Abstract: In turbulent flow of horizontal annulus,the cuttings bed is a concentrated fluid with special constitutive featrues. Starting from the mechanism and physical model of shared cuttings transport, the constitutive relationship and velocity field of bed-load cuttings transport are established through the study of the energy transfer and equilibrium of the microscopic motions of bed-load particles. From these equations,the critical hydraulies of cuttings motion into static beds, the maximum thickness of bed-load cutting layer,and that the transport of bed-load cuttings increases greatly flow resistance.

Key words: horizontal well, borehole cleaning, annular space flow, cuttings bed