The eccentric annular flow is flow with special considerations; it forms a vital part of drilling-fluid flow analysis in horizontal wells. In this work, dual-phase flow through a horizontal well is simulated with the help of three-dimensional computational fluid dynamics (CFD) Fluent package. Moreover, the Herschel-Bulkley behaviour of the nano-fluid made the problem challenging in numerical and physical aspects. The primary objective of the work is to investigate the effect of nanoparticles in ester-based fluid and compare the results with the absence of nanoparticles, moreover; to establish the relationship between different flow characteristics with the high eccentricity and the impact on cleaning of the wellbore. The nano-fluid flow characteristics include axial velocity, cuttings volume fractions and their effect on transportation of rock cuttings to the wellbore surface, and cleaning wellbore. The importance of eccentricity of the inner cylinder was analyzed as a main part of this simulation. The results verified that the nano-drilling fluid has the ability to carry and transfer cutting particles of 3, 4.45 and 7mm sizes in a highly eccentric annular flow of 0.8 eccentricity. The minimum average fluid velocity that is required to establish the non-stationary cuttings bed was at 2.86m/s.

eccentric annular flow, nano and conventional drilling fluids.