دیکشنری تخصصی مهندسی نفت - نسخه آنلاین

generally salt and/or surfactant materials designed to simulate the effect of potassium chloride in preventing clay swelling. Substitutes may work in the wellbore but generally fail in the formation where severe swelling conditions exist.

n: 1. an instrument to measure electromotive forces by comparison with a known potential difference. 2. a re- sistor used chiefly as a voltage divider.

n: a transformer that takes power from a generating station and steps up the voltage for transmission, or that takes power from the transmission line and steps down the voltage to the primary distribution level of? ,200 or 12,400 volts. See distribution transfonner.

n: a natural or artificial siliceous material commonly added to portland cement mixtures to impart certain desirable properties. Added to oilwell cements, pozzolans reduce slurry weight and viscosity, increase resistance to sulfate attack, and influence factors such as pumping time, ultimate strength, and watertightness.

n: A siliceous or siliceous and aluminous material that possesses little or no cementitious value. In a finely divided form and in the presence of moisture, however, pozzolan reacts chemically with calcium hydroxide to form compounds possessing cementitious

core removed from the formation and preserved by sealing or freezing to prevent drying or other altering of the rock or fluids.

n: a loss of pressure that results from friction sustained by a fluid passing through a line, valve, fitting, or other device.

n: 1. a scale of pressure differences in which there is a uniform variation of pressure from point to point. For example, the pressure gradient of a col- umn of water is about 0.433 pounds per square inch per foot (9.794 kilopascals per metre) of vertical elevation. The normal pressure gradient in a formation is equiva- lent to the pressure exerted at any given depth by a column of 10 percent salt water extending from that depth to the surface (0.465 pounds per square inch per foot, or 10.518 kilopascals permebe). 2. the change (along a horizontal distance) in atmospheric pressure. Isobars drawn on weather maps display the pressure gradient.

n: the variation of pressure with depth.commonly used under hydrostatic conditions(e.g. a hydrostatic column of salt water has a pressure gradient of 0.465 psi/ft).

change in pressure with depth.

n: the use of waterflooding or gas injection to provide additional formation pressure to supplement and to conserve natural reservoir drives. Although commonly begun during primary production, pressure maintenance is a form of improved recovery. See improved recovery, secondary recovery.

n: the source that provided filter loss appratus with pressure vin drilling working.