| Title | Geological Mapping of a Composite Rhyolitic Sill Intrusion in the Subsurface of the Þeistareykir Geothermal Field in Northeast Iceland |
|---|---|
| Authors | Julia Reimer |
| Year | 2026 |
| Conference | World Geothermal Congress |
| Keywords | Sill Emplacement, Rhyolite, Intrusion, Iceland, Permeability, Geothermal, Drilling, Petrel, 3D Modeling |
| Abstract | Shallow rhyolitic sill intrusions are often present in central volcanoes in Iceland and can influence both volcanic eruptions and geothermal fields. High permeability at the margins of these intrusions can store and conduct fluids, which make them suitable targets for fluid extraction from the geothermal fields. A composite rhyolitic sill has been intersected by several boreholes during exploration and development of the high temperature geothermal field at Þeistareykir in Northeast Iceland. Based on petrophysical logs, televiewer logs, and drill cuttings analyses, the extent and morphology of the sill intrusion has been mapped in the subsurface. Analysis of these data provides knowledge of the physical properties of this intrusion, its location, volume and potential origin. Additionally, variations in fracture density and orientation related to the rhyolitic sill intrusion is mapped with televiewer logs. The objective of this study is to provide a first estimate of permeability distribution surrounding the shallow composite rhyolitic sill and provide insight into optimal areas to target in future drilling projects within the Þeistareykir Geothermal Field for successful production wells. |