Ice-capable jackups can offer mobility and efficiency while drilling in shallow, ice-infested waters. However, the industry has limited experience operating jackups in ice environments, and technology gaps and uncertainties remain when assessing ice loads on multi-legged jackup units.
The Graphic Processing Unit (GPU)-based Discrete Element Method (DEM) can be applied to investigate the degree of ice effects on multi-legged jackup units. In previous applications, the DEM method was used to simulate ice interaction with structures, but computations were limited to simple interactions. Introducing a GPU platform enables a substantial increase in the number of elements characterized so that the interaction of multi-legs and ice can be modeled with greater efficiency. For example, level ice modeled with 3-D bonded spherical elements can address the buoyancy, current effects and drag force encountered in harsh environments. Additionally, the parallel bonding approach and de-bonding criteria are used to model level ice freezing and breakage.
In this investigation, the global ice loads on a jackup unit's single leg are analyzed to determine the effects of ice thickness, ice strengths and drifting velocities. The estimated ice loads are validated against full-scale data acquired from one application in Bohai Bay. Further, the mechanism of the interaction between the multiple legs and level ice is analyzed using the large-scale GPU-based simulation, the effects of sheltering and jamming are investigated and the ice loads simultaneously acting on the multiple legs are estimated to determine the total shear force and overturning moment.