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.