Wyllie time-average equation vs Gardner's equation vs RHG Equation for porosity

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Discussion Overview

The discussion revolves around the comparison of three equations used for estimating porosity from seismic velocity: the Wyllie time-average equation, Gardner's equation, and the RHG equation. Participants explore the advantages and limitations of each approach, particularly in the context of different rock types and saturation conditions.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant prefers the RHG equation, arguing that the Wyllie equation is ineffective for unconsolidated sand and only provides accurate results when saturated with brine solution.
  • Another participant notes that Gardner's equation primarily relates density to porosity without considering velocity, suggesting it may be less suitable for this context.
  • There is a request for clarification on how these three equations compare to other methods of calculating porosity, such as the imbibition method, ideal gas laws, or mercury displacement method.
  • One participant seeks confirmation that the discussion is focused on seismic velocity in water-saturated porous rocks.
  • A later reply confirms the focus on comparing the results of the three equations and discusses the advantages of the RHG equation over the others.
  • Another participant expresses interest in the topic but notes a lack of recent experience with seismic surveys, requesting links to the equations for further reference.

Areas of Agreement / Disagreement

Participants express differing opinions on the effectiveness of the Wyllie, Gardner, and RHG equations for estimating porosity, indicating that multiple competing views remain without a consensus on the best approach.

Contextual Notes

Participants have not fully resolved the limitations or assumptions inherent in each equation, nor have they clarified the specific conditions under which each method is most applicable.

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TL;DR
Wyllie time-average equation vs Gardner's equation vs RHG Equation and what these equation are different from any other approach for calculating imbition method, ideal gas laws or mercury displacement method
If you were estimating porosity from velocity, which approach would you prefer to use among Wyllie time-average equation, Gardner's equation Or RHG Equation, when and why?

My answer is RHG equation as wylllie equation don't work for unconsolidate sand and give accurate results when it is saturated with brine solution. Garnder's equation mainly relates density with porosity not accounting with velocity and RHG equation is improved one. CAn you please help me with anything i'm missing here.

Are these three equation are different from any other approach like imbition method, ideal gas laws or mercury displacement method for calculating porosity?
 
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Welcome to PF.

Would I be right in guessing that this question is about seismic velocity, in porous rocks, that are water saturated ?
 
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Baluncore said:
Welcome to PF.

Would I be right in guessing that this question is about seismic velocity, in porous rocks, that are water saturated ?
yes it is about comparing results given by three equations. It is to discuss mainley what RPG equation have advantages over wyllie and Gardner's equation and what is appropriate method among three to measure porosity from velocity in different types of rocks.
 
I am interested in the subject, but it is more than 40 years since I shot my last seismic survey.
Can you please post links to the equations.
 

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