Patent Publication Number: US-11639773-B2

Title: Systems and methods for transporting natural gas

Description:
BACKGROUND 
     This section is intended to provide relevant background information to facilitate a better understanding of the various aspects of the described embodiments. Accordingly, it should be understood that these statements are to be read in this light and not as admissions of prior art. 
     The need for transportation of gas has increased as gas resources have been established around the globe. Traditionally, only a few methods have proved viable in transporting gas from these remote locations to places where the gas can be used directly or processed into commercial products. The typical method is to simply build a pipeline to transport the gas directly to a desired location. However, building a pipeline is, in many cases, not possible due to environmental, geopolitical or economic constraints 
     Due to the limitations of pipelines, other transportation methods have emerged, such as transporting natural gas in a liquid state. However, natural gas must be treated and cooled to −160° C. (−256° F.) to be liquefied. The liquefied natural gas (“LNG”) must then be maintained at −160° C. (−256° F.) during transportation. Specialized materials and equipment must be used due to the temperatures involved with producing and storing LNG, increasing the cost to transport the natural gas. Additionally, LNG must be regasified once it reaches its destination, further increasing the costs involved with transporting LNG. 
     Further, existing methods of transporting compressed natural gas (“CNG”) may require compression, chilling, and/or heating at each location where the CNG is transferred from one storage containment system to another storage containment system. Therefore, costly equipment is required at each storage location to perform these operations when transporting and storing CNG. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure is described with reference to the following figures. The same numbers are used throughout the figures to reference like features and components. The features depicted in the figures are not necessarily shown to scale. Certain features may be shown exaggerated in scale or in somewhat schematic form, and some details of elements may not be shown in the interest of clarity and conciseness. 
         FIG.  1    is a diagram of system for transporting natural gas, according to one or more embodiments; 
         FIG.  2    is a diagram of a loading facility, according to one or more embodiments; 
         FIG.  3    shows a first step of transferring chilled compressed natural gas (“CNG”) with a liquid displacement system; 
         FIG.  4    shows a second step of transferring chilled CNG with the liquid displacement system of  FIG.  3   ; 
         FIG.  5    shows a third step of transferring chilled CNG with the liquid displacement system of  FIG.  3   ; 
         FIG.  6    is a diagram of an offloading facility, according to one or more embodiments; 
         FIG.  7    is a diagram of system for transporting natural gas, according to one or more embodiments; 
         FIG.  8    is a diagram of system for transporting natural gas, according to one or more embodiments; 
         FIG.  9    is a diagram of system for transporting natural gas, according to one or more embodiments; 
         FIG.  10    is a diagram of system for transporting natural gas, according to one or more embodiments; 
         FIG.  11    is a diagram of system for transporting natural gas, according to one or more embodiments; 
         FIG.  12    is a diagram of system for transporting natural gas, according to one or more embodiments; 
         FIG.  13    is a diagram of system for transporting natural gas, according to one or more embodiments; 
         FIG.  14    is a diagram of system for transporting natural gas, according to one or more embodiments; 
         FIG.  15    is a diagram of system for transporting natural gas, according to one or more embodiments; and 
         FIG.  16    is a diagram of system for transporting natural gas, according to one or more embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure provides systems and methods for transporting natural gas. The systems and methods provide for transportation of natural gas such that natural gas is loaded at the supply source at a constant flowrate and without interruption, and/or offloaded at the delivery location at a constant flowrate and without interruption. 
       FIG.  1    a diagram of system  100  for transporting natural gas, according to one or more embodiments. The system  100  includes a production vessel  102  receiving natural gas from an offshore gas supply source  104 , a loading facility  106 , an offshore storage system  108 , a compressed natural gas (“CNG”) carrier  110 , and a storage and offloading facility  112 . In at least one embodiment, the production vessel  102  is a floating production, storage, and offloading facility (“FPSO”). In other embodiments, the production vessel  102  may be a drillship, semi-submersible, fixed platform, or any other offshore production facility that can provide natural gas to the loading facility  106 . 
     The system also includes one or more loading buoys  114  to transfer chilled CNG between the loading facility  106  and the offshore storage system  108 . In some embodiments, additional loading buoys  114  may be utilized to transfer natural gas or chilled CNG between the production vessel  102 , the loading facility  106 , the offshore storage system  108 , the CNG carrier  110 , and/or the storage and offloading facility  112 . In other embodiments, any one or more of the transfers of natural gas or chilled CNG between the various portions of the system  100  may be done with another gas transfer mechanism (such as flexible hoses, loading arms, etc.), and without the use of a loading buoy  114 . 
     As shown in  FIG.  1   , the loading facility  106  receives natural gas from production vessel  102 . The loading facility then compresses and chills the natural gas, as described in more detail below with reference to  FIG.  2   , to a temperature of 0° C. (32° F.) or lower and a pressure of 8,274 kPa (1,200 pounds per square inch (“psi”)) or higher while maintaining the chilled CNG in a gaseous state. The loading facility  106  then uses a liquid displacement system, which is also described in more detail below with reference to  FIGS.  3 - 5   , to transfer the chilled CNG to the offshore storage system  108  while maintaining the chilled CNG in a gaseous state at or below 0° C. (32° F.) and at or above 8,274 kPa (1,200 psi). 
     Once the chilled CNG is stored in the offshore storage system  108 , the chilled CNG is held until it can be offloaded to the CNG carrier  110  and transported to the storage and offloading facility  112 . The chilled CNG is then stored in the storage and offloading facility  112  until it is decompressed, heated, and offloaded, as described in more detail below with reference to  FIG.  6   , to a pipeline or secondary storage facility that stores natural gas. The transfers between the offshore storage system  108 , the CNG carrier  110 , and the storage and offloading facility  112  are completed utilizing a liquid displacement system, as described below, to maintain the chilled CNG in a gaseous state at or below 0° C. (32° F.) and at or above 8,274 kPa (1,200 psi). 
     In at least one embodiment, the offshore storage system  108  is sized such that a constant flowrate of natural gas can be produced from the offshore gas supply source  104  without interruption and the storage of the storage and offloading facility  112  is sized such that a constant flowrate of natural gas can be offloaded to a pipeline or offsite storage facility that stores natural gas without interruption. Additionally, the CNG carrier  110  may be sized to deliver sufficient chilled CNG to accommodate the continuous, uninterrupted flow of natural gas, or multiple CNG carriers  110  may be utilized to transport the chilled CNG. In other embodiments, the offshore storage system  108 , the storage and offloading facility  112 , the CNG carrier  110 , or any combination thereof may not be sized to accommodate a continuous, uninterrupted flowrate. 
       FIG.  2    is a diagram of a loading facility  200 , according to one or more embodiments. As discussed above the loading facility  200  compresses and chills the natural gas prior to storage of the chilled CNG. As shown in  FIG.  2    the loading facility  200  includes a compression system  202 , a refrigeration system  204 , a liquid displacement system  206 , and a metering system  208 . 
     Natural gas is received by the loading facility and compressed by the compression system  202  to at least 8,274 kPa (1,200 psi) via methods known to those skilled in the art. After compression of the natural gas, it is then chilled to 0° C. (32° F.) or less by the refrigeration system, which utilizes gas refrigeration methods known to those skilled in the art. The liquid displacement system  206  is then used to move the chilled CNG to a metering system, which controls the flowrate of the chilled CNG from the loading facility  200  to a storage system. 
     The loading facility  200  may also include a production treatment system  210  that treats the incoming natural gas prior to compression. The production treatment system may remove undesired components from the natural gas, separate liquids from the natural gas, or perform any other operations necessary to prepare the natural gas for compression. Additionally, the loading facility may include a storage system  212  that stores the chilled CNG for offloading to the next step in natural gas delivery, as shown in  FIG.  1   . Further, the storage system  212  may act as the offshore storage system  108 , storing chilled CNG for offloading onto a CNG carrier. 
     The loading facility  200  may also include a power generation system  214 . The power generation system  214  utilizes a portion of the natural gas delivered to the loading facility  200  to produce electricity to power the systems of the loading facility  200 . In other embodiments, the loading facility  200  may receive electricity from a source external to the loading facility  200 . In other embodiments, the production treatment system  210 , the storage system  212 , and/or the power generation system  214  may be omitted. 
       FIGS.  3 - 5    illustrate how chilled CNG is transferred utilizing a liquid displacement system  300 , according to one or more embodiments. As shown in  FIG.  3   , two storage containers  302 ,  304  of three storage containers  302 ,  304 ,  306  in fluid communication with each other are pre-charged with a displacement fluid  308 , such as ethylene glycol and water mixture, at a similar temperature to the chilled CNG and pressure below the pressure of the chilled CNG. The third storage container  306  will receive the displacement fluid and is sized to contain the volume of displacement fluid within the liquid displacement system  300 . 
     It should be noted that, although  FIGS.  3 - 5    depict three storage containers  302 ,  304 ,  306 , any number of storage containers can be utilized to transfer the chilled CNG, provided that there is sufficient storage capacity to contain the displacement fluid within the other storage containers of the liquid displacement system. Further, the storage containers may differ in size and/or multiple storage containers may be utilized to receive the displacement fluid contained within the remaining storage containers of the liquid displacement system  300  instead of a single storage container  306 . 
     Chilled CNG  400  is flowed from a loading facility or a storage system, discussed above with reference to  FIGS.  1  and  2   , into the first storage container  302  containing the displacement fluid  308 , as shown in  FIG.  4   . The introduction of chilled CNG to the first storage container  302  causes the displacement fluid  308  to move through the remaining storage containers  304 ,  306  as it is displaced and valves or similar methods are utilized to maintain the displacement fluid at a pressure that is below the pressure of the chilled CNG. 
     As shown in  FIG.  5   , the flow of chilled CNG  400  is continued until two of the three storage containers  302 ,  304 ,  306  are filled with chilled CNG  400  and third storage container  306  is filled with the displacement fluid  308  previously contained within the first two storage containers  302 ,  304 . To transfer the chilled CNG  400  out of the storage containers  302 ,  304 , the process shown in  FIGS.  3 - 5    is reversed and displacement fluid  308  is pumped into the storage containers  302 ,  304  containing chilled CNG  400  at a pressure that is higher than the pressure of the chilled CNG. The liquid displacement system  300  allows the chilled CNG to be transferred between multiple facilities and storage systems, as shown in  FIG.  1   , without additional chilling and compression to maintain the temperature below 0° C. (32° F.) and the pressure above 8,274 kPa (1,200 psi). 
       FIG.  6    is a diagram of an offloading facility  600 , according to one or more embodiments. The offloading facility  600  includes a decompression and heating system  602 , and a metering system  604 . The offloading facility  600  receives the chilled CNG, which is then transferred to the heating and decompression system  602 . The heating and decompression system  602  lowers the pressure and raises the temperature of the chilled CNG to a temperature and pressure necessary for the end-use of the natural gas, such as introducing the natural gas to a pipeline or storage in an offsite storage facility, using methods known to those skilled in the art. Additionally, the decompression and heating system  602  may be separated into a heating system and a decompression system. The metering system  604  then controls the transfer of the heated, depressurized natural gas away from the offloading facility  600 . 
     As shown in  FIG.  6   , the offloading facility  600  may also include a storage system  606  that stores the chilled CNG prior to decompression and heating. The offloading facility  600  may further include a liquid displacement system  608 , as described above, in the case when there is no liquid displacement system on the CNG carrier  110 . The offloading facility  600  may also include a power generation system  610 . The power generation system  610  utilizes a portion of the heated and decompressed natural gas to produce electricity to power the systems of the offloading facility  600 . In other embodiments, the offloading facility  600  may receive electricity from a source external to the offloading facility  600 . In other embodiments, the liquid displacement system  608 , the storage system  606  and/or the power generation system  610  may be omitted. 
       FIG.  7    a diagram of system  700  for transporting natural gas, according to one or more embodiments. Similar to  FIG.  1   , the system  700  includes an offshore storage system  108 , a CNG carrier  110 , and a storage and offloading facility  112 . However, a modified FPSO  702  produces natural gas from an offshore gas supply source  104  and houses the compression and refrigeration systems to compress and chill the natural gas. The modified FPSO  702  acts as both the production vessel and the loading facility, converting the natural gas to chilled CNG. 
       FIG.  8    a diagram of system  800  for transporting natural gas, according to one or more embodiments. Similar to  FIG.  1   , the system  800  includes a production vessel  102  receiving natural gas from an offshore gas supply source  104 , a CNG carrier  110 , and a storage and offloading facility  112 . However, a modified offshore storage system  802  acts as both the loading facility and the offshore storage system, converting the natural gas to chilled CNG and storing the chilled CNG. 
       FIG.  9    a diagram of system  900  for transporting natural gas, according to one or more embodiments. Similar to  FIG.  1   , the system  900  includes a CNG carrier  110  and a storage and offloading facility  112 . However, a floating gas production, storage, and offloading facility (“FGPSO”)  902  produces natural gas from an offshore gas supply source  104 . The FGPSO  902  acts as a production vessel, a loading facility to convert the natural gas to chilled CNG, and an offshore storage system, storing the chilled CNG for offloading to the CNG carrier  110 . 
       FIG.  10    a diagram of system  1000  for transporting natural gas, according to one or more embodiments. Similar to  FIG.  1   , the system  1000  includes a production vessel  102  receiving natural gas from an offshore gas supply source  104  and a storage and offloading facility  112 . However, a modified CNG carrier  1002  acts as the loading facility, the offshore storage system, and the CNG carrier. 
       FIG.  11    a diagram of system  1100  for transporting natural gas, according to one or more embodiments. Similar to  FIG.  1   , the system  1100  includes a CNG carrier  110  and a storage and offloading facility  112 . However, an onshore loading and storage facility  1102  receives natural gas from a pipeline  1104 . The onshore loading and storage facility  1102  compresses, chills, and stores the natural gas from the pipeline  1104  for offloading to the CNG carrier  110 . 
       FIG.  12    a diagram of system  1200  for transporting natural gas, according to one or more embodiments. Similar to  FIG.  1   , the system  1200  includes a production vessel  102  receiving natural gas from an offshore gas supply source  104 , a loading facility  106 , an offshore storage system  108 , and a CNG carrier  110 . However, the CNG carrier  110  delivers the chilled CNG to an onshore storage and offloading facility  1202 . The onshore storage and offloading facility  1202  then injects heated, decompressed natural gas into a pipeline  1204 . 
       FIG.  13    a diagram of system  1300  for transporting natural gas, according to one or more embodiments. Similar to  FIG.  12   , the system  1300  includes a CNG carrier  110  that delivers the chilled CNG to an onshore storage and offloading facility  1202  which injects heated, decompressed natural gas into a pipeline  1204 . However, a modified offshore storage system  802  acts as both the loading facility and the offshore storage system, converting the natural gas to chilled CNG and storing the chilled CNG. 
       FIG.  14    a diagram of system  1400  for transporting natural gas, according to one or more embodiments. Similar to  FIG.  12   , the system  1400  includes a CNG carrier  110  that delivers the chilled CNG to an onshore storage and offloading facility  1202  which injects heated, decompressed natural gas into a pipeline  1204 . However, an FGPSO  902  produces natural gas from an offshore gas supply source  104 . The FGPSO  902  acts as a production vessel, a loading facility to convert the natural gas to chilled CNG, and an offshore storage system, storing the chilled CNG for offloading to the CNG carrier  110 . 
       FIG.  15    a diagram of system  1500  for transporting natural gas, according to one or more embodiments. Similar to  FIG.  12   , the system  1500  includes a production vessel  102  receiving natural gas from an offshore gas supply source  104  and an onshore storage and offloading facility  1202  which injects heated, decompressed natural gas into a pipeline  1204 . However, a modified CNG carrier  1002  acts as the loading facility, the offshore storage system, and the CNG carrier. 
       FIG.  16    a diagram of system  1600  for transporting natural gas, according to one or more embodiments. Similar to  FIG.  12   , the system  1600  includes a CNG carrier  110  that delivers the chilled CNG to an onshore storage and offloading facility  1202 , which injects heated, decompressed natural gas into a pipeline  1204 . However, an onshore loading and storage facility  1102  receives natural gas from a pipeline  1104 . The onshore loading and storage facility  1102  compresses, chills, and stores the natural gas from the pipeline  1104  for offloading to the CNG carrier  110 . 
     It should be appreciated that, although the preceding examples depict specific onshore and offshore facilities, the invention is not thereby limited. For example, the production vessel may, instead, be an onshore oil and gas production site, or a single loading facility may receive natural gas from multiple offshore production vessels, multiple onshore production sites, multiple pipelines, or any combination of production vessels, onshore production sites, and/or pipelines. Similarly, an offloading facility may deliver natural gas to multiple pipelines, multiple offsite storage facilities, or any combination of pipelines and offsite storage facilities. Further, any combination of onshore and offshore facilities shown in the preceding examples may be used to transport natural gas without departing from the scope of this disclosure. 
     FURTHER EXAMPLES INCLUDE 
     Example 1 is a system for transporting natural gas. The system includes a loading facility, a first storage system, a second storage system, and a CNG carrier. The loading facility is operable to receive, compress, and chill natural gas to a temperature at or below 0° C. (32° F.) and a pressure at or above 8,274 kPa (1,200 psi) while maintaining the natural gas in a gaseous state. The loading facility is further operable to transfer the chilled CNG at a constant flowrate while maintaining the chilled CNG in a gaseous state at or below 0° C. (32° F.) and at or above 8,274 kPa (1,200 psi). The first storage system is operable to receive chilled CNG from the loading facility at the constant flowrate, store the chilled CNG, and transfer the chilled CNG while maintaining the chilled CNG in a gaseous state at or below 0° C. (32° F.) and at or above 8,274 kPa (1,200 psi). The second storage system is operable to receive and store the chilled CNG while maintaining the chilled CNG in a gaseous state at or below 0° C. (32° F.) and at or above 8,274 kPa (1,200 psi). The CNG carrier is operable to receive chilled CNG from the first storage system, transport the chilled CNG, and transfer the chilled CNG to the second storage system while maintaining the chilled CNG in a gaseous state at or below 0° C. (32° F.) and at or above 8,274 kPa (1,200 psi). The system is sized such that the constant flowrate from the loading facility to the first storage system is maintained without interruption. 
     In Example 2, the embodiments of any preceding paragraph or combination thereof further include wherein the first storage system is located offshore. 
     In Example 3, the embodiments of any preceding paragraph or combination thereof further include wherein the first storage system is located onshore. 
     In Example 4, the embodiments of any preceding paragraph or combination thereof further include wherein the loading facility is located offshore. 
     In Example 5, the embodiments of any preceding paragraph or combination thereof further include wherein the loading facility is located onshore. 
     In Example 6, the embodiments of any preceding paragraph or combination thereof further include an offloading facility operable to receive, heat, decompress, and offload the chilled CNG into a pipeline, wherein the second storage system is further operable to transfer the chilled CNG to the offloading facility. 
     In Example 7, the embodiments of any preceding paragraph or combination thereof further include wherein the system is sized such that a constant flowrate from the second storage system to the offloading facility is maintained without interruption. 
     In Example 8, the embodiments of any preceding paragraph or combination thereof further include wherein the second storage system and the offloading facility are both located onshore or the second storage system and the offloading facility are both located offshore. 
     In Example 9, the embodiments of any preceding paragraph or combination thereof further include wherein the second storage system is located offshore and the offloading facility is located onshore. 
     Example 10 is a system for transporting natural gas. The system includes an FGPSO, a second storage system, a CNG carrier, and an offloading facility. The FGPSO includes a loading facility and a first storage system. The loading facility is operable to receive, compress, and chill natural gas to a temperature at or below 0° C. (32° F.) and a pressure at or above 8,274 kPa (1,200 psi). The loading facility is further operable to transfer the chilled CNG at a constant flowrate while maintaining the chilled CNG in a gaseous state at or below 0° C. (32° F.) and at or above 8,274 kPa (1,200 psi). The first storage system is operable to receive chilled CNG from the loading facility at the constant flowrate, store the chilled CNG, and transfer the chilled CNG while maintaining the chilled CNG in a gaseous state at or below 0° C. (32° F.) and at or above 8,274 kPa (1,200 psi). The second storage system is operable to receive and store the chilled CNG while maintaining the chilled CNG in a gaseous state at or below 0° C. (32° F.) and at or above 8,274 kPa (1,200 psi). The CNG carrier is operable to receive chilled CNG from the first storage system, transport the chilled CNG, and transfer the chilled CNG to the second storage system while maintaining the chilled CNG in a gaseous state at or below 0° C. (32° F.) and at or above 8,274 kPa (1,200 psi). The offloading facility is operable to receive, heat, decompress, and offload the chilled CNG into a pipeline, wherein the second storage system is further operable to transfer the chilled CNG to the offloading facility. The system is sized such that the constant flowrate from the loading facility to the first storage system is maintained without interruption. 
     Example 11 is a method of transporting natural gas. The method includes chilling and compressing the natural gas received at a loading facility at a constant flowrate to a temperature at or below 0° C. (32° F.) and a pressure at or above 8,274 kPa (1,200 psi) while maintaining the chilled CNG in a gaseous state. The method also includes transporting the chilled CNG to a first storage system at the constant flowrate while maintaining the chilled CNG in a gaseous state at or below 0° C. (32° F.) and at or above 8,274 kPa (1,200 psi). The method further includes transferring the chilled CNG from the first storage system to a CNG carrier while maintaining the chilled CNG in a gaseous state at or below 0° C. (32° F.) and at or above 8,274 kPa (1,200 psi) such that the flowrate from the loading facility to the first storage system is maintained without interruption. The method also includes transferring the chilled CNG from the CNG carrier to a second storage system while maintaining the chilled CNG in a gaseous state at or below 0° C. (32° F.) and at or above 8,274 kPa (1,200 psi). 
     In Example 12, the embodiments of any preceding paragraph or combination thereof further include wherein the first storage system is located offshore. 
     In Example 13, the embodiments of any preceding paragraph or combination thereof further include wherein the first storage system is located onshore. 
     In Example 14, the embodiments of any preceding paragraph or combination thereof further include wherein the loading facility is located offshore. 
     In Example 15, the embodiments of any preceding paragraph or combination thereof further include wherein the loading facility is located onshore. 
     In Example 16, the embodiments of any preceding paragraph or combination thereof further include transferring the chilled CNG from the second storage system to an offloading facility while maintaining the chilled CNG in a gaseous state at or below 0° C. (32° F.) and at or above 8,274 kPa (1,200 psi). The method also includes decompressing and heating the chilled CNG at the offloading facility. The method further includes offloading the heated, decompressed natural gas to a pipeline at a second flowrate. 
     In Example 17, the embodiments of any preceding paragraph or combination thereof further include wherein a constant flowrate from the second storage system to the offloading facility is maintained without interruption. 
     In Example 18, the embodiments of any preceding paragraph or combination thereof further include wherein the second storage system and the offloading facility are both located onshore or the second storage system and the offloading facility are both located offshore. 
     In Example 19, the embodiments of any preceding paragraph or combination thereof further include wherein the second storage system is located offshore and the offloading facility is located onshore. 
     In Example 20, the embodiments of any preceding paragraph or combination thereof further include wherein the loading facility and the first storage system are both located on an FGPSO. 
     Certain terms are used throughout the description and claims to refer to particular features or components. As one skilled in the art will appreciate, different persons may refer to the same feature or component by different names. This document does not intend to distinguish between components or features that differ in name but not function. 
     Reference throughout this specification to “one embodiment,” “an embodiment,” “embodiments,” “some embodiments,” “certain embodiments,” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the present disclosure. Thus, these phrases or similar language throughout this specification may, but do not necessarily, all refer to the same embodiment. 
     The embodiments disclosed should not be interpreted, or otherwise used, as limiting the scope of the disclosure, including the claims. It is to be fully recognized that the different teachings of the embodiments discussed may be employed separately or in any suitable combination to produce desired results. In addition, one skilled in the art will understand that the description has broad application, and the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to suggest that the scope of the disclosure, including the claims, is limited to that embodiment.