دیکشنری تخصصی مهندسی نفت - نسخه آنلاین

n: a phenomenon in which a decrease in the diameter of the borehole occurs because a plastic substance, such as salt, is being drilled. Since the temperature of the salt is higher than normal for a given depth (high temperature causes the salt to expand) and since mud weight is usually decreased when drilling such formations to maintain high penetration rates (thus decreasing the hydrostatic pressure exerted on the salt),the section of borehole in the salt zone can expand and possibly stick the drill stem. Also called salt squeeze.

n: Permanent mechanical or physical alteration that does not include rupture. Plastic deformation of rocks typically occurs at high temperatures and pressures, conditions under which rocks become relatively viscous.

a stress level, beyond the elastic limit, that produces yielding in tubulars.