Numerical Simulation of Temperature Logs in High Temperature Wells : Towards the Application to the RN-15/IDDP2 Well

In the frame of the EU Horizon 2020 DEEPEGS project and the IDDP2 project, the well RN-15 located in the Reykjanes geothermal field (Iceland) was deepened. So far, this well, namely RN-15/IDDP-2 is the deepest geothermal well drilled in Iceland with a final depth of 4,659 m,a measured bottom-hole temperature of 427°C and a fluid pressure of 34 MPa. During drilling, several temperature logs were run whilst water was injected continuously to cool down the equipment in the borehole due to the high-temperature environment. The objective of our work, as part of the DEEPEGS project, is to apply numerical simulation methods to estimate the formation temperature and fluid loss along the well path, based on the recorded temperature logs acquired under dynamic conditions, during and after drilling. This is of particular interest for the development and understanding of the deep geothermal reservoir. Our approach comprises the development of a transient thermal model in which the temperature evolution of the well and the surrounding formation is simulated. The numerical tool enables the use of the whole history of fluid circulation data. ... mehrIn this work, we first simulated synthetic models in order to investigate the feasibility of (1) using temperature logs obtained under borehole cooling conditions to estimate the static formation temperature (SFT)and (2) characterizing fluid losses from temperature logs. The results showed that applying simple temperature correction methods on the non-shut-in temperature data could lead to large errors for SFT estimation even at low flow rates. Fluid loss leads to a local gradient increase in the vertical temperature profile. The magnitude of the gradient change depends both on the percentage of fluid loss and the flow rate. However, for fluid losses below 30% or relatively high flow rates 20-50 L/s (velocities 0.5~1.3 m/s), the temperature gradient increase is independent of the flow rate. The knowledge and experience gained from the synthetic models provide insights for future work when the real temperature logging data are used to constrain the far-field formation temperature and to estimate the fluid loss. Herein, we also present some first results on the temperature analysis in the RN-15/IDDP2 well using real long-term drilling and logging data.