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|Development of a Novel Logging Tool for 450°C Super Critical Geothermal Well|
|Keywords: High Temperature Electronics, Logging Tool, Geothermal|
|Exploitation of super-critical water from deep geothermal resources can potentially give a 5-10 fold increase in the power output per well. Such an improvement represents a significant reduction in investment costs for deep geothermal energy projects, thus improving their competiveness. The ongoing European Horizon2020 DESCRAMBLE (Drilling in dEep, Super-CRitical AMBients of continental Europe) project will demonstrate the drilling of a deep geothermal well with super-critical conditions (>375°C, >220 bar) by extending an existing well to a depth of approximately 4km. State-of-the-art electronic logging tools does not operate reliably at these conditions. In the DESCRAMBLE project, SINTEF is developing a novel pressure and temperature logging tool for monitoring these supercritical conditions. The logging tool components; high temperature electronics, sensors and batteries are shielded from the environment by a heat shield (Dewar). A pressure vessel with special seals, envelops the dewar making the target specification for the tool 8 hours of logging operation time at 450°C/450 bar. Such dwell time is necessary in order to log a 4km deep well with peak temperature of 450°C. A high performance heat and pressure shield protect the electronics platform that can operate and store data up to a minimum of 200°C, with some key components targeting as high as 300°C. Having the thermal performance to be able to operate for 8 hours at 450°C also means that the tool can operate with even longer dwell time in other applications where temperature is lower. Alternatively, it can operate at the same dwell time with a lower internal temperature resulting in more available electronic components that can be used. The 32-bit RelChip RC10001 microcontroller (beta release) is used in the design under RelChip's Early Adopters Program (EAP). This and other Silicon-On-Insulator (SOI) components along with the other support circuitry are specified to temperatures exceeding 230°C. A high-temperature polyimide substrate is used to mount the components and has been tested up to 200°C in several cycles with no loss of performance. The firmware architecture and readout is presented, including workarounds for some of the shortcomings of the system. Novel battery options that have been considered in this project are discussed, but the field trials have been carried out with commercial high temperature cells from Electrochem. These cells have been tested and characterized outside of spec to be able to power the tool topside as well as downhole, which represents a vast and challenging dynamic temperature range from a power source point of view. Currently, the limiting factor for the logging tool's dwell time is the battery technology, which is specified to a maximum operating temperature of 200°C. In this work, we describe the tool requirements and discuss the design choices made with emphasis on the electronics platform and limitations imposed by the available battery technology. We will present test results from individual components at high temperature.|
|Morten Hamreoen Røed, Research Scientist