What do the electric methods of well logging measure?
Electric logging consists of lowering a device used to measure the electric resistance of the rock layers in the downhole portion of the well. This is achieved by running an electric current through the rock formation and measuring the electrical resistance that the current encounters along its way.
What are the types of well logs?
The standard well logs are the temperature log, the caliper log, and the resistivity log.
How can you tell lithology from well logs?
Lithology is also determined from the logs, because each main reservoir lithology has characteristic responses. Frequently, lithologies are derived by pattern recognition of the GR-, density-, and neutron-log responses. Some subsequent delineation wells are likely to be cored over the entire of the reservoir interval.
What is well log data?
Well logs are records of petro-physical data acquired along a borehole, providing direct information about what is in the subsurface. The data collected by logging wells can have significant economic consequences, due to the costs inherent to drilling wells, and the potential return of oil deposits.
How do you identify lithology?
Neutron and density logs each react to both lithology and porosity, so by analyzing the two logs together, one can begin to distinguish lithology from porosity. Neutron and density logs, together with a caliper measurement recorded by the density tool and a natural gamma ray log, are commonly run as a combination.
What is DRHO log?
The density correction (DRHO) curve (Fig. F88) is calculated from the difference between the short- and long-spaced density measurements and provides a further indication of the quality of the bulk density data. DRHO values in excess of 0.1 g/cm3 indicate unreliable density data.
What does a gamma ray log tell you?
Gamma ray (GR) logs measure the natural radioactivity in formations and can be used for identifying lithologies and for correlating zones. Shale-free sandstones and carbonates have low concentrations of radioactive material and give low gamma ray readings.