复合盐层套管外挤压力动态变化规律研究

Study on Casing Dynamic Loads in Complex Salt-Bed

盐岩地层套管外挤压力通常按上覆岩层压力进行设计。现场资料表明,以此为依据所设计的套管有时仍然不能满足盐层套管抗外挤强度的要求。利用研究区块复合盐岩地层上、下泥岩的岩石力学参数及地应力值,运用数值模拟方法,反演得到盐层地应力,在试验获得盐岩蠕变特性参数基础上,对套管支护的盐层井壁围岩进行蠕变分析,得到盐岩地层套管外挤压力动态变化规律。在构造应力的作用下,盐层的地应力场是非均匀的,盐岩蠕变导致套管受到的外挤压力是动态变化的。对于复合盐岩地层的套管柱设计,应该充分考虑构造应力场的非均匀性、盐岩的蠕变特性以及套管的设计寿命。

The maximum permitted external pressure of casing strings in salt bed is usually designed ac cording to overburden pressure. Field data indicate that designed casing strings based on this criteria can not meet demands of collapse strength in such formation. The in-situ stress of salt-bed was regressed after rock mechanical parameters and in-situ stresses were studied in shale formation. Then based on the salt creep properties by experiments, the dynamic casing load in salt-bed was obtained from creep analysis of salt-rock on well-bore supported by casing. Tectonic stresses cause non-uniform stress distribution in salt-bed, thus there is dynamic loading acting on casing. In casing design for salt-bed, nonuniform tectonic stresses, creep properties of saltbed, and the designed life span of casing should be taken into considerations.