Abstract:
Disclosed are pipeline systems, methods and apparatus for handling fluids in offshore oil and gas production. The systems disclosed allow subsea functional lines having diameters which differ by more than 2 standard API 5L pipeline diameters to be placed in fluid communication in such a way that the systems are piggable. Pipeline connection terminations are installed to facilitate connection of such functional lines. Such systems offer solutions to problems related to installing subsea pipeline in rough terrain, over subsea canyons and subsea scarps, installing marine risers, and long tiebacks.

Description:
FIELD 
       [0001]    The present disclosure relates to systems, methods and apparatus for conveying fluids in subsea functional lines and/or risers. The present disclosure further relates to methods of maintaining such systems. 
       BACKGROUND 
       [0002]    As subsea hydrocarbon production systems have evolved over time, certain challenges have become more problematic. One challenge is that subsea pipeline systems now cover greater areas, therefore the pipelines must traverse greater distances. Pipeline system designers would like to have greater flexibility to utilize various sizes and types of subsea pipeline, particularly as systems become larger and more complex. Another challenge is that as pipeline is laid in deeper and deeper water, the weight of the pipeline can create too much tension to safely install. Another challenge is that certain subsea production fields necessitate subsea pipeline crossing difficult geographical formations, including canyons, scarps and rough terrain. In these situations, it would frequently be desirable to utilize a flexible and/or lighter weight pipe or conduit for at least a portion of the pipeline system. 
         [0003]    A consideration which often limits the pipeline system designer&#39;s ability to design pipeline systems adapted to such challenges is the piggability of the lines in the systems. It would be desirable to have the ability to provide subsea pipeline systems including transitions between various types of pipe as well as various pipe diameters; however such systems are not piggable with current technology. It would be desirable to provide such systems while retaining the ability to effectively pig the lines of the systems. 
       SUMMARY 
       [0004]    In one aspect, a system for conveying fluids is provided which includes at least one riser having a riser diameter attached to an offshore production platform for conveying fluid to the production platform and at least one functional line located on the seabed having a functional line diameter in fluid communication with the at least one riser for conveying fluid to the at least one riser. The functional line diameter and the riser diameter differ by more than 2 standard API 5L pipeline diameters. 
         [0005]    In another aspect, a system for conveying fluids is provided which includes a subsea functional line including a first functional line and a second functional line in fluid communication with one another. The diameters of the first and second functional lines differ by more than 2 standard API 5L pipeline diameters. 
         [0006]    In another aspect, a method for maintaining either of the above systems is provided which includes pigging the system. 
         [0007]    In another aspect, a wye apparatus including a junction of at least three sections of functional line is provided wherein the diameters of two of the at least three sections of functional line differ by more than 2 standard API 5L pipeline diameters. 
         [0008]    In yet another aspect, a pipeline crossing termination is provided which includes a subsea structure capable of connecting to a first functional line and a second functional line or to a functional line and a riser such that the first functional line and the second functional line or the functional line and the riser are placed in fluid communication with one another. A pig launcher can be attached to the subsea structure such that a pig can be launched into the system of the first functional line and the second functional line or of the functional line and the riser. The diameters of the first and second functional lines or of the functional line and the riser differ by more than 2 standard API 5L pipeline diameters. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0009]    These and other objects, features and advantages of the present invention will become better understood with reference to the following description, appended claims and accompanying drawings where: 
           [0010]      FIG. 1  is a perspective view illustrating a pipeline connection terminal according to one exemplary embodiment wherein the pipeline connection terminal includes a wye. 
           [0011]      FIGS. 2A and 2B  are perspective views illustrating a pipeline connection terminal according to another exemplary embodiment wherein the pipeline connection terminal includes a pig launcher. 
           [0012]      FIGS. 3A and 3B  are perspective views illustrating a pipeline connection terminal according to another exemplary embodiment wherein the pipeline connection terminal includes coiled tubing interfaces. 
           [0013]      FIG. 4  is a perspective view illustrating a pipeline connection terminal according to another exemplary embodiment in which the pipeline connection terminal includes a booster pump. 
           [0014]      FIG. 5  is a perspective view illustrating a pipeline connection terminal according to another exemplary embodiment wherein the pipeline connection terminal includes a pig launcher. 
           [0015]      FIGS. 6A and 6B  are perspective views illustrating a pipeline connection terminal according to another exemplary embodiment wherein the pipeline connection terminal includes a wye and a pig launcher. 
           [0016]      FIGS. 7A and 7B  are perspective views illustrating a pipeline connection terminal according to another exemplary embodiment wherein the pipeline connection terminal includes multiple wyes and a pig launcher. 
           [0017]      FIGS. 8-11  are illustrations of subsea pipeline systems utilizing pipeline connection terminals according to embodiments disclosed herein. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    Embodiments are described hereinafter in which conduits for conveying fluids of differing conduit type and/or large diameter differences are utilized in a subsea production system in such a way that the conduits are in fluid communication with one another and the system is piggable. 
         [0019]    As used herein, the terms “pipeline,” “pipe,” “functional line,” “line,” and “conduit” may be used interchangeably to refer to conduits for conveying fluids which may be utilized in subsea hydrocarbon production systems. The term “riser” refers to a conduit for conveying fluids extending from the seabed to a surface location, such as a platform or vessel. 
         [0020]    In some embodiments, a system for conveying fluids is provided which includes at least one riser attached to an offshore production platform for conveying fluid to the production platform and at least one functional line located on the seabed in fluid communication with the at least one riser for conveying fluid to the at least one riser. In some embodiments, the riser can have a length of at least 10 m, even of 10 m to 5000 m. The functional line on the seabed can be a subsea pipeline for conveying oil and gas production fluids. Alternatively, the functional line on the seabed can be used to convey other fluids known to be useful in the production of oil and gas. For instance, such functional lines can be selected from oil recovery gas lines, gas lift lines, water lines, well service lines, well kill lines, scale squeeze lines, methanol lines, MEG lines and lines for tertiary recovery fluid, as will be familiar to those skilled in the art. 
         [0021]    The riser and the functional line can be different types of pipe. For instance, the functional line can be a rigid pipe while the riser can be an engineered pipe. The engineered pipe can be bonded flexible pipe, unbonded flexible pipe or multilayered composite pipe. 
         [0022]    Advantageously, the functional line diameter and the riser diameter differ by more than 2 standard API 5L pipeline diameters. More specifically, the functional line diameter can be, for example, at least 10.2 cm, even from 10.2 cm to 102 cm. The riser diameter can be, for example, at least 5.1 cm, even from 5.1 cm to 91.4 cm. Thus, systems including a combination such as, for example, a riser having a nominal pipe size (NPS) of 20 in (outer diameter of 50.8 cm) in fluid communication with a functional line having a NPS of 40 in (outer diameter of 101.6 cm) can be provided by the present disclosure. The present disclosure also provides other combinations, including, as nonlimiting examples, a riser having a NPS of 16 in (outer diameter of 40.6 cm) in fluid communication with a functional line having a NPS of 3½ in (outer diameter of 8.89 cm); and a riser having a NPS of 6⅝ in (outer diameter of 16.8 cm) in fluid communication with a functional line having a NPS of 14 in (outer diameter of 35.6 cm). 
         [0023]    A pipeline crossing termination can be located on the seabed between the functional line and the riser. The term “pipeline crossing termination” as used herein refers to a subsea structure such as a manifold capable of connecting to multiple lines and/or risers such that the lines and/or risers are placed in fluid communication with one another. In some embodiments, a pipeline crossing termination is located between the at least one riser and the at least one functional line on the seabed. The pipeline crossing termination allows lines and/or risers of different types and diameters differing by more than 2 standard API 5L pipeline diameters to be connected. 
         [0024]    In some embodiments, a system for conveying fluids is provided which includes at least two functional lines in fluid communication with one another, i.e., at least a first functional line located on the seabed and a second functional line located on the seabed. The first and second functional lines can be different types of pipe selected from rigid pipe and engineered pipe. The diameters of the first and second functional lines differ by more than 2 standard API 5L pipeline diameters. A pipeline crossing termination, as described above, can be located on the seabed between the first and second functional lines. 
         [0025]      FIG. 1  illustrates a system  100  according to one exemplary embodiment wherein a first functional line  114  is connected to second and third functional lines  112  and  110  via a wye  104 . The functional lines  114  and  110  in the embodiment illustrated differ by more than 2 standard API 5L pipeline diameters, where  114  and  112  are rigid pipe and  110  is a flexible pipe. A mudmat  102  supports the wye  104 . Also provided are valves  106  and a pipeline connector  108  as appropriate, as would be apparent to one skilled in the art. 
         [0026]    In some embodiments, the pipeline crossing termination, connecting either the at least one riser and at least one functional line located on the seabed or the at least first and second functional lines, can further include a subsea pig launcher capable of housing at least one pig and introducing a pig into the system. The pig can travel in any direction and stop at any point through the system. Through pigging the system, the functional line(s) and/or the riser(s) of the system can be maintained. Pigs capable of passing through pipeline systems have a multiple diameters and differing types of pipe are disclosed in co-pending patent application Ser. No. 13/738,740, the contents of which are incorporated herein by reference. 
         [0027]    In one embodiment,  FIGS. 2A and 2B  illustrate a pipeline crossing termination connecting a large diameter pipeline  114  with two smaller diameter pipelines  110 .  FIG. 2A  is an exploded view, and  2 B illustrates a system when pig launcher/receiver  120  is connected to the pipeline system so that a pig  121  can be inserted or removed from the system. Pig launcher/receiver  120  is oriented vertically in this embodiment. An ROV interface  116  can be provided to assist with pig launching and receiving operations. In the system illustrated, wye  104  includes four pipeline branches. Coiled tubing interfaces  118  can be provided to allow the insertion of coiled tubing into the pipeline. 
         [0028]    In some embodiments, to be described hereinafter, the pig  121  can further include one or more smaller pigs  122  contained therein which can be released into the smaller diameter pipelines  110 . 
         [0029]      FIGS. 3A and 3B  illustrate a pipeline crossing termination connecting a single large diameter pipeline  114  with a single smaller diameter pipeline  110 . In the particular embodiment illustrated, two wyes  104  are used. Two coiled tubing interfaces  118  are also included.  FIG. 3A  is an exploded view, and  3 B illustrates a system in which the coiled tubing interfaces  118  are connected to the pipeline system. 
         [0030]      FIG. 4  illustrates a system according to one exemplary embodiment in which a single large diameter pipeline  114  is in fluid communication with a single smaller diameter pipeline  110 . In this particular embodiment, a booster pump  124  is further provided for pumping fluids conveyed within the functional lines. The pipeline crossing termination can further include any of a number of other known components for use in subsea production systems. For example, it may be convenient to include a gas-liquid separator mounted on the pipeline crossing termination for separating gas and liquid fluids conveyed within the functional lines connected thereto. Other subsea system components as would be apparent to one skilled in the art may also be included. 
         [0031]      FIG. 5  illustrates a system according to one exemplary embodiment in which a pig launcher/receiver  120  oriented horizontally is connected to the pipeline system so that a pig  121  can be inserted or removed from the system. Again, as will be described further hereinafter, the pig  121  can further include one or more smaller pigs  122  contained therein which can be released into the smaller diameter pipelines  110 . 
         [0032]      FIGS. 6A  (exploded view) and  6 B (connected view) illustrate a system according to another exemplary embodiment in which a pig launcher/receiver  120  oriented vertically is connected to the pipeline system so that a pig  121  can be inserted or removed from the system. Again, as will be described further hereinafter, the pig  121  can further include one or more smaller pigs  122  contained therein which can be released into the smaller diameter pipelines  110 . 
         [0033]      FIGS. 7A  (exploded view) and  7 B (connected view) illustrate a system according to yet another exemplary embodiment in which a pig launcher/receiver  120  oriented vertically is connected to the pipeline system so that a pig  121  can be inserted or removed from the system. Again, as will be described further hereinafter, the pig  121  can further include one or more smaller pigs  122  contained therein which can be released into the smaller diameter pipelines  110 . 
         [0034]    In some embodiments, the system can also include a third functional line such that the second functional line is located between the first and third functional lines. For example, the second functional line can cross a section of rough terrain, a subsea scarp or cliff, or a subsea canyon. Each of the first, second and third functional lines can have different diameters, or two of the three functional lines have diameters that differ by more than 2 standard API 5L pipeline diameters. 
         [0035]    In some embodiments, the system includes two pipeline sections generally running in parallel with one another. This is particularly advantageous when the tension involved in installing a single large diameter line would be too great, thus prohibiting installation of a single pipeline. The tension can be further reduced by the use of lighter weight flexible conduit(s) in place of conventional rigid pipe. 
         [0036]    In some embodiments, the system can include two generally parallel risers connected to the functional line located on the seabed and also connected to the offshore production platform. Again, the two generally parallel risers can be lighter weight flexible pipe such that the stress on the connection with the platform is not excessively high. 
         [0037]    In some other embodiments, the system includes two generally parallel functional lines located on the seabed connected to a riser which is attached to an offshore production platform. Such a system can be used for various reasons, including providing flexibility to transport production fluids from multiple sources to a single riser. 
         [0038]    The first and second and optional third functional lines can be subsea pipeline conveying oil and gas production fluids. Alternatively, the functional lines can be selected from oil recovery gas lines, gas lift lines, water lines, well service lines, well kill lines, scale squeeze lines, methanol lines, MEG lines and lines for tertiary recovery fluid. 
         [0039]    The first and second and optional third functional lines can be different types of pipe, wherein the types of pipe are selected from rigid pipe and engineered pipe. The engineered pipe can be bonded flexible pipe, unbonded flexible pipe or multilayered composite pipe. 
         [0040]    The diameters of two of the first and second and optional third functional lines differ by more than 2 standard API 5L pipeline diameters. One of the functional line diameters can be at least 10.2 cm, even from 10.2 cm to 102 cm. Another of the functional line diameters can be at least 5.1 cm, even from 5.1 cm to 91.4 cm. Other combinations of pipeline diameters can be used. Thus, systems including a combination such as, for example, a functional line having a nominal pipe size (NPS) of 40 in (outer diameter of 101.6 cm) in fluid communication with a functional line having a NPS of 20 in (outer diameter of 50.8 cm) can be provided by the present disclosure. The present disclosure also provides other combinations, including, as nonlimiting examples, a functional line having a NPS of 40 in (outer diameter of 101.6 cm) in fluid communication with a functional line having a NPS of 16 in (outer diameter of 40.6 cm); a functional line having a NPS of 3½ in (outer diameter of 8.89 cm) in fluid communication with a functional line having a NPS of 6⅝ in (outer diameter of 16.8 cm); and a functional line having a NPS of 14 in (outer diameter of 35.6 cm) in fluid communication with a functional line having a NPS of 20 in (outer diameter of 50.8 cm). 
         [0041]    The present disclosure is particularly useful in certain scenarios.  FIG. 8  illustrates a subsea pipeline system  300  in one such scenario, in which pipeline crossing terminations  304  and  306  are installed on the seabed on each side of a subsea canyon. On the higher ground adjacent the canyon on each side, pipelines  308  and  310  can extend away from the c&#39;s anyon in either direction. Pipelines  308  and  310  can be larger diameter functional lines, typically rigid pipe, although other types of pipe can also be used in such a system. Extending between pipeline crossing terminations  304  and  306  can be flexible engineered pipe. Illustrated are two generally parallel functional lines  302  and  302 ′ extending across the canyon in parallel. 
         [0042]      FIG. 9  illustrates a similar scenario, in which pipeline crossing terminations  304  and  306  are installed on the seabed on each side of a subsea scarp or subsea cliff, rather than a canyon as described above. 
         [0043]      FIG. 10  illustrates another scenario, in which a pipeline crossing termination  304  is installed on the seabed at a shallower water depth, and the two parallel functional lines  302  and  302 ′ extend into progressively deeper water. 
         [0044]      FIG. 11  illustrates another scenario, in which a pipeline crossing termination  304  is installed on the seabed at the base of a marine riser  308 . In this embodiment, the pipeline crossing termination  304  acts to connect the two parallel functional lines  302  and  302 ′ on the seabed with the riser  308 , which in turn is connected to an offshore production platform  400 . 
         [0045]    In one embodiment, a novel piggable pipeline wye apparatus, also referred to as a “wye apparatus” or simply a “wye,” is provided. The wye apparatus includes a junction of at least three sections of functional line wherein the diameters of two of the at least three sections of functional line differ by more than 2 standard API 5L pipeline diameters. The wye can be mounted on the subsea structure of the pipeline crossing termination. In one embodiment, two of the at least three sections of functional line of the wye are moveable to allow a section of functional line containing a pig to be removed from the flow path. 
         [0046]    The pipeline crossing termination may be capable of isolating at least two of the functional lines connected to the pipeline crossing termination from one another, thus enabling fluid flow to be ceased in at least a portion of the pipeline system as may be needed for inspection or repair. This may be accomplished by closing valves on the pipeline crossing termination, for example. Other means will be apparent to those skilled in the art. 
         [0047]    Where permitted, all publications, patents and patent applications cited in this application are herein incorporated by reference in their entirety, to the extent such disclosure is not inconsistent with the present invention. 
         [0048]    Unless otherwise specified, the recitation of a genus of elements, materials or other components, from which an individual component or mixture of components can be selected, is intended to include all possible sub-generic combinations of the listed components and mixtures thereof. Also, “comprise,” “include” and its variants, are intended to be non-limiting, such that recitation of items in a list is not to the exclusion of other like items that may also be useful in the materials, compositions, methods and systems of this invention. 
         [0049]    From the above description, those skilled in the art will perceive improvements, changes and modifications, which are intended to be covered by the appended claims.