Determination of flow exits in the Soultz borehole GPK2 by using the brine displacement method

The article presents a method to derive synthetic flow logs from low rate injection tests in wells, which are otherwise not accessible for logging. The tests were carried out in the 5 km deep geothermal well GPK2 in the Enhanced Geothermal System (EGS) project of Soultz-sous-Forêts (France) and were aimed at characterizing the status of the well before chemical treatments. The method consists of injecting water at constant flow rates into the well initially filled with brine. The wellhead pressure record of this test is transformed into log of the flow velocity versus depth by a technique described in the paper. Applying this method to borehole GPK2, three outlets could be detected and quantified within the cased and uncased section of this borehole. The outlet in the cased section at 3860 m absorbed 15% of the total flow. This depth corresponds to a known casing restriction, which makes the borehole inaccessible for logging operations. The two other outlets are at the casing shoe at 4420 m (15%) and at 4670 m (70%).