A new approach of three-segment hydraulic model under two-phase (solid-liquid) fluid in annulus; i.e., horizontal and near horizontal section, vertical and near vertical section, and transit section is proposed to predict and interpret the cuttings transport mechanism. In particular, the model developed in this paper approaches a three-layer hydraulic model (stationary bed of drilled cuttings at the bottom, a moving-bed layer above it, and a heterogeneous suspension layer at the top) for horizontal and near horizontal sections. The existing two-layer model is modified for transit section, and one-layer model is used for the vertical and near vertical sections. This new mathematical model is presented to overcome the limitations in the existing hydraulic models used to predict cuttings transport when drilling a horizontal and deviated wells.

This paper specifically describes model development for each section, solution, and the simulation results of the integrated three-segment model. To ensure a comprehensive understanding the effects of parameters affecting cuttings transport efficiency, the simulation under hole cleaning mode was performed, that involves build-up of cuttings and cleaning out an existing cuttings bed. The results show how to obtain a reasonable pumping velocity and optimize rheology of drilling fluid with the possible lowest pressure gradient that might serve as an operational guideline during drilling. Moreover, the effects of various parameters that affect the efficiency of cuttings transport are discussed. These results are compared with published experimental data. The observed agreement and discrepancies are discussed, and further improvements on the current model are proposed.

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