欠平衡钻水平井岩屑运移可视化实验

随着我国薄层低压油气藏的开发需求,充气欠平衡钻水平井技术成为国内外钻井界关注的热点,井眼净化不畅造成钻具摩阻扭矩的增大严重制约着水平井眼的延伸能力,气液固复杂多相流动,特别是认识固相运移规律是欠平衡条件下岩屑运移的核心内容。为此,在分析水平井与直井多相流条件下的岩屑受力与运移规律异同的基础上,根据气液固流动机理以及大平面沙丘颗粒运移理论,利用大型多相流实验台架开展了水平井段岩屑运移可视化实验,研究岩屑受力、运移形式及动态运移规律,获得了井眼净化注液量、注气量、液体流速、岩屑浓度等数据,进而对比找到了模拟携岩临界速度与实测携岩临界速度的误差,用实测速度修正了水平井井筒携岩临界速度预测数学模型,研究出了能够满足现场施工设计需要的钻进和循环工况的携岩速度模型和岩屑动态运移规律,对于优化钻井施工参数以及降低钻井安全风险均有重要意义。

A visualization experiment of cuttings transport in underbalanced horizontal wells

With the increasing demand for thin layer and low pressure hydrocarbon reservoir development, aerated underbalanced horizontal drilling has become the focus in the drilling circle all over the world. The extension capacity of horizontal wells is seriously restricted by increased friction and torque due to poor borehole cleaning. Therefore, it is essential to learn about the gas liquid solid multiphase flow, especially the solid transport law, and thereby, to study how the cuttings transport under the underbalanced conditions. In view of this, we firstly analyzed the similarities and differences of horizontal and vertical wells in the cuttings force and transport law under the multiphase flow condition. Based on the gas liquid solid flow mechanism and large plane dune particle transport theory, a visualization experiment was conducted of cuttings transport in horizontal section on a large multiphase flow experimental bench, so as to study the cuttings force, transport form and dynamic transport law. Data including borehole cleaning liquid injection, gas injection, liquid flow, and cuttings concentration were obtained. Moreover, by comparison, the error was found between the simulated critical cuttings carrying velocity and the experimental one. The experimental velocity was used to modify the critical cuttings carrying mathematical model for horizontal wells. Finally, the cuttings carrying model and dynamic cuttings transport law were established, satisfying the drilling and circulation conditions required in the field construction and design, which is significantly important to optimize the parameters and mitigate safety risks in drilling.