Abstract
In the past decades, horizontal directional drilling (HDD) has been successfully used to install various pipelines in different strata. However, construction accidents such as drill‐burying and drill‐sticking occur occasionally when pipelines installed by HDD method in an unstable stratum such as sand cobble stratum. Recently, HDD with dual drill pipes was used to install pipelines in unstable stratum, and the effect is significant. The law of cuttings migration for HDD with dual drill pipes is still unclear. Therefore, it is necessary to study the law of cuttings migration in reverse circulation with dual drill pipes. This study performs numerical simulations and experimental research on the cuttings‐carrying process in reverse circulation directional drilling with dual drill pipes. Based on the assumption of dual concentric pipes, simulations of fluid‐solid two‐phase flows are conducted in different flow channels between the inner and outer drill pipes. An experimental cuttings‐carrying model is then established. By combining the results of the numerical simulations and experimental investigation, the hydraulic parameters of the dual drill pipe system are optimized, and the rationalities of the drill tool design and the grading selection are validated. The results of this study provide a reference cuttings‐carrying model during reverse circulation HDD with dual drill pipes.
Highlights
Horizontal directional drilling (HDD) is a technique for installing pipes or utility lines below ground using a surfacemonitored drilling rig that launches and places a drill string at a shallow angle to the surface and has tracking and steering capabilities [1]
The parameter of cuttings discharge rate Cuttings discharge rate (Cd) is introduced to measure the difficulty of cuttings discharge with different diameters. e value of Cd is between 0 and 1. e larger the value, the easier the cuttings are to be discharged
The law of cuttings migration of HDD with dual drill pipe is studied by experiments and simulations
Summary
Horizontal directional drilling (HDD) is a technique for installing pipes or utility lines below ground using a surfacemonitored drilling rig that launches and places a drill string at a shallow angle to the surface and has tracking and steering capabilities [1]. Compared with traditional open-cut construction, the HDD technology has the advantages of fast construction speed, small damage to the ground, and no effect on the use of existing pipelines [2, 3]. Considering these advantages, the HDD technology has been widely used in various pipelines installations. HDD with dual drill pipes was used to install pipelines in the unstable stratum, and the effect was significant. Many controllable and Advances in Civil Engineering uncontrollable factors are involved in the hole-cleaning process (i.e., the cuttings-carrying process), such as the flow velocity in the borehole annulus, the displacement of the mud pump, the viscosity of the drilling fluid, the rotational speed of the drill pipe, and the diameter of the bit waterway [11, 12]
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