Simulation on Incipient Particle Motion in Highly-Inclined Annulus

Background: Highly-inclined and horizontal wells have been widely used for the development of mature oilfield, marine oilfield, and low permeable oilfield. During drilling operations, cutting particles will accumulate in the low side of wellbore and cuttings bed may be formed, which may lead to high drag and torque, stuck pipe, and other drilling problems. We reviewed the patents about cutting bed cleaning tool. Objective: The goal of this work is to determine the incipient motion velocity or rate to re-suspend and remove the cutting particles. Methods: In this study, the random distribution function of particles is introduced to determine the percentage of incipient particle motion, and the mechanical models for rolling and lifting method considering the net gravity, drag force, lift force, additional mass force, adhesive force and flow pressure gradient force are developed to predict the incipient motion velocity or rate. Also, the model has been verified by published experimental data. Results: The critical particle size of incipient motion rate is approximately 1 mm. The incipient motion rate decreases as the height of cuttings bed decreases, and the minimum flow rate that prevents the bed formation may be estimated when bed height is small enough. Also, increasing wellbore inclination or fluid density has a positive effect on incipient motion rate, but increasing particle density or percentage of incipient particle motion has an adverse effect. Conclusion: This study may provide a guideline for designing hydraulic parameters and sand washing in the highly-inclined and horizontal wells, thereby contributingin economic production.