Porosity Concepts in Gassmann Fluid Substitution: A Simulator to Seismic Modelling Perspective

Hamed Amini, Colin MacBeth

Research output: Contribution to conferencePaper


In this study, porosity concepts in Gassmann’s fluid substitution model are examined and their implications for quantitative 4D seismic studies are discussed. Three porosity models (total porosity, effective porosity, and a movable fluid model) are compared from a simulator to seismic (sim2seis)
modelling perspective. From the three selected models, total porosity predicts the largest softening effect due to gas breakout and the smallest hardening effect from water-flooding; whereas the movable fluid model predicts the least softening due to gas breakout and the largest effects for water-flooding. Effective
porosity predictions lie between the total porosity and movable fluid models. The differences between these models are due to the proportion of fluids in the mixture which are input into Gassmann’s equations.
Sim2seis results based on different porosity models were evaluated against the observed 4D seismic. This comparison shows that the magnitude of the saturation-induced hardening and softening signals due to the movable fluid model is closer to the observed seismic. The total porosity model is in least agreement with the observed 4D seismic.
Original languageEnglish
Publication statusPublished - 2015
Event3rd EAGE Workshop on Rock Physics - Istanbul, Turkey
Duration: 15 Nov 201518 Nov 2015


Workshop3rd EAGE Workshop on Rock Physics
OtherFrom Rocks to Basin - Applying Rock Physics in Prospect Evaluation and Reservoir Characterization


  • petro-elastic model
  • Gassmann
  • effective porosity
  • total porosity
  • fluid substitution
  • simulator-to-seismic modelling


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