Thermal design for protection of downhole electronic packages

Design improvements made for downhole tools based on results obtained from the thermal analysis of the instrument package are described. Results include heat flux at the tool surface and temperature-time histories of each subsystem. The research stems from a need for tools that can survive the harsh environment present in geothermal wellbores. The high temperatures and pressures create stress on the tools that function in this environment. Improvements in the design of downhole tools lead to more accurate data obtained from the wellbore during experimentation. The analysis showed that the thermal potential and the conductance between electronics and its heat sink was too small and was misdirected. Significant improvements were achieved by increasing the available thermal capacity of the heat sink, the thermal potential between the heat sink and electronics, and the conductance of the heat transfer paths.