Transport of small cuttings in solid-liquid flow with inclined slim hole annulus

During drilling, the precipitation velocity of cuttings within an annulus depends on the density, configuration, and size of the cuttings, and on the density, viscosity, and rheological characteristics of the drilling fluid. In directional drilling in particular, it is difficult to adjust and control the cuttings. In contrast to vertical drilling, it is very important to evaluate the flow characteristics of a drilling flow field. However, research on the transfer features of cuttings is inadequate. In this study, in order to identify transfer features of cuttings, an experiment was performed under wide-ranging conditions by constructing a slim hole annulus (44 mm×30 mm) device. In this experiment, the friction coefficient, pressure loss, particle transport ratio, and particle volume fraction were measured. These quantities were influenced by particle concentration within the flow, pipe rotation, flow volume, and inclination of the annulus. In addition, a mathematical formula for volumetric concentration was deduced and compared to the test results and behavior of cuttings under the other drilling condition was made to be predicted. Therefore, this study can provide meaningful data for vertical and horizontal drilling, and for directional drilling.