大斜度井段小尺寸岩屑临界再悬浮速度力学模型

Mechanics model of critical re-suspension velocity for small-sized cuttings transportation in hole section with high inclination

陈修平 王明波 仲冠宇

中国石油大学（华东）石油工程学院，山东 青岛 266580

College of Petroleum Engineering, China University of Petroleum, Qingdao 266580, China

以往研究表明，岩屑在大斜度井段主要以翻滚形式向井口方向运移，文中提出大斜度井段小尺寸岩屑有效运移的临界环空条件——临界再悬浮环空返速。考虑钻柱旋转和颗粒间作用力的影响，分析岩屑受力，建立了临界再悬浮环空返速的预测模型。理论计算结果与现有试验数据对比显示，两者有较好的一致性。利用该模型对大斜度井段小尺寸岩屑运移过程进行分析，结果表明：直径小于0.5 mm的小尺寸岩屑颗粒更难被再悬浮；在大斜度井段，井斜角对于小尺寸岩屑的再悬浮临界环空返速影响较小；钻柱旋转有利于小尺寸岩屑颗粒的再悬浮；在一定范围内，钻井液流性指数、稠度系数值越小，越有利于小尺寸岩屑的再悬浮。

Previous studies show that cuttings are transported to wellhead by a rolling form for the hole section with high inclination, including horizontal section. A critical annular condition for the effective transportation of small-sized cuttings in highly deviated and horizontal well section is put forward, that is critical re-suspension velocity. On the basis of dynamics analysis on cuttings, a mechanical model for predicting the critical re-suspension velocity is established, which considers the effect of the rotation of drill pipe and the interparticle forces. The theoretical calculation results are compared with old experimental results, showing a good consistency. Using this model, the transportation process for small-sized cuttings is analyzed. The results show that the small-sized cuttings with diameters of less than 0.5 mm are more difficult to be re-suspended; the hole inclination has a limited effect on the critical re-suspension velocity in hole sections with high inclination; the rotation of the drill pipe is helpful for the re-suspension of small-sized cuttings; in some extent, the smaller the value of drilling fluid and consistency factor are, the more beneficial for the re-suspension of the small-sized cuttings is.

10.6056/dkyqt201304023