Natural clay. Natural clay, as opposed to commercial clay, are clay that are encountered when drilling various formations. The yield of these clay varies greatly, and they may or may not be purposely incorporated into the drilling fluid system. See: attapulgite clay, bentonite, high-yield clay, low-yield clay, clay.
Near-size plugging. A term used in describing screen plugging, referring to particles with a dimension slightly larger than the screen opening. See: blinding, plugging.
Neat cement. A slurry composed only of Portland cement and water.
Negative deck angle. The angle of adjustment to a screen deck that causes the screened solids to travel ‘‘downhill’’ (usual travel) to reach the discharge end of the screen surface. This downhill travel decreases the fluid throughput of a screen but usually lengthens the life of a screen. See: positive deck angle.
Neutralization. A reaction in which the hydrogen ion of an acid and the hydroxyl ion of a base unite to form water, the other ionic product being a salt.
Newtonian flow. See: Newtonian fluid.
Newtonian fluid. The basic and simplest fluids from the standpoint of viscosity, in which the shear force is directly proportional to the shear rate. These fluids will immediately begin to move when a pressure or force in excess of zero psi is applied. Examples of Newtonian fluids are water, diesel oil, and glycerine. The yield point as determined by direct-indicating viscometer is zero. See: Newtonian flow.
Non-conductive drilling fluid. Any drilling fluid, usually oil-based or invert emulsion drilling fluid, whose continuous phase does not conduct electricity. The spontaneous potential (SP) and normal resistivity cannot be logged, although such other logs as the gamma rays, induction, acoustic velocity, etc., can be run.
Non-dispersed. A condition in which the clays do not separate into individual platelets. Dispersion is inhibited.
Normal solution. A solution of such a concentration that it contains 1 gram equivalent of a substance per liter of solution.
