Abstract:
A subsea oil containment system, comprising: a subsea collector located near the bottom of a body of water; a surface collector located near a surface of the body of water; and a flexible riser connected to the subsea collector at a first end and extending to a second end located near the surface collector.

Description:
[0001]    This application claims the benefit of U.S. Provisional Application No. 61/376,595 filed Aug. 24, 2010, the entire disclosure of which is hereby incorporated by reference. 
     
    
     BACKGROUND 
       [0002]    When oil and gas is spilled into the sea, for example from a leaking tanker ship, a leaking pipeline, from oil seeping from an underground formation, or from oil flowing from a subsea wellhead or blowout preventer, there is a desire to collect the oil and gas and contain and transport or otherwise dispose of the oil and gas to prevent environmental damage to the sea and nearby coastlines. Various systems and methods of collecting spilled oil and gas are known in the art and set forth below: 
         [0003]    U.S. Pat. No. 4,405,258 discloses a method for storing a lighter-than-water fluid, e.g., oil, produced from the blowout of an offshore subsea well. The method includes the steps of deploying a containment dome in shallow water near the location of the seabed where the containment dome is to be located. The containment dome as an upper expanded dome-like fluid impervious membrane, a fluid impervious hollow peripheral ring attached to the periphery of the membrane to provide a depending bag-like container, and discrete water drainage means within the bag-like container for connection to pump conduit means therefrom. Wet sand from the seabed is then pumped into the bag-like container, and water is then drained from the wet sand through the water drainage means so as to provide a body of drained sand disposed within the bag-like container and providing a hollow peripheral ring as a hollow peripheral torus acting as a self-supporting structure and as an anchor for the dome-like structural unit. The dome is then charged with a buoyant amount of air and the buoyed dome is floated out to the site where the dome is to be deployed. It is then submerged by controllably releasing the air while substantially simultaneously filling the dome with water, thereby sinking the dome until the lighter-than-water fluid is captured within the dome, while such fluid substantially simultaneously displaces water from within the dome. U.S. Pat. No. 4,405,258 is herein incorporated by reference in its entirety. 
         [0004]    U.S. Pat. No. 4,643,612 discloses an oil storage barge having a concave bottom is adapted to be anchored over a subsea well or pipeline that is leaking oil. Flexible skirts extend to the ocean floor, and oil that is trapped under the barge may be stored in the barge or then transferred to another vessel. U.S. Pat. No. 4,643,612 is herein incorporated by reference in its entirety. 
         [0005]    U.S. Pat. No. 5,114,273 discloses a protective device installed to or around an offshore drilling platform for oil or gas and the device when in operation to encircle or enclose the platform with a floating containment device and attached oil containment curtain hanging from the device to the ocean floor. The pollution containment device to be submerged normally and activated to the surface when needed. This device will entrap offshore platform pollutants in a short amount of time with a minimum amount of effort and will maintain a clean environment. Other methods of offshore platform pollution containment devices are shown, including permanent non-moving oil pollution containment barriers and activated barriers that operate internally and externally of the oil platform to form an all encompassing barrier from the ocean floor to above the water surface to hold an oil spill to the platform area. U.S. Pat. No. 5,114,273 is herein incorporated by reference in its entirety. 
         [0006]    U.S. Pat. No. 5,213,444 discloses an oil/gas collector/separator for recovery of oil leaking, for example, from an offshore or underwater oil well. The separator is floated over the point of the leak and tethered in place so as to receive oil/gas floating, or forced under pressure, toward the water surface from either a broken or leaking oil well casing, line, or sunken ship. The separator is provided with a downwardly extending skirt to contain the oil/gas which floats or is forced upward into a dome wherein the gas is separated from the oil/water, with the gas being flared (burned) at the top of the dome, and the oil is separated from water and pumped to a point of use. Since the density of oil is less than that of water it can be easily separated from any water entering the dome. U.S. Pat. No. 5,213,444 is herein incorporated by reference in its entirety. 
         [0007]    U.S. Pat. No. 6,592,299 discloses a method of detecting and locating fresh water springs at sea essentially by taking salinity measurements and by methods and installations for collecting the fresh water. The collection installations comprise an immersed bell-shaped reservoir containing and trapping the fresh water in its top portion, and a pumping system for taking fresh water and delivering the fresh water via a delivery pipe, characterized in that the circumference of the bottom end of the reservoir and/or the circumference of the bottom end of a chimney inside the reservoir and open at its top end and surrounding the fresh water resurgence in part and preferably in full, follow(s) closely the outline of the relief of the bottom of the sea so as to provide leakproofing between the circumference(s) and the bottom of the sea. U.S. Pat. No. 6,592,299 is herein incorporated by reference in its entirety. 
         [0008]    There is a need in the art for one or more of the following: 
         [0009]    Improved systems and methods for collecting spilled oil and gas from a marine environment; 
         [0010]    Improved systems and methods for collecting oil and gas spilling from a subsea well; 
         [0011]    Improved systems and methods for collecting oil and gas spilling from a subsurface formation located beneath a body of water; and/or 
         [0012]    Improved systems and methods for collecting oil and gas spilling from a subsurface formation located beneath a body of water, and then burning the gas and containing the oil in a surface vessel. 
       SUMMARY OF THE INVENTION 
       [0013]    One aspect of the invention provides a subsea oil containment system, comprising a subsea collector located near a bottom of a body of water; a surface collector located near a surface of the body of water; and a flexible riser connected to the subsea collector at a first end and extending to a second end located near the surface collector. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    So that the features and advantages of the present invention can be understood in detail, a more particular description of the invention may be had by reference to the embodiments thereof that are illustrated in the appended drawings. These drawings are used to illustrate only typical embodiments of this invention, and are not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. The figures are not necessarily to scale and certain features and certain views of the figures may be shown exaggerated in scale or in schematic in the interest of clarity and conciseness. 
           [0015]      FIG. 1  is a schematic diagram depicting a wellsite positioned about a subsea reservoir, the wellsite having a containment system in accordance with an aspect of the present invention. 
           [0016]      FIG. 2A  is a schematic diagram depicting a wellsite positioned about a subsea reservoir, the wellsite having a containment system with a flexible riser in accordance with an aspect of the present invention. 
           [0017]      FIG. 2B  is a schematic diagram depicting a portion  2 B of the flexible riser of  FIG. 2A . 
           [0018]      FIG. 3A  is a cross-sectional view of the flexible riser of  FIG. 2A  taken along line  3 A- 3 A, the flexible riser having a riser support. 
           [0019]      FIG. 3B  is a cross-sectional view of the flexible riser of  FIG. 3A  with multiple riser supports. 
           [0020]      FIG. 4  is a flow chart depicting a method of deepwater containment. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    Presently preferred embodiments of the invention are shown in the above-identified figures and described in detail below. Embodiments are described with reference to certain features and techniques for containing fluids released into the sea. 
       FIG. 1: 
       [0022]      FIG. 1  is a schematic diagram depicting a wellsite  100  positioned about a subsea reservoir  102 . The wellsite  100  is provided with a containment system  101  for capturing fluids released into the sea  103 . Preferably, the containment system  101  and each of its components are configured for operability in harsh conditions and/or are transportable as needed. 
         [0023]    The wellsite  100  includes a surface collector  104  floating on the sea  103 , with a flexible riser  106  extending therebelow for receiving fluids generated from the reservoir  102 . A subsea end of the flexible riser  106  is positioned above a blow out preventer (BOP)  112  positioned on the sea floor (or mud line)  110 . The BOP  112  is positioned above a wellbore  114  that extends through the subsea floor  110  and into the reservoir  102 . The BOP  112  is in fluid communication with the wellbore  114  for receiving the fluids (e.g., gas, hydrocarbons, water, etc.) from the reservoir  102 . 
         [0024]    From time to time, fluid from the reservoir  102  may escape into the sea  103 . In some cases, a leak  130  may allow fluid to escape from the wellsite system  100  and into the sea  103  as fluid is produced from the reservoir  102 . In such cases, the containment system  101  may be employed to re-capture fluid released by one or more leaks  130 . 
         [0025]    As shown in  FIG. 1 , the subsea containment system  101  includes the flexible riser  106  positioned above the BOP  112  for receiving fluids therefrom. The flexible riser  106  preferably shifts with movement of the sea  103  that may result from, for example, currents, waves, storms, etc. The flexible riser  106  allows fluid to naturally flow from the BOP  112  to the surface, for example due to buoyancy of the oil and/or gas in the water. The fluids received by the flexible riser  106  are passed through the riser  106  and to the surface collector  104  as will be described more fully herein. 
         [0026]    Fluid drawn from the reservoir  102  and to the surface via riser  106  may be stored in the surface collector  104 . The surface collector  104  may be, for example, a separator that separates components of the fluid, such as gas and liquid. The portions of the fluid stored in the surface collector  104  may optionally be removed, for example, by burning the gas with a flare  124  or by allowing the gas to escape into the atmosphere. Preferably, the pressure of the fluid is reduced in the surface collector  104 . The remaining fluid may be passed to a vessel  120  via tubing (or hoses, floating line or off-take lines)  126  for transport, for example with a pump. The tubing  126  preferably fluidly connects the surface collector  104  to the vessel  120  for establishing fluid communication therebetween. 
       FIGS. 2A &amp; 2B: 
       [0027]      FIGS. 2A and 2B  are schematic diagrams depicting a wellsite  200  having a containment system  201 . The containment system  201  is provided with a flexible riser  206  and a surface collector  204  that may operate in the same manner as the flexible riser  106  and the surface collector  104 , respectively, of  FIG. 1 . A BOP  212  may also be provided for passing fluid from a reservoir  202  via a wellbore  214  in the same manner as the BOP  112  of  FIG. 1 . 
         [0028]    The flexible riser  206  is positioned over BOP  212  such that a leak  230  from BOP  212  (or a leak from another location) may be collected therein. Fluid passing from the BOP  212  flows into the flexible riser  206 . A funnel or other subsea collector (not shown) may optionally be positioned about the subsea end of the flexible riser  206  to facilitate flow into the flexible riser  206 . The flexible riser  206  is preferably configured to capture the fluid leaking from the BOP  212  to prevent passage of the fluid into the sea  203 . 
         [0029]    A subsea end of the flexible riser  206  is secured to sea floor  210  by mooring lines  233   a  anchored with clump weights  234   a , suction piles, or other anchoring systems as are known in the art. Clump weights and mooring lines as described herein may employ, for example, conventional mooring systems. Preferably, the flexible riser  206  is secured into position using multiple weights positioned about the BOP  212 . The flexible riser  206  is preferably secured in a detached position at about 5 to 15 m above the sea floor  210 , depending on the height of BOP  212 . This detached position is preferably provided to enable access to the BOP  212 , for example by an ROV (not shown). 
         [0030]    The flexible riser  206  extends a distance above the BOP  212  and up to or near to the surface collector  204  for passing fluid therebetween. The flexible riser  206  may be substantially vertical as shown in  FIG. 1 , or at an angle as shown in  FIG. 2A . The flexible riser  206  is preferably positioned to enable natural flow of fluid from the leak  230  about the BOP  212  and through the flexible riser  206 . Specific weights of the fluids (e.g., oil, gas, water) naturally flow within a water-continuous enclosed column extending through the flexible riser  206 . 
         [0031]    The flexible riser  206  is preferably a free standing, buoyed riser. The flexible riser  206  may be made of a flexible and/or repairable material, such as fabric, polymer and/or other material sufficiently flexible and water tight to enable the passage of fluid. The flexible material may also have a sufficient strength (e.g., about 1000N/cm) to handle high temperature, high pressure, high density, corrosive and/or other fluids produces from the subsea reservoir  202 . Preferably, the flexible riser  206  is sufficiently flexible to move with the movement of the sea  203 , while maintaining sufficient rigidity to permit the passage of fluid between the BOP  212  and the surface collector  204 . 
         [0032]    As shown in greater detail in  FIG. 2B , the flexible riser  206  has a flexible tube  236  and at least one riser support  237 . The riser support  237  may include tube rings  238 , a wire  242 , link rings  244  and a support cable  246 . A plurality of the tube rings  238  are spaced apart and positioned at various depths along the flexible tube  236  for providing support thereto. Preferably, the tube rings  238  are circular members that maintain an opening through the flexible tube  236  to facilitate the passage of fluid therethrough. The opening through the flexible tube  236  is preferably of a large diameter (e.g., from about 3 meters to about 20 meters, for example from about 5 to about 10 meters). The tube rings  238  may be integral with the flexible tube  236  (e.g., woven into the flexible tube), or attached on an inside or outside surface of the flexible tube  236 . 
         [0033]    The wire  242  and/or support cable  246  extend between the subsea floor  210  and the surface collector  204  for providing support to the flexible riser  206 . As shown, the wire  242  and support cable  246  are secured to the subsea floor  210  by clump weights  234   c . The wire  242  and/or support cable  246  are secured to the flexible riser  206  by the link rings  244 . The link rings  244  may be secured to the flexible tube  236  and/or the tube rings  238 . The same and/or separate link rings  244  may support the wire  242  and the support cable  246 . Preferably, the link rings  244  are secured to the flexible tube  236  with the wire  242  and/or support cable  246  therethrough. In this configuration, the wire  242  and support cable  246  are free to move through the link rings  244  as the flexible tube  236  moves. Wire  242  and support cable  246  are preferably positioned along an outer surface of the flexible tube  236  via the link rings  244  to provide independent movement of the wire  242 , support cable  246  and flexible tube  236 . 
       FIGS. 3A &amp; 3B: 
       [0034]    As shown in the cross-sectional views of  FIGS. 3A and 3B , one or more riser supports  237  may be positioned about the flexible tube  236 . Link rings  244  may be positioned at intervals about the flexible tube  236  to receive the wires  242  and support cables  246 . Preferably, as shown in  FIG. 3B , three riser supports  237  are provided about the flexible tube  236  at three locations 120 degrees apart. However, it will be appreciated by one of skill in the art that one or more sets of riser supports  237 , tube rings  238 , link rings  244 , wires  242  and/or support cables  246  may be provided at various locations about the flexible tube  236  as desired. 
         [0035]    Referring back to  FIG. 2A , a surface end of the flexible riser  206  extends into the surface collector  204  for passing fluid thereto. The surface end of the flexible riser  206  is secured within the surface collector by a buoy  248 . The buoy  248  has an arm  250  extending therefrom with a support line  233   b  hanging therefrom for supporting the flexible tube  206 . The support line  233   b  may be, for example, a steel cable integral with the cable  246  and/or wire  242 . The buoy  248  may have an additional support line  233   c  extending therefrom for providing further support to the flexible riser  206 . The additional support line  233   c  is preferably positioned along the flexible riser  206  between the surface and subsea ends of the flexible riser  206 . The support lines  233   b  and/or  233   c  may be linked, for example, to one or more link rings  244  secured to the flexible tube  236 . Support lines  233   d  may also be provided to anchor the flexible riser  206  to the subsea floor  210 . Clump weights  234   b  may be provided to secure the flexible riser  206  to the subsea floor  210 . 
         [0036]    The support line  233   b  preferably extends through the surface collector  204  to support the upper end of the flexible riser  206  therein. The surface collector  204  may be a conventional surface collector or floating storage for receiving fluids at the surface. As shown in  FIG. 2A  (partially in cross-section), the surface collector  204  is a cylindrically-shaped storage container or floating fence having an open bottom and open top in a ‘donut’ or ‘ring’ configuration. However, the surface collector  204  may be of a variety of shapes or sizes suitable for collection and/or separation of fluid received from the flexible riser  206 . The surface collector  204  may be configured to facilitate receipt, separation and/or transfer of the fluids generated from the leak  230 . The surface collector  204  is preferably a gravitational separator capable of separating the fluid into, for example, gas and liquids. 
         [0037]    A transfer hose  254  may be a floating hose for establishing fluid communication between the surface collector  204  and a vessel  220 . A pump  252  may also be provided for pumping fluid from the surface collector  204 , through the transfer hose  254  and to the vessel  220  for transport. One or more pumps, supply lines, exhausts, tubings, ports and/or other devices may be provided to generate the desired offloading rate. Also, one or more vessels  220  may be used in series and/or parallel. 
       FIG. 4: 
       [0038]      FIG. 4  is a flow chart depicting a method  400  of containment. The method  400  may involve positioning  470  a containment system over a BOP at a wellsite. The positioning may involve deploying at least a portion of the containment system (e.g.,  101 ,  201 ) to a wellsite (e.g.,  100 ,  200 ), installing the containment system (e.g.,  101 ,  201 ) about a BOP (e.g.,  112 ,  212 ), and removing the containment system. 
         [0039]    The method further involves supporting  472  a flexible riser of the containment system (e.g.,  101 ,  201 ) in position between the BOP (e.g.,  112 ,  212 ) and a surface collector (e.g,  104 ,  204 ). The supporting  472  may involve mooring  474  the flexible riser (e.g.,  106 ,  206 ) to a subsea floor about the BOP, mooring  476  the flexible riser in position about the surface collector, positioning  478  tube rings (e.g.,  238 ) about a flexible tube (e.g.,  248 ) of the flexible riser for providing support thereto, and/or linking  480  at least one support cable (e.g.,  246 ) along an outer surface of the flexible tube for providing flexible support thereto. 
         [0040]    The method may also involve passing  482  the fluid from the BOP (e.g.,  112 ,  212 ) to the surface collector (e.g.,  204 ) via the flexible riser (e.g.,  106 ,  206 ), separating  484  the fluid in the surface collector (e.g.,  204 ) and passing  486  at least a portion of the fluid from the surface collector (e.g.,  204 ) to a vessel (e.g.,  120 ,  220 ). In some cases, the flexible riser (e.g.,  106 ,  206 ) may be secured about the surface collector (e.g.,  204 ) with a buoy (e.g.,  248 ). The flexible riser (e.g.,  106 ,  206 ) may also be secured about the BOP (e.g.,  112 ,  212 ) with lines (e.g.,  233   a - d ) and weights (e.g.,  254 ). The vessels (e.g.,  120 ,  220 ) may be an ROV vessel for deploying an ROV (not shown) to the wellsite for activation thereof. The steps of the method may be performed in any order, and repeated as desired. 
         [0041]    In some embodiments, riser  106  and/or  206  may be made of a flexible sheet material, such as woven polyester, fiber reinforced plastic, polymer sheet such as polyethylene or polypropylene or copolymers, nylon fabric, Dacron fabric, aramid fabric, zylon fabric, or vectran fabric. 
         [0042]    It will be understood from the foregoing description that various modifications and changes may be made in the preferred and alternative embodiments of the present invention without departing from its true spirit. For example, the flexible riser may optionally be provided with devices, such as valves, ports, chokes (not shown) or other devices as desired. 
         [0043]    This description is intended for purposes of illustration only and should not be construed in a limiting sense. The scope of this invention should be determined only by the language of the claims that follow. The term “comprising” within the claims is intended to mean “including at least” such that the recited listing of elements in a claim are an open group. “A,” “an” and other singular terms are intended to include the plural forms thereof unless specifically excluded.