A novel prediction model for cuttings bed height in horizontal and deviated wells

A better understanding of cuttings accumulation in the wellbore and ensuring favorable hole-cleaning conditions are crucial for successful oil and gas drilling operations. Considering the limited ability of existing critical velocity models to predict the cuttings bed height, and these models only consider the rolling transport mode of drill cuttings, improvement and development of new models are needed. This paper presents a new model for predicting the cuttings bed height over three possible transport modes of the target bed particle: sliding, rolling, and lifting. A mechanical equilibrium relationship of the particle in the critical condition is established and to calculate the bed-friction velocity of different transport modes. The transport mode can be judged by comparison among the minimum calculated values. The mean annular velocity and cuttings bed height can be calculated according to the borehole geometry information and eccentricity. The model can be applied to drilling fluids with different flow patterns (laminar, turbulent) and different rheological models (Newtonian fluid such as water, non-Newtonian fluid conforming to Power-Law or Herschel-Bulkley models). The effects of inclination angle, cuttings size, circulation velocity, rheological parameters, eccentricity, and hole size on mean annular velocity and cuttings bed height were analyzed. Cuttings transportation experiments were carried out on a large-scale flow loop to validate the theoretical analysis results by comparison against the experimental results. This work has certain guiding significance for predicting the hole cleaning degree in the annulus, as well as the subsequent optimization of hydraulic parameters and the implementation of hole-cleaning measures.