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.]

Oilfield Mud Cleaner

Another method has also been used to create a mud cleaner using one of the main shale shakers, mostly on offshore rigs. When several linear, or balanced elliptical, shale shakers 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″ hydrocyclones have been mounted above one of the main shakers. The feed and overflow (light slurry) from the hydrocyclones are plumbed as usual. (See Chapters 8 and 9Chapter 8Chapter 9 on mud tank arrangements). 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. Usually, this is the largest flow rate expected while drilling that 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 flow line 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.