| During drilling operations,the riser will cause huge fatigue loads such as moment and shear,as well as vibration to the subsea wellhead connector,which may induce fatigue failure and cause safety hazards such as marine oil and gas leakage.This paper aiming at the problem that the 300m subsea wellhead connector in Liuhua 11-1 oilfield is subjected to nonlinear fatigue load for a long time under drilling conditions,to study the response law of fatigue characteristics drilling operations.Carry out the fatigue performance test of the key components of the subsea wellhead connector,obtain the stress fatigue life curve of the material,and construct the strain fatigue life curve of the material based on the Neuber stress-strain relationship theory and the Manson-Coffin strain life equation;Taking the actual environmental parameters as the input boundary,a coupled numerical model of drilling platform-riser-subsea wellhead-soil was established,and the time-history data of the bending moment and lateral vibration acceleration of the subsea wellhead connector were obtained through global dynamic analysis;The principle of rain flow counting and Fourier transform were used to determine the bending moment fatigue load spectrum and lateral vibration acceleration power spectral density;Based on Miner,Dowling,Smith and Huffman-Beckman fatigue damage accumulation theories,compared the response characteristics of wellhead connector fatigue damage,and finally formed a set of fatigue calculation and analysis methods for subsea wellhead connectors under the influence of wave-induced vibration.The research can provide some reference and guidance for the fatigue life evaluation of subsea wellhead connectors under drilling conditions. |
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