The probability of packer sticking is increased because of the casing deformation and crustation in casing failure well.

在套损,于套管变形、结垢等因素,进一步加大了隔卡钻可能性。

In order to prevent failure of packer and provide theoretical basis for selection of unsetting shear pin, the unsetting force of packer must he calculated in design.

为了防止隔在工作过程失效，并为解剪钉（或剪环）选择提供理论依据，必须进行解设计计算。

The causes are presented as follows: packer unloading pressure, formation damage, oil tool plugging, formation voidage, the worst formation physical properties and the effect from vicinage wells.

地层污染或工具堵塞;地层欠压;地层物性极差;邻影响等。