Fatigue Analysis Of Pipe String In Floating Casing Drilling

On the conditions of the needs in today’s deep-water oil and gas field development technical and the low international oil price,casing drilling technology has the advantage of low cost from two aspects of technology and economy will have greater market requirement.However,due to the influence of marine environment,and the shortcomings of strength and fatigue life in casing string,which will led to problems which encountered by the casing drilling technology applying on land in the ocean drilling may also occur,and may also appears new and complicated situation.The paper take application and development of casing drilling technology in the marine environment as starting point.And from the start of vibration and fatigue effects of long-term use of casing string.The paper apply the theory analysis and numerical simulation method to study the new problems which effect the casing drilling technology in the floating drilling platform application.There are three main innovations of this paper: firstly,it would the casing string in casing drilling analogy the drill string in conventional drilling.And it analysis their differences in geometry,and the problems of casing string in place of drill string,such as stress,failure,buckling,sticking and thread connection.Secondly,it bulids the analysis model and calculation procedure of casing string fatigue life estimation.It analyzed the influencing factors of fatigue failure of pipe string.It studied the vibration of casing string and calculated the fatigue damage caused by vibration.Third,the motion response of deepwater drilling platform makes the casing string of deepwater drilling operation bear more alternating stress,and fatigue failure becomes the problem that the engineering personnel must consider.The paper through the hydrodynamic module,transient dynamics analysis module and the fatigue analysis module in ANSYS Workbench,provides a kind of method to calculate the fatigue life of the casing string in deep-water casing drlling to study the fatigue failure of the casing.And through an example calculation,it gets the response to the movement of the platform in a marine environment,gets the stress-time history curve of the casing string node in the boundary conditions that is equal to platform motion degree of freedom,and then gets the dangerous node casing limited fatigue life.