1. n. [Well Completions]

A multiphase-fluid flow regime characterized by a series of liquid plugs (slugs) separated by a relatively large gas pockets. In vertical flow, the bubble is an axially symmetrical bullet shape that occupies almost the entire cross-sectional area of the tubing. The resulting flow alternates between high-liquid and high-gas composition.

See related terms: multiphase fluid flow

2. n. [Production Logging]

A multiphase-flow regime in pipes in which most of the lighter fluid is contained in large bubbles dispersed within, and pushing along, the heavier fluid. The word slug normally refers to the heavier, slower moving fluid, but sometimes to the bubbles of lighter fluid. There are also small bubbles within the liquid, but many of these have coalesced to form the large bubbles until they span much of the pipe. In gas-liquid mixtures, slug flow is similar to plug flow, but the bubbles are generally larger and move faster. As flow rates increase, slug flow becomes churn flow.

See related terms: bubble flow,  churn flow,  flow structure,  froth flow,  multiphase flow,  plug flow

3. n. [Production Testing]

A type of flow in which surface equipment may be damaged by the sudden impact of a liquid slug in a phenomenon called water hammer.