دیکشنری تخصصی مهندسی نفت - نسخه آنلاین

n: the breakdown of molecules of a substance such as a polymer when subjected to shear stress. See shear.

a joint above a piece of equipment that is designed to fail and allow recovery of the upper string.

n: a coefficient of elasticity that expresses the ratio of the force per unit area that deforms the substance laterally and the shear produced by this force.

n: a pin that is inserted at a critical point in a mechanism and designed to shear when subjected to excess stress. The shear pin is usually easy to replace.

a pin in a tool (brass, steel or aluminum) that is designed to shear or break at a certain pressure that enables a tool function.

n: the component in a blowout preventer that cuts. or shears, through drill pipe and forms a seal against well pressure. Shear rams are used in floating offshore drilling operations to provide a quick method of moving the rig away from the hole when there is no time to trip the drill stern out of the hole.

n: the component of the BOP stack (q.v.) that cuts through the drill pipe and forms aseal across the wellbore. These are used on floaters when the rig must be moved off location in an emergency.

a ram in the BOP that shears off the pipe.

n: a blowout preventer that uses shear rams as closing elements.

n: A type of vertical seismic profile in which the source is a shear-wave source rather than a compressional-wave source. Shear waves travel through the Earth at about half the speed of compressional waves and respond differently to fluid-filled rock, and so

n: this is the relative velocity of the fluid layers, divided by their normal separation distance. See also viscosity.

the rate of shearing of a fluid during a viscosity measurement. The rate of movement between plates.

n: a type of pressure relief valve in which excess pressure causes a shearing action on a pin to relieve pressure. See pressure relief valve.

n: see gel strength.

n: a measure of the shear value of fluid. The nminimum shearing stress that will produce permanent deformation. See gel strength.

the minimum shear stress that will produce permanent deformation of the fluid (gel breaking).

n: force applied to a liquid to cause it to flow.