蠕变地层套管载荷分析研究

STUDY ON CASING LOADS IN CREEP FORMATIONS

研究了蠕变地层中套管载荷的分布规律。首先,将套管看成弹性支撑,采用解析方法确定了均匀地应力条件下蠕变地层中套管的载荷。其次,采用有限元方法,研究了非均匀地应力条件下蠕变地层中套管的载荷。不论是均匀地应力还是非均匀地应力条件,经过足够长的时间,套管载荷都将接近于完全弹性解。同时,通过数值计算,得出了非均匀地应力条件下与现有套管载荷分布规律相反的结论。

The distributions of casing load with uniform and non-uniform in-situ stresses in creep formations are studied by analytical and numerical methods, respectively. Firstly, taking the casing as the elastic foundation, analytical method is employed to analyze the casing loads with uniform in-situ stresses in the creep formations. Secondly, due to the difficulty of the analytical method in treating non-uniform in-situ stresses, finite element method is used instead. It is found that, under the conditions of both uniform and non-uniform in-situ stresses, the casing load will approach the elastic solution with sufficient time duration. Furthermore, the conclusions from numerical simulation for the non-uniform in-situ stresses are just opposite to the present acknowledged ones. For example, the casing loads are determined not only by the stress difference, but also by the stiffness ratio. These new conclusions are very important for applications and laboratory experiments and need special attentions.