Gas hydrate saturation in the Krishna–Godavari basin from P-wave velocity and electrical resistivity logs

During the Indian National Gas Hydrate Program (NGHP) Expedition 01, a series of well logs were acquired at several sites across the Krishna–Godavari (KG) Basin. Electrical resistivity logs were used for gas hydrate saturation estimates using Archie’s method. The measured in situ pore-water salinity...

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Bibliographic Details
Published in:Marine and petroleum geology 2011-11, Vol.28 (10), p.1768-1778
Main Authors: Shankar, Uma, Riedel, Michael
Format: Article
Language:English
Subjects:
Archie analysis
Basins
Effective medium modeling
Electrical resistivity
Electrical resistivity log
Estimates
Gas hydrate saturation
Gas hydrates
Krishna–Godavari basin
Logs
Marine
Mathematical models
P-Wave velocity logs
Porosity
Saturation
Volumetric estimation
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Summary:During the Indian National Gas Hydrate Program (NGHP) Expedition 01, a series of well logs were acquired at several sites across the Krishna–Godavari (KG) Basin. Electrical resistivity logs were used for gas hydrate saturation estimates using Archie’s method. The measured in situ pore-water salinity, seafloor temperature and geothermal gradients were used to determine the baseline pore-water resistivity. In the absence of core data, Arp’s law was used to estimate in situ pore-water resistivity. Uncertainties in the Archie’s approach are related to the calibration of Archie coefficient ( a), cementation factor ( m) and saturation exponent ( n) values. We also have estimated gas hydrate saturation from sonic P-wave velocity logs considering the gas hydrate in-frame effective medium rock-physics model. Uncertainties in the effective medium modeling stem from the choice of mineral assemblage used in the model. In both methods we assume that gas hydrate forms in sediment pore space. Combined observations from these analyses show that gas hydrate saturations are relatively low (
ISSN:0264-8172
1873-4073
DOI:10.1016/j.marpetgeo.2010.09.008