带双心钻头底部钻具组合的分析

针对使用双心钻头钻进时扩孔尺寸不理想、钻具工作不稳定、井斜趋势引起钻头工况对钻压非常敏感等问题,对底部钻具组合的受力、变形和运动状态等方面进行了分析研究表明,由于双心钻头几何设计的独特性,工作时钻头上受有不平衡力,这使得钻头切削不稳定,且影响钻柱变形。钻柱变形后,钻头相对井底偏转,偏转的方向和角度影响钻头的有效切削面积;钻柱的运动方式,即自转和公转,也影响扩孔尺寸和钻头稳定性。通过简单试验,认为钻头的不平衡力使钻具倾向公转;另外井斜、井眼弯曲也对钻具运动状态有很大影响,表现为钻具稳定性对钻压的变化非常敏感。

Mechanical Analysis of Bottom Hole Assembly With Bicenter Bit

When drilling with bicenter bits, several problems have been encountered, such as drilling a smaller- than - expected hole, the instability of bottom hole assembly (BHA), and hole deviation tendencies that make the bit extremely weight sensitive. In this paper, forces, deformation and moving state of BHA with bicenter bit are studied. It reveals that the unusual geometry of bicenter bit results unbalanced loads. So drill collar will deform and the bit will tilt, direction and value of bit tilt angle; together with moving state of BHA, decide hole size. Through simple experiments, it has been concluded, that unbalanced forces on bit add the whirling propensity of BHA. Bore hole deviation and curvature also affect BHA's moving state, and the drilling stability is sensitive to bit weight.