Permeability and mineralogy of the Újfalu Formation, Hungary, from production tests and experimental rock characterization: Implications for geothermal heat projects

July 08, 2021

Cees J. L. Willems (1,2), Chaojie Cheng (3), Sean M. Watson (1), James Minto (4), Aislinn Williams (1), David Walls (1,4), Harald Milsch (3), Neil M. Burnside (1,4), Rob Westaway (1)
Energies, 14, Issue 14, July 2021: 4332. DOI: 10.3390/en14144332


Pannonian Basin; sandstone; permeability; X-CT scanning; XRD analysis; thin-section analysis; mercury intrusion porosimetry; numerical flow simulation


Hundreds of geothermal wells have been drilled in Hungary to exploit Pannonian Basin sandstones for district heating, agriculture, and industrial heating projects. Most of these sites suffer from reinjection issues, limiting efficient use of this vast geothermal resource and imposing significant extra costs for the required frequent workovers and maintenance. To better understand the cause of this issue requires details of reservoir rock porosity, permeability, and mineralogy. However, publicly available data for the properties of reservoir rocks at geothermal project sites in Hungary is typically very limited, because these projects often omit or limit data acquisition. Many hydrocarbon wells in the same rocks are more extensively documented, but their core, log, or production data are typically decades old and unavailable in the public domain. Furthermore, because many Pannonian sandstone formations are poorly consolidated, coring was always limited and the collected core often unsuitable for conventional analysis, only small remnant fragments typically being available from legacy hydrocarbon wells. This study aims to reduce this data gap and to showcase methods to derive reservoir properties without using core for flow experiments. The methods are thin-section analysis, XRD analysis and mercury intrusion porosimetry, and X-CT scanning followed by numerical flow simulation. We validate our results using permeability data from conventional production testing, demonstrating the effectiveness of our method for detailed reservoir characterization and to better constrain the lateral variation in reservoir properties across the Pannonian Basin. By eliminating the need for expensive bespoke coring to obtain reservoir properties, such analysis will contribute to reducing the capital cost of developing geothermal energy projects, thus facilitating decarbonization of global energy supply.

How Our Software Was Used

Dragonfly was used for the 3D reconstruction of CT data.

Author Affiliation

(1) James Watt School of Engineering, University of Glasgow, Glasgow G12 8QQ, UK.
(2) Huisman Equipment BV, 3100 AD Schiedam, The Netherlands.
(3) GFZ German Research Centre for Geosciences, Telegrafenberg, 14473 Potsdam, Germany.
(4) Department of Civil & Environmental Engineering, University of Strathclyde, James Weir Building, Glasgow G1 1XJ, UK.