Study on Structure Optimization and Cuttings Removal Efficiency of a Vortex Cuttings Cleaner

Abstract

Summary Cuttings easily accumulate in the horizontal section during the process of horizontal well drilling, causing tripping difficulty, drillpipe sticking, or even breaking. Existing hole cleaners work while the drillpipe is rotating continuously. In this paper, we describe a vortex cuttings cleaner that combines mechanical cuttings removal with hydraulic cuttings transport without drillpipe rotation. First, a 3D numerical model of vortex cuttings cleaner is established. The flow field characteristics (e.g., velocity distribution and pressure distribution) and energy conversion efficiency of different structures of cuttings cleaner are compared to define an improved structure of cuttings cleaner. Then, the annulus flow field of the cuttings cleaner with improved structure is analyzed to identify the factors influencing the cuttings removal efficiency. Finally, by comparing and analyzing the simulation results and field test results, the influence on cuttings removal efficiency of the vortex cuttings cleaner is clarified. The results show that the energy conversion efficiency of the vortex cuttings cleaner can be improved by reducing the angle of inclined tube and the number of spiral strips or increasing the rotation angle of spiral strips. Moreover, compared with the number of spiral strips, the rotation angle of spiral strips has a more significant influence. The pressure drop of the tool is also investigated. The cuttings removal efficiency increases with the increase of turbine speed, drilling fluid displacement, and viscosity and decreases with the increase of cuttings particle size. Each of these influencing factors has a critical value. When the turbine speed and drilling fluid displacement are higher than the critical values and the cuttings particle size is smaller than its critical value, the cuttings removal efficiency does not increase significantly. After the vortex cuttings cleaner is run into the hole, the circulated cuttings volume increases significantly, and the friction reduces noticeably. The vortex cuttings cleaner has a long failure-free working time, and all parts tripped out of the well are in good condition for future use. This study provides reference for the design and process optimization of hole cleaners in horizontal wells.