水平井钻柱动态摩阻扭矩计算与分析

国内近年的页岩气开采水平井井型主要有常规水平井、大斜度井和勺型水平井,为便于施工决策,有必要对上述3种井型的摩阻扭矩特性、钻压传递效率、重点关注井段或环节、极限延伸钻进长度等进行研究。为此,以上述3种水平井井型为分析对象,基于全井钻柱动力学模型和全井钻柱系统动态特性仿真计算,探究了其摩阻扭矩、载荷传递和延伸钻进情况,并在四川盆地长宁地区的3口对应井型页岩气井进行了现场应用实验。研究结果表明:(1)勺型水平井造斜段后半段的接触摩擦强度很高,造斜段后段接触强度是稳斜段接触强度的1.67倍,造斜段的总接触力是大斜度水平井的1.62倍;(2)大斜度水平井稳斜段的接触摩擦强度不仅高于造斜段,而且也高于相同井深的3种井型中的任一特征段;(3)3种井型延伸钻进中钻柱的工作应力都不大,但对于勺型水平井的弯曲段,延伸钻进时还需要重点关注稳斜段钻柱的扭断问题;(4)勺型水平井的钻压传递效率低于常规水平井和大斜度井。结论认为,该研究成果初步揭示了3种页岩气水平井井型的摩阻扭矩特性和主动载荷传递机理,指出了安全评估重点关注井段,对页岩气水平井的高效安全施工具有参考价值。

Calculation and analysis of dynamic drag and torque of horizontal well strings

In recent years, shale gas production horizontal well types mainly include conventional horizontal well, highly deviated well and scoop-shape horizontal well. For the sake of construction decision making, it is necessary to study these three types of wells from the aspects of drag and torque characteristic, weight on bit transferring efficiency, key hole sections or links and extreme penetration length. In this paper, these three types of horizontal wells were taken as the study objects. Their drag and torque, load transfer and extended reach drilling were explored based on the dynamic model of full hole drilling string and the simulation calculation of dynamic characteristics of full hole drilling string system. And the results were applied and tested on site in three shale gas wells (a conventional horizontal well, a highly deviated well and a scoop-shape horizontal well) in the Changning area, Sichuan Basin. And the following research results were obtained. First, the contact friction strength of the second half of the build-up section in the scoop-shape horizontal well is very high, and it is 1.67 times that of the hold section. The total contact force of build-up section in the scoop-shape horizontal well is 1.62 times that in the highly deviated well. Second, the contact friction strength of the hold section in highly deviated well is not only higher than that of its build-up section, but also higher than any characteristic section in the three well types of the same depth. Third, the operating stress of drilling strings during the drilling of three well types is not high, but during the extended reach drilling in the curved section of the scoop-shaped horizontal well, it is necessary to focus on the twist off of drilling string in the hold section. Fourth, the weight on bit transferring efficiency of scoop-shaped horizontal well is lower than that of conventional horizontal well and highly deviated well. In conclusion, the research results preliminarily reveal the drag and torque characteristics and active load transferring mechanisms of conventional horizontal well, highly deviated well and scoop-shape horizontal well for shale gas production, and present important hole sections for safety assessment. They can be used as references for efficient and safe construction of shale gas horizontal wells.