ARTICLE

Probabilistic facies prediction in a carbonate gas reservoir of Iran using stochastic seismic inversion and connectivity algorithm

HAMID REZA ANSARI REZA MOTAFAKKERFARD1 MOHAMMAD ALI RIAHI2
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1 Department of Petroleum Exploration Engineering, Abadan Faculty of Petroleum Engineering, Petroleum University of Technology, Abadan, Iran. ansari.hamid.r@gmail.com,
2 Institute of Geophysics, University of Tehran, Tehran, Iran.,
JSE 2015, 24(1), 15–35;
Submitted: 9 June 2025 | Revised: 9 June 2025 | Accepted: 9 June 2025 | Published: 9 June 2025
© 2025 by the Authors. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution -Noncommercial 4.0 International License (CC-by the license) ( https://creativecommons.org/licenses/by-nc/4.0/ )
Abstract

Ansari, H.R., Motafakkerfard, R. and Riahi, M.A., 2015. Probabilistic facies prediction in a carbonate gas reservoir of Iran using stochastic seismic inversion and connectivity algorithm. Journal of Seismic Exploration, 24: 15-35. Inversion methods are valuable tools for obtaining reservoir properties from seismic data. However, results of the seismic inversion are band-limited due to band-limited source wavelet. Therefore, the low and high frequency information is lost in seismic traces. In order to overcome this problem, well logs and seismic data were used together in a seismic inversion algorithm using stochastic methods. In this paper, the stochastic inversion method was based on spectral simulation to create acoustic impedance realizations. Also, an initial broad-band model was derived from kriging of the well log data. Then, spectral simulation was applied for the seismic inversion. This method was conducted on one of the marine carbonate gas fields in Iran and the results were compared with deterministic inversion. In the second part of this study, acoustic impedance realizations and rock density volume, obtained from the previous section, were combined with instantaneous frequency as the input of an unsupervised neural network for clustering the three rock facies and a vector quantizer network was utilized for this purpose. The network results were calibrated with porosity in the well location and provided threshold parameters to conduct the connectivity facies analysis. Finally, the connectivity algorithm was applied to all the realizations of stochastic inversion results to achieve highly probable favorable facies.

Keywords
stochastic inversion
unsupervised neural network
probabilistic facies
connectivity algorithm
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Journal of Seismic Exploration, Electronic ISSN: 0963-0651 Print ISSN: 0963-0651, Published by AccScience Publishing