The Analysis On Coupled Vibration Of Drill String With Platform And Its Simulation In Deep-water Drilling

In presence, deep-water drilling is one of the advanced drilling technology at home and abroad. The bad oceanic environment brings very big difficulty to drilling engineering. With the world's decreasing for oil and gas reserves and demand increases, undersea oil and gas exploration has been developed to deep water and ultra deep-water gradually. Deep-water drilling technology problems have increasingly attracted people's attention, related technical problems in deep-water drilling also become a focus of the study, drillstring vibration problem for deep-water drilling is one of problems.First, the vibration problem of semi-submersible drilling platform has been analyzed. For anchor positioned semi-submersible drilling platform is example, semi-submersible drilling platform vertical vibration is estimated, by using finite element method a variety of translational, torsional vibration and various vibration coupled vibration model of semi-submersible drilling platform are established, the rule of various vibraiton are obtained.Second, the mechanical problems of the marine riser in deep-water drilling project are studied. Through the analysis of the complex mechanical environment of riser, the basic kinetic equation of marine riser has established using linear micro-element method. Under the across drift of the platform the marine riser for quasi-static conditions is analyzed, the laws of deformation and stress of marine riser are obtained under platform drift; the dynamic behavior of marine riser has been studied, lateral vibration of marine riser and dynamic response under a variety of loads are analysed, the lateral vibration spectrum, vibration mode and the law of the dynamic response under platform drift are obtained.Third, a variety of drillstring vibration problem of deep-water drilling has been studied. Taking into account the complexities of deep-water drilling project, drillstring axial vibration of horizontal part drilling and drillstring axial vibration of vertical part drilling are studied. Drill string lateral vibration of the horizontal part drilling and the lateral vibration of drill string of vertical part drilling are studied. Drill string torsional vibration of the horizontal part drilling, "stick-slip"of Extended Reach part and drill string torsional vibration of vertical part drilling are analyzed. The mechanical models are astablished by using linear, nonlinear and finite element method, the frequency rules are obtainend and the rules are used for actual problem.Forth, a variety of coupled vibration problem in deep-water drilling is analysed. The vibrations of drill string under the existence of fluid damping are studied by using linear micro-element method, the law of a variety of fluid damping vibration of the drill system is obtained. Coupled vibration of the drill string under marine riser vibration is studied, random contact mechanics model of the riser and the drill string is established by using FEM, the deformation and contact of riser and drill string under drilling platform drift are analyzed, and the effect about dynamic behavior of platform to the system of marine riser and drill string are studied. Various freedom degrees of coupled vibration of drill string is studied by using finite element method, the axial, lateral and torsional coupled vibration of drillstring are simulated, a variety of coupled vibration of drill string are obtained. The effect of vibration of the drilling platform to the dynamic behavior of drill string is analysed, the mechanical model of drill string dynamic response under platform vibration is established by using FEM, the rule of vibration is obtained using decoupled analysis.This paper has highly targeted and practical on mechanical issue of the deep-water drilling, includes the platform vibration, marine riser mechanics and drill string vibration, and a variaty of coupled vibraiton, it can provide reliable theoretical basis for the design and construction safety of deep-water drilling.