Optimising spudcan shape for mitigating horizontal and moment loads induced on a spudcan penetrating near a conical footprint

Abstract

The horizontal force and moment induced on a spudcan as it penetrates next to an existing seabed footprint have been identified as one of the key challenges in the offshore oil and gas industry. This paper assesses the potential of changing and then optimising the spudcan foundation shape to mitigate the spudcan-footprint interaction. Large-deformation finite-element (LDFE) analyses are performed using the Coupled Eulerian-Lagrangian (CEL) approach with the simple elastic-perfectly plastic Tresca soil model modified to enable strain softening and to incorporate strain-rate dependency of the shear strength. The spudcan shape was optimised by parametric analyses varying the spudcan’s skirt length, underside profile, and number of holes through the spudcan periphery. A spudcan with a flatter (or even concave) underside profile and with holes was shown to significantly reduce the induced horizontal force and moment during reinstallation next to an existing footprint. However, use of skirts has an adverse influence. Based on the results, an optimised spudcan shape is proposed.