System for sensing riser motion

An offshore drilling and/or production system, comprising:

• a dynamically positionable vessel having a vessel riser management system interface;
• a lower marine riser package (LMRP) for connection to a subsea wellhead and having an umbilical cord termination junction box and a LMRP riser management system interface electrically and optically connected to the umbilical cord junction box;
• an umbilical cord connected between the umbilical cord termination box and the vessel to provide a communication line between the LMRP and the vessel, the umbilical cord stored and deployed by an umbilical cord spool positioned on the vessel;
• a riser having an upper section connected to the vessel and a lower section connected to the LMRP;
• the riser having a lower flex joint connected to an upper portion of the LMRP, the lower flex joint having a lower flex joint angle (LFJA);
• the riser having an upper flex joint to flexibly connect the vessel to the upper section of the riser, the upper flex joint having an upper flex joint angle (UFJA);
• a subsea riser measurement instrument module electrically connected to the LMRP riser management system interface and connected to the lower flex joint to provide real-time three-dimensional dynamic orientation data for the lower section of the riser;
• a surface riser measurement instrument module electrically connected to the vessel riser management system interface and connected to the upper flex joint to provide three-dimensional dynamic orientation data for the upper section of the riser;
• and
• a computer carried by the vessel and having a memory associated therewith and riser management system analyzing software stored in the memory, the riser system analyzing software responsive to orientation data from the subsea and the surface riser measurement instrument modules to analyze riser dynamic behavior.

A method for analyzing riser dynamic behavior of a riser system extending between a floating vessel and a subsea wellhead system to enhance monitoring of the riser system, the method comprising the steps of:

• providing the riser with a riser measurement instrument module on a selected portion of the riser;
• forming dynamic orientation data for the selected portion of the riser utilizing the riser measurement instrument module;
• determining a dynamic three-dimensional angle of inclination for the selected portion of the riser from the dynamic orientation data;
• and
• determining a riser selected portion angle for the selected portion of the riser from the dynamic three-dimensional angle of inclination for the selected portion of the riser.

A method for analyzing riser dynamic behavior of a riser system extending between a floating vessel and a subsea wellhead system to enhance monitoring of the riser system, the method comprising the steps of:

• providing a computer having memory, a table of predetermined riser structural models stored in the memory;
• providing the riser with a riser measurement instrument module on an upper portion of the riser;
• forming dynamic orientation data for the upper portion of the riser utilizing the riser measurement instrument module;
• determining an angle of inclination for the upper portion of the riser from the upper riser portion dynamic orientation data;
• and
• determining a real-time riser three-dimensional dynamic structure representing a real-time structure of the riser utilizing the determined angle of inclination for the upper portion of the riser and the table of predetermined riser structural models.

A method for analyzing riser dynamic behavior of a riser system extending between the method of a floating vessel and a subsea wellhead system to enhance monitoring of the riser system, comprising the steps of:

• providing the riser with at least one of a subsea riser measurement instrument module positioned on a lower portion of the riser and a surface riser measurement instrument module positioned on an upper portion of the riser;
• forming linear and angular acceleration data for the riser utilizing the at least one of the subsea riser measurement instrument module and the surface riser measurement instrument module;
• and
• analyzing the linear and angular acceleration data for the riser to thereby determine an existence and magnitude of vortex induced vibration.

A method for analyzing riser dynamic behavior of a riser system, extending between a subsea wellhead system and a floating vessel carrying a computer having memory, to enhance monitoring of the riser system, the method comprising the steps of:

• providing a database of riser vibration signatures stored in the memory of the computer;
• forming acceleration data for the riser utilizing a riser measurement instrument module;
• generating a riser vibration value time series for the riser from the acceleration data for the riser;
• and
• analyzing the riser vibration value time series by comparing the riser vibration value time series to the database of riser vibration signatures.

A method for analyzing riser dynamic behavior of a riser system extending between a floating vessel and a subsea wellhead system to enhance monitoring of the riser system, the method comprising the steps of:

• providing the riser with a subsea riser measurement instrument module on a lower portion of the riser and a surface riser measurement instrument module on an upper portion of the riser;
• forming dynamic orientation data for the lower portion of the riser utilizing the subsea riser measurement instrument module;
• determining a dynamic three-dimensional angle of inclination and heading for the lower portion of the riser from the lower riser portion dynamic orientation data;
• forming dynamic orientation data for the upper portion of the riser utilizing the surface riser measurement instrument module;
• determining a dynamic three-dimensional angle of inclination and heading for the upper portion of the riser from the upper riser portion dynamic orientation data;
• determining a tilt and a bearing of the riser from the dynamic three-dimensional angle of inclination of the lower riser section and the upper riser section;
• and
• determining, from the determined tilt and bearing of the riser, a vessel offset distance between a vertical axis extending from the wellhead and a dynamic position of the vessel.