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The photoelectric factor (PeF) was introduced in the early-1980's as a supplementary measurement to the bulk density measurement by Schlumberger, who signaled its appearance by the designation 'Lithodensity' log.

The log measures the photoelectric absorption factor, P e, which is defined as (Z/10) 3.6 where Z is the average atomic number of the formation. P e is unitless, but since it is proportional to the photoelectric cross section per electron, it is sometimes quoted in barns/electron.

The litho-density log is a new form of the formation density log with added features. It is typified by Schlumberger’s Litho-Density Tool (LDT). These tools have a caesium-137 source emitting gamma rays at 0.662 MeV, a short-spaced and a long-spaced detector in the same way as the basic formation density tool.

The Photoelectric Factor (PeF) Log. The photoelectric factor (PeF) was introduced in the early-1980's as a supplementary measurement to the bulk density measurement and records the absorption of low-energy gamma rays by the formation in units of barns per electron.

Potential ambiguities of this type can be resolved by reference to the photoelectric factor (PeF) curve which has been recorded as fairly standard practice by almost all service companies since the mid-1980's.

Jan 1, 1994 · The photoelectric index (Pe) is a supplementary measurement by the latest generation of density logging tools, and records the absorption of low-energy gamma rays by the formation in units of barns per electron.

Aug 14, 2023 · The photoelectric factor (PEF) is an important well-logging tool to distinguish between different types of reservoir rocks because PEF measurement is sensitive to elements with high atomic numbers. Furthermore, the ratio of rock minerals could be determined by combining PEF log with other well logs.

It discusses how density and PEF are measured, the principles behind the logs, and their applications. Density logs measure bulk density and can be used to calculate porosity. PEF logs measure effective photoelectric absorption and are useful for lithology identification.

Sep 4, 2024 · Photoelectric Factor (PEF) Log: Helps differentiate between lithologies within low-GR zones. Example: A low GR zone with high PEF might indicate limestone, while a low GR zone with low PEF might indicate sandstone.