The influence of gas hydrate morphology on reservoir permeability and geophysical shear wave remote sensing

Sahoo, Sourav ORCID: https://orcid.org/0000-0001-9644-8878; Best, Angus ORCID: https://orcid.org/0000-0001-9558-4261. 2021 The influence of gas hydrate morphology on reservoir permeability and geophysical shear wave remote sensing. Journal of Geophysical Research: Solid Earth, 126 (11). 10.1029/2021JB022206

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Abstract/Summary

We show that direct estimates of the permeability of hydrate-bearing geological formations are possible from remote measurements of shear wave velocity (Vs) and attenuation (Qs−1). We measured Vs, Qs−1 and electrical resistivity at time intervals during methane hydrate formation in Berea sandstone using a laboratory ultrasonic pulse-echo system. We observed that Vs and Qs−1 both increase with hydrate saturation Sh, with two peaks in Qs−1 at hydrate saturations of around 6% and 20% that correspond to changes in gradient of Vs. We implemented changes in permeability with hydrate saturation into well-known Biot-type poro-elastic models for two- and three-phases for low (Sh < 12%) and high (Sh > 12%) hydrate saturations respectively. By accounting for changes in permeability linked to hydrate morphology, the models were able to describe the Vs and Qs−1 observations. We found that the first Qs−1 peak is caused by a reduction of permeability during hydrate formation associated with a transition from pore-floating to pore-bridging hydrate morphology; similarly, the second Qs−1 peak is caused by a permeability reduction associated with a transition from pore-bridging hydrate morphology to an interlocking network of hydrate in the pores. We inverted for permeability using our poro-elastic models from Vs and Qs−1. This inverted permeability agrees with permeability obtained independently from electrical resistivity. We demonstrate a good match of our models to shear wave data at 200 Hz and 2 kHz frequencies from the literature, indicating the general applicability of the models.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1029/2021JB022206
Programmes:	NOC Programmes > Ocean BioGeosciences
ISSN:	2169-9313
Date made live:	06 Jan 2022 17:20 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/531510

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