Location of Mud Cleaners In a Drilling Fluid System2014-01-09
Mud cleaners are normally positioned in the same location as desilters in a drilling-fluid system. Frequently, the desilters, or hydrocyclones, are used in the unweighted portion of a borehole by diverting the underflow away from the mud tanks. When a weighting agent, barite or hematite, is added to the system, screens are placed on the mud cleaner shakers. Solids discarded from the hydrocyclones are sieved to discard solids mostly larger than barite and return solids smaller than the screen size with most of the liquid phase. Practical tip: Barite goes in, screens go on.Another method has been used to create a mud cleaner using the main shale shaker, mostly on offshore rigs. When several linear, or balanced elliptical, shale shaker are needed to handle flow in the upper part of a well bore, fewer shakers can handle the flow after the hole size decreases and the mud weight is increased. Rigs have been modified so that as many as twenty 4-inch hydrocyclones have been mounted above one of the main shakers. The feed and overflow (light slurry) from the hydrocyclones are plumbed as usual. All of the desilter underflow is discarded in the unweighted part of the hole as usual, while the shale shaker is screening drilling fluid from the flow line. This is normally the largest flow rate expected while drilling the well. As the well gets deeper, a weighted drilling fluid is required, and usually the flow rate is lower. When barite goes in, a valve prevents flowline drilling fluid from going to one of the main shale shakers. The desilter underflow is diverted onto the shale shaker screen so that the shale shaker becomes a mud cleaner.