# Experimental Analysis of Shale Cuttings Migration in Horizontal Wells
## 1 Introduction  
In recent years, shale gas has garnered significant attention as a clean energy source due to its abundant resources, low carbon emissions, and environmental benefits. The exploration and development of shale gas reservoirs have been facilitated by the utilization of horizontal well technology, which is essential for overcoming the low permeability and non-uniformity of these reservoirs [1, 2]. However, challenges arise during the drilling of long horizontal sections, as the accumulation of flaky cuttings at the bottom of the annulus poses a significant operational concern. The deposition of cuttings along the low side of thewellbore can result in an increased contact surface between the drill tool and the cuttings, leading to higher torque and surface pressure. If necessary actions are not implemented in a timely manner, this situation may eventually lead to a stuck pipe [3; 4; 5; 6]. During the early drilling operations, vertical wells were predominantly drilled, resulting in a straightforward process for carrying cuttings. However, advancements in drilling technology have led to the widespread utilization of directional, highly deviated, and horizontal wells, thereby making borehole purification due to cuttings migration a critical aspect of drilling operations. Although research on cuttings transported by drilling fluids dates back to the 1940s, it was not until the 1980s that the focus shifted towards cuttings carried by highly deviated and horizontal wells. [PERSON] conducted experiments on vertical pipe flow to examine the impact of various factors (including flow rate, rheological properties, cuttings size, drilling fluid density, rotational speed, and drilling rate) on cuttings transport at varying pipe and casing dimensions [7]. [PERSON] developed a critical cuttings transport velocity model based on experimental data to optimize drilling fluid flow and rheological properties for varying inclines [8]. [PERSON] examined the hydrodynamic mechanisms of cuttings migration in highly inclined wells and formulated a validated cuttings transport model [9]. [PERSON] conducted experiments on deviated wells to investigate the impact of different drilling parameters on flow velocity, elucidating the movement of cuttings in the lower section of the annulus and the suspension mechanism within the annulus [10]. Building upon fluid mechanics theory, [PERSON] developed a mechanical model for the migration of annular cuttings, incorporating various well angles, including high-angle, medium-angle, and vertical wells, into a unified framework [11]. [PERSON] developed a model for cuttings slip-off velocity based on drilling fluid viscosity through experimental analysis. This model incorporates modifications for cuttings diameter, well inclination angle, and drilling fluid density, and is specifically applicable to well inclinations ranging from 55 to 90 degrees [12]. [PERSON] introduced a critical cuttings-carrying velocity model for drilling extended reach wells using coiled tubing, and concurrently developed a drag coefficient model that considers the apparent viscosity of the fluid [13; 14]. This model accurately predicts the final velocity of a solid ball in a non-Newtonian stationary fluid with high engineering precision. [PERSON]'s comprehensive experimental findings on cuttings of varying sizes (ranging from 0.45 mm to 3.3 mm) demonstrate notable variances in cuttings transport across different casing dimensions [15]. [PERSON] conducted extensive experimental investigations to elucidate the principles governing cuttings transport at various inclinations and fluid velocities, culminating in the development of an empirical model for the cross-sectional area of cuttings beds [16]. Based on [PERSON]'s model, [PERSON] developed a computational model to forecast the velocity of suspended cuttings migration across a range of inclinations, from vertical to horizontal wells (0-90\({}^{\circ}\)) and determined the optimal flow rate for various drilling fluid rheological properties [17].