Research On Mechanical Behavior Of Deepwater Conductor And Drilling Riser In Installations

The installations of deepwater conductor and drilling riser are two unique characteristics distinguishing deepwater drilling from onshore and offshore drilling,which are also the difficulties and keys directly relating the safety and efficiency even success of deepwater drilling.Jetting of conductor is the first step of well construction to provide a stable subsea wellhead and lay foundations for subsequent drilling operations.Deepwater drilling riser is an important connection equipment between subsea wellhead and floating drilling vessel.Only after the complete installation of drilling riser,artificial drilling mud can be used to ensure the deepwater drilling operation under safe control.The mechanics of deepwater conductor and drilling riser in installation is complex,which brings about huge challenges to safe operations.Therefore,it is great significance for us to study the mechanical behavior of them in installation to ensure the performance and efficiency of deepwater drilling.The finite element models are established to analyze the bearing capacity of deepwater conductor by programing constitutive model with consideration of different contact surface models of pile-soil.Based on this,the lateral deformation of deepwater conductor is simulated with contact mechanics model and contact element model,and the vertical bearing capacity is simulated with coulomb friction model and Goodman element contact model in ABAQUS software,respectively.Besides,the parameter sensitivity analysis is done to give a comprehensive understanding of deepwater conductor bearing capacity.The analysis models and control equations describing the lateral static,lateral dynamic,and,longitudinal dynamic mechanical behavior of drilling riser in installation are established with consideration of the unique boundary conditions.The key parameters controlling the mechanics of drilling riser in installation are revealed through solving the control equations.Then,the sea surface current velocity,surface wind velocity,wave height and wave period are selected as the evaluation factors of marine environment,and the fleet angle of riser top section,Mises equivalent stress,axial dynamic load at riser bottom and the transverse resonance,are considered as the limiting factors restricting the further complicated of the marine environment.Based on this,the installation window is obtained according to the comprehensive analysis of the mechanics mentioned above,and the parameters sensitive analysis of the installation window is discussed.Finally,the experimental facility of tubular mechanics under deepwater conditions is established,and the system is debugged to output internal pressure,external pressure,axial force and bending moment simultaneously.Based on this facility,the local mechanics of drilling riser in installation is simulated using underwater strain testing technique,and real stress state is obtained through analyzing the valid data after the simulation experiments.