Investigating the discrepancy between gas and liquid permeability in the Gassum and Skagerrak Formations. GEOTHERM - Geothermal energy from sedimentary reservoirs - Removing obstacles for large scale utilization. Innovation Fund Denmark: project 6154-00011B (Final report in WP3)

This report summarises the results of the research project “Investigating the discrepancy between gas and liquid permeability in the Gassum and Skagerrak Formations”. The project is part of WP3 in the project GEOTHERM – Geothermal energy from sedimentary reservoirs – Removing obstacles for large scale utilization, funded by the Innovation Fund Denmark (IFD). The objective is to increase our understanding of the observed difference between measured gas and liquid permeability in order to improve our prediction of the permeability of a geological reservoir from geophysical well logs combined with data obtained from measurements of permeability in the laboratory.

Permeability represents the ability of rock material to conduct fluid flow and is one of the most important properties of porous media when evaluating a geothermal project. Since liquid permeability may be difficult and time consuming to measure accurately, often the gas permeability is measured in the laboratory to estimate reservoir permeability even though it is the liquid permeability that is of interest for evaluation of the reservoir performance. In theory, the permeability is independent of the fluid used for the permeability measurements. However, this is not always so, and often the permeability to liquid is significantly lower than that to gas. Therefore, a detailed series of laboratory experiments have been conducted to investigate the discrepancy between measured gas and liquid permeability for sandstone core specimens from the Skagerrak and the Gassum Formation in the North Jutland region.