Mono bore riser adapter

Abstract

A riser adapter system for coupling a mono-bore riser to a dual bore subsea wellhead assembly with a main bore and an annulus bore, includes an upper adapter with an upper bore offset from a radially centered point of a downward facing face of the upper adapter. The upper bore is in fluid communication with a riser bore of the mono-bore riser. A lower adapter has a first end selectively mated to the downward facing face of the upper adapter and an opposite facing second end. The lower adapter has a lower bore offset from a central axis of the lower adapter. The downward facing face of the upper adapter and the second end of the lower adapter are alternately mated to the subset wellhead assembly so that the riser bore is alternately in fluid communication with the main bore and the annulus bore of the subsea wellhead assembly.

What is claimed is: 
     
         1 . A riser adapter system for coupling a mono-bore riser to a dual bore subsea wellhead assembly with a main bore and an annulus bore, the riser adapter system comprising:
 an upper adapter with an upper bore offset from a radially centered point of a downward facing face of the upper adapter, the upper bore being in fluid communication with a riser bore of the mono-bore riser;   a lower adapter with a first end selectively mated to the downward facing face of the upper adapter and an opposite facing second end, the lower adapter having a lower bore offset from a central axis of the lower adapter; and wherein   the downward facing face of the upper adapter and the second end of the lower adapter are alternately mated to the subsea wellhead assembly so that the riser bore is alternately in fluid communication with the main bore and the annulus bore of the subsea wellhead assembly.   
     
     
         2 . The riser adapter system according to  claim 1 , wherein the lower adapter is alternately located on a side wing of the subsea wellhead assembly and mated to the downward facing face of the upper adapter. 
     
     
         3 . The riser adapter system according to  claim 1 , wherein the upper bore is selectively in fluid communication with the main bore of the subsea wellhead assembly. 
     
     
         4 . The riser adapter system according to  claim 1 , wherein the lower bore is selectively in fluid communication with the annulus bore of the subsea wellhead assembly. 
     
     
         5 . The riser adapter system according to  claim 1 , wherein the upper bore has a diameter generally equal to the diameter of the main bore of the subsea wellhead assembly, and the lower bore has a diameter generally equal to the diameter of the annulus bore. 
     
     
         6 . The riser adapter system according to  claim 1  , wherein the upper adapter includes an upper connector member alternately securing the upper adapter to the subsea wellhead assembly and the lower adapter, the upper connector member being remotely operated vehicle operable. 
     
     
         7 . The riser adapter system according to  claim 1 , wherein the lower adapter includes a lower connector member alternately securing the lower adapter over the annulus bore of the subsea wellhead assembly and to a side wing of the subsea wellhead assembly. 
     
     
         8 . The riser adapter system according to  claim 1 , wherein the subsea wellhead assembly includes an emergency disconnect package and the annulus bore extends through the emergency disconnect package, and wherein the lower adapter is alternately located on a side wing of the emergency disconnect package and in fluid communication with the annulus bore of the subsea wellhead assembly. 
     
     
         9 . The riser adapter system according to  claim 1 , wherein when the lower bore of the lower adapter registers with the annulus bore, the second end of the lower adapter seals across the main bore. 
     
     
         10 . A riser adapter system for coupling a mono-bore riser to a dual bore subsea wellhead assembly with a main bore and an annnlus bore, the riser adapter system comprising:
 a stress joint secured to an end of the mono-bore riser, the stress joint having an upper bore aligned with a riser bore of the mono-bore riser and offset from a center point of a downward facing face of the stress joint;   a lower adapter alternately located on a side wing of the subsea wellhead assembly and engaged with the downward facing face of the stress joint, the lower adapter having a lower bore offset from a central axis of the lower adapter; and wherein   the riser bore is alternately in fluid communication with the main bore through the upper bore and in fluid communication with the annulus bore through the upper bore and the lower bore.   
     
     
         11 . The riser adapter system according to  claim 10 , wherein when the riser bore is in fluid communication with the main bore, the downward facing face of the upper adapter seals across the annulus bore. 
     
     
         12 . The riser adapter system according to  claim 10 , wherein when the riser bore is in fluid communication with the annulus bore, an end of the lower adapter seals across the main bore. 
     
     
         13 . The riser adapter system according io  claim 10 , wherein the stress joint includes an upper connector member alternately securing the upper connector member to the subsea wellhead assembly and the lower adapter, the upper connector member being remotely operated vehicle operable. 
     
     
         14 . The riser adapter system according to  claim 10 , further alternately comprising:
 a flow path from the riser bore, through the stress joint, and to the main bore, that is free of an angle; and   a flow path from the riser bore, through the upper bore, the lower bore, and to the annulus bore, that is free of an angle.   
     
     
         15 . A method for coupling a mono-bore riser to a dual bore subsea wellhead assembly with a main bore and an annulus bore, the method comprising:
 (a) securing an upper adapter to the mono-bore riser so that a riser bore of the mono-bore riser is in fluid communication with an upper bore of the upper adapter;   (b) securing tbe upper adapter to the subsea wellhead assembly so that the riser bore is in fluid communication with the main bore;   (c) lifting the upper adapter off of the subsea wellhead assembly, rotating the upper adapter 180 degrees, and lowering the upper adapter onto a lower adapter, the lower adapter having a lower bore; and   (d) securing the lower adaptor to the subsea wellhead assembly so that the riser bore is in fliud communication with the annulus bore.   
     
     
         16 . The method according to  claim 15 , wherein tbe upper bore is offset from a center point of a downward facing face of the upper adapter, and wherein step (b) includes sealing across the annulus bore with the downward facing face. 
     
     
         17 . The method according to  claim 15 , wherein the lower adapter has a first end and a second end and the lower bore is offset from a from a central axis of the lower adapter, and wherein step (c) includes engaging a downward facing face of the upper adapter with the first end of the lower adapter and step (d) includes sealing across the main bore with the second end. 
     
     
         18 . The method according to  claim 15 , wherein:
 step (b) includes aligning the upper bore with the main bore along a central axis of the main bore, providing a flow path from the riser bore, through the upper bore, and to the main bore, that is free of an angle; and   step (d) includes aligning the lower bore with the annulus bore along a central axis of the annulus bore, providing a flow path from the riser bore, through the upper bore, the lower bore, and to the annulus bore, that is free of an angle.   
     
     
         19 . The method according to  claim 15 , wherein step (c) includes lowering the upper adapter onto the lower adapter on a side wing of the subsea wellhead assembly and securing a downward facing face of the upper adapter to a first end of the lower adapter. 
     
     
         20 . The method according to  claim 15 , further comprising after step (d), lifting the lower adapter off of the subsea wellhead assembly, rotating the lower adapter 180 degrees, and lowering the lower adapter onto a side wing of the subsea wellhead assembly, then securing the upper adapter to the subsea wellhead assembly so that the riser bore is in fluid communication with the main bore.