Inverse flow zone characterization using distributed temperature sensing in a deep geothermal production well located in the Southern German Molasse Basin

Sep 14, 2026

Uploaded by Cipher

Hydraulically active zones in geothermal wells require precise localization and characterization to support reliable reservoir understanding. Conventional approaches often rely on spinner flow meter interpretations during cold-water injection, but production logging is limited once electric submersible pumps are installed. A 3.7 km deep production well in Munich demonstrated a permanent optical-fiber installation enabling distributed temperature sensing during production. An energy and mass balance inversion derived formation inflow profiles matching earlier flow-meter analyses.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages8

Reading Time20 min

AccessFree to download

Introduction

Geological Setting and studied well

Adv. Geosci., 58, 101–108, 2023 [https://doi.org/10.5194/adgeo-58-101-2023](https://doi.org/10.5194/adgeo-58-101-2023)[ ](https://doi.org/10.5194/adgeo-58-101-2023)© Author(s) 2023 . This work is distributed under the Creative Commons Attribution 4 .0 License. Inverse ﬂow zone characterization using distributed temperature sensing in a deep geothermal production well located in the Southern German Molasse Basin Felix Schölderle, Daniela Pfrang, and Kai Zosseder Chair of Hydrogeology, Technical University of Munich, Munich, 80333, Germany Correspondence: Felix Schölderle (felix.schoelderle@tum.de) Received: 15 June 2022 – Revised: 12 December 2022 – Accepted: 21 December 2022 – Published: 10 January 2023 Abstract. The localization and characterization of hydraulically active zones in a geothermal well is a major task in understanding the hydro geothermal reservoir. This is often done based on interpretations of spinner ﬂow meter measurements that are performed at the end of the well test while injecting cold water. Once a production well is equipped with an electric submersible pump, data collection inside the reservoir and monitoring of the ﬂow zones is usually barely possible. In a 3.7 km (MD) deep geothermal production wellin Munich, Germany, it was successfully demonstrated in 2019 that a permanently installed optical ﬁber cable could close this measurement gap. We used this ﬁber-optic monitoring system to collect distributed temperature data once the well was set into production. We inversely modeled the inﬂow from the formation into the borehole from the production temperature data with an energy and mass balance model. The derived ﬂow proﬁle correlates with previous ﬂow meter analysis and indicates that a karstiﬁed region at the very top of the reservoir is the driving factor for hydraulicsand obtained production temperature. Qualitatively, the two proﬁles acquired by distributed temperature sensing (DTS) and ﬂow meter are matchable, yet the production inﬂow proﬁle by DTS logging is more differentiated compared to spinner ﬂow meter logs interpretation during injection. 1 Introduction Reservoir characterization is a key for ensuring secure and sustainable usage of geothermal resources. One major task is the localization of productive zones in the reservoir, respectively ﬂow zones inside a well and the quantiﬁcation of the contribution of the single zones to the produced amount of thermal water. Typically, production logging tools equipped with ﬂow meter spinners are used in geothermal wells to estimate hydraulically active zones during injection of water (Schlumberger, 1997) . Additionally, wireline temperature runs can be analyzed for non-linearity indicating potential high permeable zones inside a well (e.g., Lim et al., 2020) . During production, data logging in the reservoir is difﬁcult, as permanent deep monitoring tools are rare and in case the well is a production well and equipped with an electric submersible pump (ESP), the deepest measurement point is usually located directly at the bottom of the pump. Monitoring tools below the ESP are not yet standard, but are feasible, as demonstrated in 2019 in a geothermal production wellin Munich, Germany, where a ﬁber-optic cable was installed along a free hanging sucker rod in the middle of the wellbore (Schölderle et al., 2021) . This cable enables seismic campaigns via distributed acoustic sensing (DAS) technology, temperature monitoring via distributed temperature sensing (DTS) and measuring point pressure and temperature (P =T ) at a gauge spliced into the cable on top of the reservoir. Due to its high spatial and temporal resolution, DTS technology, often via cemented cable or wireline designs, has become increasingly popular in geothermal applications in recent years, for both monitoring wellbore stability (e.g., Reinsch, 2012) and reservoir characterization (e.g., Sakaguchi and Matsushima, 2000) . Wellbore temperature, respectively heat can be

FAQs

Why are hydraulically active zones difficult to monitor during geothermal production?

Production logging is hard because permanent deep monitoring tools are rare and, with electric submersible pumps installed, the lowest standard measurement point is usually at the bottom of the pump.

What measurement system enables temperature-based monitoring during production?

A permanently installed optical fiber cable allows distributed temperature sensing (DTS) in the reservoir during production, creating distributed temperature data for inverse modeling.

How is inflow from the formation derived from DTS temperature data?

Inflow is inversely modeled using an energy and mass balance model, back-calculating a flow profile from production temperature observations.

Sep 14, 2026

Uploaded by Cipher