The Prince field in Ewing Bank Block 1003 in the Gulf of Mexico was developed using a "Moses" Tension Leg Platform in a water depth of 455m (1492 ft). Two 12-inch Export Steel Catenary Risers (SCRs) connected to the TLP were designed for oil and gas transportation. The Prince field water depth is the shallowest so far for SCRs connected to a floating structure. Having the SCRs in such relatively shallow water provided many challenges to the SCRs designers, as well as the TLP hull designers. The SCR design required large departure angles of 24 degrees to mitigate the touchdown area stresses and to accommodate the TLP surge (i.e. near and far) motions. The large SCR departure angles resulted in long suspended sections of the SCRs and consequently long sections were required on the seabed. Also, the SCR configuration caused high static and dynamic horizontal loads that were directed to the TLP hull. The motions of the TLP in this water depth affect the entire SCR length and thus, the fatigue and the corresponding fracture mechanics assessment became a very significant aspect of the SCR design. This paper gives a brief introduction to the Prince TLP and its two export SCRs. It also provides an insight into the challenges faced and overcome during their design. The fatigue approach and results with data from the fatigue test programs are also presented. A summary of the fracture mechanics assessment and the critical flaw sizes derived based on BS 7910 (1999) are given.
展开▼
