Experimental study of cuttings transport with non-Newtonian fluid in an inclined well using visualization and ERT techniques

Hole cleaning is a concern in directional or horizontal well drilling operation where drill cuttings tend to settle in the lower annulus section. A lab-scale experiments were performed with different non-Newtonian fluids in a 6.16-meter-long, 4.5-inch × 2.5-inch transparent annulus test section to investigate cuttings transport behaviour. This experimental study focused on understanding the cuttings transport mechanism in the annulus section with high-speed imaging technology. The movement of cuttings in the inclined annular section was captured with a high-speed camera at 2000 frames per second. Also, cuttings bed movement patterns at different fluid velocity and inner pipe rotation were captured with a DSLR video camera. The electrical resistance tomography (ERT) system was used to quantify the cuttings volume fraction in the annulus. Different solid bed height and cuttings movement were observed based on fluid rheology, fluid velocity and inner pipe rotation. The mechanistic three layers cuttings transport model was visualized with the experimental procedure. This study showed that solid bed height is significantly reduced with an increase in the inner pipe rotation. This study also identified that cutting bed thickness largely depends on fluid rheology and wellbore inclination. The image from the high-speed camera identified a downward trend of some rolling particles in the annulus due to gravitational force at a low mud velocity. Visual observation from high-speed camera identified a helical motion of solid particles when drill pipe is in contact with solid particles and rotating at higher RPM. Different cuttings movement patterns such as: rolling, sliding, suspension, helical movement, downward movement were identified from the visualization of a high-speed camera.