Method and system for return of drilling fluid from a sealed marine riser to a floating drilling rig while drilling

System adapted for use with a structure for drilling in a floor of an ocean using a rotatable tubular and drilling fluid when the structure is floating at a surface of the ocean, the system comprising:

• a riser having a top, bottom and an internal diameter;
• a housing disposed above a portion of said riser, said housing having a first housing opening to discharge the drilling fluid received from said riser;
• an assembly having an inner member, said inner member rotatable relative to said housing and having a passage through which the rotatable tubular may extend;
• a seal moving with said inner member to sealably engage the tubular;
• and
• a flexible conduit for communicating the drilling fluid from said first housing opening to the structure whereby the structure is movable independent of said housing when the tubular is rotating.

Method for sealing a riser while drilling in a floor of an ocean from a structure floating at a surface of the ocean using a rotatable tubular and pressurized drilling fluid, comprising the steps of:

• positioning a housing above a portion of the riser;
• allowing the floating structure to move independent of said housing;
• communicating the pressurized drilling fluid from said housing to the structure;
• compensating for relative movement of the structure and said housing during said step of communicating;
• and
• attaching a flexible conduit between an opening of said housing and the floating structure for said step of compensating for relative movement of the structure and said housing.

Method for communicating drilling fluid from a casing fixed relative to an ocean floor to a structure floating at a surface of the ocean while rotating within the casing a tubular, comprising the steps of:

• fixing a housing with the casing adjacent a first level of the floating structure;
• allowing the floating structure to move independent of said housing;
• moving the drilling fluid from the tubular up the casing to a second level of the floating structure above said housing;
• and
• rotating the tubular relative to said housing, wherein
• a seal is within said housing, and
• said seal contacts and moves with the tubular while the tubular is rotating.

Method for sealing a riser while drilling in a floor of an ocean from a structure floating at a surface of the ocean using a rotatable tubular and pressurized drilling fluid, comprising the steps of:

• positioning a housing above a portion of the riser;
• allowing the floating structure to move independent of said housing;
• communicating the pressurized drilling fluid from the riser to the structure;
• compensating for relative movement of the structure and said housing during the step of communicating, and
• using a flexible conduit in said step of communicating the pressurized drilling fluid to the structure.

Method for sealing a riser while drilling in a floor of an ocean from a structure floating at a surface of the ocean using a rotatable tubular and pressurized drilling fluid, comprising the steps of:

• removably inserting a rotatable seal in a portion of the riser;
• allowing the floating structure to move independent of the riser;
• communicating the pressurized drilling fluid from the riser to the structure, and
• compensating for relative movement of the structure and the riser with a flexible conduit.

System adapted for use with a structure for drilling in a floor of an ocean using a rotatable tubular and drilling fluid when the structure is floating at a surface of the ocean, the system comprising:

• a riser fixed relative to the floor of the ocean;
• a housing disposed above a portion of said riser, said housing having a first housing opening to discharge the drilling fluid received from said riser;
• an assembly having an inner member, said inner member rotatable relative to said housing and having a passage through which the rotatable tubular may extend;
• a seal moving with said inner member to sealably engage the tubular;
• the floating structure movable independent of said assembly when the tubular is rotating;
• and
• a second housing opening in said housing and a rupture disk blocking said second housing opening to block fluid communication from said housing.

Method for sealing a riser while drilling in a floor of an ocean from a structure floating at a surface of the ocean using a rotatable tubular and pressurized drilling fluid, comprising the steps of:

• positioning a housing above a portion of the riser;
• allowing the floating structure to move independent of said housing;
• communicating the pressurized drilling fluid from said housing to the structure;
• compensating for relative movement of the structure and said housing during the step of communicating;
• and
• removing an assembly from said housing whereby the housing internal diameter is substantially the same as the riser internal diameter.

System adapted for use with a structure for drilling in a floor of an ocean using a rotatable tubular and drilling fluid when the structure is floating at a surface of the ocean, the system comprising:

• a riser positioned relative to the floor of the ocean, said riser having a top, bottom and an internal diameter;
• an assembly removably disposed above a portion of said riser having an inner member, a radially outwardly disposed outer member, and a plurality of bearings, wherein
• said inner member is rotatable relative to said riser and has a passage through which the rotatable tubular may extend, and
• said plurality of bearings are interposed between said inner member and said radially outwardly disposed outer member;
• a seal moving with said inner member to sealably engage the tubular;
• and
• the floating structure movable independent of said assembly when the tubular is rotating.

System adapted for use with a structure for drilling in a floor of an ocean using a rotatable tubular and drilling fluid when the structure is floating at a surface of the ocean, the system comprising:

• a housing adapted for positioning above a portion of a riser, said housing having a first housing opening to discharge the drilling fluid received from the riser, and
• an assembly removably positioned within said housing, wherein
• said assembly has a sealing member, which rotates relative to said housing, and seals the tubular when the tubular is rotating, and
• the floating structure moves independent of said assembly when the tubular is rotating.

System adapted for use with a structure for drilling in a floor of an ocean using a rotatable tubular and drilling fluid when the structure is floating at a surface of the ocean, the system comprising:

• an assembly adapted for removable positioning above a portion of a riser having an inner member, a radially outwardly disposed outer member, and a plurality of bearings, wherein
• said inner member is rotatable relative to the riser and has a passage through which the rotatable tubular may extend, and
• said plurality of bearings are interposed between said inner member and said radially outwardly disposed outer member;
• a seal moving with said inner member to sealably engage the tubular;
• and
• the floating structure movable independent of said assembly when the tubular is rotating.