Pilot-scale study on the suspension of drill cuttings: Effect of fiber and fluid characteristics

Abstract

Drilling operation smoothness is essential to minimize drilling non-productive time (NPT). Inadequate cuttings transport can result in cuttings bed build-up in the wellbore low side, jeopardizing the whole drilling operation. Modifying base fluid properties can prevent the associated risks with poor hole cleaning. Fiber sweeps enhanced hole-cleaning performance and increased cuttings transport to the surface with a negligible increase in fluid viscosity. This experimental investigation examines the effect of fibers on the cuttings carrying capacity of carboxyl methylcellulose (CMC) based polymeric fluids. The carrying capacity of the fluids is assessed by measuring the suspended and deposited cuttings/solids concentrations after a predefined quiescent period. Synthetic monofilament fiber of 0.9 specific gravity, 100 μm diameter, and two different lengths (3 and 12 mm) were used. Polymer concentrations were 0.747 and 1.1 wt %, while fiber concentration was varied from 0.00 to 0.08 wt%. The investigation was performed using a vertically configured annular test section (150 cm long) with a rotating inner shaft speed. Experimental results indicate that increasing fiber or/and polymer concentrations significantly improved cuttings carrying capacity of the fluids in suspending fine (1 mm) particles.

In most cases, the carrying capacity of the fluids in suspending coarse cuttings (3 and 6 mm particles) was slightly improved with the addition of polymer and fiber. Although the rotation of the inner shaft substantially reduced the deposition of fine particles but did not prevent the settling of coarse cuttings. In addition, short fibers demonstrated better performance than long ones in improving the carrying capacity of the fluids. Utilizing long and short mixed fibers at a specific proportion improved the cuttings carrying capacity of the fluid better than unmixed fiber.