Toward fracture porosity assessment by gravity forward modeling for geothermal exploration (Sankt Gallen, Switzerland).

Altwegg, Pierrick and Schill, Eva and Abdelfettah, Yassine and Radogna, Pier-Vittorio and Mauri, Guillaume (2015) Toward fracture porosity assessment by gravity forward modeling for geothermal exploration (Sankt Gallen, Switzerland). Geothermics, 57. pp. 26-38. DOI: https://doi.org/10.1016/j.geothermics.2015.05.006

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Official URL: https://doi.org/10.1016/j.geothermics.2015.05.006

Abstract

Fracture porosity is a crucial parameter in hydrocarbon and geothermal reservoir exploration and a major challenge in the absence of nearby exploration wells. The Sankt Gallen geothermal project targets a fault zone that affects Mesozoic sediments at a depth of about 4500 m. Spatial extension of these sediments, a major fault zone and indication for graben structures in the crystalline basement are observed in 3D seismic. Both the graben and the fault zone coincide with negative gravity anomalies acquired and analyzed during this study. Forward modeling of gravity anomalies based on a 3D seismic survey is used to estimate possible fracture porosity. After stripping gravity effects of geothermally irrelevant geological units from the residual anomaly, most likely only local structures related to the fault zone account for remaining anomalies. Synthetic case study on the effect of density variation and considerable gas content in the well support possible fracture porosity between about 4% and 8%.

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Item Type: Article
Uncontrolled Keywords: Fracture porosity, Gravity, Stripping, Reservoir characterization, Fractured reservoir
Subjects: Methodology > Other-additional study
Region > Switzerland > St. Gallen
Inducing technology > Geothermal energy production
Project: S4CE > ST GALLEN: geothermal project