Study on the static behavior of installing a deep-water drilling riser on a production platform

Abstract

Riser interference caused by wake effects between adjacent risers severely threatens the safety during riser installation process on a Dry-Tree Tension Leg Platform (TLP) system. Due to the ignorance of interference effect, the static deflection of the drilling riser during installation is highly over-estimated in previous work. To obtain a static behavior of a drilling riser during installation, this paper built a dual-riser model where two risers are arranged in tandem and considered as Bernoulli beam subjected to steady ocean current. The modified Huse model is applied to study the interference between object risers. Then, the structural equation is solved by Finite-Difference-Method (FDM). Case studies show that an upstream production riser can largely reduce the deflection of a downstream hung-off drilling riser, hence increasing the probability of the collision of two risers. The influence of water depth, riser wall thickness, Blowout Preventer (BOP) weight, etc. are also studied. Finally, the current condition based weather windows with respect to wind and tidal current velocity are obtained corresponding to different operation conditions. Results show that installing a drilling riser with lower BOP weight in shallow water is most feasible for multi-riser TLP systems. Moreover, drilling riser installation operability can be improved by increasing the top tension of the production riser.