The deep well GEN-1ST-A1(Geretsried,Bavaria)-Unlocking a geothermal reservoir

摘要

The Upper Jurassic”Malm”formation is a prominent geothermal reservoir in the South German Molasse Basin.The geothermal play type is a fracture and fades controlled carbonate succession in a foreland basin,which is characterized by its wedge shaped geometry and deepening strata towards the mountain range.A number of geothermal projects have been developed successfully in the Munich region,where flow rates of more than 100 l/s at reservoir temperatures of about 100°C are realized.South of Munich in the deep Molasse Basin,the geothermal industry is lacking extensive drilling operation in spite of the large geothermal potential in the”Malm”carbonates.Vie well GEN-1ST-A1 is the only research well in Bavaria accessing the”Malm”in a depth range of more than 4.5 km TVD.The project started as a commercial asset and used conventional 3D seismic surveying and directional drilling.The exploration resulted in a dry well,which was then further developed in the research project”Dolomitkluft”,supported by the Federal Ministry for Economic Affairs and Energy(BMWi).The research goal was to drill into a fault zone and to better characterize the permeability structure.The applied methods encompassed coring,acid stimulation and extensive hydraulic testing.The production test revealed a temperature of 155°C at a non-economic productivity,which is significantly lower than the injectivity.Therefore,a second research phase will use proppants to keep identified fractures open during production.This geothermal project shows that the required technology is similar to methods in non-conventional oil and gas E&P.