1. n. [Production Logging]
A record of one or more in-situ measurements that describe the nature and behavior of fluids in or around the borehole during production or injection. Production logs are run for the purpose of analyzing dynamic well performance and the productivity or injectivity of different zones, diagnosing problem wells, or monitoring the results of a stimulation or completion. The term is sometimes extended to include logs run to measure the physical condition of the well, for example cement bond and corrosion logs. The earliest production logs consisted of temperature logs (1930s) and flowmeters (1940s), to which were soon added fluid-density and capacitance logs (1950s). Flow-rate measurements were gradually improved by the development of tracer logs and improvement to the basic spinner flowmeter. These techniques were adequate for near-vertical wells with single or biphasic flow, but could be misleading in highly deviated, and especially horizontal, wells. New techniques were developed starting in the 1980s. These techniques focused on local probes to measure holdup at different points in the borehole, nuclear techniques to analyze the total holdup of all three phases, and phase-velocity logs for the analysis of individual fluids. At the same time, complex flow structures and flow regimes have been studied more extensively using flow loops.
For more details, see The Defining Series: Production Logging Principles
See: cement bond log, differential-temperature log, distributed temperature log, fluid-density log, gas-holdup log, holdup log, noise log, radial differential temperature log, radioactive-tracer log, spinner flowmeter, water-flow log