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AVA Analysis of BSR in Fractured filled Gas-hydrates Reservoir in Krishna-Godavari Basin, India

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Journal of the Geological Society of India

Abstract

Gas-hydrates, a major unconventional energy resources of the future, are delineated by seismic experiment through the identification of an anomalous reflector, known as the bottom simulating reflector or BSR on seismic data. The amplitude variation with angle (AVA) from the BSR can be used for quantitative assessment of gas-hydrates and free-gas across the BSR. We have performed the AVA analysis of BSR in the Krishna Godavari (KG) basin of India, where gas-hydrates have been recovered in fractured shale by Exp-01 of Indian National Gas Hydrates Program. The study shows negative intercept and positive gradient along two perpendicular seismic lines, one passing through the well at site-10 of Exp-01. The intercept of −0.01 to −0.15 and gradient of 0.01 to 0.4 are interpreted as class-IV anomaly, which is due to anisotropy caused by fractures filled with gas-hydrates. We have modelled the observed AVA pattern using anisotropic equation for horizontally symmetric transversally isotropic (HTI) media in which gas-hydrates occur in the fractures, roughly aligned at angle of 45° above the BSR and patchy gas distribution below the BSR. The results show 0–31% variable gas-hydrates in fractured morphology and 0–11% free gas below the BSR respectively.

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Acknowledgements

The Director, CSIR-NGRI Director, WIHG are thanked for their kind consent to publish this work. The Ministry of Petroleum & Natural Gas, the Ministry of Earth Sciences and the Dept. od Sci. & Tech., GoI are acknowledged for financial support. The Oil & Natural Gas Corporation Limited and the Directorate General of Hydrocarbons are thanked for providing the seismic and well log data for pursuing research on gas-hydrates. KS acknowledges SERB-DST for providing him with the JC. Bose Fellowship. This is a Wadia contribution no: WIHG/0076 and CSIR-NGRI contribution No. NGRI/Lib/2022/Pub-20

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  1. CSIR-National Geophysical Research Institute, Uppal Road, Hyderabad, 500 007, India

    Vivekanand Pandey

  2. Wadia Institute of Himalayan Geology, 33 GMS Road, Dehradun, 248 001, India

    Kalachand Sain

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  1. Vivekanand Pandey
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  2. Kalachand Sain
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Correspondence to Kalachand Sain.

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Pandey, V., Sain, K. AVA Analysis of BSR in Fractured filled Gas-hydrates Reservoir in Krishna-Godavari Basin, India. J Geol Soc India 98, 1253–1260 (2022). https://doi.org/10.1007/s12594-022-2160-5

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