Determination of drilled solids in a drilling fluid depends on an accurate determination of the mud weight, the total solids in the drilling fluid, and the density of the drilling-fluid ingredients. For example, with a freshwater 11-ppg drilling fluid containing 2.6 SG low-gravity solids and 4.2 SG barite, a change in only 1%vol measured solids concentration makes a 2%vol change in calculated low-gravity solids. In Table 12.4, for an 11-ppg drilling fluid, a 13%vol solids concentration would indicate 6%vol, and a 12%vol solids concentration would indicate 4%vol.
Mud cleaners are equally effective for both weighted and unweighted drilling fluids and effectively lower both drilling fluid expenses and disposal costs.
Usually, if solids are being removed with shale shakers, a mud cleaner will probably be beneficial. Solids removed by mud cleaners will cover a wide range of quantities depending on formations drilled, borehole stability, dispersion of solids as they move up the borehole, type of drill bit, type of drilling fluid, and other variables.
An estimate of the low-gravity solids content of the mud cleaner screen discard can be made by weighing the discard. Since the solids concentration will be around 60% volume, the mud weight will be a reasonable predictor of the low-gravity solids concentration. For lowgravity solids with a specific gravity (SG) of 2.6 and a barite SG of 4.2,