No abstract

As oil and gas exploration is moving to deeper waters, a key challenge is to design risers in harsh environments. Steel catenary risers (SCR) are cost-effective solutions that have been used in offshore developments due to their simplicity and robustness. However, stresses at the touchdown zone (TDZ), in such configurations are very large in ultra-deep waters for FPSOs in harsh environments leading the solution to become unfeasible in some fields. Therefore, steel lazy-wave risers (SLWR), are the market solutions for those fields. Nonetheless, SLWRs are, normally, longer risers with buoyancy modules, which increases installation time and overall cost. Gimbal Joint Riser (GJR) provides an alternative to reduce stresses at TDZ in SCRs. It is a patented device that comprises a series of hinged connection elements placed around a flexible pipe. This mechanism articulates, absorbing the energy coming from the motion of the hang-off, thus reducing stresses at TDZ. GJR is currently under qualification process. Recently, an experimental campaign involving two small scale models have been concluded. This paper brings a summary of the improvement in the GJR development obtained from these tests. A numerical model has been built to represent the experiments and the results of the calibrated real scale model derived from the experimental outputs are also presented. Results show a significant mitigation in the compressive wave at the TDZ of between 50% to 70% reduction in energy in comparison to SCRs.

No abstract

This paper presents the procedure for the calibration of a soil model represented by P-Y curves in the global finite element model of a drilling riser system using onboard measured data. In the case of lack of real data or data uncertainty regarding the soil properties of one specific well location, the soil model can be calibrated using measured data during the drilling campaign. The calibration procedure improves the accuracy on the prediction of the wellhead bending moment and stresses along the conductor pipe based on global riser analyses performed during the operation to assure the integrity of the well structure and thus, safe operations.