A drilling fluid cleaner is a combination of a hydrocyclone and an ultra-fine shale shaker. The overflow from the hydrocyclone returns to the drilling fluid system. The underflow falls onto the shale shaker, where the drilling fluid that passes through the screen returns to the circulation tank, and the system discharges the material remaining on the screen. The screen mesh size can range from 80 to 325 mesh. The drilling fluid cleaner mainly recovers barite from weighted drilling fluid and removes residual drill cuttings larger than barite. When the weighted drilling fluid passes through the hydrocyclone, a large amount of barite remains in the underflow. Passing through the fine screen, the barite returns to the circulation tank (along with some fine rock cuttings), and the shale shaker continuously removes rock cuttings larger than the screen openings.
Working Principle of the Drilling Fluid Cleaner
When the weighted drilling fluid passes through the shale shaker, desander, and desilter, the size of the removed rock cuttings decreases sequentially. However, because some solid particles are relatively small, they will still remain in the drilling fluid.
While hydrocyclones remove solids from weighted drilling fluids, a significant amount of barite remains in the underflow. A fine-mesh sieve under the hydrocyclone removes large rock cuttings, while the barite passes through the sieve and returns to the circulation tank. This is the basic principle of drilling fluid cleaners.
Before the advent of drilling fluid cleaner systems, after the weighted drilling fluid passed through a shale shaker, a centrifuge removed even finer solid particles. Centrifuges were the only mechanical purification equipment in use.
Recently developed linear or elliptical shale shakers have been equipped with ultra-fine screens, with mesh sizes reaching 100-325 mesh. Field practice has shown that using a 150-mesh screen on a drilling fluid shale shaker is no longer particularly difficult. If the upstream shale shaker uses 150 mesh or higher, operators do not need a cleaner for weighted drilling fluid. However, a desliming device is still required for non-weighted drilling fluids.
