Experimental study of free settling of cuttings in newtonian and non-newtonian drillings fluids: drag coefficient and settling velocity

In this paper, is the free settling of cuttings in newtonian and non-newtonian drilling fluids experimentally investigated. The cuttings used in the experiments have densities ranging from 1.17 to 4.10 g/cm3 and diameters from 0.2 to 5.06 mm. The fluids used are water, CMC drilling fluid and the drilling fluid for the continental deep drilling project in F.R. Germany (KTB). Two settling patterns of cuttings have been observed- stable settling and swinging settling. For particles with reynolds number greater than 100, the cutting settling is swinging, whereas the settling is stable for particles with reynolds number smaller than 100. New predictive expressions for the drag coefficient of cuttings and for the settling velocity of cuttings are developed for both stable settling and swinging settling.