Linsel, A. ; Weinert, S. ; Bär, K. ; Hinderer, Matthias (2019)
Thermo-Hydraulic Heterogeneity Assessment Across First-Order Hiatal Surfaces – A Case Study from the Post-Variscan Nonconformity.
Geo Münster 2019. Münster, Germany (22.09.-25.09.2019)
Konferenzveröffentlichung, Bibliographie

Kurzbeschreibung (Abstract)

The Post-Variscan Nonconformity (PVNC) is a first-order hiatal surface that spreads across central Europe and constitutes a major diachronous lithological and petrophysical contrast within the Paleozoic to Mesozoic strata. Recently, deep geothermal heat and power projects target resources at the PVNC. This requires quantitative information of the lithological architecture and physical heterogeneity across this surface as they govern the reservoir quality during exploitation.

In this study, the lithological architecture and thermo-hydraulic heterogeneity across the PVNC are characterized for two cored scientific wells of 68 and 80 m length in a proximal outcrop analogue area of the Upper Rhine Graben, where Rotliegend volcano-sedimentary cover rocks are nonconformingly overlying igneous Paleozoic basement rock. Thermophysical (thermal conductivity, thermal diffusivity, specific heat capacity) and hydraulic (porosity, matrix permeability) laboratory measurements and geological logging, including the rock quality designation index, form the datasets of this study. Multivariate geostatistical methods are used for spatial heterogeneity analysis.

The cover rocks, comprising breccias, conglomerates, wackes, arenites and mudstones from an alluvial fan depositional environment interfingering with effusive basalts, display low to very low hydraulic matrix permeability and intermediate thermal conductivity. Debris flows and sheet floods represent the most abundant sedimentary elements. Rock quality designation index of the basement rocks that comprise altered, weathered and deformed diorite, granite and quartz-monzodiorite, is reduced in the palaeo weathering zone and in local dykes forming potential pathways for fluid flow.

Thermal properties clearly group into the observed lithological and depositional classes, however, the palaeo weathering zone levels off the physical contrast in the topmost part of the basement due to alteration and grain framework disaggregation. Significant linear and non-linear positive correlations between the hydraulic parameters were discovered. Thermal and hydraulic parameters correlate negatively. Semivariance of each reservoir parameter is strongly increasing across the PVNC, hence statistical interpolations including this horizon should be based on robust semivariance models.

Frage zum Eintrag

Redaktionelle Details anzeigen