新型减摩阻工具的射流振荡动力学机理

在水平井段钻进时,钻柱与井壁之间的摩阻将抵消一部分钻压,使钻压很难传递到钻头,降低了钻压传递效率。为了降低钻井摩阻、提高钻进效率,研制出了一种新型射流振荡减摩阻工具(以下简称新工具),开展了新工具的动力学和振动减摩阻特性研究,进行了新工具算例分析与室内实验测试,并对其结果进行了对比分析。研究结果表明:①新工具能够产生射流振荡效果,形成脉冲压力波动,使钻柱产生轴向振动,减小钻柱与井壁之间的摩擦阻力;②结合实际工况条件,随着钻压和转盘转速增大,钻头转速波动范围增大,产生钻柱黏滑现象的可能性降低;③算例分析与实验测试结果得到的振动速度均呈现明显的非线性规律,能够反映钻柱的真实振动特性。结论认为,算例计算与实验测试结果一致,验证了新工具结构设计的合理性和计算结果的准确性;新工具有效降低了水平井的钻井摩阻,不仅为实现油气井高效钻井提供了技术支持,也为新条件下的油气井钻井工具开发提供了参考。

Dynamic mechanism of fluidic oscillation of a new friction reducing tool

In the drilling process of horizontal section, the friction between the drill string and the borehole wall offsets partial weight on bit (WOB), so the WOB can be hardly transferred to the drilling bit, resulting in the decrease of the WOB transfer efficiency. In order to decrease the drilling friction and increase the drilling efficiency, we developed a new type of fluidic oscillation friction reducing tool (hereinafter "a new tool" for short) in this paper. Its dynamics and vibration antifriction characteristics were investigated. In addition, calculation example analysis and laboratory test were carried out, and their results were comparatively analyzed. And the following research results were obtained. First, this new tool can generate the effect of fluidic oscillation and result in pulse pressure fluctuation, so that axial vibration is generated on the drill string and the friction between the drill string and the borehole wall is decreased. Second, in the actual working conditions, the fluctuation range of the drill bit speed increases and the occurrence possibility of the stick-slip phenomenon on the drill string decreases as the WOB and the rotating speed of the rotary table increase. Third, the vibration speed obtained by the example analysis and the experimental test presents obvious nonlinear laws, which can reflect the true vibration characteristics of the drill string. In conclusion, the coincidence between the example calculation and the experimental test result verifies the rationality of the new tool's structural design and the accuracy of the calculation result. This new tool can decrease the drilling friction of horizontal well effectively, and it can not only provide a technical support for the high-efficiency drilling of oil and gas wells, but also the theoretical reference for the development of oil and gas well drilling tools in new conditions.