The drive to obtain more accurate petrophysical information from deeper wells has led to the demand for operating various downhole tools at higher temperatures for longer time periods. If the borehole temperature reaches values higher than 175°C, it is considered a high temperature (HT) well. In HT wells, reliability of the electronic components of the logging tools is a major concern. One way to address the concern is through using a thermal flask to reduce the heat flow rate from the formation to the tool and evenly distribute the heat generated by the internal electronic components.
Optimizing the design of the aforementioned thermal flask is very important in providing a longer operative time for the tool before the temperature of the sensitive electronic parts reaches a critical threshold. To obtain the sensitive parameters for designing the flask, the thermal transport inside the tool must be accurately modeled.
In this work, high fidelity FEA and CFD-based transient thermal models are developed for thermal transport in a flask for an ultra-high temperature wireline tool. Two models with different levels of complexity are presented. The models are verified by experimental results and the physical insights obtained from them presented. The predictive capability of the models is used to provide recommendations for safe operating time for various environmental conditions which prevail in the formations. The results obtained from the models can also be used for optimizing the performance of the future generation of the tool and reducing the amount of time spent in unnecessary trip outs.
