دیکشنری تخصصی مهندسی نفت - نسخه آنلاین

n: a siliceous volcanic rock that is finely ground and subjected to extreme heat. The resulting release of water leaves the rock particles considerably expanded and thus more porous. Expanded perlite is sometimes used in cement to increase its yield and decrease its density without an appreciable effect on its other properties.

n: a siliceous ash rock which is grinded and processed under the hyperthermic situation,usually used to improve the mud making rate of the cement slurry and decline the density

n: cement that expands as it sets to form a tighter fit around casing and formation.

n: refer toswelling cement

cement with additives that promote volumetric cement expansion.

n: a multiplying factor used when calculating gas flow rate. This factor corrects for the reduction in fluid density that a compressible fluid experiences when it passes through an orifice as a result of the increased fluid velocity and the decreased static pressure. Also called expansibility factor.

n: a device that converts the energy of a gas or vapour stream into mechanical work by expanding the gas or vapour through a turbine.

the weighted average using probabilities as weights. For decisions involving uncertainty, the concept of expected value provides a rational means for selecting the best course of action and for forcasting portfolio level performance.

n: a risk analysis process that multiplies expected gain or loss of a decision by its probability of occurrence and averages all possible outcomes to choose the action with the highest expected benefit.

n: a motor with an enclosure designed to contain an internal explosion and to prevent ignition of surrounding gases or vapours by sparks that may occur in the motor.

n pi: the limits (based on time of exposure, concentration of material, means of contact, and material toxicity) of worker exposure to hazardous materials without ill effect. Exceeding exposure limits set for various materials can result in temporary health problems, chronic illness, acute illness, or death.

n: a special bit nozzle, often used on large bits, that lengthens the nozzle and therefore places the jet of drilling fluid exiting the nozzle close to the bottom of the hole. With large bits, where regular nozzles can be relatively distant from the bottom of the hole, the cleaning power of the jet of drilling fluid may be lost because the velocity, or speed, of the jet diminishes rapidly after it exits the nozzle. By extending the length of the nozzles, the jets are placed closer to bottom for maximum cleaning.

n: the spray head which is longer than ordinary spray head

n: 1. a substance added to drilling mud to increase viscosity without adding clay or other thickening material. 2. an additive that assists in getting greater yield from a sack of cement. The extender acts by requiring more water than required by neat cement.