#Orcaflex 2rd limiting stress iso
The Landing string pipe selection was carried out in accordance with ISO 13628-7 to meet the pressure, tension and bending requirements. AS Mosley could draw on many years of experience to conservatively estimate the bending requirements prior to global riser analysis being carried out.
To meet the long lead time for the landing string joints, the order had to be made well in advance of the detailed design of the system. However, in deep water the landing string tensions are substantially higher which utilises more structural capacity with a negative impact on operability, particularly at high pressure. Furthermore, fatigue damage of the SSTT resulting from waves and vessel motions is much more significant in shallow water conditions. Shallow water is challenging as small vessel offsets can impose high loads in the subsea equipment. Shah Deniz has high pressure (12000 psi) sour service wells covering a wide range of water depths (70m to 580m). While the Caspian Sea has calm environmental conditions, other challenges existed. Optimising the angle limits for all operations is critical to minimise the cost of completing each well. This means that the permissible flex joint angle limits with the landing string and SSTT are much lower than for normal marine riser drilling operations. Furthermore, it is important to ensure for all landed and latched (L&L) operations that the landing string can be safely unlatched and pulled clear of the lower flex joint during emergency conditions in readiness for disconnecting the lower marine riser package (LMRP).Īccommodating landing string unlatch for all L&L operations restricts the lower flex joint angle. Running operations impose very tight limits as the large diameter control equipment passes through the restrictive upper and lower flex joints. During completion operations, the tubing hanger and Subsea Test Tree (SSTT) are run and landed through the marine riser.
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