Formation Description Logs

FDLPetrophysical interpretation with an accurate answer, fast turn-around time and an expert overview of each product by the Chief Petrophysicist. The modern oil company uses reservoir characterizations to explore and exploit increasingly difficult oil reserves. Amongst the data required is the most accurate description of each well in terms of lithology, porosity and fluids. CGG’s Formation Description Log (FDL) provides an accurate petrophysical interpretation of the borehole logs from wireline and LWD tools.

Petrophysics evaluates those properties relating to the pore system and its fluid distribution and flow characteristics. This is achieved by application and interpretation of downhole “logging” measurements of the physical properties of the subsurface, in most cases in combination with measurements on core samples.


The main source of information for FDL petrophysical interpretations is taken from:

  • Logs, acquired via well log/LWD tools

  • Mudlog data and cuttings

  • Cores and sidewall samples

Lithology is determined by geologists working with cores and rock cuttings. Rock data can be combined with log characteristics to identify depositional environments and characterize how these change vertically and geographically throughout the reservoir.

Our petrophysicists determine the reservoir and fluid characteristics:

  • Thickness (bed boundaries)

  • Lithology (rock type)

  • Porosity

  • Fluid saturations

  • Fluid identification & characterization

Petrophysical interpretations are used to identify and evaluate:

  • Hydrocarbon reservoirs

  • Hydrocarbon sources

  • Seals

  • Aquifers

The CGG Solution: Formation Description Log

  • Full log interpretation

  • Depth matching and environmental corrections completed

  • All original source data provided

  • Audit trail provided

  • Standard and customized templates available

  • Consistent stratigraphic tops

  • Fast turn-around time

  • Chief petrophysicist quality controlling all outputs

Using such a clear set of information the oil company can properly understand and evaluate a prospect. Using the analyses in a number of wells over a field/ region will give the geoscientists the tools to create the full reservoir characterization study.

Modern logs are relatively straightforward to analyze, however older data can present a greater challenge!"

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