WO2016036690A1

WO2016036690A1 - System and method for small scale marine transpoation of cryogenic hydrocarbons

Info

Publication number: WO2016036690A1
Application number: PCT/US2015/047865
Authority: WO
Inventors: Kenneth D. Nelson; Alan B. Nierenberg
Original assignee: Excelerate Energy Limited Partnership
Priority date: 2014-09-05
Filing date: 2015-09-01
Publication date: 2016-03-10

Abstract

A system and method for small scale marine transportation of cryogenic hydrocarbons is described. A small scale cryogenic hydrocarbon marine transportation system includes a plurality of swap barges each having a cryogenic hydrocarbon capacity of 25,000 m3 or less, and a semisubmersible transfer ship, where the plurality of swap barges and the semisubmersible transfer ship cooperate to provide uninterrupted delivery of cryogenic hydrocarbons to a marine delivery location, and access to the marine delivery location is through an inlet or an estuary, wherein the semisubmersible transfer ship transports each of the plurality of swap barges on deck across open water, and the plurality of swap barges self- propel through the inlet or estuary to the inland water delivery location.

Description

Title: SYSTEM AND METHOD FOR SMALL SCALE MARINE

TRANSPORTATION OF CRYOGENIC HYDROCARBONS

BACKGROUND

1. FIELD OF THE INVENTION

Embodiments of the invention described herein pertain to the field of cryogenic hydrocarbons. More particularly, but not by way of limitation, one or more embodiments of the invention enable a system and method for small scale marine transportation of cryogenic hydrocarbons.

2. DESCRIPTION OF THE RELATED ART Hydrocarbons that are gaseous at ambient temperatures and pressures, such as natural gas and ethane, are often transported by marine vessels as sub-cooled liquids. A liquefied hydrocarbon is produced by cooling the hydrocarbon below its boiling point (for natural gas, about -160 °C at atmospheric pressure, depending on cargo grade; for ethane about -89 °C). The liquefied hydrocarbon may be transported and stored in cryogenic containers slightly above atmospheric pressure. Upon reaching the location of intended use, the liquefied hydrocarbon may be converted back to its gaseous form by adding heat and thereby raising the temperature above its boiling point.

Marine vessels designed for transporting cryogenic hydrocarbons are conventionally large carrier vessels. A typical carrier vessel may have a capacity of 138,000 m³, 150,900 m³, 173,400 m³, and can be as large as 260,000 m³, capable of delivering 800 Million ft³ per day of gas. Such vessels may be nearly 300 meters in length and between 40 and 50 meters in beam.

However, often there are inland water locations that are not accessible by conventional cryogenic hydrocarbon carriers. In such instances the water may be too shallow, or the inlet too narrow to accommodate a large vessel without time intensive and costly dredging. Such locations may contain existing power plants in need of fuels, which in many instances currently employ diesel fuel, but would benefit from a lower cost, lower emission, cleaner burning fuel such as natural gas or ethane if it were accessible to the power plant. Mountains, rainforests, permitting or public opposition may make building a pipeline for a cleaner burning fuel infeasible, leaving marine transportation as the best option. Areas in the Caribbean, Norway and Japan are exemplary locations which may suffer from such predicaments.

Simply building a smaller version of a cryogenic carrier vessel is not a satisfactory solution because a smaller vessel would not be capable of providing a sufficient supply of fuel to the inland water power plants. One approach to provide gas to isolated coastal communities has been gas distribution systems which employ large tankers and shuttle boats. In such systems, large tankers supply liquefied gas to shuttle boats. The shuttle boats obtain the liquefied gas from the large tankers using ship-to-ship transfer, and deliver it to coastal stations. The problem with shuttle boat systems is that they require multiple transfers of the cryogenic hydrocarbons, which can result in large quantities of the cryogenic hydrocarbon being lost as "boil-off gas, and the transfers are time consuming. In a typical example, a liquefied gas may be transferred a first time from a liquefaction facility to a large tanker, transferred a second time from the tanker to a shuttle vessel, and transferred a third time from the shuttle vessel to the delivery location. Each of these cargo transfers is time consuming and subject to boil-off losses.

Other conventional approaches to providing gas to isolated coastal communities have been use of a tow for the full duration of a voyage, articulated tug barge (ATB) or integrated tub barge (ITB) combinations. The problem with simple tows is that they are limited in speed of transport between loading and discharge ports to speeds less than about 8 knots. These tows may be pushed in calm weather, but require a change to a tow line pull in heavier weather. ATBs and ITBs have high capital costs and are often too large to navigate shallow water applications.

A marine transportation system capable of reaching smaller and more remote locations, whilst still providing adequate supply and minimizing boil-off gas losses and transfer time, may assist current diesel power plants in switching to natural gas or ethane, reducing emissions and power costs. Therefore, there is a need for a system and method for small scale marine transportation of cryogenic hydrocarbons. SUMMARY

Embodiments described herein generally relate to a system and method for small scale marine transportation of cryogenic hydrocarbons. A system and method for small scale marine transportation of cryogenic hydrocarbons is described. An illustrative embodiment of a cryogenic hydrocarbon marine transportation system includes a marine delivery location located through restricted shallow water and aquatically coupled to a cryogenic hydrocarbon supply source, the marine delivery location including a jetty having a first berth, a second berth and a transfer platform in between the first and second berths, the restricted shallow water navigable by a swap barge, the swap barge including at least one cryogenic hydrocarbon cargo tank, wherein the at least one cryogenic hydrocarbon cargo tank carries cryogenic hydrocarbon from the cryogenic hydrocarbon supply source and provides the cryogenic hydrocarbon to the marine delivery location when the swap barge is moored at one of the first or second berths, a semisubmersible transfer ship comprising a deck, wherein the semisubmersible transfer ship is convertible between: a ballasted position, wherein the deck is submerged below a surface of water and the swap barge is loaded onto the deck when the semisubmersible transfer ship is in the ballasted position, and a travel position, wherein the deck is above the surface of water and the swap barge is secured on the deck when the semisubmersible transfer ship is in the travel position, wherein the cryogenic hydrocarbon is transported from the supply source to the marine delivery location by the swap barge, and wherein the swap barge is transported proximate to the restricted shallow water on the deck of the semisubmersible transfer ship. In some embodiments, the restricted shallow water is one of an inlet or an estuary. In certain embodiments, there are a plurality of swap barges and each of the plurality of swap barges has a cryogenic hydrocarbon capacity of 25,000 m³ or less. In some embodiments, the swap barge further includes a self-propulsion system. In certain embodiments, there are a plurality of swap barges, wherein a first swap barge of the plurality of swap barges is moored at the first birth and providing the cryogenic hydrocarbon to the marine delivery location, and wherein a second swap barge of the plurality of swap barges moors at the second birth and connects to the marine delivery location before the first swap barge is depleted of cryogenic hydrocarbon. In some embodiments, at least a portion of the restricted shallow water comprises a water depth less than about 10 meters deep.

An illustrative embodiment of a method for marine transportation of cryogenic hydrocarbons includes loading a cryogenic cargo tank onboard a swap barge with cryogenic hydrocarbons at a cryogenic hydrocarbon supply source, navigating the loaded swap barge to a first water location proximate to the cryogenic hydrocarbon supply source, ballasting a semisubmersible transfer ship at the first water location such that a deck of the semisubmersible transfer ship is submerged, floating the loaded swap barge onto the submerged deck, deballasting the semisubmersible transfer ship into a travel position once the loaded swap barge is above the deck, transporting the semisubmersible transfer ship with swap barge on deck to a second water location, the second water location proximate to a marine delivery location, wherein restricted shallow water couples the second water location and the marine delivery location, ballasting the semisubmersible transfer ship to allow the loaded swap barge to float from the deck, propelling the swap barge from the second water location through the restricted shallow water to the marine delivery location, and delivering cryogenic hydrocarbon from the swap barge to the marine delivery location. In some embodiments, the marine delivery location comprises at least two berths and there are at least two swap barges, and wherein a first swap barge of the at least two swap barges connects to the marine delivery location at a first berth of the at least two berths and delivers cryogenic hydrocarbon before a second swap barge of the at least two swap barges moored at a second berth of the at least two berths is depleted of cryogenic hydrocarbon. In certain embodiments, the swap barge self-propels from the second water location to the marine delivery location. In some embodiments, at least a portion of the depth of the restricted shallow water is less than about 10 meters deep.

An illustrative embodiment of a cryogenic hydrocarbon marine transportation system includes a plurality of swap barges, wherein each swap barge has a cryogenic hydrocarbon capacity of 25,000 m³ or less, and a semisubmersible transfer ship, wherein the semisubmersible transfer ship and the plurality of swap barges cooperate to provide sequential delivery of cryogenic hydrocarbon to a marine delivery location, wherein access to the marine delivery location is through one of an inlet or an estuary, wherein the semisubmersible transfer ship transports each of the plurality of swap barges on deck across open water, wherein the plurality of swap barges self-propel through the one of the inlet or the estuary to the marine delivery location, and wherein the cryogenic hydrocarbon is provided to the marine delivery location during transitions when a first swap barge of the plurality of swap barges is depleted of cryogenic hydrocarbon and a second swap barge of the plurality of swap barges begins delivery. In some embodiments, the marine delivery location includes a dual berth transfer platform. In some embodiments, the marine delivery locations requires less than 1.5 metric ton per annum (MTPA) of cryogenic hydrocarbon.

In further embodiments, features from specific embodiments may be combined with features from other embodiments. For example, features from one embodiment may be combined with features from any of the other embodiments. In further embodiments, additional features may be added to the specific embodiments described herein. BRIEF DESCRIPTION OF THE DRAWINGS

Advantages of the present invention may become apparent to those skilled in the art with the benefit of the following detailed description and upon reference to the accompanying drawings in which:

FIG. 1 is a schematic diagram of gaseous hydrocarbon liquefaction facility of an illustrative embodiment.

FIG. 2 is a schematic diagram of a swap barge of an illustrative embodiment. FIG. 3A is a perspective view of a submersible transfer ship of an illustrative embodiment with a shallow draft.

FIG. 3B is a perspective view of a submersible transfer ship of an illustrative embodiment with a deep draft.

FIG. 4 is a perspective view of a submersible transfer ship of an illustrative embodiment loaded with a swap barge.

FIG. 5 is a top plan view of a marine delivery location of an illustrative embodiment located through restricted shallow water.

FIG. 6 is a schematic diagram of an exemplary marine delivery location with a plurality of offloading berths of an illustrative embodiment.

FIGs. 7A-7E are schematic diagrams of a system for the transportation of cryogenic hydrocarbons of an illustrative embodiment.

FIG. 8 is a flowchart of a method for small scale marine transportation of cryogenic hydrocarbons of an illustrative embodiment.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and may herein be described in detail. The drawings may not be to scale. It should be understood, however, that the embodiments described herein and shown in the drawings are not intended to limit the invention to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the scope of the present invention as defined by the appended claims.

DETAILED DESCRIPTION

A system and method for small scale marine transportation of floating hydrocarbons will now be described. In the following exemplary description, numerous specific details are set forth in order to provide a more thorough understanding of embodiments of the invention. It will be apparent, however, to an artisan of ordinary skill that the present invention may be practiced without incorporating all aspects of the specific details described herein. In other instances, specific features, quantities, or measurements well known to those of ordinary skill in the art have not been described in detail so as not to obscure the invention. Readers should note that although examples of the invention are set forth herein, the claims, and the full scope of any equivalents, are what define the metes and bounds of the invention.

As used in this specification and the appended claims, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to a berth includes one or more berths.

"Coupled," "coupling", or "couples" refers to either a direct connection or an indirect connection (e.g., at least one intervening connection) between one or more objects or components. The phrase "directly attached" means a direct connection between objects or components.

As used herein, the term "swap barge" means a barge including one or more tanks for storing cryogenic hydrocarbons (cryogenic hydrocarbon containment).

As used in this specification and the appended claims, "shallow" with respect to waters traversed by a swap barge, means 10 meters or less in depth.

As used in this specification and the appended claims, "deep water location" means a water location more than 10 meters in depth.

As used herein, the term "small scale" with respect to cryogenic hydrocarbon transport means one or more delivery vessels which are each capable of carrying 25,000 m³ or less of cryogenic hydrocarbon.

One or more embodiments of the invention provide a system for small scale marine transportation of cryogenic hydrocarbons, such as liquefied natural gas (LNG), liquefied petroleum gas (LPG) or ethane. Illustrative embodiments may allow inland water power plants and/or isolated coastal communities access to natural gas, petroleum gas or ethane supplies that may not otherwise be provided economically. Liquefied gas may be transferred from a liquefaction facility to a swap barge, which swap barge may be berthed at or proximate to a liquefaction facility. The swap barge carrying the cryogenic cargo may then rendezvous with a submersible transfer ship and be loaded onto a submersible transfer ship. The submersible transfer ship may be used for long haul transportation of the swap barge at speeds between about 12 and 16 knots. The swap barge may be offloaded from the submersible transfer ship at an offshore location proximate to the delivery location, and travel the last leg of the journey through restricted shallow water to the delivery location. At the delivery location, the swap barge may berth and offload its cargo to a regasification facility or storage tanks. Once the swap barge has been offloaded from the submersible transfer ship, the submersible transfer vessel may return proximate to the liquefaction facility to retrieve a second swap barge. The second swap barge may arrive at the delivery location and dock at a second offload berth prior to depletion of the first swap barge. When a swap barge has been depleted of cargo, it may rendezvous with the submersible transfer ship, and travel onboard the submersible transfer ship back to the liquefaction facility to be reloaded with cargo. In this way, delivery of cryogenic cargo may continue uninterrupted (continuously) during transitions from one swap barge to the next. Illustrative embodiments of the invention may reduce transfers of cargo, and the elimination of each cargo transfer may reduce transport time and boil-off losses. Illustrative embodiments may improve the speed of transport between loading and discharge ports as comparted to simple tug, ATB or ITB combinations.

Illustrative embodiments may be suitable for applications where access at one or both ends of the liquefied hydrocarbon supply chain are in or located through shallow water typically less than 30 feet (10 meters) in depth. Various embodiments of the invention include shallow water access at the loading or offloading end of the supply chain or at both the loading and offloading end of the supply chain. Various combinations of the components of illustrative embodiments may be implemented to tailor a supply chain for a specific consumer requirement for cryogenic hydrocarbon supply. Specific supply requirement profiles (usage/consumption profiles) may be analyzed to determine the most effective application of supply chain components for meeting consumer needs.

Illustrative embodiments may provide faster transport in both calm and heavier weather conditions, as compared to simple tow applications. The submersible transfer ship of illustrative embodiments may operate at speeds between about 12 knots and 16 knots, as compared to less than about 8 knots for a tow. Illustrative embodiments may allow a single transfer vessel to serve as the means of transport for multiple swap barges in a supply chain. In some embodiments, one swap barge may be in the process of being filled at a shallow water or other loading facility, a second swap barge may be transported to the offloading facility, while a third swap barge is being discharged at a shallow water offloading facility. The swap barge of illustrative embodiments maybe outfitted with thrusters and an operating station that may allow the swap barge to be transported under its own power to a shallow water wharf or jetty. In some embodiments, the swap barge may be transferred from the submersible transfer vessel to berth and from berth to submersible transfer vessel by a suitably sized tug boat.

The system of illustrative embodiments may include a land-based, dockside or offshore liquefaction facility, which liquefaction facility may include associated gas gathering, treatment and processing facilities, as well as liquefaction trains well known to those of skill in the art. The cryogenic hydrocarbons may then be transferred to a floating cryogenic swap barge, which may be moored at a jetty at a liquefaction facility. The liquefaction facility may include a dual berth to allow for an uninterrupted loading procedure. With a dual berth, an empty swap barge need not wait for a full swap barge to disconnect prior to beginning loading operations. The floating cryogenic swap barge may berth at a dock proximate to a liquefaction facility, storage tank and/or be coupled to a liquefaction facility or cryogenic storage tank by piping, hard arms and/or hoses. In some embodiments, the swap barge may be loaded at a land based liquefaction facility and be carried by truck or rail to the water for further travel over oceans, rivers or lakes.

FIG. 1 is an illustrative embodiment of a swap barge loading facility that serves as and/or is supplied by a liquefied hydrocarbon supply source. As shown in FIG. 1, gaseous hydrocarbons may be transported to liquefaction facility 110 through pipeline 105. Once the gas is received at liquefaction facility 110, it may be pre-treated at pretreatment facilities 115, after which it may be liquefied at liquefaction facility 110. Swap barge 200 may be moored at a berth adjacent to liquefaction facility 1 10, where tanks 205 may be cooled-down, if needed, and receive liquefied cryogenic hydrocarbon into cooled cargo tanks 205. Liquefaction facility 110 may supply swap barges 200 with liquefied hydrocarbon.

FIG. 2 is an illustrative embodiment of a swap barge. As shown in FIG. 2, swap barge 200 may comprise one or more floating cryogenic storage tanks with a capacity of about 6,000 m³ of cryogenic hydrocarbons each. Cargo tanks 205 may be type C cargo tanks, membrane-type cargo tanks or another cargo tank known to those of skill in the art. When type C cargo tanks 205 are employed, boil-off gas losses during cryogenic hydrocarbon transfer operations may be further reduced. Swap barge 200 may include an onboard handling system to provide both movement restraint and dockside control of swap barge 200 during loading and unloading operations. Unlike conventional barges, swap barge 200 may be capable of self-propulsion, for example to allow "last mile" maneuvering without tug boat assistance. In one example, swap barge 200 may include an external thruster. Power and navigation systems onboard swap barge 200 may be determined based on individual applications of illustrative embodiments. Swap barge 200 may have a shallower draft than traditional small scale cryogenic hydrocarbon vessels such as articulated tug barges (ATBs) or integrated tug barges (ITBs), allowing swap barge 200 access to the immediate proximity of a power plant or other inland and/or restricted shallow water location. This may be an improvement over conventional small scale transportation methods since illustrative embodiments enable access to a liquefaction and/or regasification facility without the need for dredging, which may be costly and time consuming. In some embodiments, swap barge 200 may be about 70 meters in length and 20 meters in beam. In certain embodiments, swap barge 200 may be a shallow- water vehicle or barge modified for self-propulsion. In alternative embodiments, swap barge 200 may not be capable of self-propulsion, but may be pulled by tug boats in shallow waters when it is not carried by submersible transfer ship 300 (shown in FIG. 3A).

Swap barge 200 may be carried during long haul transportation by submersible transfer ship 300. FIGs. 3A and 3B are an illustrative embodiment of a submersible transfer ship. In an exemplary embodiment, submersible transfer ship 300 may be about 115 meters in length overall, 22 meters in beam and include two main engines having 3,500 brake horsepower. Submersible transfer ship 300 may accommodate swap barge 200 on deck 305. Swap barge 200 may be loaded or unloaded onto submersible transfer ship 300 at a deep and/or open water location in a river, sea or ocean, such as first deep water location 700 (shown in FIG. 7A) or second deep water location 705 (shown in FIG. 7A). Submersible transfer ship 300 may submerge the majority of its structure by bringing ballast water into the hull, located beneath submersible transfer ship 300, until deck 305 of submersible transfer ship 300 is lower than the draft of swap barge 200. Swap barge 200 may then float on deck 305 while deck 305 is submerged below the water's surface. Submersible transfer ship 300 may deballast to pick up swap barge 200 as a cargo once swap barge is positioned above deck 305. Submersible transfer ship 300 may transform from a deep to a shallow draft by deballasting, and thereby become a surface vessel. Swap barge 200 may then be secured to deck 305 using tie downs, a locking device, or other securing mechanism known to those of skill in the art.

FIG. 3A is an illustrative embodiment of submersible transfer ship 300 as a surface vessel. FIG. 3B is an illustrative embodiment of submersible transfer ship 300 with a deep draft (submerged). Once swap barge 200 has been secured onto deck 305, submersible transfer ship 300 may proceed to transport swap barge 200 to an area near the inland, restricted and/or shallow water destination at about 12 to 16 knots, for example up to the point where the waterway becomes too shallow or too narrow for the submersible transfer ship 300 to navigate. FIG. 4 is an illustrative embodiment of a swap barge 200 secured as cargo on a submersible transfer ship 300. Submersible transfer ship 300 may be a dual fuel vessel capable of burning low sulfur marine diesel oil (LSMDO) and/or natural gas.

Upon arrival in proximity to the delivery location, for example from about 1 to 10 nautical miles of the delivery location (e.g., last leg or last "mile"), swap barge 200 may be offloaded from submersible transfer ship 300 at an open or deep water location, such as second deep water location 705 (shown in FIG. 7A). Submersible transfer ship may ballast to a deep draft to permit swap barge to offload and/or to allow an empty swap barge 200 returning from the delivery location 600 to be loaded. Submersible transfer ship 300 may then return with the empty swap barge 200 back to the location of production to reload with cryogenic hydrocarbon. In some embodiments, the location of production and/or supply may be relatively close to the location of delivery, for example 7, 10 or 12 days round trip. Swap barge 200 that is loaded with cargo may proceed from the deep water drop-off location (second deep water location 705) through the shallow and/or narrow waters to the delivery location.

FIG. 5 is an exemplary restricted shallow water location that may benefit from illustrative embodiments. As illustrated in FIG. 5, although delivery location 600 (e.g., a power plant) is located on the water and/or at the shoreline, access is infeasible with a traditional hydrocarbon carrier vessel, such as an LNG carrier (LNGC), tanker or regasification vessel, due to the shallowness and/or narrowness of restricted water 510. Conventional ship-to-ship transfers at delivery location 600 is similarly impossible due to the narrowness of restricted water 510, which may for example be 100 yards in width, 60 yards in width, or less. Restricted water 510 may be an inlet or estuary. Swap barge 200 may proceed through narrow restricted water 510 to delivery location 600. Delivery location 600 may be located on an island or other area requiring less than 1.5 MTPA of hydrocarbons. In certain embodiments, delivery location 600 may require more than 1.5 MTPA of hydrocarbons, but about 1.5 MTPA or less is the general capacity which may most benefit from the "small scale" transportation of illustrative embodiments due to the capacity of swap barge 200, which may for example be 25,000 m³ or less. Swap barge 200 may be self- propelled or may be pulled by a tug boat through restricted water 510. In some embodiments, swap barge 200 may be self-propelled to reduce operating costs.

FIG. 6 is an illustrative embodiment of a delivery location 600, such as a power plant. Delivery location 600 may include one or more offload berths 605, in which swap barge 200 may dock to deliver its cargo of cryogenic hydrocarbons, which may for example be LNG, ethane, liquefied petroleum gas (LPG) or another cryogenic hydrocarbon. In FIG. 6, a dual berth is shown including two berths 605 and a single jetty 660 with transfer platform 645 placed between berths 605. Transfer platform 645 may be a mooring platform or mooring dolphin and receive cryogenic hydrocarbons from cargo tanks 205. A berthing arrangement such as illustrated in FIG. 6, including dual berth 605, jetty 660 and transfer platform 645 may provide advantages over a conventional loading or offloading facility berth. Conventional facilities provide for the mooring of single vessel at a defined berth location for the purpose of loading or discharging. When the vessel completes loading or discharge, the vessel departs the conventional berth and another vessel may be moored at the conventional berth to be loaded or discharged. In contrast, dual berth 605 may provide for an uninterrupted flow of gas to the consumer during the time that swap barges 200 are being exchanged. Illustrative embodiments may enable a full swap barge 200 to be securely moored, the transfer arrangement to be connected, and the flow of cryogenic hydrocarbon from the full swap barge 200 to be established before flow of cryogenic hydrocarbon from the spent swap barge 200 is stopped and the spent (empty) swap barge departs the dual berth 605.

Berths 605 may include mooring lines 635 and/or deadman anchors 640 to secure swap barge in place. Hoses 610 and pipes 655 may transfer the cryogenic hydrocarbon cargo to regasification facility 615 and/or storage tanks at delivery location 600. Hoses 610 may be hoses, a hard arm on jetty 660 or floating hoses. Transfer platform 645 may include hose reels 650 with lifting davit. In the embodiment shown in FIG. 6, culvert 630 may provide walkway access to jetty 660. The regasified cargo may then be transferred to a power plant 620 through gas tie-in 625. In the embodiment shown in FIG. 6, the cryogenic cargo is transferred directly from cargo tanks 205 to regasification facility 615, without the need for intermediate storage. Intermediate storage may be provided based on the needs of delivery location 600.

FIGs. 7A-7E are an illustrative embodiment of system for the transportation of cryogenic hydrocarbons. As shown in FIGs. 7A-7E, submersible transfer ship 300 may continuously (subject to routine maintenance or repairs) voyage between first deep water location 700 and second deep water location 705, and back again. During the voyage of submersible transfer ship 300, it may transport one or more swap barges 200a, 200b and/or 200c between first and second deep water locations 700, 705. In the embodiment illustrated in FIG. 7A, first swap barge 200a is being loaded with cryogenic hydrocarbons at liquefaction facility 110, second swap barge 200b is unloading cryogenic hydrocarbon at delivery location 600, and third swap barge 200c with loaded cargo tank 205 is propelling from liquefaction facility 1 10 towards first deep water location 700 where it will rendezvous with submersible transfer ship 300. As shown in FIG. 7B, third swap barge 200c has been floated onto submersible transfer ship 300 as cargo at first deep water location 700, and submersible transfer ship 300 with third swap barge 200c on deck 305 travels towards second deep water location 705. In FIG. 7B, second swap barge 200b continues to unload cryogenic hydrocarbons at delivery location 600. In FIG. 7C, submersible transfer ship 300 has arrived at second deep water location 705, which is proximate to delivery location 600, such as for example a half, one or two nautical miles from delivery location 600. Once at second deep water location 705, submersible transfer ship 300 ballasts to a deep draft, and third swap barge 200c offloads and proceeds through restricted water 510. In FIG. 7D, third swap barge 200c has docked at delivery location 600, which may include dual berths 605. Once third swap barge 200c has connected to delivery location 600 at one of the dual berths 605 and commenced delivery, second swap barge 200b, then-emptied of cargo, proceeds through restricted water 510 and loads onto submersible transfer ship 300 at second deep water location 705. Submersible transfer ship 300 may then transport back towards first deep water location 700 with empty second swap barge 200b on deck 305 (shown in FIG. 4). As shown in FIG. 7E, second swap barge 200b has returned to liquefaction facility 110 for reloading its cargo tank 205 with cryogenic hydrocarbons, and first swap barge 200a, now loaded with cryogenic hydrocarbon, proceeds to rendezvous with submersible transfer ship 300 to be transported to second deep water location 705 and repeat the cycle.

In this way, for each barge 200, cryogenic hydrocarbon is only transferred twice throughout each loading and unloading cycle: once when swap barge 200 is loaded with cryogenic hydrocarbon at liquefaction facility 110, and the second time when swap barge 200 delivers cryogenic hydrocarbon at delivery location 600. Illustrative embodiments are in contrast to prior methods making use of ship-to-ship transfer and requiring three transfers with associated boil-off losses. In addition, once each swap barge 200 is gassed-up, it may stay gassed-up except for routine inspection and maintenance requirements. Reduction in the need for gassing up cargo tanks may further reduce transport time. Further, loading and unloading swap barge 200 onto a semi-submersible vessel 300 takes less time than ship-to- ship transfer of a cargo of cryogenic hydrocarbons. For example, it may take 6 hours for a swap barge 200 to be loaded onto a submersible transfer ship 300 and 6 hours to unload, but 25 hours to transfer a 25,000 m³ cargo of cryogenic hydrocarbon at 1000 mVhr from one carrier to another. Table 1 sets forth an exemplary, non-limiting, time-table of transport events of illustrative embodiments as follows:

In FIG. 7A-7E, three swap barges 200a, 200b and 200c are shown. Throughout the transport cycle of the embodiment illustrated in FIGs. 7A-7E, one swap barge 200 is being loaded with cryogenic hydrocarbon; one swap barge 200 is being transported by submersible transfer ship 300 towards delivery location 600; and one swap barge 200 is unloading cargo at delivery location 600. In illustrative embodiments, the swap barge 200 in transport may arrive at a delivery berth 605 prior to depletion of the swap barge 200 unloading cargo. Once the submersible transfer ship 300 arrives at the drop-off (second deep water location 705), it may await the spent swap barge 200 that has unloaded its cargo before returning to production first deep water location 700 to unload the empty swap barge 200 and pick up a loaded swap barge 200.

Illustrative embodiments may allow for uninterrupted and/or continuous delivery of cryogenic hydrocarbon to a marine delivery location. While a first swap barge 200 is delivering cryogenic hydrocarbon at delivery location 600, a second swap barge 200 loaded with cryogenic hydrocarbon may begin mooring and connecting to delivery location 600. The second swap barge 200 may connect at the unloading facility before the first swap barge 200 is depleted, and begin delivering cryogenic hydrocarbons as soon as the first swap barge 200 terminates. In this way, deliveries may be scheduled such that there is no interruption in delivery while swap barges 200 are exchanged, and cryogenic hydrocarbons may be delivered continuously for as long as they are needed at the delivery location.

In some embodiments, submersible transfer ship 300 may deliver swap barges 200 to multiple delivery locations in relatively close proximity, rather than remaining idle whilst awaiting swap barges 200 to unload and/or propel to the rendezvous location. For example, submersible transfer ship may alternate between drop-off locations. In another example, some swap barges 200 may travel from second deep water location 705 (drop-off location) to delivery location 600, and some swap barges may travel from second deep water location 705 (drop-off location) to a second delivery location, for example, one on the opposite side of an island from delivery location 600. In some embodiments, delivery location 600 may include more than two berths 605, such as three or four berths 605 in order to facilitate continuous delivery of cryogenic hydrocarbons.

FIG. 8 is an illustrative embodiment of a method for small scale transportation of cryogenic hydrocarbons. At step 800, a gaseous hydrocarbon may be liquefied at liquefaction facility 110. The liquefied hydrocarbon, such as LNG, LPG or ethane, may then be transferred onto a swap barge 200 at step 805. Step 805 may include mooring swap barge 200 to a jetty at liquefaction facility 110, connection of hoses, and/or gas-up and cool-down of cargo tanks 205 as necessary. Loading of liquefied hydrocarbon onto cargo tanks 205 on swap barge 200 may for example be at 1000 m³/h and take about 12 hours (for 12,000 m³ capacity). The swap barge 200, loaded with cryogenic hydrocarbon, may then self-propel to a first offshore, deep water location 700 at step 810. At step 815, a submersible transfer ship 300 may submerge at first deep water location 700 and take-on the loaded swap barge 200 as cargo on deck 305. The submersible transfer ship may then emerge and transport the loaded swap barge 200 to a drop-off, second open deep water location 705 at step 820. The submersible transfer ship 300 may submerge for a second time at second deep water location 705 at step 825 to allow loaded swap barge 200 to offload proximate to delivery location 600. At step 830, swap barge 200 may self-propel through restricted water 510 to an unloading berth 605. At step 835, the swap barge may connect to the delivery facility (delivery location 600) and unload its cryogenic cargo at berth 605. At step 840, once emptied, the empty swam barge 200 may disconnect from delivery location 600 and once again rendezvous with submersible transfer ship 300 at second deep water location 705. Submersible transfer ship 300 may submerge and load empty swap barge 200 at step 845. At step 850, submersible transfer ship 300 may emerge and transport empty swap barge 200 to first deep water location 700. Once unloaded from submersible transfer ship 300, empty swap barge 200 may return to liquefaction facility 1 10 for reloading. Gassing up a second time may not be necessary. Steps 805 through 850 may then be repeated.

A system and method for small scale marine transport of cryogenic hydrocarbons has been described. Illustrative embodiments may allow delivery of cryogenic hydrocarbons to locations previously unable to be reached by marine carriers carrying cryogenic cargo, for example power plants located on narrow and/or shallow inlets or estuaries. Delivery may be faster and less capital intensive than traditional tug boats, ATBs or ITBs. This may allow for localities currently employing diesel fuel for power to switch to natural gas or ethane, which are cheaper and cleaner burning fuels. Transport time and boil-off losses may also be reduced due to the reduction in transfers of the cryogenic hydrocarbon from one vessel to another.

Further modifications and alternative embodiments of various aspects of the invention may be apparent to those skilled in the art in view of this description. Accordingly, this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the general manner of carrying out the invention. It is to be understood that the forms of the invention shown and described herein are to be taken as the presently preferred embodiments. Elements and materials may be substituted for those illustrated and described herein, parts and processes may be reversed, and certain features of the invention may be utilized independently, all as would be apparent to one skilled in the art after having the benefit of this description of the invention. Changes may be made in the elements described herein without departing from the scope and range of equivalents as described in the following claims. In addition, it is to be understood that features described herein independently may, in certain embodiments, be combined.

Claims

CLAIMS:

1. A cryogenic hydrocarbon marine transportation system comprising:

a marine delivery location located through restricted shallow water and aquatically coupled to a cryogenic hydrocarbon supply source, the marine delivery location comprising a jetty having a first berth, a second berth and a transfer platform in between the first and second berths;

the restricted shallow water navigable by a swap barge;

the swap barge comprising:

at least one cryogenic hydrocarbon cargo tank, wherein the at least one

cryogenic hydrocarbon cargo tank carries cryogenic hydrocarbon from the cryogenic hydrocarbon supply source and provides the cryogenic hydrocarbon to the marine delivery location when the swap barge is moored at one of the first or second berths;

a semisubmersible transfer ship comprising a deck, wherein the semisubmersible transfer ship is convertible between:

a ballasted position, wherein the deck is submerged below a surface of water and the swap barge is loaded onto the deck when the semisubmersible transfer ship is in the ballasted position; and

a travel position, wherein the deck is above the surface of water and the swap barge is secured on the deck when the semisubmersible transfer ship is in the travel position;

wherein the cryogenic hydrocarbon is transported from the supply source to the

marine delivery location by the swap barge, and wherein the swap barge is transported proximate to the restricted shallow water on the deck of the semisubmersible transfer ship.

2. The system of claim 1, wherein the restricted shallow water is one of an inlet or an estuary.

3. The system of claim 1, wherein there are a plurality of swap barges and each of the plurality of swap barges has a cryogenic hydrocarbon capacity of 25,000 m³ or less.

4. The system of claim 1, wherein the swap barge further comprises a self- propulsion system.

5. The system of claim 1, wherein there are a plurality of swap barges, wherein a first swap barge of the plurality of swap barges is moored at the first birth and providing the cryogenic hydrocarbon to the marine delivery location, and wherein a second swap barge of the plurality of swap barges moors at the second birth and connects to the marine delivery location before the first swap barge is depleted of cryogenic hydrocarbon.

6. They system of claim 1 , further comprising a cryogenic hydrocarbon delivery system, the cryogenic hydrocarbon delivery system comprising one of cryogenic floating hoses, cryogenic pipes, hard arms or a combination thereof, and wherein when the swap barge is moored at one of the first or second berths, the cryogenic hydrocarbon delivery system extends between the at least one cryogenic hydrocarbon cargo tank and a regasification facility at the marine delivery location.

7. The system of claim 6, wherein the transfer platform comprises hose reels with lifting davit and a culvert provides walkway access to the jetty.

8. The system of claim 1, wherein at least a portion of the restricted shallow water comprises a water depth less than about 10 meters deep.

9. The system of claim 1, wherein the cryogenic hydrocarbon is liquefied natural gas (LNG).

10. The system of claim 1, wherein the cryogenic hydrocarbon is ethane.

11. The system of claim 1 , wherein the cryogenic hydrocarbon is liquefied petroleum gas (LPG).

12. A method for marine transportation of cryogenic hydrocarbons comprising:

loading a cryogenic cargo tank onboard a swap barge with cryogenic

hydrocarbons at a cryogenic hydrocarbon supply source; navigating the loaded swap barge to a first water location proximate to the cryogenic hydrocarbon supply source;

ballasting a semisubmersible transfer ship at the first water location such that a deck of the semisubmersible transfer ship is submerged;

floating the loaded swap barge onto the submerged deck;

deballasting the semisubmersible transfer ship into a travel position once the loaded swap barge is above the deck;

transporting the semisubmersible transfer ship with swap barge on deck to a second water location, the second water location proximate to a marine delivery location, wherein restricted shallow water couples the second water location and the marine delivery location;

ballasting the semisubmersible transfer ship to allow the loaded swap barge to float from the deck;

propelling the swap barge from the second water location through the restricted shallow water to the marine delivery location; and

delivering cryogenic hydrocarbon from the swap barge to the marine delivery location.

13. The method of claim 12, wherein the marine delivery location comprises at least two berths and there are at least two swap barges, and wherein a first swap barge of the at least two swap barges connects to the marine delivery location at a first berth of the at least two berths and delivers cryogenic hydrocarbon before a second swap barge of the at least two swap barges moored at a second berth of the at least two berths is depleted of cryogenic hydrocarbon.

14. The method of claim 12, wherein the swap barge self-propels from the second water location to the marine delivery location.

15. The method of claim 12, wherein during ballasting the deck of the

semisubmersible transfer ship is submerged below a surface of water prior to the loaded swap barge floating from the deck.

16. The method of claim 12, wherein the swap barge propels to the marine delivery location by tug boat.

17. The method of claim 12, wherein the semisubmersible transfer ship transports the swap barge at between about 12-16 knots.

18. The method of claim 12, wherein a distance between the cryogenic hydrocarbon supply source and the first water location is less than about 10 nautical miles.

19. The method of claim 18, wherein at least a portion of the depth of the restricted shallow water is less than about 10 meters deep.

20. A cryogenic hydrocarbon marine transportation system comprising:

a plurality of swap barges, wherein each swap barge has a cryogenic

hydrocarbon capacity of 25,000 m³ or less; and

a semisubmersible transfer ship;

wherein the semisubmersible transfer ship and the plurality of swap barges cooperate to provide sequential delivery of cryogenic hydrocarbon to a marine delivery location, wherein access to the marine delivery location is through one of an inlet or an estuary;

wherein the semisubmersible transfer ship transports each of the plurality of swap barges on deck across open water;

wherein the plurality of swap barges self-propel through the one of the inlet or the estuary to the marine delivery location; and

wherein the cryogenic hydrocarbon is provided to the marine delivery location during transitions when a first swap barge of the plurality of swap barges is depleted of cryogenic hydrocarbon and a second swap barge of the plurality of swap barges begins delivery.

21. The system of claim 20, wherein the marine delivery location comprises a dual berth transfer platform.

22. The system of claim 20, wherein the marine delivery location requires less than about 1.5 metric ton per annum (MTPA) of cryogenic hydrocarbons.