CROSS-REFERENCE TO RELATED APPLICATIONS
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This application claims benefit of U.S. provisional patent application Ser. No. 61/493,752 filed Jun. 6, 2011, and entitled “Subsea Pressure Relief Device,” which is hereby incorporated herein by reference in its entirety.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
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1. Field of the Invention
The disclosure relates generally to systems and methods for managing over pressurization of subsea equipment. More particularly, the disclosure relates to burst disc assemblies and methods of using such assemblies to relieve excessive fluid pressure in subsea equipment such as conduits, pipelines, and fluid containment devices.
2. Background of the Technology
In producing oil and gas from offshore wells, an offshore production system includes flowing hydrocarbons from a subterranean formation through a production string to a wellhead at the sea floor. From the wellhead, hydrocarbons may flow into tubular risers that provide a fluid conduit from the wellhead to the surface, where the hydrocarbons and other fluids may be collected in a receiving facility located on a platform or other vessel. Alternatively, intermediate components may be connected between the wellhead and risers, such as a choke/kill manifold, containment disposal manifold, capping stack, or other various types of subsea equipment. At times, temporary flow lines from the wellhead to a receiving facility or other containment target, such as an existing reservoir, may be installed.
The transfer of fluids from the wellhead to a receiving facility or other containment target often involves flow from a high pressure system to a relatively low pressure system. Normally, the flow of hydrocarbons from a subsea formation is controlled by a primary pressure containment system, such as a series of valves installed on the wellhead, risers, and the receiving facility at the surface designed to withstand anticipated operating pressures emanating from the wellhead. However, such pressures may be erratic, resulting in unanticipated high fluid pressures entering the production system and possibly over pressurizing components of the pressure containment system.
For instance, offshore oil production may take place at depths thousands of feet below the surface, where the ambient water pressure may exceed several thousand pounds per square inch (PSI) at temperatures below 50° F. Such pressure and temperature conditions lead to the formation of hydrocarbon gas hydrates, which may enter the production system. As the hydrates flow up the riser towards the surface, decreasing pressure within the riser at shallower depths allows the hydrates to disassociate into water and gas and rapidly expand, violently ejecting fluid from the riser at the surface. Moreover, back pressure within the pressure containment system may be generated by closing valves or from other processes, which may lead to an over pressurization of equipment in the system. In all such instances, it may be important to prevent pressure from building up in any interconnecting flow lines. Such an imbalance of pressures could also build up due to hydrate formation, sudden pressure changes in the well bore, or back pressure from valve closings or other processes performed on the system.
Many primary pressure containment systems are active in nature, requiring operator monitoring and intervention, and the use of hydraulic, electrical, or acoustic signals to activate the system in the case of an unanticipated over pressurization. The reliance on operator intervention may be problematic in certain situations, such as when inclement weather due to a tropical storm or hurricane forces the evacuation of a production platform, limiting the ability of operators to monitor and manage any unanticipated pressurizations.
Further, because of the immense depths and associated hydrostatic pressures, effectuating repairs of subsea equipment in the production system often requires that equipment and tools be handled by deep diving, remotely operated vehicles (ROVs). Due to the need for ROVs, repairing or replacing subsea equipment damaged by an unanticipated over pressurization may be cumbersome, time consuming and expensive. Thus, in the case of an unanticipated over pressurization, in order to reduce costs and quicken the time frame of repair it is necessary to ensure that the amount of subsea equipment damaged by the over pressurization is minimized and may be quickly and easily isolated and replaced.
Accordingly, there remains a need in the art for devices and methods for managing unanticipated excessive pressurizations of subsea environment. Such devices and methods would be particularly well received if the pressure setting at which the pressure relief device operates could be easily adjusted. Further, it would be advantageous if the pressure relief device could act passively, not requiring operator monitoring and actuation or the input of any hydraulic, electrical, or acoustic signal for actuation. Still further, it would be advantageous if the pressure relief device could be retrieved and replaced with relative ease.
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OF THE DISCLOSURE
These and other needs in the art are addressed in one embodiment by a device for relieving pressure in a subsea component. In an embodiment, the device comprises a housing including an inner cavity, an open end in fluid communication with the inner cavity, and a through bore extending from the inner cavity to an outer surface of the housing. In addition, the device comprises a connector coupled to the open end. The connector is configured to releasably engage a mating connector coupled to the subsea component. Further, the device comprises a burst disc assembly mounted to the housing within the through bore. The burst disc assembly is configured to rupture at a predetermined differential pressure between the inner cavity and the environment outside the housing.
These and other needs in the art are addressed in another embodiment by a method for relieving pressure within a subsea conduit. In an embodiment, the method comprises (a) deploying a pressure relief device subsea. The pressure relief device includes a housing having an inner cavity and a through bore extending from the inner cavity to an outer surface of the housing, and a burst disc assembly mounted to the housing within the through bore. In addition, the method comprises (b) coupling the pressure relief device to the subsea conduit. Further, the method comprises (c) transferring fluid pressure from the subsea conduit to the inner cavity.
These and other needs in the art are addressed in another embodiment by a device for relieving pressure in a subsea fluid conduit. In an embodiment, the device comprises a manifold including an inlet end and a plurality of outlet ends. In addition, the device comprises a connector coupled to the inlet end of the manifold. The connector is configured to releasably engage a mating connector coupled to the fluid conduit. Further, the device comprises a plurality of valve spools. Each valve spool is coupled to one of the outlet ends of the manifold. Each valve spool includes a valve configure to control a flow of fluids through the corresponding valve spool. Still further, the device comprises a plurality of burst disc assemblies. One burst disc assembly is disposed in a through bore in each valve spool. Each burst disc assembly is configured to rupture at a predetermined differential pressure between the inner cavity and the environment outside the housing.
Embodiments described herein comprise a combination of features and advantages intended to address various shortcomings associated with certain prior devices, systems, and methods. The various characteristics described above, as well as other features, will be readily apparent to those skilled in the art upon reading the following detailed description, and by referring to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
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For a detailed description of the apparatus, systems and methods disclosed herein, reference will now be made to the accompanying drawings in which:
FIG. 1 is a schematic view of an offshore hydrocarbon production system;
FIG. 2 is an isometric view of the containment and disposal manifold assembly of FIG. 1 including an embodiment of a pressure relief device in accordance with the principles described herein;
FIG. 3 is a side view of the containment and disposal manifold assembly of FIG. 2;
FIG. 4 is an isometric view of the pressure relief device of FIG. 2;
FIG. 5 is a side view of the pressure relief device of FIG. 4;
FIG. 6 is a cross-sectional view of the pressure relief device of FIG. 4;
FIG. 7A is a cross-sectional view of one of the burst disc assemblies of FIG. 4;
FIG. 7B is a top view of one of the burst disc assemblies of FIG. 4;
FIG. 8 is a schematic view of the upper riser assembly and lower riser assembly of the free standing riser of FIG. 1;
FIG. 9 is an isometric view of the pressure relief device coupled to the lower riser assembly of FIG. 8;
FIG. 10 is a side view of the pressure relief device of FIG. 9;
FIG. 11 is a cross-sectional view of the pressure relief device of FIG. 9;