A comparison of rock physics models for fluid substitution in carbonate rocks

Ali Misaghi; Sajjad Negahban; Martin Landrø; Abdolrahim Javaherian

doi:10.1071/EG09035

RESEARCH ARTICLE

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A comparison of rock physics models for fluid substitution in carbonate rocks

Ali Misaghi ¹ ³ ⁵ Sajjad Negahban ² Martin Landrø ³ Abdolrahim Javaherian ⁴

+ Author Affiliations

- Author Affiliations

¹ Dana Geophysics Company, Golestan Street, Iran Zamin Avenue, Shahrak-e-Qods, Tehran 1465865187, Iran.

² Amirkabir University of Technology, No. 242, Hafiz Street, Tehran, P.O.B. 15875-4413, Iran.

³ Norwegian University of Science and Technology, S.P. Andersens vei 15A, 7491 Trondheim, Norway.

⁴ Institute of Geophysics, University of Tehran, North Karegar Avenue, Tehran 1435944411, Iran.

⁵ Corresponding author. Email: ali.misaghi@gmail.com

Exploration Geophysics 41(2) 146-154 https://doi.org/10.1071/EG09035
Submitted: 25 July 2009 Accepted: 17 February 2010 Published: 7 June 2010

Abstract

Rock physics models play a crucial role in seismic reservoir characterisation studies. The optimal rock physics model for a sandstone reservoir might be significantly different from that of a carbonate reservoir. There are several theories that compare the elastic properties of dry and saturated rocks. These models have mainly been explained by poroelastic theories or effective medium theories. The Gassmann’s model which is commonly used in petroleum rock physics is suitable for rocks with spherical and interconnected pores at low frequencies. These assumptions do not necessarily meet the conditions of carbonate rocks. In this work, two additional models, the differential effective medium (DEM) model and the self-consistent (SC) model have been examined for several carbonate samples. Ultrasonic 30 carbonate and 5 sandstone core samples from an oilfield in south-west Iran were measured in the laboratory. The results show that the DEM model gives the best compatibility with the dense and low porous carbonate samples. These results are confirmed by well log data from the same area.

Key words: carbonate reservoirs, differential effective medium model, Gassmann’s model, rock physics, self-consistent model.

Acknowledgement

The authors acknowledge the Research Institute of Petroleum Industry of Iran (RIPI) for permission to use the data. Martin Landrø thanks the Norwegian Research Council for financial support to the ROSE project at NTNU.

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