UNVEILING PATTERNS IN THE INTERACTION BETWEEN RISERS AND SEABED

Resumo

Risers play an important role in offshore production systems by conveying oil, gas and other
fluids from subsea wells to floating production units (FPU) or vice versa. Free hanging (catenary) risers
using flexible pipes have been the most conventional configuration in Brazilian production assets, but
the participation of steel catenary risers has long been fostered by oil companies and their technological
partners. The most challenging sections of free hanging risers are the vicinity of their top end and the
touchdown zone (TDZ). This investigation focuses on the latter section, by examining the static
interaction between riser and seabed, which is described by Skempton’s backbone curve. Besides the
external pressure and possible wall compression, the curvatures often impose the strongest constraints
to the riser design space. Parametric studies using finite element methods, non-dimensional analysis and
statistics seem to be promising route to assess the riser response. The results documented herein are
limited to static response with no marine current or wave loads, focusing on the maximum curvature
along the TDZ, and they supply zero-order approximations to studies which aim at describing the
dynamic response using asymptotic approximation techniques.