钻柱与实钻水平井眼接触形态及摩阻影响分析

Analysis on the Form of Contact Between a Drill String and Drilled Horizontal Wellbore and the Effects of Friction

刘清友 敬俊 祝效华

LIUQingyou JINGJun ZhuXiaohua

西南石油大学机电工程学院, 四川 成都 610500 西华大学流体及动力机械教育部重点实验室, 四川 成都 600300 “煤矿灾害动力学与控制”国家重点实验室·重庆大学, 重庆 沙坪坝 400044

School of Mechatronic Engineering, Southwest Petroleum University, Chengdu, Sichuan 610500, China MOE Key Laboratory of Fluid and Power Machinery, Xihua University, Chengdu, Sichuan 600300, China State Key Laboratory of Disaster Dynamics and Control of Coal Mine, Chongqing University, Shapingba, Chongqing 400044, China

水平井钻进过程中，地层结构、钻具振动、钻头侧向力、岩屑沉积等因素易导致实钻井眼轨迹发生连续小幅偏斜。该种偏斜虽不会引起实钻井眼轨迹的严重偏离，但将改变钻柱与井壁的接触形态。受现有测井方法的限制，该种偏斜常被忽略。通过理论分析与仿真，研究水平段井眼轨迹在井斜平面内连续小幅偏斜波动条件下的钻柱与井壁接触形态及其对摩阻的影响。研究认为，钻柱与偏斜波动水平井眼间易发生"悬跨"接触，该现象降低了现有解析法求解钻柱力学相关问题假设条件"钻柱与井壁连续接触"的合理性。钻柱自重和轴向力对悬跨钻柱弯曲位移及悬跨接触最大临界跨距的影响最大。悬跨接触将减小钻柱与井壁的接触面积、增大钻进摩阻。

During horizontal wellbore drilling, factors like the stratigraphy, vibrations of the drilling tool, lateral forces on the drill bit, and beds of cuttings tend to cause slight but continuous deflections in the trajectory of the drilled wellbore. Although these deflections will not induce severe deviations in the trajectory of the drilled wellbore, they will nonetheless alter the nature of the contact between the drill string and the walls of the well. This form of deflection is often neglected due to the limitations of current well-logging methods. Through theoretical analyses and simulations, we have studied the nature of the contact between a drill string and the walls of a well when a horizontal wellbore trajectory continuously fluctuates in small deflective fluctuations within the well' s plane of inclination, as well as its effects on frictional forces. This study reveals that "suspended spans" often occurs in the contact between the drill string and a horizontal wellbore undergoing deflective fluctuation, and this questions the rationality of the assumption that the drill string and the walls of the well are continuously in contact, which is often invoked in current analytical methods for solving questions related to drill string mechanics. The drill string' s weight and axial forces are the most important factors in determining the bending displacements and maximum critical span of a drill string in "suspended span" contact. These "suspended span" contacts will decrease the contact area between a drill string and the walls of the well, and increase drilling friction.

10.11885/j.issn.16745086.2016.01.31.02