In a horizontal well drilling operation, a part of generated drill cuttings tends to settle down at a lower annular section. Formation of sand bed causes several operational issues such as low rate of penetration and stuck drill pipe. In this study, a lab-scale experimental work is carried out to investigate hole cleaning in the extended reach and horizontal drilling operation. This work focuses on the visualization of the flow behaviour of drill cuttings in the horizontal annular section. A 6.16 m-long horizontal well test section with an outer diameter of 4.5 inch (11.43 cm) and an inner diameter of 2.5 inch (6.35 cm) is used in this study. Four non-Newtonian Herschel-Bulkley fluids are tested as the drilling mud. Solid glass beads of 2.5–3.0 mm with a density of 2650 kg/m³ are utilized as the drill cuttings with two different solid concentrations. The flow behaviour in the horizontal annular section is analyzed with a high-speed imaging technology at 2000 frames/second and electrical resistance tomography (ERT) technique. The effects of fluid rheology, fluid velocity, drill pipe rotation, and eccentricity on the cuttings transport are investigated. This study showed that an optimum drill pipe rotation of 80 RPM and a minimum transport performance number (TPN) of 70 is required for efficient hole cleaning in horizontal well section. This study also reveals that fluid rheology has a significant effect on the minimum transport velocity (MTV). A flow regime analysis revealed that a turbulent flow regime is required for effective hole cleaning without sand bed formation. The mechanistic three-layer model of cuttings transport is experimentally verified with high-speed visualization techniques. Furthermore, this study introduces the concept of estimating the instantaneous annular solid volume fraction by the ERT system as well as visualization of solid bed distribution in the annulus section.

在水平井钻探操作中，所产生的钻屑的一部分倾向于沉降在下部环形部分处。沙床的形成会引起一些操作问题，例如渗透率低和钻杆卡死。在这项研究中，进行了实验室规模的实验工作，以研究大范围和水平钻井作业中的孔清洁。这项工作着眼于水平环形截面中钻屑流动行为的可视化。在这项研究中，使用了一条6.16 m长的水平井测试段，其外径为4.5英寸（11.43厘米），内径为2.5英寸（6.35厘米）。测试了四种非牛顿的Herschel-Bulkley流体作为钻井液。2.5–3.0 mm的固体玻璃珠，密度为2650 kg / m ³被用作具有两种不同固体浓度的钻屑。使用2000帧/秒的高速成像技术和电阻层析成像（ERT）技术分析水平环形截面中的流动行为。研究了流体流变学，流体速度，钻杆旋转和偏心率对岩屑运移的影响。这项研究表明，水平井段的有效孔清洗需要最佳的钻杆旋转速度为80 RPM，最小输送性能数（TPN）为70。这项研究还表明，流体流变学对最小传输速度（MTV）有显着影响。流态分析表明，湍流态是有效的孔清洁而不需要沙床形成所必需的。机械屑的三层模型通过高速可视化技术进行了实验验证。此外，本研究还介绍了通过ERT系统估算瞬时环形固体体积分数的概念，以及在环空段中可视化固体床分布。