Identifying Gas-bearing Carbonate Reservoir Using Extended Elastic Impedance

Document Type: Research Paper


1 Ph.D. Candidate, Institute of Geophysics, University of Tehran, Tehran, Iran

2 Professor, Institute of Geophysics, University of Tehran, Tehran, Iran

3 M.S. Student, Institute of Geophysics, University of Tehran, Tehran, Iran

4 Geophysics Expert, KPE Co., Tehran, Iran


It is difficult to identify the carbonate reservoirs by using conventional seismic reflection data, especially in cases where the reflection coefficient of the gas-bearing zone is close to that of the carbonate background. In such cases, the extended elastic impedance (EEI) as a seismic reconnaissance attribute with the ability to predict fluids and lithology can be used. It allows for a better distinction between seismic anomaly caused by lithology and the one caused by the fluid content. The EEI attribute extends the available reflection angles and applies different weights to the intercept and gradient values so as to extract the petrophysical properties of the rock at a specific incident angle. Using the EEI attribute, we can estimate the elastic parameters such as shear impedance; the ratio of the compressional velocity to shear velocity; Poisson’s ratio; and bulk, Lame, and shear moduli, and petrophysical properties, including porosity, clay content, and water saturation. The known reservoirs in the study area are three oil-bearing formations namely, Surmeh (Arab), Gadvan (Buwaib), and Dariyan (Shuaiba), and three gas-bearing formations, including Kangan, Dalan, and Faraghan. The Dehram group is composed of Kangan (Triassic), Dalan, and Faraghan (Permian) formations. Permian carbonates of Kangan–Dalan and its equivalent Khuff have regionally been developed as a thick carbonate sequence in the southern Persian Gulf region. In this paper, parameters ๐œ†๐‘ and ๐œ‡๐œŒ extracted from the EEI method are used to characterize a carbonate reservoir. Our results show that the EEI can highlight the difference between the reservoir and non-reservoir formation to identify the gas-bearing areas.


  • Extended elastic impedance (EEI) can be used as a seismic reconnaissance attribute with the ability to predict reservoir fluids and lithology.
  • EEI allows for a better distinction between seismic anomaly caused by lithology and the one caused by the fluid content.
  • Recognizing gas-bearing intervals by applying the EEI will ultimately reduce the drilling risk and cost in areas with carbonate reservoirs.
  • Application of EEI leads to the more reliable estimation of porosity and fluid saturation in carbonate reservoirs.
  • The proposed methodology illustrates the advantage of using ๐œ†๐œŒ and ๐œ‡๐œŒ for discriminating the reservoir rock properties, as compared to the conventional Vp and Vs analysis.


Main Subjects

Alhusseini, M.I., Origin of the Arabian Plate Structures: Amar Collision and Najd Rift, Geo Arabia, Vol. 5, No. 4, p. 527–542, 2000.
Aki, K. and Richards, P. G., Quantitative Seismology: Theory and Methods: W. H. Freeman and Co., 1980.
Russell B., and Russell H., CGG Veritas Company, an Overview of AVO and Inversion, 9th Biennial International Conference & Exposition, Petroleum Geophysics, 2012.
Chehrazi A., and Albouyeh M., Application of Extended Elastic Impedance (EEI) Inversion to Reservoir from Non-reservoir Discrimination of Ghar Reservoir in One Iranian Oil Field Within Persian Gulf, Journal of Geophysics and Engineering, Vol. 15, No. 4, p. 1204–1213, 2018.
Connolly, P., Elastic Impedance, The Leading Edge, Vol. 18, No.4, p. 438–452, 1999.
Ghazban F., Petroleum Geology of the Persian Gulf, Tehran University and National Iranian Oil Company, 2007.
Goodway, W., Chen, T., and Downton, J., Improved AVO Fluid Detection and Lithology Discrimination Using Lamé Petrophysical Parameter, CSEG RECORDER, Vol. 22, No. 7, p. 3–5, 1997.
Gray, D., and Andersen, E., The Application of AVO and Inversion to The Estimation of Rock Properties: Recorder, Vol. 26, No. 5, p. 36–40, 2001.
Ensley, R. A., Comparison of P- and S-Wave Seismic Data: A New Method for Detecting Gas Reservoirs: Geophysics, Vol. 49, No. 4, p. 1420–1431, 1984.
Hampson-Russell, Guide to Emerge: PDF in The Hampson-Russell Software Package, 2007.
Husseini, M.I., Upper Paleozoic Tectono-sedimentary Evolution of The Arabian and Adjoining Plates. Journal of The Geological Society of London, Vol. 149, No. 3, p. 419–429, 1992.
Hyeonju K., Gwang H. L., and Seonghoon M., Prediction of Reservoir Properties Using Extended Elastic Impedance Inversion, Economic and Environmental Geology, Vol. 48, No. 2, p. 115–130, 2015.
Kadkhodaie A, Nosrati A, Amini A, Chehrazi A, Mehdipour V, and Moslemnezhad T, Reservoir Properties Distribution in The Framework of Sequence Stratigraphic Units: A Case Study from The Kangan Formation, Iranian Offshore Gas Field, The Persian Gulf Basin, Journal of Natural Gas Science and Engineering, Vol. 65, p. 1–15, 2019.
Li, Y. Y., and Downton, J., Application of Amplitude Versus Offset in Carbonate Reservoirs: Reexamining the Potential, SEG Expanded Abstracts, p. 166–169,, 2000.
Li, Y., Downton, J., and Goodway, B., Recent Applications of AVO to Carbonate Reservoirs in the Western Canadian Sedimentary Basin: The Leading Edge, Vol. 22, No. 7, p. 670–674, 2003.
Nairn AEM and Alsharhan, AS, Sedimentary Basins and Petroleum Geology of the Middle East, Elsevier, Netherlands, 1997.
Neves, F.A., Mustafa, H. M. and Rutty, P.M., Pseudo-gamma Ray Volume from Extended Elastic Impedance Inversion for Gas Exploration: The Leading Edge, Vol. 23, No. 06, p. 536–540, 2004.
 Whitcombe, D., Connolly, P., Reagan, R. and Redshaw T., Extended Elastic Impedance for Fluid and Lithology Prediction, Geophysics, Vol. 67, 3999 1, p. 63–67, 2002.