A SHIP AND A METHOD FOR BRINGING LIQUIFIED GAS FROM AN ONSHORE TERMINAL ACROSS A SEA TO A SUBSURFACE PERMANENT STORAGE RESERVOIR

Abstract

A ship and a method are for bringing liquified gas, such as liquified carbon dioxide, CO.sub.2, from an onshore terminal for captured gas across a sea to a subsurface permanent storage reservoir. The ship has a loading line for communicating liquified gas from the onshore terminal into at least one vessel, and a processing plant. The processing plant of the ship has an injection processing module configured for injecting liquified gas into the subsurface permanent storage reservoir, wherein the injection processing module is operatively connected to the at least one vessel and an injection line provided with a connector for connecting to a flexible injection hose being in fluid communication with the subsurface permanent storage reservoir.

Claims

1. A ship for bringing liquified gas, such as liquified carbon dioxide, CO.sub.2, from an onshore terminal across a sea to a subsurface permanent storage reservoir, the ship comprising a loading line for communicating liquified gas received from the onshore terminal into at least one vessel onboard the ship, and a processing plant, wherein the processing plant comprises: an injection processing module comprising an injection pump configured for injecting liquified gas into the subsurface permanent storage reservoir; wherein the injection processing module is operatively connected to the at least one vessel and a gas injection line provided with a connector for connecting to a flexible injection hose extending from a subsea connection point being connected to a well of the subsurface permanent storage reservoir, wherein the ship is a shuttle tanker comprising a storage tank having a larger volume than the at least one vessel, wherein a portion of the at least one vessel is housed within the storage tank.

2. The ship according to claim 1, wherein the processing plant further comprises a liquifying processing module configured for liquifying gas, wherein the at least one vessel is in loop communication with the liquifying processing module so that gas evaporated from the liquified gas within the at least one vessel is liquified in the liquifying processing module and communicated back into the at least one vessel.

3. The ship according to claim 1, wherein the at least one vessel comprises a first portion and a second portion, the first portion extending above a main deck of the ship, and wherein pipes for communicating gas from the at least one vessel to the process plant are connected to the first portion of the at least one vessel.

4. The ship according to claim 3, wherein the second portion of the at least one vessel extends into the storage tank having a larger volume than the at least one vessel.

5. The ship according to claim 4, wherein the at least one vessel comprises a plurality of vessels extending into the storage tank.

6. The ship according to claim 1, wherein the at least one vessel being oblongness, wherein a longitudinal axis of the vessel is substantially perpendicular to a surface of a main deck of the ship.

7. The ship according to claim 1, wherein the ship is provided with at least one of a Dynamic Positioning System and an anchoring system allowing for free weathervaning.

8. The ship according to claim 1, wherein the ship is a superannuated shuttle tanker, wherein a portion of the at least one vessel is housed within a storage tank originally installed in the shuttle tanker.

9. A method for bringing liquified gas, from an onshore terminal, across a sea to a subsurface permanent storage reservoir, the method comprising: transferring the liquified gas from the onshore terminal to a ship according to claim 1, wherein the method further comprises: bringing the ship to and positioning the ship with respect to an inlet of the subsurface permanent storage reservoir; providing fluid communication between the at least one vessel of the ship and the inlet of the subsurface permanent storage reservoir; and injecting the liquified gas from the at least one vessel into the permanent subsurface storage reservoir via the injection processing module of the process plant.

10. The method according to claim 9, further comprising providing the process plant with a liquifying processing module configured for liquifying gas, the liquifying processing module configured for being set in loop communication with the at least one vessel for re-liquifying gas evaporated from the liquified gas within the at least one vessel.

11. The method according to claim 9, wherein the positioning of the ship with respect to the inlet of the subsurface permanent storage reservoir is provided by dynamic positioning.

12. The method according to claim 9, wherein the positioning of the ship with respect to the inlet of the subsurface permanent storage reservoir is provided by a free weathervaning anchoring system.

13. The method according to claim 9, wherein providing fluid communication between the at least one vessel and the inlet of the subsurface permanent storage reservoir comprises connecting an injection line of the ship to an upper end portion of a flexible injection hose configured for communicating fluid through the inlet of the subsurface permanent storage reservoir.

14. A method comprising using a superannuated crude oil shuttle tanker adapted for bringing liquified gas from an onshore terminal for captured gas directly to a subsurface permanent storage reservoir.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In the following is described examples of preferred embodiments illustrated in the accompanying drawings, wherein:

[0054] FIG. 1a shows a principle drawing of a ship in a loading state at an onshore terminal, and a subsequent reservoir injecting state wherein the ship is operatively connected to a subsurface permanent storage reservoir;

[0055] FIG. 1b shows in larger scale a principle drawing of the ship in FIG. 1a being in the reservoir injecting state;

[0056] FIG. 2a shows in larger scale a principle drawing of a side view of the ship;

[0057] FIG. 2b shows the ship in FIG. 1 seen from above;

[0058] FIG. 2c shows in larger scale detail A of FIG. 2a; and

[0059] FIG. 3 shows a simplified process outline of an embodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

[0060] In the description, positional indications such as for example above, below, right, refer to the position shown in the figures.

[0061] Same or corresponding elements are indicated by same reference numerals. For clarity reasons some elements may in some of the figures be without reference numerals.

[0062] A person skilled in the art will understand that the figures are just principle drawings. The relative proportions of individual elements may also be strongly distorted.

[0063] The examples are related to a liquified gas in the form of captured CO.sub.2 that has been captured and liquified by CO.sub.2 emitters and that has been transported to the onshore terminal. However, it should be noted that the liquified gas may be other liquified gases as mentioned above wherein there may be a desire of permanently safe storage in a subsurface reservoir.

[0064] In the figures, the reference numeral 1 indicates a ship according to the invention. In the embodiment shown, the ship, here shown as a tanker 1, comprises compartments 3 wherein each compartment 3 houses a plurality of vertical vessels 5 arranged adjacent each other and configured for holding liquified carbon dioxide (CO.sub.2).

[0065] A first portion of the vertical vessels 5 extends above a main deck 7 of the ship, while a second portion of the vertical vessels 5 is housed within the compartments 3.

[0066] In the embodiments shown, the ship 1 is a superannuated crude oil shuttle tanker designed with crude oil storage tanks that are modified to form the compartments 3 for housing the CO.sub.2 vessels 5. The originally designed storage tanks are modified by providing opening or openings for the top portion of the CO.sub.2 vessels 5. The rest of the storage tanks that form the compartments 3 of the ship or tanker 1 according to the invention, are maintained substantially as designed for the superannuated crude oil shuttle tanker. Therefore, substantially no redesign of the load carrying structure of the superannuated crude oil tanker is required.

[0067] FIG. 1a shows a principle drawing of a ship 1 being in a loading state at an onshore terminal OT for captured CO.sub.2 (indicated as Pos. 1 in the figure), and in a subsequent reservoir injecting state (indicated as Pos. 2 in the figure) wherein the ship 1 has moved across the sea S and is operatively connected to a subsurface permanent storage reservoir R via a Subsea Connection Point (SCP) to a well W for the subsurface permanent storage reservoir. However, the principle shown in FIG. 1 may also be applicable for a so-called Direct Shuttle Loading (DSL) wherein a first ship (indicated as Pos. 1 in FIG. 1a) is moored at a loading jetty (not shown), and a second ship (indicated as Pos. 2 in FIG. 1a). In said DSL, the first ship and second ship are operated in a substantially continuous operation between the loading jetty and the location of the subsurface permanent storage reservoir.

[0068] A person skilled in the art will appreciate that the Subsea Connection Point may be operatively connected to a plurality of wells. The subsurface permanent storage reservoir R is in the embodiment shown an abandoned petroleum reservoir. The SCP is operatively connected to a flexible injection hose RP wherein an end portion of the flexible injection hose RP is provided with a submerged loading buoy SL. In an inactive position, the submerged loading buoy SL floats in an equilibrium position approximately 30-50 meters below sea level. The submerged loading buoy SL is moored to a seabed SB by means of anchor lines (not shown).

[0069] As an alternative to connecting the ship 1 to the subsurface permanent storage reservoir R via a submerged loading buoy SL, the ship 1 may be connected to the subsurface permanent storage reservoir R via a catenary anchor leg mooring (CALM) or similar connection mechanisms allowing for communication of fluid from ship 1 to seabed SB.

[0070] In the reservoir injecting state (Pos. 2 to the right in FIG. 1a), the ship 1 is kept at a desired position by means of a Dynamic Positioning System DPS to automatically maintain the ship's position and heading by using its own propellers and thrusters T as indicated in FIG. 1b. It should be noted that prior to commencing the injection of the CO.sub.2, the submerged loading buoy SL shown in FIG. 1a is operatively connected to the ship 1 as shown in FIG. 1b.

[0071] Turning now to FIGS. 2a-2c, the ship 1 is provided with a compartment 15 at a bow of the ship 1. The compartment 15 comprises a conical recess and lifting appliances (not shown) for lifting the submerged loading buoy SL into the compartment 15 and securing the loading buoy SL within the compartment (see FIG. 1b) as will be appreciated by a person skilled in the art.

[0072] The ship 1 comprises a loading line 20 having connector 21 for connecting to a terminal loading line TL (see FIG. 1a). The loading line 20 is connected to distribution manifolds 22 operatively connected to each vessel 5 (ninety-six shown in FIG. 2b) via submanifolds 24, one for each row of vessels 5 within each cluster of vessels 5 defined by the each of the six compartments 3 shown in FIG. 2b.

[0073] The manifolds 22 and submanifolds 24 comprises four parallel pipeline systems as will be explained below.

[0074] The loading line 20 discussed above is connected to the vessels 5 via loading pipelines forming a first pipeline system of the manifolds 22 and submanifolds 24.

[0075] The ship 1 further comprises a processing plant 10. The processing plant 10 comprises a liquifying processing module 12 configured for liquifying gaseous CO.sub.2, and an injection processing module 14 configured for injecting liquified CO.sub.2 into the subsurface permanent storage reservoir R. Injection pumps (see FIG. 3) of the injection processing module 14 are configured for an injection pressure adapted to a pressure in the subsurface permanent storage reservoir R.

[0076] During loading of the liquified CO.sub.2 from the onshore terminal OT, and until the CO.sub.2 is injected into the subsurface permanent storage reservoir, some of the liquified CO.sub.2 will undergo a phase change from liquified state to gas state, i.e., some of the CO.sub.2 will evaporate.

[0077] Instead of releasing the CO.sub.2 to the atmosphere, the evaporated CO.sub.2 is communicated into the liquifying processing module 12 configured for liquifying gaseous CO.sub.2 via a degassing line 120 operatively connected to each of the vessels 5 via degassing pipelines forming a second pipeline system of the manifolds 22 and submanifolds 24. In the liquifying processing module 12, the gaseous CO.sub.2 is reliquefied and returned to the vessels 5 via a return conduit 122 and degassing return pipelines forming a third pipeline system of the manifolds 22 and submanifolds 24. Thus, degassing line 120 and the return conduit 122 is arranged in a loop comprising the vessels 5 and the processing module 12. The liquifying processing module 12 comprises a pressure increasing device and a cooling element known per se.

[0078] The injection processing module 14 of the process plant 10 is operatively connected to the vessels 5 via an injection module supply line 140. The injection module supply line 140 is operatively connected to each of the vessels 5 via injection supply pipelines forming a fourth pipeline system of the manifolds 22 and submanifolds 24. In the injection processing module 14, the liquified CO.sub.2 is further pressurised and heated by a heating element before it is communicated into an injection line 142 and into the subsurface permanent storage reservoir R (see FIG. 1a) via the buoy SL and the flexible injection hose RP. The injection line 142 bypasses the manifolds 22 as best seen in FIG. 2c.

[0079] The liquified CO.sub.2 flowing in the injection line 142 may typically be heated to a temperature of for example 4 C. to avoid formation of ice plugs in the injection line 142 and in the flexible injection hose RP. The heating element of the injection processing module may comprise a heat exchanger. Such a heat exchanger may be configured for heat exchange with for example sea water or exhaust from a combustion engine of the ship 1.

[0080] From the above it should be appreciated that a length of the flexible injection hose RP is extremely limited as compared with an injection pipeline running from an onshore terminal to an inlet of a subsurface permanent storage reservoir as suggested in the Northern Lights Project Concept Report mentioned above. Further, a ship bringing the captured CO.sub.2 to a position above a subsurface permanent storage reservoir R is flexible in that no new pipeline infrastructure has be installed in the seabed when a storage reservoir has been saturated and a new subsurface permanent storage reservoir is required.

[0081] Due to the liquifying processing module 12 of the ship 1, the ship 1 may be in a standby position relatively nearby the relevant storage reservoir for several days without losing any of the CO.sub.2 load caused by evaporation of the liquified CO.sub.2. Keeping the ship 1 in a standby position may be necessary for example due to harsh weather conditions or a que of ships waiting for access to the submerged loading buoy SL.

[0082] Turning now to FIG. 3 showing a process outline for the process from an onshore terminal OT, via the ship 1 to the subsurface connection point SCP operatively connected to for example, but not limited to, a submerged loading buoy SL as shown in FIGS. 1a-2b, or a catenary anchor leg mooring (CALM) or similar connection mechanisms allowing for communication of fluid from ship 1 to seabed SB.

[0083] In FIG. 3, elements forming part of the ship or tanker 1, is indicated within dash-dot lines. Further, elements forming part of the injection module 14 are indicated by hatching.

[0084] The liquified CO.sub.2 is transferred from one or more tanks of an onshore terminal OT, via terminal loading line TL, to the at least one vessel 5 of the ship 1. The terminal loading line TL comprises a loading line pump OP. The CO.sub.2 may in this stage have a pressure of for example 15 bar and a temperature of 25 C. An equalisation line RL extends from the vessel 5 to the tanks of the onshore terminal OT so that the volume of the liquified CO.sub.2 pumped out of the onshore terminal tanks is compensated by evaporated CO.sub.2 from the vessel 5 of the ship 1.

[0085] After finishing loading of the CO.sub.2 into the vessel 5, the loading line TL and the equalization line RL are disconnected from the ship 1 whereinafter the ship 1 starts its crossing to a location of the subsurface permanent storage reservoir.

[0086] At the location of the subsurface permanent storage reservoir, the vessel 5 of the ship 1 is operatively connected to the subsurface permanent storage reservoir via a floating buoy system.

[0087] The floating buoy system may be a CALM (catenary anchor leg mooring) buoy, or an anchor moored submerged loading buoy, including a swivel, which will allow for free weathervaning of the ship when connected. The selection of buoy system will depend on water depth and weather conditions on location. Thus, in FIG. 3, the reference numeral 15 indicates a connection point between the flexible injection hose RP and the ship 1.

[0088] When commencing the injection operation, the injection module 14 is activated. The injection module 14 comprises a transfer pump 143 configured for increasing the pressure of the liquified CO.sub.2 flowing into a heater 144. In the heater 14, the pressure may be for example 50 bar. The heater 144 is configured for increasing the temperature of the liquified CO.sub.2 to avoid phase transition of the CO.sub.2 from liquified state to solid state when flowing through the flexible injection hose RP and the subsea connection point SCP. The temperature of the liquified CO.sub.2 flowing out of the heater 144 is adapted to an ambient temperature of the flexible injection hose RP at a lower end portion thereof, and an injection pressure provided by an injection pump 145 arranged downstream of the heater 144. The injection pressure is adapted to a pressure within the subsurface reservoir. The liquified CO.sub.2 being injected may for example have a temperature of 4 C. and a pressure of 120 bar.

[0089] The process outline shown in FIG. 3 further comprises a vaporization unit 147 arranged in a loop 148 operatively connected to an outlet and an inlet of the vessel 5. The vessel 5 may comprise a plurality of vessels as shown in FIGS. 1a-2c. The purpose of the vaporization unit 147 is to compensate for the volume of liquified CO.sub.2 being injected into the reservoir, and thus maintaining the desired pressure within the vessel 5 (or vessels).

[0090] The process outline shown in FIG. 3 further comprises a liquifying processing module 12 forming part of the processing plant 10. The liquifying processing module is configured for liquifying gaseous CO.sub.2 evaporating from the vessel 5 during loading of the liquified CO.sub.2, and during transport from the onshore terminal OT and until the process of injecting the liquified CO.sub.2 into the subsurface permanent storage reservoir R commences. The CO.sub.2 liquified by means of the liquifying processing module 12 is communicated back into the vessel 5 via return conduit 122. Thus, substantially no load is lost.

[0091] The ship 1 may further comprise a control system 17 known per se for controlling a wellhead control package comprising subsea valves and the well of the subsurface permanent storage reservoir R. The control system 17 is configured for supplying hydraulic power, monoethylenglycol (MEG), electrical power and signals to the wellhead. The hydraulic power may be provided by means of a water based hydraulic power system being in fluid communication with ambient water. The control system 17 is further operatively connected to a chemical injection line 17 for injecting for example monoethylenglycol into the subsea connection point SCP and the flexible injection hose RP prior to disconnecting the ship from the flexible injection hose RP so that the flexible injection hose and subsea connection point is prepared for a new load of CO.sub.2.

[0092] In an alternative embodiment (not shown) a control system corresponding to the system 17 discussed above, may be arranged separately from the ship 1, for example from a distant offshore platform operatively connected to the subsea connection system SCP.

[0093] A person skilled in the art will appreciate that any subsea connection point provided with a flexible injection hose must be provided with an emergency system being activatable in the event of emergency disconnect from a ship operatively connected to a flexible injection hose. An emergency disconnect will typically occur in a situation wherein the ship is subject to an uncontrolled drive- or drift-off. For a flexible injection hose configured for receiving liquified CO.sub.2, such an emergency system will be configured for operating independently of the ship and will comprise an accumulator and a reservoir containing an antifreeze agent to maintain pressure in the flexible injection hose when disconnecting from the ship in case of an emergency.

[0094] From the disclosure herein, it will be appreciated that the present invention has great advantages as compared with prior art solutions. No re-loading of liquified CO.sub.2 collected from an onshore terminal OT is required as the ship 1 brings the collected CO.sub.2 directly to a location above the subsurface permanent storage reservoir R wherein the ship 1 is connected to a flexible injection hose RP. Thus, apart from a flexible injection hose RP, subsea structures, and an appurtenant connection point, no additional onshore or offshore injection facility and infrastructure is required between the onshore terminal OT and the subsea connection point SCP. The invention therefore represents a cost-effective alternative, while at the same time representing a limited CO.sub.2-footprint. The system is flexible as regards various subsurface permanent storage reservoir.

[0095] It should be noted that the fluid flow within the lines, conduits and manifolds are controlled by means of pumps and valves which are controlled from a control room of the ship.

[0096] It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb comprise and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article a or an preceding an element does not exclude the presence of a plurality of such elements.