Enhancing Subsea Well Integrity Through Standardized Comparison of Analysis and Measurement Results

Abstract During subsea drilling operations, integrity of the well structure must be accounted for to secure the required safety level. The well will be subjected to dynamic bending and shear loads when a blowout preventer (BOP) is connected. The driving forces for these loads are complex, as it comprises of rig motions, hydrodynamic loading of the riser and riser/BOP resonance behaviour. Uncertainties in how the well structure interacts with the surrounding soil further enhances the complexity of integrity assessment. Site specific simulation models are typically prepared in planning phase to ensure that the expected extreme and fatigue loads will not exceed the capacities of well. During the operational phase, load history and well stability are amongst integrity parameters that can be tracked through monitoring systems installed on the BOP and riser. Over the last decade, 4Subsea has been involved in both upfront simulations and measurements of the actual response for numerous subsea wells. Comparing large data sets related to integrity parameters from simulations and measurements can be used to uncover trends in the accuracy of the simulation models. Improving accuracy and reducing unnecessary conservatism in the analysis models may reduce cost and simplify planning of upcoming drilling operations. This paper proposes a generalized method to compare simulation results and measurements with respect to riser angles and loads acting on the wellhead. Comparisons of analysis results and measurement data, acquired through a standardized monitoring system, are presented and general trends discussed. The evaluated dataset consists of simulated and measured response from 69 drilling operations conducted on 47 distinct subsea wells with 9 semi-submersible rigs, in the North Sea, Barents Sea and the Norwegian Sea.