There have been discussions which lead to a number of hypotheses related to the presence of the liquid column inside geothermal wellbores in vapor-dominated reservoirs. Previous hypotheses suggested that this phenomenon is due to condensation and the existence of liquid in the reservoir. The phenomenon is uncommon due to the liquid column temperature at the borehole was identified as compressed liquid. Therefore, we may not infer the liquid column is from liquid reservoir due to the temperature below the saturation temperature. Numerical study was performed to understand the physical process of this phenomenon. A coupled wellbore-reservoir model was built to simulate the mass and heat balance using TOUGH2. The model is based on a cylindrical, homogenous reservoir geometry with a wellbore located at the center of the model. Feedzone and bottomhole reservoir pressures were taken from PT Spinner survey. The well bleed-off model was built and simulated to test the condensation process. The result does not prove significant liquid volume contributed from condensation process. This result brought us to propose other hypothesis of which the liquid column is related to the involvement of drilling mud during drilling stage. Our proposed hypothesis clearly represents the real condition considering there was a good agreement between the simulated and measured pressure temperature profile versus depth. Through our data calibration, unexpectedly this study found the existence of an additional feedzone at the deeper depth which could not be detected by PTS survey due to low permeability fractured rock or minimum mass flow rate. Ultimately, the determination of the origin and process of liquid column may help having a more reliable interpretation of subsurface profile, considering the similar cases were also reported in other vapor-dominated geothermal reservoirs.

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