System and methodology for establishing a fatigue life of a subsea landing string

Abstract

A technique facilitates monitoring of a location susceptible to fatigue due to loading experienced along a subsea landing string or other subsea tubing string. Initially a location or locations susceptible to fatigue may be determined along the subsea tubing string. At least one sensor, e.g. a strain sensor, is placed along the tubing string proximate the location susceptible to fatigue. The strain sensor or sensors can then be used to collect data regarding loading incurred at the location. The loading data can then be used to determine fatigue at the location and/or at a device proximate the location.

What is claimed is: 
     
         1 . A system for use in a well application, comprising:
 a blowout preventer disposed along a seafloor;   a subsea landing string extending into the blowout preventer, the subsea landing string comprising a plurality of landing string devices coupled by tubular members;   a plurality of sensors mounted on at least one of the tubular members, the sensors being operated to monitor stress loading at one or more specific locations along the subsea landing string; and   a data recorder positioned to receive data from the plurality of sensors, the data providing an indicator of component fatigue at one or more locations.   
     
     
         2 . The system as recited in  claim 1 , wherein the plurality of sensors comprises a strain gauge. 
     
     
         3 . The system as recited in  claim 1 , wherein the plurality of sensors comprises an accelerometer. 
     
     
         4 . The system as recited in  claim 1 , wherein the plurality of sensors comprises a strain gauge and an accelerometer. 
     
     
         5 . The system as recited in  claim 1 , wherein the plurality of landing string devices comprises a retainer valve, the plurality of sensors being coupled to at least one tubular member connected to the retainer valve. 
     
     
         6 . The system as recited in  claim 1 , wherein the plurality of landing string devices comprises a subsea test tree, the plurality of sensors being coupled to at least one tubular member connected to the subsea test tree. 
     
     
         7 . The system as recited in  claim 1 , further comprising a sensor mounted on a quick connect. 
     
     
         8 . The system as recited in  claim 1 , further comprising a telemetry system for transmitting sensor data from the plurality of sensors to a surface location. 
     
     
         9 . The system as recited in  claim 8 , further comprising a surface processing system for receiving the sensor data, processing the sensor data, and outputting an estimate of fatigue life with respect to at least one of the landing string devices. 
     
     
         10 . A method, comprising:
 determining a location susceptible to fatigue along a subsea landing string;   locating at least one sensor proximate the location susceptible to fatigue;   deploying the subsea landing string into cooperation with a subsea blowout preventer;   recording data from the at least one sensor; and   determining a fatigue life estimate of a component of the subsea landing string based on the data.   
     
     
         11 . The method as recited in  claim 10 , wherein determining comprises determining location susceptible to fatigue based on tensile loading and wave loading. 
     
     
         12 . The method as recited in  claim 10 , wherein locating the at least one sensor comprises locating a plurality of sensors on tubular sections of the subsea landing string. 
     
     
         13 . The method as recited in  claim 10 , wherein locating the at least one sensor comprises locating the sensor along a tubular section of the subsea landing string connected with a landing string device. 
     
     
         14 . The method as recited in  claim 10 , wherein locating the at least one sensor comprises locating the sensor along a tubular section of the subsea landing string connected with a retaining valve. 
     
     
         15 . The method as recited in  claim 10 , wherein locating the at least one sensor comprises affixing the at least one sensor directly to a subsea landing string device. 
     
     
         16 . The method as recited in  claim 10 , further comprising transmitting the data to the surface in real time. 
     
     
         17 . The method as recited in  claim 10 , wherein locating comprises locating a strain sensor along a tubular element of the subsea landing string. 
     
     
         18 . A method, comprising:
 determining a location susceptible to fatigue along a subsea tubing string;   placing a plurality of strain sensors proximate the location;   using the plurality of strain sensors to collect data regarding loading at the location; and   monitoring fatigue of a tubing string device by maintaining a log of the data collected.   
     
     
         19 . The method as recited in  claim 18 , wherein placing comprises placing the plurality of sensors along tubular elements coupled to a landing string component of the subsea tubing string; and wherein monitoring comprises processing the data collected to determine an estimated fatigue life of the landing string component. 
     
     
         20 . The method as recited in  claim 18 , further comprising using a telemetry system to transmit the data to the surface.