LET扣钻具在塔里木油田的应用

Talimu Oil Field Development Using a Last-Engaged-Thread-Height Reduction of Pin Drill Tool

为了降低钻具接头螺纹齿根的应力集中，减少钻铤、稳定器、转换接头等失效事故的发生，根据降低公扣大端啮合齿高度的设计思路开发了一种新型钻具螺纹LET扣。主要介绍了LET扣的设计、加工及现场试验情况。LET扣钻具的加工、现场使用结果表明，LET扣钻具容易加工，不影响修扣次数、上卸扣操作及其使用性能，能够显著提高钻具的疲劳寿命，具有一定的推广应用价值，而且LET扣钻具螺纹与API标准螺纹具有互换性。

In order to reducing the stress concentration on the base of thread in drilling tool substitute to cutting down the accidents on drill collar, stabilizer, crossover etc., a new type of drill tool thread, Last-Engaged Thread (LET) height reduction of pin is designed, combining with the designing thoughts of reducing the engaged height of pin. This paper mainly introduces the designing, processing and field testing of LET pin,showing the properties: easily processing, no affect on maintenance of pin, make up and break out, extending the fatigue life and wide application.