Marine Subsea Assemblies

Abstract

A lower riser assembly connects a riser to a seabed mooring and to a subsea hydrocarbon fluid source. The assembly includes sufficient intake ports to accommodate flow of hydrocarbons from the hydrocarbon fluid source, as well as optional flow assurance fluid. The upper end of the member has a profile suitable for fluidly connecting to the riser. The lower end of the member includes a connector suitable for connecting to the seabed mooring. An upper riser assembly connects the riser to a near-surface subsea buoyancy device and to a surface structure. The assembly includes sufficient outtake ports to accommodate flow of hydrocarbons from the riser through a subsea flexible conduit to the surface structure. The upper end of the member includes a connector for connecting to a subsea buoyancy device. The lower end of the member comprises a profile suitable for fluidly connecting to the riser.

1 . An assembly for connecting a subsea riser to a seabed mooring and to a subsea hydrocarbon fluid source, comprising:
 a generally cylindrical member having a longitudinal bore, a lower end, an upper end, and an external generally cylindrical surface, the member comprising sufficient intake ports extending from the external surface to the bore to accommodate flow of hydrocarbons from the hydrocarbon fluid source as well as inflow of a functional fluid, at least one of the intake ports fluidly connected to a production wing valve assembly,   the upper end of the member comprising a profile suitable for fluidly connecting to a subsea riser, and   the lower end of the member comprising a connector suitable for connecting to a seabed mooring.   
     
     
         2 . The assembly of  claim 1  wherein the generally cylindrical member comprises:
 a subsea wellhead housing, the lower end modified by connecting a transition joint thereto, the transition joint comprising said sufficient intake ports, 
 the upper end of the subsea wellhead housing fluidly connected to an external tieback connector fluidly connecting the subsea wellhead housing to a riser stress joint, 
 the subsea wellhead housing having an internal seal profile adapted to seal with an internal tieback connector, the internal tieback connector fluidly connecting an inner subsea riser to the internal seal profile, and 
 the internal tieback connector having a nose seal which seals into the subsea wellhead internal seal profile, the nose seal providing pressure integrity between an internal flow path in the inner riser and an annulus between the inner riser and a substantially concentric outer riser. 
 
     
     
         3 . The assembly of  claim 2  wherein the production wing valve assembly is fluidly connected to a subsea source through a subsea flexible conduit. 
     
     
         4 . The assembly of  claim 2  wherein the riser stress joint is in turn fluidly connected to the outer riser. 
     
     
         5 . The assembly of  claim 2  comprising ROV-operated valves for controlling flow through the internal flow path in the inner riser and the annulus. 
     
     
         6 . The assembly of  claim 2  comprising one or more hot stab ports for ROV intervention and/or maintenance. 
     
     
         7 . The assembly of  claim 1  wherein
 the generally cylindrical member comprises a high-strength metal forging fluidly connected to a production riser pup joint via a lower cross-over joint and threaded connector, the forging comprising said longitudinal bore, lower end, upper end, external generally cylindrical surface, and said sufficient intake ports, 
 the lower end of the metal forging comprising the connector suitable for connecting to the subsea mooring. 
 
     
     
         8 . The assembly of  claim 1 , wherein the generally cylindrical member comprises a forged, high-strength steel intake spool fluidly connected to a gooseneck assembly, the gooseneck assembly fluidly connected to a subsea source through a subsea flexible conduit, the intake spool also comprising a connector allowing connection to a source of a functional fluid. 
     
     
         9 . An assembly for connecting a subsea riser to a subsea buoyancy device and to a surface structure comprising:
 a generally cylindrical member having a longitudinal bore, a lower end, an upper end, and an external generally cylindrical surface, the member comprising sufficient outtake ports extending from the bore to the external generally cylindrical surface to accommodate flow of hydrocarbons from the riser, and at least one port allowing flow of a functional fluid in the longitudinal bore, at least one of the outtake ports fluidly connected to a production wing valve assembly for fluidly connecting the member to the surface structure with a subsea flexible conduit,   the upper end of the member comprising a connector suitable for connecting to a subsea buoyancy device, and   the lower end of the member comprising a profile suitable for fluidly connecting to the riser.   
     
     
         10 . The assembly of  claim 9  wherein the member comprises a drilling spool adapter having a first end fluidly connected to a tubing head, the tubing head comprising one or more outtake ports, the tubing head connected to a casing head having a stem joint fastened thereto, the casing head also comprising one or more ports for admitting a flow assurance fluid. 
     
     
         11 . The assembly of  claim 10  wherein the stem joint is fluidly connected to an outer concentric riser. 
     
     
         12 . The assembly of  claim 11  comprising an adjustable tubing hanger fluidly connecting an inner riser to the tubing head. 
     
     
         13 . The assembly of  claim 12 , wherein the production wing valve assembly comprises first and second flow control valves for controlling flow in the inner riser and in an annulus between the inner riser and the outer riser. 
     
     
         14 . The assembly of  claim 9  wherein the production wing valve assembly comprises one or more ROV hot-stab ports allowing a flow assurance fluid to flow into an inner riser and an annulus between the inner riser and an outer riser, the flow assurance fluid selected from the group consisting of nitrogen or other gas phase, heated seawater or other water, and organic chemicals. 
     
     
         15 . The assembly of  claim 9  wherein the generally cylindrical member comprises an offtake spool having the upper end and the lower end, a padeye flange connected to the upper end of the offtake spool, and a hanger spool connected to the lower end of the offtake spool, wherein the offtake spool and the hanger spool define the longitudinal bore. 
     
     
         16 . The assembly of  claim 15  wherein the offtake spool comprises a second bore substantially perpendicular to the longitudinal bore and fluidly connecting the longitudinal bore to one of the production wing valve assemblies through one of the outtake ports. 
     
     
         17 . The assembly of  claim 16  wherein the production wing valve assembly comprises a gooseneck conduit and two emergency shutdown (ESD) valves fluidly connected inline of the gooseneck conduit, one of the ESDs being hydraulically actuated, and the second ESD being electronically actuated. 
     
     
         18 . The assembly of  claim 15  wherein the hanger spool comprises a third bore substantially perpendicular to the longitudinal bore and fluidly connecting an annulus defined by the hanger spool and an internal riser joint with an annulus access valve assembly. 
     
     
         19 . The assembly of  claim 18  wherein the annulus access valve assembly comprises one or more ROV-operable valves. 
     
     
         20 . The assembly of  claim 19  wherein the annulus access valve assembly is fluidly connected to a source of flow assurance fluid. 
     
     
         21 . The assembly of  claim 9  further comprising a production bore offtake spool fluidly and mechanically connected to a substantially vertical conduit and to a production tubing, the production tubing in turn fluidly connected to a bend restrictor through a subsea API flange, a high pressure subsea connector, another subsea API flange connection, and optionally a QDC subsea connector, the bend restrictor connected to the upper subsea flexible conduit which extends in a catenary loop to the surface structure, and wherein the substantially vertical conduit fluidly connects in series to an adapter which in turn fluidly connects to a hanger spool, an API flange, a casing head via another API flange, a stem joint welded to the casing head, and to the outer riser via a threaded connection into a stem joint, the offtake spool including a shackle flange allowing connection to the subsea buoyancy device. 
     
     
         22 . The assembly of  claim 21  further comprising an ROV-operable ESD fluidly connected in a section of the conduit. 
     
     
         23 . The assembly of  claim 22  further comprising a support bracket which supports production tubing an angle σ to the conduit, and also supports a bend shield which provides a mechanical barrier between the production tubing and the conduit, where the angle σ ranges from 0 to about 180 degrees. 
     
     
         24 . The assembly of  claim 23  further comprising a connection to the hanger spool for connecting a gooseneck for delivery of heated water to the hanger spool from a surface vessel. 
     
     
         25 . The assembly of  claim 24  wherein the gooseneck comprises, in order starting at the hanger spool, an API flange, a section of tubing, a high pressure subsea connector, a subsea API connector and API flange, and a bend restrictor. 
     
     
         26 . The assembly of  claim 25 , wherein the inner riser is positioned inside of the adapter, the hanger spool, and the casing head, creating the annulus between an inner surface of the hanger spool and the inner riser. 
     
     
         27 . The assembly according to  claim 9 , further comprising components allowing circulation of a functional fluid, such as heated water, through the annulus. 
     
     
         28 . The assembly according to  claim 27  comprising an offtake spool fluidly connected to a hanger spool, the hanger spool in turn fluidly connectable to a tapered stress joint of the free standing riser. 
     
     
         29 . The assembly according to  claim 28 , further comprising a first block elbow includes an inner bore which intersects with and is substantially perpendicular to a bore in the offtake spool, a second block elbow having an inner bore which is also substantially perpendicular to the offtake spool bore but which does not intersect the offtake spool bore, and a gooseneck conduit fluidly connected to the first block elbow providing a flow path for hydrocarbons in combination with first block elbow bore. 
     
     
         30 . The assembly according to  claim 29 , further comprising first and second emergency shutdown valves in the gooseneck conduit, the gooseneck conduit fluidly connected to a subsea connector in turn fluidly connected to the upper subsea flexible conduit. 
     
     
         31 . The assembly according to  claim 27 , wherein the components allowing circulation of a functional fluid through the annulus comprises a subsea connector, a conduit and one or more valves in the conduit, the conduit fluidly connected to the hanger spool.