Physical property characterization of the Waipapa greywacke: an important geothermal reservoir basement rock in New Zealand

Melia, Aurelio, Faulkner, Daniel Roy ORCID: 0000-0002-6750-3775 and McNamara, David Daniel ORCID: 0000-0001-9789-2436 (2022) Physical property characterization of the Waipapa greywacke: an important geothermal reservoir basement rock in New Zealand. GEOTHERMAL ENERGY, 10 (1). 11-.

Access the full-text of this item by clicking on the Open Access link.

Official URL: http://dx.doi.org/10.1186/s40517-022-00218-2

Abstract

<jats:title>Abstract</jats:title><jats:p>Greywacke basement rocks in New Zealand host conventional geothermal reservoirs and may supply important hotter and deeper geothermal energy resources in the future. This work combines petrological analyses and physical property measurements of Waipapa greywacke, a basement unit hosting New Zealand geothermal reservoirs, in order to understand better how structurally controlled flow networks develop and channel geothermal fluids within it. Results show intact Waipapa greywacke has high tensile and triaxial compressive strengths, and low intrinsic permeability (~ 10<jats:sup>–21</jats:sup> m<jats:sup>2</jats:sup>). Permeability of intact Waipapa greywacke does not increase significantly during triaxial loading to failure and is accompanied by minimal changes ultrasonic wave velocities. These data taken together suggest that microcrack development during brittle deformation is very limited. Upon failure, the permeability increases by two orders of magnitude and shows similar permeability to tests performed on synthetic, single, mode I fractures in intact Waipapa greywacke. Permeability persists in Waipapa greywacke fractures under confining pressures of at least 150 MPa. It is concluded that Waipapa greywacke rocks will not allow fluid flow through the matrix of the rock and that substantial geothermal fluid flow will only occur through macrofracture networks.</jats:p>

Item Type:	Article
Uncontrolled Keywords:	Geothermal, Greywacke, Permeability, Fracture, Rock properties, Basement rock
Divisions:	Faculty of Science and Engineering > School of Environmental Sciences
Depositing User:	Symplectic Admin
Date Deposited:	09 Sep 2022 15:03
Last Modified:	15 Mar 2024 01:24
DOI:	10.1186/s40517-022-00218-2
Open Access URL:	https://geothermal-energy-journal.springeropen.com...
Related URLs:	Author Publisher
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3164042