超深井小钻工具接头螺纹结构研制与应用

为适应塔里木油田深井和超深井勘探与开发的恶劣工况,同时针对其深井、超深井小钻工具的疲劳失效问题,研制了一种特殊螺纹（TMXT36）结构的超深井小钻工具,该特殊螺纹结构减少了每英寸的牙数,加长了外螺纹接头最末完全扣到外台肩的距离,比常规的螺纹多设计了3 扣,减小其刚性,增加了弹性,从而提高其抗疲劳寿命（2.5 倍）;该螺纹结构将扣根的最大应力转移到了接触面较宽的螺纹导向面上,降低了螺纹根部的疲劳缺口敏感系数（3.5）。该特殊螺纹与油田现有的NC38、TX60 和TH90 螺纹有限元对比分析得出:TMXT36 的应力集中系数和其疲劳缺口敏感系数为最小,其抗疲劳寿命比其他螺纹接头提高了2.5 倍,其试制成品在塔里木油田得到了应用和验证。

Development and application of screw structure of miniature drilling tool for super-deep wells

A miniature drilling tool with special screw (TMXT36) structure was developed to cope with unfavorable exploration and development conditions in deep and super-deep wells in the Tarim Oilfield and to prevent fatigue failure of miniature drilling tool in such wells. The special screw has the number of teeth in every inch reduced, and the distance between the end of external screwed joint and the external shoulder increased. Moreover, with three threads more than conventional screws, the new screw has rigidity reduced and elasticity enhanced to promote the fatigue-resistant service life. The new screw structure can effectively transfer the maximum stress onto the relatively wide guiding surface of screw to minimize fatigue notch sensitivity coefficients at the root section of the screw. Finite-element comparative analysis was made for performances of the new screw with NC38, TX60 and TH90 screws currently used in the oilfield. The results show that TMXT36 has the minimum stress concentration coefficient and fatigue notch sensitivity coefficient, whereas the fatigue-resistant service life is 2.5 times longer than other screwed joints. Prototypes of the screw have been deployed and vilified in the Tarim Oilfield.