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Comparison of stress-dependent geophysical, hydraulic and mechanical properties of synthetic and natural sandstones for reservoir characterization and monitoring studies

Comparison of stress-dependent geophysical, hydraulic and mechanical properties of synthetic and natural sandstones for reservoir characterization and monitoring studies
Comparison of stress-dependent geophysical, hydraulic and mechanical properties of synthetic and natural sandstones for reservoir characterization and monitoring studies
Synthetic rock samples can offer advantages over natural rock samples when used for laboratory rock physical properties studies, provided their success as natural analogues is well understood. The ability of synthetic rocks to mimic the natural stress dependency of elastic wave, electrical and fluid transport properties is of primary interest. Hence, we compare a consistent set of laboratory multi‐physics measurements obtained on four quartz sandstone samples (porosity range 20–25%) comprising two synthetic and two natural (Berea and Corvio) samples, the latter used extensively as standards in rock physics research. We measured simultaneously ultrasonic (P‐ and S‐wave) velocity and attenuation, electrical resistivity, permeability and axial and radial strains over a wide range of differential pressure (confining stress 15–50 MPa; pore pressure 5–10 MPa) on the four brine saturated samples. Despite some obvious physical discrepancies caused by the synthetic manufacturing process, such as silica cementation and anisotropy, the results show only small differences in stress dependency between the synthetic and natural sandstones for all measured parameters. Stress dependency analysis of the dry samples using an isotropic effective medium model of spheroidal pores and penny‐shaped cracks, together with a granular cohesion model, provide evidence of crack closure mechanisms in the natural sandstones, seen to a much lesser extent in the synthetic sandstones. The smaller grain size, greater cement content, and cementation under oedometric conditions particularly affect the fluid transport properties of the synthetic sandstones, resulting in lower permeability and higher electrical resistivity for a similar porosity. The effective stress coefficients, determined for each parameter, are in agreement with data reported in the literature. Our results for the particular synthetic materials that were tested suggest that synthetic sandstones can serve as good proxies for natural sandstones for studies of elastic and mechanical properties, but should be used with care for transport properties studies.
0016-8025
Falcon-Suarez, Ismael Himar
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Amalokwu, Kelvin
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Delgado-Martin, Jordi
c96ce7fb-5094-4fb2-b6a0-7bbdf6ed47e7
Callow, Ben
19f1a5fe-cabd-4c49-a84f-dc7de0e3c462
Robert, Katleen
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North, Laurence
65837b6b-40f1-4a1c-ba66-ec6ff2d7f84b
Sahoo, Sourav K.
6dab0376-36df-44c5-9f36-cb4a29d9b03b
Best, Angus I.
cad03726-10f8-4f90-a3ba-5031665234c9
Falcon-Suarez, Ismael Himar
9e8022b5-8799-4326-8d5b-0ed46de3b25a
Amalokwu, Kelvin
a88bc1e5-5577-49a6-a503-fcd9ea12d8fe
Delgado-Martin, Jordi
c96ce7fb-5094-4fb2-b6a0-7bbdf6ed47e7
Callow, Ben
19f1a5fe-cabd-4c49-a84f-dc7de0e3c462
Robert, Katleen
49e4bfa2-0999-41ec-b50d-65c0f8896583
North, Laurence
65837b6b-40f1-4a1c-ba66-ec6ff2d7f84b
Sahoo, Sourav K.
6dab0376-36df-44c5-9f36-cb4a29d9b03b
Best, Angus I.
cad03726-10f8-4f90-a3ba-5031665234c9

Falcon-Suarez, Ismael Himar, Amalokwu, Kelvin, Delgado-Martin, Jordi, Callow, Ben, Robert, Katleen, North, Laurence, Sahoo, Sourav K. and Best, Angus I. (2018) Comparison of stress-dependent geophysical, hydraulic and mechanical properties of synthetic and natural sandstones for reservoir characterization and monitoring studies. Geophysical Prospecting. (doi:10.1111/1365-2478.12699).

Record type: Article

Abstract

Synthetic rock samples can offer advantages over natural rock samples when used for laboratory rock physical properties studies, provided their success as natural analogues is well understood. The ability of synthetic rocks to mimic the natural stress dependency of elastic wave, electrical and fluid transport properties is of primary interest. Hence, we compare a consistent set of laboratory multi‐physics measurements obtained on four quartz sandstone samples (porosity range 20–25%) comprising two synthetic and two natural (Berea and Corvio) samples, the latter used extensively as standards in rock physics research. We measured simultaneously ultrasonic (P‐ and S‐wave) velocity and attenuation, electrical resistivity, permeability and axial and radial strains over a wide range of differential pressure (confining stress 15–50 MPa; pore pressure 5–10 MPa) on the four brine saturated samples. Despite some obvious physical discrepancies caused by the synthetic manufacturing process, such as silica cementation and anisotropy, the results show only small differences in stress dependency between the synthetic and natural sandstones for all measured parameters. Stress dependency analysis of the dry samples using an isotropic effective medium model of spheroidal pores and penny‐shaped cracks, together with a granular cohesion model, provide evidence of crack closure mechanisms in the natural sandstones, seen to a much lesser extent in the synthetic sandstones. The smaller grain size, greater cement content, and cementation under oedometric conditions particularly affect the fluid transport properties of the synthetic sandstones, resulting in lower permeability and higher electrical resistivity for a similar porosity. The effective stress coefficients, determined for each parameter, are in agreement with data reported in the literature. Our results for the particular synthetic materials that were tested suggest that synthetic sandstones can serve as good proxies for natural sandstones for studies of elastic and mechanical properties, but should be used with care for transport properties studies.

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GP_2017_0141_R2_all_final - Accepted Manuscript
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Accepted/In Press date: 26 September 2018
e-pub ahead of print date: 1 October 2018

Identifiers

Local EPrints ID: 425758
URI: http://eprints.soton.ac.uk/id/eprint/425758
ISSN: 0016-8025
PURE UUID: 8df8eac1-722a-4486-8e74-5819ab9dff52
ORCID for Ben Callow: ORCID iD orcid.org/0000-0003-2296-1702

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Date deposited: 02 Nov 2018 17:30
Last modified: 26 Nov 2021 06:48

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Contributors

Author: Ismael Himar Falcon-Suarez
Author: Kelvin Amalokwu
Author: Jordi Delgado-Martin
Author: Ben Callow ORCID iD
Author: Katleen Robert
Author: Laurence North
Author: Sourav K. Sahoo
Author: Angus I. Best

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