BRPI1008151B1 - method for implementing a gas storage container below the water surface and system for storing an underwater gas - Google Patents

Abstract

METHOD FOR EXTENDING A GAS STORAGE CONTAINER UNDER THE WATER SURFACE, AND, SYSTEM FOR STORING A SUBMARINE GAS A method for extending a gas storage container below the surface of the water which comprises coupling an upper end of the storage container is described. gas in a deployment device positioned on the water surface. The gas storage container has a total dry weight and a lower end opposite the upper end. The gas storage container also includes a storage tank defining an inner region inside the tank and an outer region outside the tank. Furthermore, the method comprises lowering the gas storage container below the water surface with the deployment apparatus. Additionally, the method comprises pumping a buoyancy control gas into the inner region of the tank. The buoyancy control gas in the inner region of the tank generates a buoyant force that acts on the gas storage container.

Description

DECLARATION ON RESEARCH AND DEVELOPMENT SPONSORED BY THE FEDERAL GOVERNMENT

[001] Not applicable.

BACKGROUND OF THE INVENTION Field of the Invention

[002] The invention relates in general to subsea gas storage systems. More particularly, the invention relates to the implementation and removal of subsea gas storage systems.

Fundamentals of Technology

[003] Oil at standard temperature and pressure conditions (CNTP) is a relatively dense liquid and is therefore suitable for transportation by tankers and storage in tanks, thus enabling a global market for oil. However, since natural gas is a CNTP gas, it is less suitable for transportation by tankers and storage in tanks. Consequently, most of the natural gas is transported through pipelines, which are based on a local source or supply, thus limiting natural gas to a general local market.

[004] A primary challenge in the development of a global natural gas industry is that natural gas, in CNTPs, is extremely diffuse, and thus has relatively little economic value, for a given volume, compared to oil (a difference of three orders of magnitude at $ 7 / MCF for natural gas and $ 50 / BBL for oil). Because of this difference in economic value for a given volume of natural gas vs. oil and the gaseous state of natural gas at CNTP, transporting natural gas over CNTP over long distances is not economically viable. Various methods for achieving more favorable gas value ratios for a given volume, such as compressing or liquefying natural gas, are commonly used to make the transmission and storage of natural gas more economically attractive. Compression is the most commonly used method used to transport natural gas in piping systems. For sea transport, liquefaction is used to create Liquefied Natural Gas (GLN) and compression is used to create Compressed Natural Gas (LPG). However, once natural gas has reached its desired destination, LNG and LPG undergo some processing to adjust the natural gas to conditions (for example, pressure, temperature, etc.) suitable for standard piping systems.

[005] Like transport, the storage of natural gas has also presented challenges. Natural gas at CNTP is normally stored in relatively large underground natural caves. In such cases, the storage of natural gas depends on the location and availability of such underground storage caves (for example, underground natural salt caves). Additionally, there have been many accidents related to these caves, including fires and explosions. GLN and GLP also have storage complications. Typically, GLN is stored offshore in pressurized or cryogenic containment tanks, both of which are relatively expensive and dangerous. Because of the risks and dangers of LNG storage on land, it has also become increasingly difficult to locate LNG regasification units in spite of the large market demands. GNP has not been used for natural gas storage, possibly because of the lack of availability of efficient storage media.

[006] Submarine oil storage systems have been implemented on the ocean floor, namely, the Harding platform in the North Sea and Dubai Oil Storage tanks in the Middle East. However, subsea storage of natural gas has not yet been achieved, although it offers some important technical advantages over conventional onshore gas storage systems and methods. The US patent specification 2008/0041291 and 2009/0010717, each of which is hereby incorporated by reference in its entirety for all purposes, reveals apparatus and methods for storing natural gas, both GLN and GNP, on the floor oceanic. Although the apparatus and methods revealed in these publications offer some advantages, more conceivable mechanisms for the implementation, removal and repositioning of the revealed systems involve devices that are relatively complicated and complex.

[007] Thus, there is still a need in technology for natural gas storage systems. Such systems and methods would be particularly well received if they offered the potential for little danger and risks to life and property, and could be implemented and repositioned with conventional equipment.

SUMMARY OF THE INVENTION

[008] These and other needs in technology are addressed in a modality by a method to implement a gas storage container below the surface of the water. In one embodiment, the method comprises (a) coupling an upper end of the gas storage container to an implementation apparatus positioned on the water surface. The gas storage container has a total dry weight and a lower end opposite the upper end. The gas storage container also includes a storage tank defining an inner region inside the tank and an outer region outside the tank. Furthermore, the method comprises (b) lowering the gas storage container below the water surface with the implementation apparatus. In addition, the method comprises (c) pumping a flotation control gas to the inner region of the tank for (b). The flotation control gas in the inner region of the tank generates a flotation force that acts on the gas storage container for (b).

[009] These and other needs in technology are addressed in another modality by a method. In one embodiment, the method comprises (a) arranging a gas storage container on the ocean floor. The gas storage container has an upper end distal to the ocean floor and a lower end fitting the ocean floor and includes a gas storage tank defining an inner region inside the tank and an outer region outside the tank. The gas storage tank also includes a first inlet for fluid communication with the inner region, a first valve that controls the flow of fluid through the first inlet, a port for fluid communication with the inner and outer region. Furthermore, the method comprises (b) pumping a buoyancy control gas through the first valve and the first inlet to the inner region to generate a buoyant force acting on the gas storage vessel. Additionally, the method involves displacing water in the internal region with the flotation control gas. In addition, the method comprises (d) draining water through the door from the inner region to the outer region. In addition, the method comprises moving the gas storage container from the ocean floor towards the surface.

[0010] These and other needs in technology are addressed in another way by a system for storing underwater gas. In one embodiment, the system comprises an underwater gas storage container. The storage container includes a gas storage tank defining an inner region inside the tank and an outer region outside the tank. The tank has an upper end and a lower end opposite the upper end. The gas storage tank also includes a gas inlet adapted to flow the gas to the inner region, the air inlet adapted to drain air to the inner region, a port in fluid communication with the inner region and the outer region. In addition, the gas storage tank includes a valve adapted to control the flow of gas through the gas inlet. In addition, the gas storage tank includes a valve adapted to control the flow of air through the air inlet.

[0011] Thus, modalities described herein comprise a combination of features and advantages designed to address various drawbacks associated with certain devices, systems and methods of the prior art. These various features described above, as well as other resources, will be easily apparent to those skilled in the art by reading the following detailed description, and by reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] For a detailed description of the preferred embodiments of the invention, reference will now be made to the accompanying drawings, in which:

[0013] Figure 1 is a schematic cross-sectional view of an embodiment of an underwater gas storage container;

[0014] Figure 2 is a schematic cross-sectional view of the subsea gas storage container of figure 1 during subsea implementation;

[0015] Figure 3 is a schematic cross-sectional view of the subsea gas storage container of figure 1 during anchoring on the ocean floor;

[0016] Figure 4 is a schematic cross-sectional view of the subsea gas storage container of figure 1 anchored on the ocean floor for subsea gas storage operations;

[0017] Figure 5 is a schematic cross-sectional view of the subsea gas storage container of figure 1 during the removal of the ocean floor from removal and / or repositioning operations;

[0018] Figure 6 is a schematic cross-sectional view of the subsea gas storage container of figure 1 during the lifting phase of the removal and / or repositioning operations;

[0019] Figure 7 is a schematic cross-sectional view of the subsea gas storage container of figure 4 illustrating the hydrostatic pressure of sea water and the pressure of the stored gas;

[0020] Figure 8 is a schematic view of a system for supplying gas and extracting gas from the subsea gas storage container of figure 4;

[0021] Figure 9 is a schematic cross-sectional view of an embodiment of an underwater gas storage container anchored on the ocean floor for underwater gas storage operations;

[0022] Figure 10 is a schematic cross-sectional view of an embodiment of an underwater gas storage container anchored on the ocean floor for underwater gas storage operations;

[0023] Figure 11 is a modality of a combined water / air pumping system to implement the subsea gas storage container of figure 1;

[0024] Figure 12 is a front view of an embodiment of a compartmentalized underwater gas storage container;

[0025] Figure 13 is a schematic top view of the subsea gas storage container of figure 11;

[0026] Figure 14 is a schematic cross-sectional view of the subsea gas storage container of figure 11; and

[0027] Figures 15 and 16 are schematic views of the implementation system for implementing, removing, lifting and repositioning the subsea gas storage container.

DETAILED DESCRIPTION OF THE INVENTION

[0028] The following discussion is concerned with various modalities of the invention. Although one or more of these modalities may be preferred, the disclosed modalities should not be interpreted, or otherwise used, as a limitation on the scope of the disclosure, including the claims. In addition, those skilled in the art understand that the following description has a wide application, and the discussion of any modality should only be exemplary of that modality, and is not intended to imply that the scope of the disclosure, including the claims, is limited to that modality.

[0029] Certain terms are used throughout the following description and claims to refer to particular features or components. As is apparent to those skilled in the art, different people can refer to the same resource or component by different names. This document is not intended to distinguish components or features that differ in name, but in function. The figures in the drawing are not necessarily to scale. Certain features and components here may be shown exaggerated in scale, or in a somewhat schematic form, and some details of conventional elements may not be shown for the sake of clarity and conciseness.

[0030] In the following discussion and in the claims, the terms "including" and "comprising" are used in a comprehensive manner, and thus should be interpreted as "including, but without limitations". Also, the terms "couple" or "couple" must mean both an indirect and a direct connection. Thus, if a first device is coupled to a second device, that connection can be through a direct connection, or through an indirect connection through other devices, components and connections. Furthermore, in the form used here, the terms "axially" and "axially" generally mean along or parallel to a central axis (for example, the central axis of a body or a door), while the terms "radial" and “Radially” means generally perpendicular to the central axis. For example, an axial distance refers to a distance measured along or parallel to the central axis, and a radial distance means a distance measured perpendicular to the central axis.

[0031] Modalities described herein comprise a combination of features and advantages designed to address various drawbacks associated with certain prior art devices, systems and methods. For example, modalities described here provide apparatus, systems and methods for installing and removing underwater gas storage that offer the potential for hydrate prevention / overflow implementation, relocation and control, compared to conventional apparatus, systems and methods. The various characteristics described above, as well as other resources, will be easily apparent to those skilled in the art by reading the following description, and referring to the attached drawings.

[0032] Referring now to figures 1-6, a modality of an underwater gas storage apparatus or container 10 is shown schematically. In figure 1, container 10 is shown on the sea surface before being submerged at the bottom of the sea. sea; in figure 2, the container 10 is shown being lowered into the sea water 3 for underwater implementation; in figure 3, the container 10 is shown being anchored on the ocean floor 4; in figure 4, the container 10 is shown anchored on the ocean floor 4 during subsea gas storage operations; in figure 5, the container 10 is shown disengaging from the ocean floor 4 during removal and / or repositioning operations; and, in figure 6, the container 10 is shown being lifted off the ocean floor 4 after the ocean floor 4 has been disengaged during removal and / or repositioning operations.

The container 10 has a central or longitudinal axis 15 and extends between an upper end 10a and a lower end 10b. Furthermore, container 10 includes a thin-walled rigid storage tank 20, a mud skirt 30 at the lower end 10b, and a ballast chamber 40 containing ballast 41 near the lower end 10b between the tank 20 and the skirt 30 Container 10 is designed to be deployed and positioned underwater in a vertical orientation with the axis 15 generally perpendicular to the ocean floor and the upper end 10a positioned above the lower end 10b. As will be described in more detail below, during implementation operations, the design of the container 10 including the ballast chamber 40 and associated ballast 41 below the tank 20 improves the stability of the container 10, since the center of gravity of the container 10 is positioned below the float center of the container 10.

[0034] Referring further to figures 1-6, the relatively thin-walled tank 20 functions as a gas storage tank. Tank 20 comprises rigid walls preferably made of steel or composite material. For a typical steel design, the wall thickness would basically depend on the predicted pressure differential observed in tank 20. For most subsea applications, the wall thickness will vary from about 0.5 inch (12.7 millimeters) to about 1.5 inch (38.1 millimeters). The walls may include reinforcement ribs (not shown) to assist in reinforcing the walls. The reinforcement ribs can be both inside and outside the tank, with a preference for the outside of the tank because of its ease of construction and inspection. Additionally, the placement of reinforcement ribs on the outside of the tank (for example, tank 20) prevents the ribs from interfering with the mechanical gas storage equipment arranged inside the tank, such as the gas storage bag 50 described in more detail. Next. The top of the tank 20 can be formed from either a hemispherical or elliptical head typical of pressure vessel fabrication. It can alternatively be a reinforced panel construction with a flat top surface.

[0035] The storage tank 20 defines an inner region or chamber 21 inside the tank 20 and an outer region 22 outside the tank 20. In this embodiment, a flexible gas storage bag 50 is arranged inside the inner chamber 21, thus dividing chamber 21 in a first region 21a within chamber 21 and bag 50, and a second region 21b within chamber 21, but outside bag 50. Furthermore, gas storage bag 50 includes a stored gas port 51. It should be noted that when the bag 50 is collapsed (i.e., emptied), the volume of the second region 21b is close to zero.

[0036] The storage tank also includes a buoyancy control gas outlet 23 and a buoyancy control gas inlet 24, each in fluid communication with the second region 21b. In this embodiment, the buoyancy control gas outlet 23 is at the upper end 10a, and the buoyancy control gas inlet 24 is positioned distal from the upper end 10a and proximal to the ballast chamber 40. Airflow 6 outward and into the second region 21b through outlet 23 and inlet 24, respectively, is controlled by an outlet valve 23a and an inlet valve 24a, respectively. Although the flotation control gas 6 can comprise any suitable gas, in embodiments described herein, the flotation control gas 6 is air, and thus the flotation control gas 6 can also be referred to as air 6. As shown in the figures 2 and 5, during implementation of the container 10 and detaching the container 10 from the ocean floor 4, air 6 is pumped through the inlet 24 and the associated valve 24a to the second region 21b to maintain or increase the buoyant forces acting on the container 10 ; and, as shown in figure 3, during anchoring of the container 10 on the ocean floor 4, air 6 in the second region 21b is exhausted through the outlet 23 and associated valve 23a in the sea water 3 outside the tank 20 to decrease the buoyancy forces that act on container 10.

[0037] Referring further to figures 1-6, the storage tank 20 also includes a stored gas conduit 25 in fluid communication with the stored gas port 51 in the gas storage bag 50. In this embodiment, the conduit of stored gas 25 and gas port 51 are positioned at the upper end 10a, however, in other embodiments, the stored gas duct (eg, stored gas duct 25) and the gas port (for example, gas port 51) can be arranged in other suitable locations. The flow of stored gas 5 into or out of gas storage bag 50 through conduit 25 and gas port 51 is controlled by a valve 25a. In this embodiment, a conduit 25, port 51 and valve 25a are used to drain the stored gas 5 into and out of the storage tank 20. In another embodiment, more than one conduit (for example, conduit 25), gas port (for example, gas port 51) and valve (for example, valve 25) can be used to flow the storage gas to the tank (for example, tank 20). A control system (not shown) can be used to control each valve 23, 24, 25 from the surface.

[0038] The storage tank 20 additionally includes a through port 26 distal from the upper end 10a and generally proximal to the ballast chamber 40. Port 26 is essentially a through hole or opening in the lower portion of the storage tank 20 that allows communication of fluid between the outer region 22 and the second region 21b. It should be noted that the flow through port 26 is not controlled by a valve or other flow control device. Thus, port 26 allows free flow of fluid between regions 21b, 22. Without being limited by this or any other particular theory, the flow of fluid through port 26 will depend on the depth of container 10 and the associated hydrostatic pressure of water. 5, the pressure of the stored gas 5 in the first region 21b (if any) and the pressure of the buoyancy control gas in the second storage region 21b (if any). During subsea gas implementation and storage operations (figures 2 and 4), sea water 3 can seep through port 26 into or out of tank 2 and the second region 21b; during anchoring operations (figure 3), sea water 3 seeps through port 26 to tank 20 and the second region 21b; during disengagement of container 10 from the ocean floor 4 (figure 5), sea water 3 seeps through port 26 out of tank 20 and the second region 21b; and, during lifting operations (figure 6), air 6 flows out of the tank and the second region 21b.

[0039] Referring specifically to figure 1, in general, the tank 20 and the container 10 can have any suitable geometry including, without limitation, rectangular, cylindrical, spherical, etc., and any suitable size. In general, the size of the tank 20 and the container 10 will depend, at least in part, on the desired volume within the tank 20 for gas storage. In this embodiment, the container 10 and the tank 20 are cylindrical. In addition, the tank 20 and the container 10 can be of any suitable size. In general, the size of the tank 20 and the container 10 will depend, at least in part, on the desired volume within the tank 20 for gas storage. The container 10 has a total axial length L10 measured between the ends 10a, b, and the tank 20 has a total axial length L20 measured between the upper end 10a and the ballast chamber 40. In addition, the container 10 has an outer diameter maximum D10 and tank 20 has a maximum external diameter D20. In this embodiment, the diameter D10 and the diameter D20 are the same. In general, container 10 and tank 20 can have any suitable length L10, L20 and diameters D10, D20. For most subsea gas storage applications, the length L10 is preferably at least 50 feet (15.24 meters) . In an exemplary embodiment, the length L10 is about 50 feet (15.24 meters), L20 is about 40 feet (12.19 meters), and the diameters D10, D20 are preferably each about 26 feet (7, 92 meters). The primary design considerations when determining lengths L10, L10 and diameters D10, D20 are the total gas storage volume and dry weight of the container 10. To maintain a given gas storage volume as the diameter (for example , diameter D20) increases, the length of the tank (for example, length L20) decreases, and vice versa. In addition, as will be described in more detail below, as the length of the tank decreases, the pressure requirements of the tank design decrease (that is, the maximum pressure differential that the tank has to be designed to support decreases). Thus, to reduce the design pressure requirements of the tank for a particular gas storage volume, the diameter or width of the tank can be increased and the length or height of the tank can be decreased. A larger tank diameter can also improve the anchoring capabilities for a given volume of gas storage in the tank. On the other hand, it should be noted that the dynamic loading observed by the container (for example, container 10) during underwater implementation and removal increases with the diameter or width of the tank. Consequently, the final geometry of the container and associated tank can also be influenced by the pressure requirements of the tank design, the anchoring requirements and consideration of dynamic loads observed by the tank during underwater implementation and removal.

[0040] The flexible gas storage bag 50 is designed to expand when the pressure in the first region 21a is greater than the pressure in the second region 21b, and to contract when the pressure in the first region 21a is less than the pressure in the second region 21b . In addition, when the first region 21a is substantially empty, the flexible storage bag 50 assumes a generally collapsed configuration. For example, as best shown in figures 2, 3, 5 and 6, during the implementation, anchoring, removal and lifting operations, the first region 21a is substantially empty and the bag 50 is collapsed. However, as shown in figure 4, during subsea gas storage operations, the first region 21a is at least partially filled with stored gas 5 and the bag 50 is expanded at least partially. In addition, as shown in figures 2, 3, 5 and 6, during implementation, anchoring, removal and lifting operations, the second region 21b comprises sea water 3 and air 6; and, as shown in figure 4, during subsea gas storage operations, the second region 21b comprises sea water 3.

[0041] Referring briefly to figure 4, modalities described here are generally aimed at undersea storage of natural gas, in which case stored gas 5 is natural gas. However, in general, the stored gas (for example, stored gas 5) can be any gas for which submarine storage is desired (for example, CO2). For storage of submarine natural gas (ie stored gas 5 is natural gas), bag 50 provides physical separation of stored gas 5 in the first region 21a and sea water 3 in the second region 21b, thereby reducing and / or eliminating the potential for undesirable hydrate formation and undesirable methane releases.

[0042] In general, bag 50 can comprise any flexible, malleable and expandable bag suitable for gas storage. A variety of gas storage bags currently on the market can be used for the 50 bag. An example of a bag that can be used for the 50 bag is the Large Fuel Bladdeer manufactured and sold by Interstate Products of Sarasota, Florida. Most conventional gas storage bags are made of vinyl, polyester or flexible, malleable and expandable polymer material. For relatively large tanks that provide a relatively large gas storage volume, conventional gas storage bags may be unsuitable (for example, not able to handle the desired gas storage volume and / or pressures) and / or cost prohibitive for design and construction. Consequently, for relatively large gas storage tanks, it may be desirable to provide multiple gas storage bags or a compartmentalized tank, each compartment having its own dedicated gas storage bag. Either way, each bag must be placed in fluid communication with the stored gas line so that the stored gas can flow in and out of each bag or compartment. Such designs may allow the use of conventional gas storage bags, or the design of new inexpensive bags. In addition, such designs can provide some advantages in terms of minimizing environmental impacts, should a relatively small bag or compartment break, compared to the rupture of a single large bag.

[0043] Referring briefly to figure 7, the hydrostatic pressure 61 and associated seawater forces 3 in the outer region 22, the pressure 62 and associated seawater forces 3 in the second region 21b inside the tank 20 and the pressure 63 and associated forces of the gas stored 5 in the bag 50 are shown schematically during subsea gas storage operations. Without being limited by this or any particular theory, the hydrostatic pressure 61 of sea water 3 outside tank 20 increases with depth and, since port 26 allows free movement of sea water 3 in and out of the tank 20, seawater pressure 62 within tank 20 also varies with depth and corresponds to hydrostatic pressure 61 of seawater 3 in outer region 22 at equivalent depth. In addition, without being limited by this or any particular theory, although the pressure 63 of the gas stored 5 in bag 5 may vary over time (for example, as gas 5 is pumped into or removed from bag 50), the pressure 63 of gas stored 5 in bag 50 and in the first region 21a is substantially uniform everywhere within bag 50. In particular, the gas pressure gradient is relatively small compared to the water pressure gradient and therefore , the gas pressure differential at the height of the bag (eg bag 50) is negligible.

[0044] During subsea gas storage operations, if the pressure 63 of the stored gas 5 in the bag 50 is less than the pressure 62 of the sea water 3 in the second region 21b in a region along the interface 27 of the bag 50 and the sea water 3 in tank 20, then bag 50 will be compressed in that region and sea water 3 will flow into tank 20 through port 26. However, if the pressure 63 of gas stored 5 in bag 50 is greater than the pressure 62 of seawater in a region along interface 26, then bag 50 will expand in that region and seawater 3 will flow out of tank 20 through port 26. Thus, bag 50 and the gas stored inside bag 5 will compress and expand based on any pressure differential across the bag 50 along interface 27. Since the pressure 62 of any seawater 3 inside the tank 20 decreases as the depth decreases, any pressure differential between the gas pressure 63 and water pressure 62 inside tank 20 will tend to be the largest near the upper end 10a.

[0045] Flexible bags for gas storage may rupture or burst if the pressure inside the bag is sufficiently greater than the pressure outside the bag. In other words, flexible gas storage bags are typically designed and classified to withstand a maximum pressure differential, which can be referred to as a “burst” or “burst” pressure differential. During the radial expansion of the bag 50 (that is, before the bag 50 fits the wall of the tank 20), the bag 50 is subjected to the pressure differential between the stored gas 5 in the bag 50 and the sea water 3 radially positioned between the bag 50 and tank 20 in the second region 21b. The maximum pressure differential observed by the bag 50 during radial expansion is the pressure differential close to the upper end 10a. Bag 50 is preferably designed to withstand the maximum pressure differential predicted near the upper end 10a during radial expansion, and designed and sized to expand radially outward to fit with the walls of the tank 20 before the maximum pressure differential near the end upper 10a to reach the overflow pressure differential of bag 50. For example, as shown schematically in figure 1, the upper portion of the bag (for example, bag 50) can be oversized (that is, larger than the lower portion of the bag) to ensure that the top portion of the bag subject the maximum pressure differential during radial expansion fits the rigid tank walls before the burst pressure differential is reached. Since the bag 50 expands to fit with the tank 20, the rigid walls of the tank 20 (opposite the bag 50) support the maximum pressure differential. Thus, tank 20 is preferably designed to withstand at least the maximum pressure differential predicted between hydrostatic pressure 61 and pressure 63 near the upper end 10a.

[0046] Referring again to figures 1-6, the skirt 30 works to positively fit the ocean floor 4 and restrict and / or prevent the lateral movement of the container 10 once positioned on the ocean floor 4 for gas storage operations. The skirt 30 extends axially downward from the ballast chamber 40 and circumferentially around the entire periphery of the container 10, thereby defining a recess 31 at the lower end 10b. As shown in figure 3, during anchoring of the container 10, the container 10 is pushed downwards and the skirt 30 is pushed onto the ocean floor 4. As the skirt 30 penetrates the ocean floor 4, the recess 31 is filled with mud. The lateral movement of the container 10 is restricted by the mud that fits both the inside and the outside of the skirt 30, as well as the suction that can arise within the recess 31 between the container 10 and the ocean floor 4.

[0047] During the anchoring of the container 10 on the ocean floor 4 (figure 3) and underwater gas storage operations (figure 4), suction forces within the recess 31 between the container 10 and the ocean floor 4 is generally desirable, since this tends to push the container 10 into place in the present invention 4 and resist the movement of the container 10, once seated on the ocean floor 4. However, during operations to remove and / or reposition the container 10, such suction forces they are undesirable because they increase the vertical lift force that has to be exerted on the container 10 to lift the container 10 off the ocean floor 4. Consequently, in this embodiment, the container 10 includes a suction control device 34 which can increase or decrease the suction forces in the recess 31. The suction control apparatus 34 comprises a fluid conduit 35 extending to recess 31 and a valve 36. The fluid conduit 35 is in fluid communication with recess 31 and valve 36 controls the flow of fluid in and out of recess 31 - when valve 36 is in a closed position, flow through conduit 34 is restricted and / or impeded and, when valve 36 is in a closed position, flow through conduit 34 is allowed.

[0048] The suction control apparatus 34 is operated controllably to increase or decrease the suction forces within the recess 31, in the desired manner. As shown in figure 3, while anchoring the container 10 to the ocean floor 4, the suction control device 34 can be used to generate and / or increase the suction forces in the recess 31 to pull the container 10 to fit with the ocean floor 4 and propel the skirt 30 towards the ocean floor 4. Suction forces in the recess 31 can also be generated and / or increased by the suction control device 34 during subsea gas storage operations (figure 4) to ensure that the container 10 be properly seated on the ocean floor 4 in the desired orientation. Suction forces inside recess 31 are generated and / or increased with the suction control device 34 by opening valve 36 (if not yet open) and pumping a mixture of seawater mud (designated by reference number 7) out of recess 31 through conduit 35 and valve 36. On the contrary, as shown in figure 5, to initiate the disengagement of container 10 from the ocean floor 4, such control device 34 can be used to reduce suction forces in the recess 31. In particular, suction forces within recess 31 are reduced with the suction control device 34 by opening valve 36 (if not yet open) and pumping sea water 3 through conduit 35 and valve 36 to inside the recess 31.

[0049] Referring again to figures 1-6, as previously described, ballast 41 is contained in ballast chamber 40. In general, ballast 41 can comprise any type of ballast. For example, ballast 41 may comprise permanent solid ballasts (for example, concrete ballast), removable solid ballasts (for example, hematite, magnetite, etc.), seawater 5 or combinations thereof. However, to minimize the volume and size of the ballast chamber 40, while still providing sufficient weight, ballast 41 is preferably a relatively dense solid ballast, such as hematite or magnetite.

[0050] Ballast 41 can be installed in ballast chamber 40 on the surface or at a depth. Installing ballast 41 on the surface is usually easier, since it is more easily monitored and controlled. However, the installation of ballast 41 on the surface can increase the demands on the crane (or other device on the surface) which controllably implements the container 10 from the surface.

[0051] In general, ballast 41 counterbalances the vertical fluctuation forces resulting from stored gas 5 and / or air 6 in tank 20. The amount and weight of ballast 41 is chosen to achieve the desired total dry weight of container 10. For embodiments described herein, the dry weight of the container 10 is preferably greater than the total buoyancy forces acting on the container during all operational phases of the container 10 (for example, implementation, anchoring, gas storage, detaching, removing and repositioning the container 10). During implementation and anchoring of the container 10 (figures 2 and 3), the difference between the dry weight of the container 10 and the buoyant forces acting on the container 10 allows the submersion and lowering of the container 10 on the seabed; during gas storage operations (figure 4), the difference between the dry weight of the container 10 and the buoyant forces acting on the container 10 restricts the movement of the container 10 and maintains the position of the container 10 on the ocean floor 4; during disengagement of container 10 from the ocean floor (figure 5) and elevation of container 10 (figure 6) for removal and / or repositioning, the differences between the dry weight of container 10 and the buoyant forces acting on container 10 allows for elevation controlled and managed, as will be described in more detail below.

[0052] The implementation of a large container or gas storage system on the ocean floor from a floating vessel involves some challenges that are not typical of most marine operations and subsea installations because of the relatively large size and weight of the container. gas storage compared to standard subsea equipment (eg, cranes) and associated lifting facilities. Because of the relatively large size and weight of an underwater gas storage container, the static implementation loads can be quite expressive, and in addition there may also be large dynamic loads associated with the relative movement between the gas storage container and the container of the floating installation during the installation itself. In particular, the static charge alone of a reasonably sized and practical submarine gas storage container implemented with gravity anchoring will significantly reduce and limit the total number of potential installation containers available worldwide. Some, if any, of the installation containers capable of handling the expected static loads are designed to provide sink compensation and thus are unlikely to be qualified to handle the expected dynamic implementation loads. Consequently, the implementation methods described herein use buoyant forces to decrease the required lifting capacity and circumferential load of the surface equipment used to implement the gas storage container.

[0053] Referring now to figure 2, during underwater implementation of container 10, flotation control gas or air 6 is used to reduce the static charge of container 10. Specifically, container 10 is connected at the top end 10a to a implement on the surface, such as a crane. As previously described, the dry weight of the container 10 is preferably greater than the maximum buoyant forces acting on the container 10 during implementation and thus the container 10 naturally wants to start sinking. It should be noted that the maximum possible buoyant forces resulting from air 6 in tank 20 during implementation occur when the second region 21b is completely filled with air 6 from the upper end 10a to port 26. No greater buoyancy can be achieved during implementation, since any additional air volume simply leaves tank 20 through port 26.

[0054] The implementation apparatus connected at the upper end 10a applies a vertical lift force upwards at the upper end 10a and from the container 10 to manage and control the rate at which the container 10 submerges in the sea. The vertical lift force exerted by the implementation apparatus can also be referred to with the circumferential load. The lift applied to the upper end 10a and the design of the container 10 with its buoyancy center above its center of gravity maintain the substantially vertical orientation of the container 10 during implementation. As container 10 is lowered into the sea, sea water 3 in the outer region 22 flows through port 26 to the second region 21b inside the tank 20. With valve 23a closed, as container 10 is below, sea water 3 continues to flow into the second region 21b and the air 6 in the second region 21b is compressed according to the ideal gas law. As a result, the buoyant force acting on the container 10 decreases. This effect tends to be the largest near the sea surface because the initial air pressure 6 in the second region 21b is relatively low, and a small increase in the depth of the water can drastically reduce the buoyancy of container 10. However, the greatest depths, the change in air pressure 6 in the second region 21b for a given change in depth is constant (linear with water density), however, the initial air pressure 6 is relatively high, and thus the volume of air 6 in the second region 21b is much smaller.

[0055] With no action to counteract the decrease in buoyancy forces acting on the container 10 as it is lowered into the sea, the maximum circumferential load capacity of the implementation device on the surface can be exceeded, potentially resulting in damage to the device of implementation and / or loss of control of the implementation of container 10. However, during implementation of the modalities described here, valve 24a is opened and air 6 is pumped through valve 24a and inlet 24 to the second region 21b of tank 20 during the implementation process to maintain sufficient buoyancy. In particular, during implementation, detaching, removing and repositioning the container 10 (i.e., any time the surface implementing apparatus applies a holding force to the container 10) the total weight of the container 10 minus the buoyancy force is preferably greater than zero (to prevent an uncontrolled rise of the container 10) and less than the maximum circumferential load capacity of the implementing apparatus (to ensure that the maximum circumferential load capacity is not exceeded).

[0056] Air pumping 6 to the second region 21b during implementation can be achieved on the surface very efficiently with standard marine compressors, which are generally suitable for high volume and low pressure specifications. However, as the depth of the container 10 increases and the air 6 in the second region 21b continues to be compressed, the pumping requirements increase, and thus larger and / or more specialized marine compressors may be required.

[0057] Referring now to figure 3, once the container 10 reaches the ocean floor 4, the skirt 30 starts to contact and penetrate the ocean floor 4. To anchor the container 10 on the ocean floor 4, the valve 24a is closed and the pumping of air 6 through the inlet 24 to the second region 21b is interrupted, and the valve 23a is opened to allow any air 6 in the second region 21b to leave the inner region 21b. As air 6 exits tank 20 over the surface, seawater 3 seeps through port 26 and fills the rest of the second region 21b, thereby reducing and / or eliminating the buoyant forces acting on container 10. As the buoyant forces decrease, the skirt 30 penetrates the ocean floor 4 further by the weight of the container 10. To improve the seating of the container 10, the suction control device 34 can be used, as previously described, to increase the suction force in recess 31 and push container 10 further into the ocean floor 4. Once the anchoring is completed, valve 23a can be closed, the implementing apparatus can be decoupled from container 10, a gas supply it can be coupled to conduit 25, and valve 25a can be opened to allow gas to flow 5 into the gas storage bag 50.

[0058] As previously described, a gravity-based anchoring technique is employed to anchor container 10 to the ocean floor 4. Specifically, ballast 41 is a fixed ballast that provides a sufficient load to anchor container 10 to the ocean floor 4. However, in other embodiments, alternative means of anchoring can be used to attach the subsea gas storage container (eg container 10) to the ocean floor. For example, pegs can be used to anchor the container to the ocean floor. Piles can be driven, sucked, blasted, or combinations of these. Although alternative anchoring techniques can be employed, gravity anchoring is generally more suitable for repositioning operations in which container 10 is lifted from the location on the ocean floor 4 and moves to a different location on the ocean floor 4. In such cases, the use of gravity anchoring eliminates the need to implement additional piles on the seabed and buries the new piles in the ocean floor 4 to anchor container 10 in its new location.

[0059] Referring now to figure 6, during gas storage operations, valve 25a is opened and valves 23a, 24a are closed. As the volume of gas 5 in the bag 50 increases, the resulting buoyant forces also increase. However, as previously described, the quantity and weight of ballast 41 is established in such a way that the total weight of the container 10 is greater than the maximum possible buoyancy forces resulting from the stored gas 5. Consequently, the container 10 remains anchored on the ocean floor. 4 as the volume of gas 5 in the tank 20 increases during storage operations.

[0060] Referring now to figures 5 and 6, to remove and / or reposition the container 10, the container 10 must first be detached from the ocean floor 4 (figure 5) and then raised and moved to the desired location ( figure 6). As shown in figure 5, in this embodiment, to initiate the disengagement of container 10 from the ocean floor 4, stored gas 5 is emptied from bag 50, valve 25a is closed, and valve 23a is closed (if not yet closed). Furthermore, the implementing apparatus is coupled to the upper end 10a of the container 10 and applies upward force to the container 10, the valve 24a is opened and air 6 is pumped through the valve 24a and the inlet 24 to the second region 21b of tank 20. As air 6 is pumped into tank 20, it naturally rises to the top of tank 20 and starts displacing sea water 3 in the second region 21b, thereby increasing the buoyant forces acting on the container 10. The displaced sea water 3 is free to exit tank 2 through port 26. In addition to the lift and buoyancy forces acting on the container 10, the suction control device 34 can be used, as previously described, to decrease the suction in recess 31 and assist in the initial lifting of container 10 off the ocean floor 4.

[0061] As best shown in figure 6, once the container 10 is detached from the ocean floor 4, it can be lifted to the surface, or lifted and repositioned in a different underwater location. To continue lifting container 10, valves 23a and 25a are held in closed positions, and valve 36 is closed. In addition, the implementing apparatus continues to apply a vertical lift to container 10 and air 6 continues to be pumped through valve 24a and inlet 24 to the second region 21b. As the depth of the tank 20 decreases, the hydrostatic pressure of the sea water 3 decreases and the air 6 in the second region 21b expands. The expansion of air 6 in the second region 21b and the continuity of pumping air 6 to the second region 21b continues to increase the buoyant forces acting on the container 10. However, regardless of the depth of the container 10, the air expansion 6 on the tank 20, and the volume of air 6 pumped into tank 20, the buoyancy forces acting on the container 10 cannot exceed a predetermined maximum buoyancy force defined by the location of the port 26. In particular, the maximum buoyancy force acting in container 10 because of air 6 in tank 20 occurs when the second region 21b is completely filled with air 6 from the upper end 10a to port 26. Any additional volume of air 6 will simply leave tank 20 and the second region 21b through the port 26. Thus, the location of port 26 defines the maximum possible buoyant force acting on container 10 - the closer port 26 is to the upper end 10a, the lower the maximum possible buoyant force el because of air 6 and, the closer the door 26 is to the lower end 10b, the greater the maximum possible buoyancy force because of the air 6. The axial position of the door 26 along the tank 20 is preferably established in a manner such that the maximum possible buoyancy force of air 6 is less than or equal to the total weight of container 10, and in such a way that the total weight of container 10 minus the maximum possible buoyancy force for air 6 is greater than zero and less than the maximum circumferential load capacity of the implementation apparatus. As a result, the container 10 can be lifted in a controlled manner by the implementing apparatus without exceeding the maximum circumferential loading capacity, and without accelerating uncontrollably to the surface by the action of a continuously increasing buoyancy force as the air continues to expand. as the depth decreases.

[0062] Once anchored for subsea gas storage operations, gas 5 can be supplied or extracted from the gas storage container 10. Referring briefly to figure 8, the gas line 25 of the subsea gas storage container 10 is placed in fluid communication with a buoy 80 tied in place by mooring cables 81, 82 connected to anchors 83, 84 on the ocean floor 4. Buoy 80 can be connected to a GNP tanker 90 and / or placed in fluid communication with a gas pipe on the ocean floor 91. Gas 5 can be provided in container 10 via pipe 91, float 80 and / or tanker 90, or discharged from container 10 in pipe 19, float 80 and / or tanker 92, as desired. It should be noted that figure 8 illustrates an exemplary subsea configuration, however, a variety of other subsea configurations employing the subsea gas storage container modes described here are possible.

[0063] As previously described with reference to figures 5 and 6, in an embodiment, to initiate the disengagement of container 10 from the ocean floor 4, stored gas 5 is emptied from bag 50, valve 25a is closed, and valve 23a is closed (if not yet closed). Furthermore, the implementing apparatus is coupled to the upper end 10a of the container 10 and applies upward force to the container 10, the valve 24a is opened and air 6 is pumped through the valve 24a and the inlet 24 to the second region 21b of tank 20. Once the container 10 is detached from the ocean floor 4, to continue lifting the container 10, the implementing apparatus continues to apply a vertical lift to the container 10 and air 6 continues to be pumped through the valve 24a and inlet 24 in the second region 21b. Thus, in the mode described above with reference to figures 5 and 6, only air 6 is provided to provide buoyancy (that is, it does not have stored gas 5 to provide buoyancy). However, in other embodiments, the buoyancy provided by the stored gas 5 stored in the gas storage tank 20 can be leveraged during undocking, removal, repositioning or combination thereof. For example, to initiate the detachment of the gas storage container 10 from the ocean floor 4, all the gas stored 5 in the tank 20 may not be discharged from the tank 20, but instead, part of the stored gas 5 may be left inside from tank 20, or additional stored gas 5 can be added to tank 20. Once the desired amount of stored gas 5 is in tank 20, valve 25a is closed and valve 23a is closed (if not yet closed). In addition, the implementing apparatus is coupled to the upper end 10a of the container 10 and applies an upward holding force to the container 10. Then, the valve 24a is opened and air 6 is pumped through the valve 24a and the inlet 24 to the second region 21b of the tank 20. As air 6 is pumped into the tank 20, it naturally rises to the top of the second region 21b and displaces water 3 in the second region 21b. Water 3 inside the tank 20 is free to flow through port 26 to the outside region 22 as the volume of air 6 inside the tank 20 increases. When the lift applied to the container 10 plus the buoyancy provided by the air 6 and stored gas 5 in the tank 20 exceeds the dry weight of the container 10 and any suction force between the container 10 and the ocean floor 4, the container 10 disengages from the ocean floor. Once the container 10 detaches from the ocean floor 4, the removal and repositioning process is similar to that previously described with reference to figures 5 and 6. Namely, to continue lifting the container 10, the implementation apparatus continues to apply a vertical lift force in container 10 and air 6 continues to be pumped through valve 24a and inlet 24 to the second region 21b. Thus, in this modality, the buoyancy of the air 6 and gas stored 5 in the tank 20 are leveraged during the disengagement and removal processes.

[0064] In these previously described container modalities 10, a flexible gas storage bag 50 is employed to store gas 5 and maintain the physical separation of stored gas 5 and sea water 3 within the tank 20 to prevent hydrate formation. However, in other embodiments, alternative means can be employed to separate gas 5 and sea water 3 within the tank (for example, tank 20). For example, referring now to figure 9, an embodiment of a submarine gas storage container 10 is shown schematically arranged on the ocean floor 4 for submarine gas storage operations. Container 100 is substantially the same as container 10 previously described, except that container 100 employs a floating diaphragm system 110 to physically separate stored gas 5 from seawater 3 within tank 20, opposite a flexible gas storage bag (e.g., bag 50). Specifically, the floating diaphragm system 110 comprises a rigid plate or diaphragm 111 that is supported by air bubbles 112, which can be added during the implementation process and before storage of gas 5 in tank 20. The air bubble 112 allows that diaphragm 111 floats on top of seawater 3 in tank 20, although diaphragm 111 may have a higher density than seawater 3. However, the density of diaphragm 111 is greater than the density of gas 5 within the tank 20, and so diaphragm 111 remains positioned below gas 5. A dynamic slide seal 113 is formed between diaphragm 111 and tank 20. Seal 113 extends annularly around the entire circumference of diaphragm 111 and restrains and / or prevents the axial flow of sea water 3 and gas 5 through diaphragm 111, and thus restricts and / or prevents gas 5 from coming into contact with sea water 3. The seal 113 can be formed by any suitable means, including, without limitation s, a set of lubricated bag that extends radially from diaphragm 111 to tank 20. In this embodiment, a liquid hydrate inhibitor 115 that inhibits the formation of hydrates is arranged in tank 20 between gas 5 and diaphragm 111. Inhibitor of hydrates 115 can be injected into tank 20 via gas conduit 25 and valve 25a, or another inlet positioned above diaphragm 111 (for example, a dedicated chemical injection inlet). The hydrate inhibitor 115 has a higher density than gas 5, and thus the hydrate inhibitor 115 naturally flows down into tank 20 until it is positioned over diaphragm 111. In general, hydrate inhibitor 115 can be any suitable known hydrate inhibitor.

[0065] As well as another example, a barrier fluid can be used to separate gas 5 and sea water 3 inside the tank (for example, tank 20). Referring now to figure 10, an embodiment of the subsea gas storage container 150 is shown schematically arranged on the ocean floor 4 for subsea gas storage operations. Container 150 is substantially the same as container 10 previously described, except that container 150 employs a barrier fluid system 160 to physically separate stored gas 5 from seawater 3 within tank 20, opposite a gas storage bag flexible (eg bag 50). Specifically, the barrier fluid system 160 comprises a barrier fluid 1612 axially disposed between gas 5 and sea water 3. Barrier fluid 161 has a density less than that of sea water 3 and greater than that of gas 5 Barrier fluid 161 is preferably immiscible in both sea water 3 and gas 5. An example of barrier fluid is described in US patent application specification reports 2008/0041291 and 2009/0010717, each of which is subject to incorporated in its entirety by reference for all purposes. Those systems describe a perfectly immiscible fluid in both water and gas. In practice, fluids of this type are difficult to find. The method that is revealed here offers the potential to use a much wider range of available and environmentally acceptable fluids. Furthermore, in this embodiment, a liquid hydrate inhibitor 162 that inhibits the formation of hydrates is arranged in tank 20 between gas 5 and barrier fluid 161. Hydrate inhibitor 162 and / or barrier fluid 161 can be injected into the tank 20 through gas duct 25 and valve 25a, or other inlet. Hydrate inhibitor 152 has a density greater than gas 5 and less than barrier fluid 161. In general, hydrate inhibitor 115 can be any suitable known hydrate inhibitor. Various sensors can be employed in container 150 to provide potential overflow alert, gas release, release of barrier fluid 161, or combinations of these for a surrounding environment.

[0066] In one embodiment, a dead oil fluid, which is slightly miscible in both sea water 3 and gas 5, can be used as the barrier fluid (for example, barrier fluid 161). Hydrates can form as gas 5 or sea water 3 moves through the dead oil barrier and comes into contact with each other. Consequently, hydrate formation is relatively slow. In addition, by injecting sufficient hydrate inhibitors (eg, methanol) before discharging or discharging gas 5, the effects of hydrate can be minimized, while still allowing environmentally friendly materials to be used.

[0067] As previously described, during the implementation of the container 10 (figure 2), the air pumping requirements increase as the depth of the container 10 increases because of the compression of the air 6 in the second region 21b. For deep applications, the air pressure requirements can be substantial. Referring now to Figure 11, for such deep applications, a combined air / water pumping system 180 can be employed to pump air 6 into the tank 20 during implementation. System 180 comprises a fluid conduit 181 extending to valve 24a and inlet 24, an air inlet line 182 coupled to conduit 181, and a water inlet line 183 coupled to conduit 181 above the inlet line of air 181. Water 3 is pumped through the water inlet line 183 and to the conduit 181, and air 6 is pumped through the air inlet line 182 to the conduit 181. Water 3 is preferably pumped at a volumetric flow rate. enough to push and transfer air 6 down in conduit 181 to inlet 24 and tank 20. In this way, the drag load imposed on air 6 inside conduit 181 by water 3 in conduit 181 must always be greater than the buoyancy of the air bubbles 6 in flue 181. As air bubbles 6 move downwards, they decrease in size according to the ideal gas law. Thus, the system 180 has to be designed in such a way that the water flow 3 below in the conduit 181 is high enough to achieve air transfer 6 for the depth of the installation.

[0068] The combined air-water pumping system 180 offers the potential to eliminate high compression requirements on the surface, since the hydrostatic water column performs this function. Consequently, standard equipment can be used to perform pumping operations, which are inherently safe because high pressures are reached at depths without requiring high pressure components on the surface close to workers.

[0069] Referring further to figure 11, once the combined air-water solution reaches tank 20, air 6 rises in the second region 21b to increase buoyancy and water 3 is free to exit tank 20 through the door 26. In this way, the air 6 reaches its desired effect and the amount of water 3 that is added is not critical and simply leaves the tank 20 through the port 26.

[0070] Submarine gas storage vessel modalities 10, 100, 150 above described included a single tank (for example, tank 20) and a single chamber or volume for gas storage (for example, first region 21a, inner region 21) for gas storage. However, in other embodiments, the subsea gas storage container or system may include multiple gas storage tanks. Such modalities can be referred to as compartmentalized submarine gas storage vessels or systems, since the total stored gas is divided between multiple submarine gas storage tanks. Compartmentalized subsea gas storage containers offer the potential to reduce the amount of gas leaking to the sea floor by spreading the volume of gas stored in multiple tanks. In addition, compartmentalization offers the potential to reduce manufacturing costs, as smaller flexible bags are typically easier to design and build.

[0071] Referring now to Figures 12-14, an embodiment of a compartmentalized underwater gas storage container 220 is shown. The container 200 has a central axis 250 and extends between an upper end 200a and a lower end 200b . In addition, container 200 includes a plurality of rigid thin-walled storage tanks 220 and a base 260 positioned below tanks 220. Container 200 is designed to be deployed and positioned on the seabed with tanks 220 in a vertical orientation with the upper end 200a positioned above the lower end 200b.

[0072] Each tank 220 is substantially the same tank 200 previously described. Namely, each tank 220 comprises rigid walls, preferably made of steel or composite material. Furthermore, each storage tank 220 defines an inner region or chamber 221 and an outer region 222. A flexible gas storage bag 250, previously described, is disposed within the inner chamber 221 of each tank 220, thus dividing the chamber 221 in a first region 221a inside chamber 221 and a bag 250, and a second region 221b inside chamber 221, but outside bag 250. Each gas storage bag 250 includes a stored gas port 251. As best shown in figure 12, the walls of each tank 220 include external reinforcement ribs to assist in reinforcing the walls. In addition, a float control gas outlet 223 and a float control gas inlet 224 are provided in each storage tank 220. In this embodiment, each float control gas outlet 223 is in fluid communication with a collector tube or conduit 223b, and each flotation control gas inlet 224 is in fluid communication with a collector tube or conduit 224b. The outlet valve 223a controls the flow of float control gas or air 6 through outlets 223 and the manifold 223b, and the inlet valve 224a controls the flow of float control gas or air 6 through the manifold 224b and gas inlets 224. Thus, in this embodiment, an outlet valve 223a controls the exhaust 6 of each tank 220, and an inlet valve 224a controls the flow of air 6 for each tank 220. However, in other embodiments, each tank (for example, each tank 220) can have its own float control gas inlet valve and / or float control gas outlet valve independently. In such an embodiment, the flow of flotation control gas into and out of each tank can be controlled independently to vary the fluctuation forces acting on different tanks.

[0073] Referring further to figures 12-14, each storage tank 220 also includes a stored gas line 225 in fluid communication with the gas port 251 of its associated gas storage bag 250. In this embodiment, each Stored gas line 225 is in fluid communication with the collecting pipe or gas line 225b. The flow of a stored gas 5 into and out of each gas storage bag 250 through the collection tube 225b, each conduit 225 and each gas port 251 is controlled by a gas valve 225a. Thus, in this embodiment, a gas valve 225a controls the flow of stored gas 5 into and out of each bag 250. However, in other embodiments, each tank (for example, each tank 220) may have its own gas valve independently controlled, in such a way that the flow of gas into or out of each bag (e.g., each bag 250) can vary. In addition, as previously described, each storage tank 220 includes a through port 226 positioned near the bottom end of its associated tank 220.

[0074] In general, each tank 220 can have any suitable size and geometry. In this embodiment, each tank 220 has the same size and cylindrical geometry. In general, the size of each tank 220 and, consequently, the overall size of the container 220 will depend, at least in part, on the desired volume for storage of submarine gas. A given volume of gas can be stored in a single relatively large tank, or stored in multiple smaller gas tanks in a compartmentalized submarine gas storage container. However, in general, smaller gas storage tanks are simpler and less expensive to build, compared to large gas storage tanks. Consequently, a compartmentalized subsea gas storage container, such as container 200, may be cheaper to manufacture than a subsea gas storage container that employs a relatively large tank to store the same volume of total gas. In addition, compartmentalized underwater gas storage containers are best suited for previously described implementation methods that employ temporary buoyancy. For example, it may be desirable to use only part of the buoyancy when lowering the system, and compartmentalization makes this process simpler and more robust.

[0075] Referring further to Figures 12-14, the base 260 of the container 200 includes a ballast chamber 240 containing ballast 241 and a plurality of mud skirts 230 at the lower end 200b. The ballast chamber 240 is positioned axially between the tanks 220 and the skirts 230. In this embodiment, a mud skirt 230 is provided for each tank 220. However, in general, one or more mud skirts can be provided.

[0076] Mud skirts 230 work to positively fit the ocean floor 4 and restrict and / or prevent the lateral movement of the container 200 once positioned on the ocean floor 4 for gas storage operations. Each skirt 230 is substantially the same skirt 30 previously described. During anchoring of container 200, container 200 is pushed downwards and each skirt 230 is pushed into the ocean floor 4. A suction control device similar to the suction control device 34 previously described can be provided for one or more of the skirts 230 to control the suction forces inside the skirts 230 during anchoring and removal operations. For example, a suction control device (for example, suction control device 34) can be provided for each skirt 230 to assist in leveling the container 200 once positioned. In particular, differential suction can be provided between skirts 230 to vary the suction forces acting on different portions of the container 200.

[0077] Referring also to figures 12-14, ballast 241 is contained in ballast chamber 240. In this embodiment, a single ballast chamber 240 extends under each tank 220. However, in other modalities, each tank (for example, each tank 220) can have its own distinct ballast chamber. In general, ballast 241 counterbalances the upward vertical fluctuation forces resulting from gas 5 and / or air 6 stored in tanks 220. The amount and weight of ballast 241 is chosen to achieve the desired total dry weight of container 200. As with the container 10 previously described, the dry weight of the base 200 is preferably greater than the total buoyancy forces acting on the container 200 during all the operational phases of the container 200 (for example, implementation, anchoring, gas storage, detachment, removal and repositioning of container 200). In addition, during the implementation, removal and repositioning of the container 200 (that is, any time the surface implementing apparatus applies a holding force to the container 10), the total weight of the container 200 minus the buoyant forces acting on the container 200 is preferably greater than zero (to prevent uncontrolled rise of container 200) and less than the maximum circumferential load capacity of the implementing apparatus (to ensure that the maximum circumferential load capacity is not exceeded.

[0078] In this embodiment, each tank 220 includes a gas storage bag 250 and is adapted to store gas 5 in order to maximize the volume or gas storage capacity of container 200. However, in other embodiments, one or more of the tanks of a compartmentalized submarine gas storage container (for example, tanks 220 of container 200) can serve as a dedicated ballast cell that can be used to provide buoyancy during installation and then flooded during anchoring.

[0079] Container 200 is operated in a similar manner to container 10 previously described. Specifically, during subsea implementation, container 200 is connected by a releasable coupling 270 at the upper end 200a to a surface implementation apparatus (for example, a crane on a surface vessel). The weight of the container 200 is preferably greater than the maximum buoyant forces acting on the container 200 during implementation, and thus the container 200 naturally wants to sink. The maximum possible buoyancy forces resulting from air 6 in tanks 220 during implementation occur when the second region 221b of each tank 220 is completely filled with air 6 from the upper end 200a to its respective port 226. A buoyant force cannot be achieved larger while container 200 is submerged, as any additional air volume in any tank 220 will simply exit through port 226. Correspondingly, the maximum possible buoyancy force of each tank 220 can be adjusted by varying the axial position or height of the port 226.

[0080] The implementation apparatus connected to the coupling 270 applies a vertical lift force upwards in the container 200 to manage and control the rate at which the container 200 submerges in the sea. As container 200 is lowered into the sea, sea water 3 in an external region 222 flows through ports 226 of tanks 220. With valve 223a closed, sea water 3 continues to flow into the second region 221b, the air 6 in the second region 221b is compressed and the buoyancy provided by tanks 220 decreases. However, during implementation of container 200, valve 224a is open and air 6 is pumped through valve 224a, manifold 224a and inlets 224 to the second region 221b of each tank 220 to maintain sufficient buoyancy. In particular, during implementation, detaching, removing and repositioning the container 10 (that is, any time the surface implementing apparatus applies a holding force to the container 10), the total weight of the container 10 minus the buoyancy force it is preferably greater than zero (to prevent an uncontrolled rise of the container 10) and less than the maximum circumferential load capacity of the implementing apparatus (to ensure that the maximum circumferential load capacity is not exceeded).

[0081] Once container 200 reaches ocean floor 4, skirts 230 begin to contact and penetrate ocean floor 4. In order to anchor container 200 to ocean floor 4, valve 224a is closed and air pumping 6 through the collecting tube 224b and inlet 224 is stopped, and valve 223a is opened to allow any air 6 in the second region 221b of each tank 220 to escape. As air 6 leaves tanks 220, sea water 3 seeps through ports 226 and fills the remainder of the second region 221b of each tank 220, thereby reducing and / or eliminating the buoyancy of tanks 220. As the buoyancy of container 200 is reduced, skirts 230 further penetrate the ocean floor 4 by the weight of container 200. To improve seating, a suction control device can be employed, as previously described. Once the anchoring is complete, valve 223a can be closed, coupling 270 can be released to disconnect the implement apparatus from container 200, an air supply can be coupled to the manifold 225b, and valve 225a can be opened to allow gas to flow 5 through the manifold 225b and valve 225a into the gas storage bags 250.

[0082] During gas storage operations, valve 225a is opened and valves 223a, 224a are closed. As the volume of gas 5 in each bag 250 increases, the buoyancy of each tank 220 also increases. However, as previously described, the quantity and weight of ballast 241 is established in such a way that the total weight of the container 200 is greater than the maximum possible buoyancy forces resulting from the stored gas 5. Consequently, the container 200 remains anchored on the ocean floor. 4 as the volume of gas 5 in each tank 220 increases.

[0083] To remove and / or reposition container 220, container 200 must first be detached from the ocean floor 4, and then lifted and moved to the desired location. To initiate the disengagement of container 200 from the ocean floor 4, stored gas 5 is emptied from each bag 250, valve 225a is closed and valve 223a is closed (if not yet closed). Furthermore, the surface implementing apparatus is coupled to the container 200 via coupling 270, an upward holding force is applied to the container 200 by the implementing apparatus, valve 224a is opened and air 6 is pumped through valve 224a , collecting tube 224b, and inlets 224 for the second region 21b of each tank 220. As air is pumped into each tank 220, air 6 rises to the top of each tank 220 and begins to displace sea water 3 in the tank 220, thus increasing the buoyancy of each tank 220 and container 200. The displaced sea water 3 is free to leave each tank 220 through its port 226. In addition to the lift and buoyancy forces acting on container 200, a suction control can be employed, as previously described, to decrease the suction forces between the container 200 and the ocean floor.

[0084] Once the container 200 is detached from the ocean floor 4, it can be lifted to the surface or lifted and replaced in a different location on the seabed. To continue lifting the container 200, valves 223a and 225a are held in closed positions. In addition, the implementing apparatus continues to apply a vertical lift to container 200 and air 6 continues to be pumped through valve 224a, manifold 224b, and inlets 24 to each tank 220. As the depth of tank 20 decreases, the hydrostatic pressure of sea water 3 decreases and the air 6 in each tank 220 expands. The expansion of air 6 in each tank 220 and the continuity of pumping air 6 for each tank 220 continues to increase the buoyancy of each tank 220 and container 200. However, regardless of the depth of container 200, the expansion of air 6 in tank 20, and the volume of air 6 pumped to each tank 220, the buoyancy of each tank 220 and the container 200 cannot exceed a maximum predetermined buoyancy defined by the location of ports 226. As previously described, the maximum buoyancy of each tank 220 because of air 6 occurs when the second region 221b is completely filled with air 6 from the upper end 200a to port 226. Any additional volume of air 6 will simply leave tank 220 and the second region 221b through port 226.

[0085] As previously described, the container 200 is implemented on the seabed as a simple structure or unit. However, in some applications, it may be desirable to implement container 200 in separate parts, and then mount container 200 on the seabed. For example, base 260 can be deployed and anchored to the ocean floor, and then tanks 220 can be deployed and attached to the top of the previously anchored base 260. Upon removal and repositioning, base 260 can be left in place or removed along with tanks 220. In this way, the overall weight and complexity of the lift can be minimized, although there may be some additional complication involved in coupling tanks 20 and base 260 to the depth.

[0086] As previously described, during the implementation of gas storage container modalities described herein (e.g. container 10, container 200, etc.) the total weight of the gas storage container minus the buoyancy of the container is preferably greater than zero and less than the maximum circumferential load capacity of the implementation apparatus on the surface. As a result, the static charge of the gas storage container is small enough to allow controlled implementation with conventional surface-implementing equipment, such as cranes mounted on surface vessels. However, dynamic loads must also be taken into account because the total trapped mass and added mass above and below the container are substantial. The mass of the total system combined with the fact that the floating implementation apparatus can move dynamically with wave excitations can create significant dynamic loads.

[0087] Because of the carrying capacity and sinking compensation requirements, implementation with conventional lifting cable can be difficult. In addition, since crane cables generally cannot withstand rotational torques, the crane cable and any supply or control lines that extend from the floating implementation vessel to the subsea gas storage vessel (for example, buoyancy control air supply) may be twisted and / or damaged. As a result, submarine gas storage container arrangements described herein are preferably implemented on the seabed with a column of tubes.

[0088] Referring now to Figures 15 and 16, an embodiment of an underwater gas storage container implementation system 300 is shown. In this embodiment, system 300 is shown implementing the previously described underwater gas storage container 200 . The system 300 includes a floating surface vessel 310 and a tube column 320. The surface vessel 310 includes a platform 311 that supports the tube column 320 and the container 200 attached to the lower end of the tube column 320 with releasable coupling 270 Thus, the tube column 310 extends from the floating surface vessel 310 to the storage container 200. In this embodiment, the surface vessel 310 also includes a 312 crane. A buoyancy control gas supply line 330 also extends from the floating surface vessel 310 to a gas storage container 200. Supply line 330 is in fluid communication with valve 224a and manifold 224b, and supplies gas or buoyancy control air 6 during implementation, removal and repositioning of container 200. In modalities using a combined air / water pumping system (for example, the combined air / water pumping system 180 shown in figure 11) to supply air 6 to subsea tanks, the combined air / water solution can be delivered to subsea tanks with supply line 330. In this embodiment, the tube column 320 includes an in-line damping device 325 that absorbs and dissipates hydraulic loads.

[0089] System 300 modalities provide several potential advantages over conventional crane cable implementation systems. Compared to crane cables, drill pipes and tube columns, they offer the potential for increased load capacity. Furthermore, since the tube column (eg tube column 320) is rigid, its rotation can be controlled on the surface with conventional equipment associated with the platform (eg platform 311) such as a top drive or rotary table. As a result, twisting of any of the supply lines (for example, supply line 330) around the tube column can be reduced and / or completely eliminated. In addition, the loading capacities of most drilling platforms (for example, platform 311) are substantially greater than the loading capacities of most cranes, and thus the implementation with a column of tubes and drilling platform offers the potential to improve the and improve control over the subsea gas storage container. In addition, most conventional drilling platforms offer the potential for better sink compensation. Specifically, the displacement block provides a certain amount of sink compensation when it supports the tube column (for example, tube column 320). When the tube column is removed from the displacement block on slips, sinking compensation can be provided by the damping device (for example, damping device 325) in line with the tube column.

[0090] Although embodiments described herein include a single gas storage tank (eg container 10) or multiple gas storage tanks that are coupled together to form a single structure (eg container 200), realizing that a plurality of separate gas storage containers can be grouped under the sea to form a larger subsea gas storage facility or farm. When joining storage containers, standard subsea architectures can be used.

[0091] Modalities disclosed here can serve a variety of applications. For example, modalities disclosed here can be used to store natural gas produced during a well test operation offshore where the operator does not want to commission the construction of a pipeline to export gas before the reservoir has been produced enough to assess its characteristics and condition. As another example, modalities described here can be used to store natural gas in locations close to the pipeline network, regardless of the previous existence of naturally occurring caves. Thus, modalities described here offer the potential to reduce the dependence on the availability of natural caves for the storage of gas. In addition, modalities described herein can be used to store gas in remote locations of human life and property, thus offering the potential to reduce the risk associated with gas storage.

[0092] Although preferred modalities have been shown and described, modifications of them can be made by those skilled in the art without departing from the scope and precepts here. The modalities described here are only exemplary, and not limiting. Many variations and modifications of the systems, apparatus and processes described herein are possible and are within the scope of the invention. For example, the relative dimensions of various parts, the materials from which the various parts are made, and other parameters can be varied. Accordingly, the scope of protection is not limited to the modalities described here, but is limited only by the following claims, the scope of which must include all equivalents of the subject matter of the claims.

Claims (31)

1. Method for implementing a gas storage container (10, 200) below the water surface (3), wherein the method comprises: (a) coupling an upper end (10a, 200a) of the gas storage container ( 10, 200) to an implementation apparatus (310) positioned on the water surface (3), in which the gas storage container (10, 200) has a total dry weight and a lower end (10b, 200b) opposite the upper end (10a, 200a), and that the gas storage container (10, 200) includes a storage tank (20, 220) defining an internal region (21, 221) within the storage tank (20, 220) and an outer region (22, 222) outside the storage tank (20, 220); and (b) lowering the gas storage container (10, 200) below the water surface (3) with the implementation apparatus (310); characterized by the fact that it additionally comprises: (c) pumping a buoyancy control gas (6) into the internal region (21, 221) of the storage tank (20, 220) during (b), in which the control gas of buoyancy (6) in the internal region (21, 221) of the storage tank (20, 220) generates a buoyant force acting on the gas storage container (10, 200) during (b); and (d) ensuring that the dry weight of the gas storage container (10, 200) minus the buoyancy force is greater than zero and less than a maximum load capacity of the implementing apparatus (310) during (b). 2. Method according to claim 1, characterized by the fact that the submarine gas storage container (10, 200) additionally comprises: a first inlet (25, 225) adapted to flow a stored gas (5) to the inner region (21, 221); a second inlet (24, 224) adapted to flow the buoyancy control gas (6) to the inner region (21, 221); a fluid port (226, 226a) extending through the storage tank (20, 220) and communicating with the inner region (21, 221) and the outer region (22, 222); a first valve (25a, 225a) adapted to control the flow of stored gas (5) through the first inlet (25, 225); and a second valve (24a, 224a) adapted to control the flow of the flotation control gas (6) through the second inlet (24, 224). 3. Method according to claim 2, characterized by the fact that the second valve (24a, 224a) is opened during (c), and (c) additionally comprises pumping the flotation control gas (6) from the surface of the water (3) through the second valve (24a, 224a) and the second inlet (24, 224) into the inner region (21, 221) of the storage tank (20, 220). 4. Method, according to claim 3, characterized by the fact that it additionally comprises preventing the flotation control gas (6) from escaping from the internal region (21, 221) to the external region (22, 222) through a first outlet (23, 223) in the submarine gas storage container (10, 200) for (c) with a third valve (23a, 223a). 5. Method, according to claim 2, characterized by the fact that it additionally comprises allowing water to flow freely between the inner region (21, 221) and the outer region (22, 222) through the door (226, 226a) during (b). 6. Method according to claim 3, characterized in that the coupling of an upper end (10a, 200a) of the gas storage container (10, 200) to an implementation apparatus (310) in (a) comprises coupling a column of tubes (320) to the upper end (10a, 200a) of the gas storage container (10, 200), wherein the tube column (320) has a longitudinal axis and extends from the storage container gas (10, 200) to the implementation apparatus (310); and wherein lowering the gas storage container (10, 200) below the water surface (3) in (b) comprises lowering the gas storage container (10, 200) with the tube column (320). Method according to claim 6, characterized in that coupling an upper end (10a, 200a) of the gas storage container (10, 200) to an implementation apparatus (310) in (a) comprises coupling a supply line (330) at the second inlet (24, 224); and in which pumping a buoyancy control gas (6) into the internal region (21, 221) of the storage tank (20, 220) in (c) comprises pumping the buoyancy control gas (6) from the surface below in the line supply (330) to the inner region (21, 221) of the storage tank (20, 220). 8. Method according to claim 7, characterized by the fact that pumping a flotation control gas (6) in the internal region (21, 221) of the storage tank (20, 220) in (c) comprises pumping water along with the flotation control gas (6) down the supply line (330) to the inner region (21, 221). Method according to claim 7, characterized in that it additionally comprises resisting the rotation of the tube column (320) and the gas storage container (10, 200) about the longitudinal axis of the tube column ( 320) during (b). 10. Method according to claim 6, characterized in that it comprises supporting and lowering the tube column (320) and the gas storage container (10, 200) during (b) with a platform (311) of the implementation apparatus (310). 11. Method according to claim 1, characterized in that it comprises supporting and lowering the gas storage container (10, 200) in (b) with a crane of the implementing apparatus (310). 12. Method according to claim 4, characterized in that it additionally comprises: (e) anchoring the gas storage container (10, 200) on the ocean floor after (b). 13. Method according to claim 12, characterized by the fact that (e) comprises based on gravity to anchor the gas storage container (10, 200) on the ocean floor or use piles to anchor the gas storage container (10, 200) on the ocean floor. 14. Method according to claim 12, characterized by the fact that (e) comprises: (e1) fitting the ocean floor to the lower end (10b, 200b) of the gas storage container (10, 200); (e2) closing the second valve (24a, 224a); (e3) opening the third valve (23a, 223a); and (e4) exhaust the float control gas (6) from the inner region (21, 221) of the storage tank (20, 220) to the outer region (22, 222) through the third valve (23a, 223a) and from the first exit (23, 223). 15. Method according to claim 14, characterized by the fact that (e) additionally comprises: (e5) allowing water to flow through the port (226, 226a) to the inner region (21, 221) during (e4 ). 16. Method, according to claim 15, characterized by the fact that it comprises: (e6) penetrating the ocean floor with a mud skirt (30, 230) at the lower end (10b, 200b) of the gas storage container ( 10, 200). 17. Method according to claim 16, characterized in that (e) additionally comprises (e7) pumping water from a space that extends between the lower end (10b, 200b) of the gas storage container (10, 200 ) and the ocean floor to anchor the gas storage container (10, 200) to the ocean floor. 18. Method according to claim 15, characterized in that it additionally comprises (f) storing the gas (5) in the gas storage tank (20, 220). 19. Method according to claim 18, characterized by the fact that (f) comprises: (f1) opening the first valve (25a, 225a); (f2) flow the gas (5) through the first valve (25a, 225a) and the first inlet (25, 225) to the gas storage tank (20, 220). 20. Method according to claim 19, characterized by the fact that (f) additionally comprises: (f3) draining the gas (5) through the first valve (25a, 225a) and the first inlet (25, 225) to a flexible ace storage bag (50, 250). 21. Method, according to claim 20, characterized by the fact that (f) additionally comprises: (f4) displacing water in the storage tank (20, 220) with the gas (5) draining into the gas storage bag flexible (50, 250); (f5) drain water through the door (226, 226a) from the inner region (21, 221) to the outer region (22, 222). 22. A system for storing a submarine gas (5) comprising: a submarine gas storage container (10, 200) including a gas storage tank (20, 220) defining an internal region (21, 221) within the tank storage (20, 220) and an outer region (22, 222) outside the storage tank (20, 220), where the storage tank (20, 220) has an upper end and a lower end opposite the upper end ; wherein the gas storage tank (20, 220) includes a gas inlet (25, 225) adapted to flow the gas (5) to the inner region (21, 221), an air inlet (24, 224) adapted to flow air to the internal region (21, 221), a port (226, 226a) in fluid communication with the internal region (21, 221) and the external region (22, 222); a valve (25a, 225a) adapted to control the flow of gas (5) through the gas inlet (25, 225); and a valve (24a, 224a) adapted to control the air flow through the air inlet (24, 224), characterized by the fact that it also comprises a flexible gas storage bag (50, 250) disposed in the internal region ( 21, 221) of the storage tank (20, 220), in which the flexible gas storage bag (50, 250) is adapted to store the gas (5) and includes a communicating gas port (51, 251) fluid with the gas inlet (25, 225); wherein the flexible storage bag (50, 250) has a first end proximal to the upper end of the storage tank (20, 220) and a second end opposite the first end, where the gas port (51, 251) is arranged at the first end, and wherein the first end of the storage bag (50, 250) is oversized with respect to the second end of the storage bag (50, 250); 23. System according to claim 22, characterized by the fact that the submarine gas storage container (10, 200) additionally comprises: an air outlet (23, 223) adapted to exhaust air from the internal region (21, 221) to the outer region (22, 222), where the air outlet (23, 223) is positioned at the upper end of the storage tank (20, 220); and a valve (23a, 223a) adapted to control the flow of air through the air outlet (23, 223). 24. System according to claim 22, characterized by the fact that the submarine gas storage container (10, 200) additionally comprises: a ballast chamber (40) coupled to the lower end and the ballast (41) disposed in the ballast chamber (40); and a mud skirt (30, 230) extending from the ballast chamber (40). 25. System according to claim 24, characterized by the fact that the submarine gas storage container (10, 200) additionally comprises: a suction control device (34) coupled to the storage tank (20, 220) and adapted to control the suction forces within the mud skirt (30, 230). 26. System according to claim 22, characterized in that the flexible gas storage bag (50, 250) has a collapsed position when the storage bag (50, 250) is empty and an expanded position when the storage bag (50, 250) contains the gas (5). 27. System according to claim 22, characterized by the fact that the storage bag (50, 250) is positioned between the door (226, 226a) and the upper end. 28. System according to claim 22, characterized by the fact that it additionally comprises: an implementation apparatus (310) on the water surface (3) and adapted to implement the gas storage container (10, 200) on the bottom the sea; a column of tubes (320) extending from the delivery apparatus (310) to the gas storage container (10, 200); wherein the tube column (320) has an upper end positioned on the implementation apparatus (310) and a lower end coupled to the submarine gas storage container (10,200). 29. System according to claim 28, characterized by the fact that the tube column (320) includes an in-line damping device (325). 30. System according to claim 28, characterized in that the implementation apparatus (310) includes a platform (311) that supports the tube column (320) and the gas storage container (10, 200) . 31. System according to claim 22, characterized by the fact that the gas storage container (10, 200) has a central axis and a total dry weight; wherein the inner region (21, 221) comprises a first section extending axially from the upper end to the door (226, 226a), the first section having a total volume; where the total volume times the water density is less than the dry weight.

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