The Influence of Super-critical CO2 Saturation on the Mechanical and Failure Properties of a North Sea Reservoir Sandstone Analogue

12 Pages Posted: 5 Apr 2021

See all articles by Luke Griffiths

Luke Griffiths

Norwegian Geotechnical Institute

Jérémie Dautriat

Government of the Commonwealth of Australia - CSIRO Energy

Joonsang Park

Norwegian Geotechnical Institute

Ismael Vera Rodriguez

NORSAR

Kamran Iranpour

NORSAR

Guillaume Sauvin

Norwegian Geotechnical Institute

Joel Sarout

Government of the Commonwealth of Australia - CSIRO Energy

Lars Grande

Norwegian Geotechnical Institute

Volker Oye

NORSAR

Magnus Soldal

University of Oslo - Department of Geosciences; Norwegian Geotechnical Institute

David N. Dewhurst

Government of the Commonwealth of Australia - CSIRO Energy; CO2CRC Ltd

Nazmul Haque Mondol

University of Oslo - Department of Geosciences

Jung Chan Choi

Norwegian Geotechnical Institute

Date Written: March 17, 2021

Abstract

Large-scale geological carbon storage in the North Sea will involve injecting CO2 in a super-critical state into deep saline aquifers. As CO2 is injected, stress changes due to fluid pressure and temperature changes may result in deformation and potentially may result in microseismicity if existing faults are reactivated. Microseismicity may provide additional information on in situ stress conditions and the progression of the CO2 plume. To assess failure criteria in the reservoir, we must know the mechanical response of reservoir sandstone due to injection of super-critical CO2 (scCO2) under reservoir stress conditions. This includes fracturing processes at the microstructural scale as well as at the macroscopic scale by reactivation of existing fractures. We conducted three triaxial tests on a sandstone analogue to deep North Sea reservoir rock: once pressurized, samples were saturated with either scCO2, brine, or a brine-scCO2 mixture. Each sample was then deformed axially to induce a through-going fracture, which was then reactivated—first by increasing the pore pressure under anisotropic stress conditions, then by axial reloading with a constant pore pressure. Throughout testing, we monitored acoustic emissions (AE) and measured ultrasonic P-wave velocities. AE were located within the sample, and their relative magnitudes were calculated, as well as their source mechanisms for a subset of high signal-noise ratio events. We observed:

• Higher strength and stiffness for the sample saturated only with scCO2 than for samples containing brine, and a brine-scCO2 mixture.
• No clear difference in fracture strength for samples with different fluid saturations.
• Higher energy events released from fracturing of the stronger and stiffer scCO2-saturated rock.
• For all samples, the AE response during fracture reactivation was more energetic and had a higher frequency content at higher effective stresses (by axial loading) than at lower effective stresses (by pore pressure increase).

We found fluid saturation to have only a slight influence on the mechanical and failure properties. We observed no significant weakening with scCO2 saturation that might otherwise cause undesired inelastic deformation within the reservoir.

Keywords: North Sea, sandstone, super-critical CO2, laboratory testing, acoustic emissions, microseismicity

Suggested Citation

Griffiths, Luke and Dautriat, Jérémie and Park, Joonsang and Vera Rodriguez, Ismael and Iranpour, Kamran and Sauvin, Guillaume and Sarout, Joel and Grande, Lars and Oye, Volker and Soldal, Magnus and Dewhurst, David N. and Mondol, Nazmul Haque and Choi, Jung Chan, The Influence of Super-critical CO2 Saturation on the Mechanical and Failure Properties of a North Sea Reservoir Sandstone Analogue (March 17, 2021). Proceedings of the 15th Greenhouse Gas Control Technologies Conference 15-18 March 2021, Available at SSRN: https://ssrn.com/abstract=3818808 or http://dx.doi.org/10.2139/ssrn.3818808

Luke Griffiths (Contact Author)

Norwegian Geotechnical Institute ( email )

PO Box 3930 Ullevaal Stadion
Oslo, N-0855
Norway

Jérémie Dautriat

Government of the Commonwealth of Australia - CSIRO Energy ( email )

10 Murray Dwyer Circuit
Mayfield West, New South Wales 2304
Australia

Joonsang Park

Norwegian Geotechnical Institute ( email )

PO Box 3930 Ullevaal Stadion
Oslo, N-0855
Norway

Ismael Vera Rodriguez

NORSAR ( email )

Kjeller
Norway

Kamran Iranpour

NORSAR ( email )

Kjeller
Norway

Guillaume Sauvin

Norwegian Geotechnical Institute ( email )

PO Box 3930 Ullevaal Stadion
Oslo, N-0855
Norway

Joel Sarout

Government of the Commonwealth of Australia - CSIRO Energy ( email )

10 Murray Dwyer Circuit
Mayfield West, New South Wales 2304
Australia

Lars Grande

Norwegian Geotechnical Institute ( email )

PO Box 3930 Ullevaal Stadion
Oslo, N-0855
Norway

Volker Oye

NORSAR ( email )

Kjeller
Norway

Magnus Soldal

University of Oslo - Department of Geosciences ( email )

P.O. Box 1047
Oslo, 0316
Norway

Norwegian Geotechnical Institute ( email )

PO Box 3930 Ullevaal Stadion
Oslo, N-0855
Norway

David N. Dewhurst

Government of the Commonwealth of Australia - CSIRO Energy

10 Murray Dwyer Circuit
Mayfield West, New South Wales 2304
Australia

CO2CRC Ltd

11 – 15 Argyle Place South
Carlton
Australia

Nazmul Haque Mondol

University of Oslo - Department of Geosciences ( email )

P.O. Box 1047
Oslo, 0316
Norway

Jung Chan Choi

Norwegian Geotechnical Institute ( email )

PO Box 3930 Ullevaal Stadion
Oslo, N-0855
Norway

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