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Formation Evaluation Log In Mud Logging

This article is one of 5 important articles about Mud logging unit equipment. These articles explain in detail the equipment used in standard mud logging units.

Surface mud logging is not complex in principle, does not interfere with the drilling process, and the results are available almost immediately. The Formation Evaluation Log (Figure 1-1) is recorded simultaneously with the drilling of the hole. Detailed data on the physical characteristics of the subsurface strata is collected and analyzed as it becomes accessible at the surface.

This information is continuously evaluated and control of certain phases of the drilling operation is exercised by the operator based on the interpretation of the results. Besides almost immediately indicating the presence of any potentially productive zone, the Formation Evaluation Log serves as a basis for modifying the drilling program to ensure a safe and cost-efficient program. It is also an important corroborative and correlative tool. 

What does Formation Evaluation Log contain?

A comprehensive Formation Evaluation Log contains the following information: 

  • Total combustible hydrocarbon gases from the drilling fluid
  • Chromatographic analysis of the total gas for individual gas content (methane to pentane) in ppm
  • Total combustible gas from drill cuttings
  • Oil from drilling fluid and drill cuttings
  • Detailed rate of penetration curve
  • Lithologic composition and description (including estimated visual porosity)
  • Drilling fluid characteristics
  • Data pertinent to the well’s operation, such as coring points, casing points, trips for new bit, drillstem tests, etc.
  • Bit data, carbide lag information, borehole deviations, and other pertinent engineering information
  • Hydrocarbon show reports, conventional and sidewall core reports, and test reports