套管钻井中套管疲劳损伤模型研究

根据套管材料的疲劳应力寿命曲线推导出了套管构件的疲劳应力寿命曲线;结合疲劳损伤理论,通过定义套管疲劳损伤量和疲劳损伤强度2个基本参数,对套管疲劳损伤进行度量,建立了套管疲劳累积损伤计算模型。由现场套管钻井实例分析结果可知,位于井口的套管疲劳损伤程度最大;采用单因素分析法,当转速一定时,套管的疲劳损伤随着井深的增加而减小;当钻压固定不变时,套管的疲劳损伤随转速的增大而增大。该模型对于套管的疲劳损伤评估具有重要的指导意义。

Study of Fatigue Damage Model of Casing in Casing Drilling

Based on the stress-life curve of casing material,stress-life curve of casing component is deduced.Then according to fatigue damage theory,two parameters of fatigue damage in one stress cycle and fatigue damage strength of casing sting were defined,so calculation model of casing fatigue damage was established.The analysis results of casing drilling showed that the fatigue damage of casing string in well head was the most serious.By analysis method of single fact,when the rotation speed was constant,the fatigue damage of casing string in one stress cycle decreases with well depth increasing.The fatigue damage increased with the rotation speed increasing while the pressure was kept constant.It is significant for fatigue damage evaluation of casing string during the course of casing drilling.