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A mud engineer (correctly called a Drilling Fluids Engineer, but most often referred to as the "Mud Man") works on an oil well or gas well drilling rig, and is responsible ensuring the properties of the drilling fluid, also known as drilling mud, are within designed specifications. ==Use of mud== (詳細はhydrostatic pressure on the borehole wall to prevent uncontrolled production of reservoir fluids, lubricates and cools the drill bit, carries the drill cuttings up to the surface, forms a "filter-cake" on the borehole wall to prevent drilling fluid invasion, provides an information medium for well logging, and helps the drilling by fracturing the rock from the jets in the bit. To fulfill these tasks effectively, the mud contains carefully chosen additives to control its chemical and rheological properties. Drilling mud is usually a shear thinning non-Newtonian fluid of variable viscosity. When it is under more shear, such as in the pipe to the bit and through the bit nozzles, viscosity is lower which reduces pumping-power requirements. When returning to the surface through the much roomier annulus it is under less shear stress and becomes more viscous, and hence better able to carry the rock cuttings. Bentonite is commonly used as an additive to control and maintain viscosity, and also has the additional benefit of forming a mud-cake (also known as a filter cake) on the bore-hole wall, preventing fluid invasion.〔http://www.glossary.oilfield.slb.com/Display.cfm?Term=bentonite Schlumberger Oilfield Glossary – Bentonite〕 Barite is commonly used to "weight" the mud to maintain adequate hydrostatic pressure down-hole. This is critical in a drilling operation to avoid a kick and ultimately a blowout from uncontrolled production of formation fluids. The "mud-pits" at the surface have their levels carefully monitored, since an increase in the mud level indicates a kick is taking place, and may require shutting in the well and circulating heavier weighted drilling mud to prevent further formation fluid or gas production. Drilling fluid must be chemically compatible with the formations being drilled. Salinity must be chosen so as not to cause clay swelling or other problems. Mud can be "oil-based" or "water-based". In many areas oil-based muds are being phased out, as they are less environmentally friendly, although in some formations they are necessary because of chemical compatibility issues. Offshore rigs typically use synthetic oil based mud. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Mud engineer」の詳細全文を読む スポンサード リンク
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