专用取套工具弧形扶正块参数优化设计

斜井取套施工中，为防止套管与套铣管柱内壁发生磨损，所使用的套铣头内壁安装有滚珠式凸形扶正块，但该设计不仅存在滚珠失效而无法滚动的风险，更为严重的是在点接触形式下往往产生较大的接触应力，使得套管极有可能发生塑性破坏，这2种因素驱使下极易切坏套管导致取套施工失败。本着改变扶正块与套管接触形式的目的，在轴套式套铣头改进方案的基础上，提出了弧形扶正块的设计构想，基于两者接触时的力学条件及几何关系，实现了扶正块最小宽度及最小个数的参数优化，从提高修井液流速的角度实现了高度与宽度的匹配，从而减小两者间的接触应力，为安全取套施工的顺利进行提供保障。

Structure parameters optimization of curved centralizing-block for special extracting tools

For centering casings in washover string，the washover shoes collocate rolling balls on their inner wall in the process of extracting casing in deviated well. But there may exist a risk of balls′ failure that will lead casing worn out. More seriously，a large contact stress generated by point contact may cause casing′s failure.
The above factors might result in failure of extracting casing. For changing the contact form between centralizing-block and casing，on the basis of shaft sleeve，this paper proposed the design of the curved centralizing-block. By considering spatial geometrical relations when they contact each other，the authors optimized the minimum width and minimal number of blocks，thus reducing contact stress for the process of extracting tools. All this have guaranteed the smooth construction of extracting casing in deviated well.