大庆油田致密油平台三维水平井钻柱摩阻分析

平台水平井是大庆油田致密油开发的主要形式，平台布井的方式导致部分水平井轨道出现三维井段。钻井施工中三维水平井较二维水平井钻柱摩阻更大，限制着水平井的延伸极限。在软杆理论模型的基础上，通过分析三维井段钻柱与井壁的接触形式，给出钻柱挫动的计算模型，采用Landmark软件模拟与实际施工情况相结合的方法进行了验证。模拟结果表明，三维井段钻柱与井壁的接触面积大于二维井段，扭方位时的井斜角大小与钻柱摩阻正相关，三维水平井整体摩阻系数达到0.4以上。钻井设计和施工过程中应根据三维井段钻柱摩阻规律，优化设计水平井轨道和井身结构、合理分配钻具组合中加重钻杆位置、提高钻井液润滑性、采用降摩减阻工具等方式降低钻柱摩阻，提高平台水平井的延伸长度，以保证致密油平台的高效开发。

Analysis of friction upon drill string for 3D horizontal wells ontight oil platform in Daqing Oilfield

Platform horizontal wells are the main form to develop tight oil in Daqing Oilfield. The way placing wells on platform leads to 3D well sections in some horizontal well trajectories. During drilling process, compared with 2D horizontal wells, 3D horizontal wells have greater friction upon drill string, which limits the extension limit of horizontal wells. On the basis of the soft string theoretical model, by analyzing the contact form between the drill string and the borehole wall in the 3D well section, the model calculating shifting of the drill string was given, which was verified by integrating Landmark software simulation with actual drilling situation. The simulation results show that the contact area between the drill string and the borehole wall in the 3D well section is larger than that of the 2D well section, that the deviation angle is positively correlated with the friction upon drill string when adjusting orientation, and that the overall friction coefficient of 3D horizontal wells is above 0.4. During design process or drilling process, it is necessary to reduce the friction upon drilling string according to the friction generation law in the 3D well section, and some means may help, such as optimizing horizontal well trajectory and wellbore structure, reasonably allocating the position of the heavier drill pipe in drilling tool assembly, improving the lubricity of drilling fluid, and selecting friction reduction tools. Reducing the friction upon drilling string can effectively lengthen platform horizontal wells, which will ensure efficient development of tight oil platforms.