and adapted to be elevated above the surface of the body of water;

rigid tripod supporting legs adapted for supporting compression loads, said support legs fixedly connecting said first and second tanks in permanently fixed spaced relationship relative to each other;

liquid passage means connecting said first and second storage tank for the transporting of water and water-immiscible liquid to said first and second storage tanks;

means for selectively filling said first and second storage tanks with water and water immiscible liquid; and,

means for providing a ballast having a weight that is greater than the buoyant force which acts upon said apparatus when it is placed in a -body of water thereby insuring the anchoring of the combination.

References Cited UNITED STATES PATENTS 2,908,141 10/1959 Marsh.

3,076,205 2/1963 Schultz 114-5 3,113,699 12/1963 Crawford et al. 61-465 3,159,130 12/196'4 Vos 6l--46.5 X

70 -LAVERNE D. GEIGER, Primary Examiner.

H. S. BELL, Assistant Examiner.

UNITED STATES PATENT oEFICE CERTIFICATE OF CORRECTION Patent No. 3,381 ,481 May 7, 1968 Robert S. Chamberlin et al.

It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 4, line 61, "12" should read 23 Column 8, line 16, "showning" should read showing Column l2, line 4, "a tall" should read at all Signed and sealed this 23rd day of December 1969.

(SEAL) Attest.-

:Edviml M. member, Jr. WILLIAM E. SCHUYLER, JR.

Attesting Officer Commissioner of Patents