套管开窗侧钻中钻头弯矩分析

Analysis of bending moment on the bit in sidetrack drilling

李子丰 张欣 王鹏 李润启

LI Zifeng ZHANG Xin WANG Peng LI Runqi

燕山大学石油工程研究所，河北秦皇岛　066004

Petroleum Engineering Institute, Yanshan University, Qinhuangdao 066004, China

在油田开采的过程中，为了达到提高采收率等目的，很多油田都在现场应用了开窗侧钻技术，并且取得了显著的经济效益。在以往的对下部钻具组合受力的分析中，一般默认钻头为铰支，与地层间无弯矩。然而，在实际的开窗侧钻过程中，钻头与地层和套管不均匀偏心接触，必然存在钻头弯矩。因此，在合理假设的基础上，通过数值积分的方法，建立了求解钻头弯矩的数学模型，并且应用Visual Basic2008语言编写求解、分析软件，最后给出了一个计算实例。结果分析表明：钻头弯矩是一个随着钻头的钻进逐渐变化的过程。钻头刚接触套管壁的时候弯矩比较大，随着和地层接触面积增大，弯矩逐渐变小，当钻头全部处在地层中，钻头的弯矩为零。

In the process of reservoir development, so as to achieve the purpose of enhanced oil recovery, many reservoirs applied sidetrack techniques and had achieved remarkable economic benefit. In the past, the stress analysis of the bottom hole assembly is indicated that the drill bit is hinged and no moment with formation. However, in the actual operating environment of drilling, the drill bit keeps touch eccentric with casing and formation, there must be moment on the drill bit. Therefore, given some of reasonable assumptions, the mathematical model is established through the method of numerical integration. The software of mechanical analysis is developed with Visual Basic 2008. At last, an application to field is provided. The results show: bending moment on the bit is gradually changing process with the drilling progress, the value of the moment is relatively large when the bit beginning to touch with the casing, with the contact area increasing, which will be reducing gradually. It is easy to know that bending moment on the bit is zero when the bit is completely in the formation.