Effects of Pipe Rotation on the Performance of Fibrous Water-Based Polymeric Fluids in Horizontal Well Cleanout

Summary The deposition of rock cuttings is a problem commonly faced during drilling, completion, and intervention operations. Using polymer-based fluids is a common technique to improve horizontal downhole cleaning. However, these fluids cannot always guarantee an efficient wellbore cleanout. One way to enhance cleanout efficiency is by rotating the drillpipe to mitigate the settling of solids and facilitate their removal. However, drillstring rotation often increases equivalent circulating density (ECD). Therefore, in this study, we explore how the impact of rotation on hole cleaning can be synergized by using fibrous water-based polymeric fluids to perform cleanout at reduced rotational speeds with limited effect on ECD. The flow loop used for this study consists of a 48-ft long eccentric annular (5×2.375 in.) test section. Each experiment began by forming a stationary bed of natural sand (an average diameter of 1.2 mm) in the test section. High-viscosity and low-viscosity polymer-based suspensions with and without fibers were used. The drillpipe rotation speed was varied from 0 to 150 rev/min. In each experiment, the flow rate was increased from 35 to 195 gal/min stepwise. The bed perimeter was measured at equilibrium condition for every test flow rate until a complete bed cleanout was achieved. In addition, the friction pressure loss was measured. Rotational viscometers were also used to measure fluid rheology before and after each test. Fiber particles improve the carrying capacity of the fluid by reducing solid settling and minimizing the redeposition of particles. The results demonstrate the effectiveness of fiber in synergizing pipe rotation effects on hole cleanout performance in horizontal wellbores. Fiber’s impact is more pronounced when used with low-viscosity fluid. The cleanout performance of the low-viscosity fluid is amplified significantly with rotation, almost entirely cleaning the bed at 75 gal/min and a rotational speed of 50 rev/min, compared with more than 195 gal/min without rotation. Even more improvement could be achieved by adding a small amount of fiber (0.04wt%). In addition, the fiber improved the cleanout performance of the high-viscosity fluid. The enhancement, however, was not as noticeable as with the low-viscosity fluid. In general, rotation combined with low-viscosity fibrous fluid exhibits the best cleaning performance. This is because rotating the pipe resuspends the settled solids, which are then easily carried by fibrous fluid that has high solids carrying capacity.