Wang Peng, Ni Hongjian, Wang Ruihe, Liu Weili, Lu Shuangfang
Research Institute of Unconventional Oil & Gas and Renewable Energy, China University of Petroleum (East China), Qingdao 266580, China.
School of Petroleum Engineering, China University of Petroleum (East China), Qingdao 266580, China.
Materials (Basel). 2017 Sep 1;10(9):1015. doi: 10.3390/ma10091015.
A modified model for predicting the friction force between drill-string and borehole wall under in-plane vibrations was developed. It was found that the frictional coefficient in sliding direction decreased significantly after applying in-plane vibration on the bottom specimen. The friction reduction is due to the direction change of friction force, elastic deformation of surface asperities and the change of frictional coefficient. Normal load, surface topography, vibration direction, velocity ratio and interfacial shear factor are the main influence factors of friction force in sliding direction. Lower driving force can be realized for a pair of determinate rubbing surfaces under constant normal load by setting the driving direction along the minimum arithmetic average attack angle direction, and applying intense longitudinal vibration on the rubbing pair. The modified model can significantly improve the accuracy in predicting frictional coefficient under vibrating conditions, especially under the condition of lower velocity ratio. The results provide a theoretical gist for friction reduction technology by vibrating drill-string, and provide a reference for determination of frictional coefficient during petroleum drilling process, which has great significance for realizing digitized and intelligent drilling.
建立了一种改进的模型，用于预测平面振动下钻柱与井壁之间的摩擦力。研究发现，对底部试样施加平面振动后，滑动方向的摩擦系数显著降低。摩擦力减小是由于摩擦力方向改变、表面微凸体的弹性变形以及摩擦系数的变化。法向载荷、表面形貌、振动方向、速度比和界面剪切因子是滑动方向摩擦力的主要影响因素。对于一对确定的摩擦表面，在恒定法向载荷下，通过将驱动方向设置为沿最小算术平均攻角方向，并对摩擦副施加强烈的纵向振动，可以实现较低的驱动力。改进后的模型能够显著提高振动条件下摩擦系数的预测精度，尤其是在较低速度比的条件下。研究结果为钻柱振动减摩技术提供了理论依据，为石油钻井过程中摩擦系数的确定提供了参考，对实现数字化和智能化钻井具有重要意义。
