Bottom tensioned offshore oil well production riser

A bottom tensioned riser system for conveying petroleum from an offshore oil well on a sea floor to a platform floating above, the riser system comprising:

• a tubular conduit comprising a plurality of individual tubular riser pipes, the conduit being suspended from the platform and having a bottom end extending downward therefrom in a substantially vertical direction and toward the sea floor;
• and
• a connection and tensioning assembly disposed at the bottom end of the conduit, the connection and tensioning assembly comprising:
• a flexible jumper connecting the bottom end of the conduit to the well;
• a weight applying a vertical tension in the conduit;
• and
• constraining means for constraining the bottom end of the conduit against horizontal movement, while enabling the conduit to move freely in a vertical direction and to pivot freely about the bottom end thereof in response to motions of the platform;
• wherein the constraining means comprises:
• a plumb bar pivotally connected to the bottom end of the conduit and having a lower end with a base plate mounted thereon, the base plate containing a plurality of apertures;
• and
• a guide base disposed on the sea floor and having a plurality of upstanding guide posts, each guide post being slidably received in a corresponding one of the apertures in the base plate.

A bottom tensioned riser system for conveying petroleum from an offshore oil well on a sea floor to a platform floating above, the riser system comprising:

• a tubular conduit comprising a plurality of individual tubular riser pipes, the conduit being suspended from the platform and having a bottom end extending downward therefrom in a substantially vertical direction and toward the sea floor;
• and
• a connection and tensioning assembly disposed at the bottom end of the conduit, the connection and tensioning assembly comprising:
• a flexible jumper connecting the bottom end of the conduit to the well;
• a weight applying a vertical tension in the conduit;
• and
• constraining means for constraining the bottom end of the conduit against horizontal movement, while enabling the conduit to move freely in a vertical direction and to pivot freely about the bottom end thereof in response to motions of the platform;
• wherein the constraining means comprises:
• the weight being connected to the bottom end of the conduit by a pivoting joint;
• three guide rails attached to the sea floor;
• and
• three rigid arms, each having an upper end pivotally attached to the weight and a lower end pivotally attached to a respective shoe, and wherein each of the shoes is retained in a corresponding one of the guide rails for horizontal movement.

A bottom-tensioned riser system for conveying petroleum from an offshore oil well on a sea floor to a platform floating above, the riser system comprising:

• a tubular conduit suspended from the platform and having a bottom end extending downward therefrom in a substantially vertical direction and toward the sea floor;
• a flexible jumper connecting the bottom end of the conduit to the well;
• and
• a connection and tensioning assembly disposed at the bottom end of the conduit, the connection and tensioning assembly comprising:
• a weight connected to the bottom of the conduit and applying a vertical tension in the conduit;
• and
• a telescopic piling connected to the bottom end of the conduit by a pivot joint and slidably retained in a piling guide sunk into the sea floor, thereby constraining the bottom end of the conduit against horizontal movement, while enabling the conduit to move freely in a vertical direction and to pivot freely about the bottom end thereof in response to motions of the platform.

A bottom-tensioned riser system for conveying petroleum from an offshore oil well on a sea floor to a platform floating above, the riser system comprising:

• a tubular conduit suspended from the platform and having a bottom end extending downward therefrom in a substantially vertical direction and toward the sea floor;
• a flexible jumper connecting the bottom end of the conduit to the well;
• and
• a connection and tensioning assembly disposed at the bottom end of the conduit, the connection and tensioning assembly comprising:
• a weight connected to the bottom of the conduit and applying a vertical tension in the conduit;
• and
• means for constraining the bottom end of the conduit against horizontal movement, while enabling the conduit to move freely in a vertical direction and to pivot freely about the bottom end thereof in response to motions of the platform;
• wherein the means for constraining comprises:
• a plumb bar pivotally connected to the bottom end of the conduit and having a lower end with a base plate mounted thereon, the base plate containing a plurality of apertures;
• and
• a guide base disposed on the sea floor and having a plurality of upstanding guide posts, each guide post being slidably received in a corresponding one of the apertures in the base plate.

A bottom-tensioned riser system for conveying petroleum from an offshore oil well on a sea floor to a platform floating above, the riser system comprising:

• a tubular conduit suspended from the platform and having a bottom end extending downward therefrom in a substantially vertical direction and toward the sea floor;
• a flexible jumper connecting the bottom end of the conduit to the well;
• and
• a connection and tensioning assembly disposed at the bottom end of the conduit, the connection and tensioning assembly comprising:
• a weight connected to the bottom of the conduit and applying a vertical tension in the conduit;
• and
• means for constraining the bottom end of the conduit against horizontal movement, while enabling the conduit to move freely in a vertical direction and to pivot freely about the bottom end thereof in response to motions of the platform;
• wherein the means for constraining comprises:
• a pivoting joint connecting the weight to the bottom end of the conduit;
• a plurality of guide rails attached to the sea floor;
• a shoe slidably received on each of the guide rails for horizontal movement thereon;
• and
• a plurality of arms, each having an upper end pivotally attached to the weight and a lower end pivotally attached to a respective shoe.