Coupling model of wellbore heat transfer and cuttings bed height during horizontal well drilling

Horizontal well drilling is a powerful means of exploring and developing unconventional oil and gas reservoirs. However, cuttings are easily deposited at the bottom of the annulus of the horizontal well section. They, thus, form a cuttings bed and affect the wellbore flow and heat transfer during drilling. Currently, no wellbore heat transfer model considers the impact of cuttings beds. Therefore, a coupling model of wellbore heat transfer and cuttings bed height was established and validated using field data in this study. Despite the model's accuracy being dependent on the precise distribution of the cuttings bed height, it better aligns with the wellbore heat transfer characteristics during horizontal well drilling. Using this model, the influences of the circulation time, circulation flow rate, drill pipe rotation speed, rate of penetration, and inlet temperature on the wellbore heat transfer were investigated. Subsequently, measures to reduce the downhole temperature were proposed. In a case study, in comparison with models that do not consider the cuttings bed, the downhole temperature calculated by the new model was 1.3 °C higher. By increasing the circulation flow rate, controlling the drill pipe rotation speed and rate of penetration, and reducing the drilling fluid inlet temperature, we lowered the downhole temperature by 13.3 °C. This provided support for achieving one-trip drilling in a 215.9 mm borehole.