水力振荡器降低摩擦阻力影响的分析

Analysis on the Influence of Frictional Resistance Reduction by Hydraulic Oscillator

在斜井钻进中,钻具基于重力影响会自然贴合下井壁,并与井壁产生静摩阻,滑动钻进中则进一步演变为托压现象,常导致工具面摆置困难、机械钻速降低、单趟钻进尺减少等问题;若活动钻具不及时,则有可能引发钻具粘卡事故,严重时可致单井报废。因此,降低摩阻、减缓托压已然成为安全钻井的重要环节。摩阻大小由钻柱自重在井眼轨迹法线方向上的分力和静摩擦系数来决定。在滑动钻进中,技术人员往往通过向泥浆中添加润滑剂或进行短起下(目的为修整井壁)等方式来降低静摩擦系数,从而达到降低摩阻、减缓托压的目的。由经典物理可知静摩阻大于滑动摩阻,因此,可以通过把静摩阻转化为动摩阻来减缓托压。通过摩阻成因分析、水力振动器作用机理及其在苏里格气田、玉门油田和大庆油田等多口井的现场使用情况来评价水力振荡器的使用效果,并通过玉门油田鸭K1-7井现场试验来分析水力振荡器使用中的注意事项。

In deviated well drilling, drill stems will naturally be pressed close to the borehole wall on the bottom side owing to the gravity with static frictional resistance produced, which will further evolve into backing pressure and lead to toolface, lower ROP and reduced drilling footage in a single trip ; if not timely moving about the pipe, sticking accident is likely occur and even more with well abandoned. Therefore, friction reduction and backing pressure relieving become important parts of safe drilling. The magnitude of friction is decided by the component force and static friction coefficient of drill strings weight in borehole trajectory normal direction. In sliding drilling, some ways such as adding lubricant into the mud or making a short tirp （for borehole dressing） were adopted to reduce the static friction coefficient for the purpose of reduc- ing friction and relieving backing pressure. In term of the classical physics, the static friction is greater than sliding friction; therefore, backing pressure relieving can be achieved by transforming the static friction into slide friction. In this pa- per, the application effects are evaluated based on the cause analysis on the friction, the mechanism of hydraulic oscillator and its application in Sulige gasfiled and Yumen, Daqing as well as some other oilfields. And the matters of attention in the use of hydraulic oscillator are discussed through the field test in Ya K1 -7 well of Yumen oilfield.