Development of a Novel Logging Tool for 450°C Geothermal Wells

Abstract

Exploitation of super-critical geothermal resources demands novel downhole logging tools, which are important for evaluating the formation properties, inspection of the well completion and for optimizing production and maintenance. For deep wells with temperatures above 350°C, state-of -the-art electronic logging tools lack the performance to operate reliably. Currently, the operator is limited to coarse temperature measurements using mechanical tools based on bourdon tubes or observation of physical processes such as melting.
In this work, we describe the development status and main research areas in developing a pressure and temperature logging tool for the ongoing H2020 DESCRAMBLE (Drilling in dEep, Super-CRitical AMBients of continentaL Europe) project. Our target specification for the autonomous tool is 8 hours operation time at 450°C/450 bar. We expect such performance to be necessary in order to log a 4km deep well with maximum temperature of 450°C. The tool consists of a high performance heat and pressure shield that protects a high temperature electronics platform that can operate and store data at a minimum of 200°C, targeting 300°C. More specifically, we describe the design choices made for the mechanical sealing, heat shield, high temperature electronics and sensors, and battery technology. In addition, we will present some preliminary lab test results.