Method of riser deployment on a subsea wellhead

Abstract

The riser assembly is plugged adjacent its bottom end either as it is made up or after full makeup or anywhere in between. A heavy fluid is either added to the riser string as it is made up or delivered into the string after makeup to displace seawater or other fluids that may have been in the riser as it is assembled. The floating rig can be secured over the subsea well head and the riser now full of heavy fluid is less prone to be displaced by wave action and preferably simply dangles straight down so that the connection to the subsea wellhead can be simply accomplished. The effect of wave action is minimized or eliminated when deciding placement of the floating rig with respect to the wellhead. Repositioning of the rig takes less effort and is needed less frequently.

1 . A method of connecting a riser to a subsea wellhead comprising:
 assembling the riser;   installing a plug in said riser:   adding a heavy material in the riser above the plug;   lowering said riser toward the wellhead; and   connecting the riser to the wellhead.   
   
   
       2 . The method of  claim 1 , comprising:
 making said riser resist deflection from current forces due to said heavy material.   
   
   
       3 . The method of  claim 2 , comprising:
 positioning a rig closer to being over the wellhead due to reduced riser deflection from current when holding said heavy material.   
   
   
       4 . The method of  claim 1 , comprising:
 installing and setting said plug as said riser is assembled at the surface;   filling in said heavy material as additional riser sections are added at the surface.   
   
   
       5 . The method of  claim 1 , comprising:
 installing said plug after said riser is fully assembled and lowered;   displacing seawater in said riser with said heavy material.   
   
   
       6 . The method of  claim 5 , comprising:
 sealing off said riser with said plug after said displacing.   
   
   
       7 . The method of  claim 1 , comprising:
 using a liquid as said heavy material.   
   
   
       8 . The method of  claim 7 , comprising:
 including solids in said liquid.   
   
   
       9 . The method of  claim 1 , comprising:
 using a gel as said heavy material.   
   
   
       10 . The method of  claim 1 , comprising:
 removing said plug after said connecting.   
   
   
       11 . The method of  claim 10 , comprising:
 bringing the plug up the riser with flow from the well.   
   
   
       12 . The method of  claim 10 , comprising:
 drilling or milling the plug to remove it.   
   
   
       13 . The method of  claim 1 , comprising:
 said installing further comprises using an inflatable plug, a mechanically set plug, non-elastomer plug or a wiper plug landing on a seat.