基于井下环形空间液固流动特性的数值模拟

Numerical Simulation of Liquid-solid Flow Characteristics in the Downhole Annular Space

钻井是开发石油资源一个非常重要的环节和技术手段,井中岩屑易在井眼底部形成岩屑床,导致下钻遇阻、蹩泵甚至卡钻,因此岩屑运移机理的研究对钻井作业来说至关重要。通过对现场实际情况的调研,在分析岩屑床的形成及危害的基础上,对钻井液携岩效果的影响因素和岩屑床的清除办法进行了探讨,提出了将提高钻井液环空返速、适当增加钻杆转速,改善钻井液性能与机械清除岩屑相结合的方法。运用Solid Works对井下环形空间进行建模与装配,得到井下环形空间的三维模型。使用软件建立井下环形空间的简化模型,通过应用FLUENT中动网格部分的UDF编写成功地实现了钻杆的旋转。运用FLUENT数字模拟软件,通过对流体非定常流的数值模拟,对岩屑在环形空间的运移规律进行研究,模拟条件更加接近实际情况,结果更加精确,可以为钻井井眼清洁工作提供科学参考。

Drilling is a very important link and technical mean in development of oil resources. Cuttings in the well are easy to form the cuttings bed at the bottom of the borehole, which will cause slacking off, pump bouncing and even sticking. So the research of cuttings migration mechanism is very important to the drilling operations. Based on investigation of the actual situation of the field and analysis of the cuttings bed＇s formation and damage, influence factors of cuttings carrying capacity and removal methods of cuttings bed were discussed, and the method of improving the annular return velocity, increasing the speed of the drill rod and combination of improving the performance of drilling fluid and mechanical removal of cuttings were put forward. SolidWorks was used to model and assemble the annular space; 3D model of the annular space was obtained. The software was used to establish a simplified model of the annular space. Through application of the UDF writing in the moving grid of FLUENT, the rotation of the drill rod was achieved successfully. Using the digital simulation software FLUENT, through the numerical simulation of fluid unsteady flow, the migration rule of cuttings in the annular space was studied. The simulation conditions are more close to the actual situation, the result is more accurate, and it can provide scientific reference for drilling hole cleaning.