Combined fiber-optic monitoring technologies to assist borehole completion

Reliable well completion and monitoring technologies are a prerequisite to achieve safe, sustainable and efficient use of geothermal reservoirs. Since borehole completion is a high-risk process, we tested how distributed fiber optic sensing technologies can aid monitor the completion process continuously in space and real time. To evaluate the success of the operation conventional well logging tools and other methods can only be used after the completion and show snapshots of discrete points in time.We present results from a case study in Berlin, where a 450 m deep exploration well was completed for Aquifer Thermal Energy Storage (ATES) purpose. To simultaneously measure distributed temperature (DTS) and distributed elastic and static strain (DAS and DSS) a fiber optic cable was installed behind the production tubing. The combined evaluation of the different fiber optic technologies evidences the potential to observe previously untraceable processes, such as changes in subsurface flow paths due to clogging. Further, the unwanted process of caving can be identified and the rise of gravel or cement observed. This allows to react on site, and subsurface risks will be considerably mitigated.
The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)