US20120213587A1

US20120213587A1 - Deepwater containment systems with flexible riser and methods of using same

Info

Publication number: US20120213587A1
Application number: US13/214,957
Authority: US
Inventors: John Charles Le Bas; Vladimir Fedotov; Yile Li
Original assignee: Shell Oil Co
Current assignee: Shell USA Inc
Priority date: 2010-08-24
Filing date: 2011-08-22
Publication date: 2012-08-23

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

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

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:
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.
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.
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.
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.
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.
There is a need in the art for one or more of the following:
Improved systems and methods for collecting spilled oil and gas from a marine environment;
Improved systems and methods for collecting oil and gas spilling from a subsea well;
Improved systems and methods for collecting oil and gas spilling from a subsurface formation located beneath a body of water; and/or
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

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

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.

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.

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.

FIG. 2B is a schematic diagram depicting a portion 2B of the flexible riser of FIG. 2A.

FIG. 3A is a cross-sectional view of the flexible riser of FIG. 2A taken along line 3A-3A, the flexible riser having a riser support.

FIG. 3B is a cross-sectional view of the flexible riser of FIG. 3A with multiple riser supports.

FIG. 4 is a flow chart depicting a method of deepwater containment.

DETAILED DESCRIPTION

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:

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.
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.
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.
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.
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 & 2B:

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.
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.
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).
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.
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.
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.
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 & 3B:

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.
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.
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.
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:

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.
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.
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.
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.
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.
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.

Claims

1. 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.

2. The system of claim 1, wherein the subsea collector comprises a containment cap located over a source of oil located on the bottom of the body of water.

3. The system of claim 1, wherein the subsea collector comprises a containment cap open to a blow out preventer (BOP) and the body of water.

4. The system of claim 1, wherein the subsea collector is anchored to the bottom of the body of water with one or more clump weights and/or piles.

5. The system of claim 1, further comprising a diffuser connected to the second end of the riser.

6. The system of claim 1, wherein the surface collector comprises an open bottom surface, the open bottom surface located above the second end of the riser.

7. The system of claim 1, wherein the surface collector comprises a sealed top surface, the surface collector comprising a first outlet for gases near a top of the collector, and comprising a second outlet for liquids near a bottom of the collector.

8. The system of claim 1, wherein the surface collector comprises a sealed top surface, the surface collector comprising a first outlet for gases near a top of the collector, and comprising a flare connected to the first outlet.

9. The system of claim 1, wherein the surface collector comprises a sealed top surface, wherein the top surface of the surface collector is submerged in the body of water at a depth from about 20 to about 60 meters.

10. The system of claim 1, wherein the surface collector comprises an open top surface, wherein the open top surface comprises a first outlet for gases, and comprising a second outlet for liquids near a bottom of the collector.

11. The system of claim 1, further comprising a vessel fluidly connected to the surface collector by a hose, the vessel adapted to store and/or transport at least a portion of liquids in the surface collector.

12. The system of claim 11, the surface collector further comprising a pump connected to the hose.