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|MOISTURE-RESISTANT SEALING MATERIALS FOR DOWNHOLE HPHT ELECTRICAL FEEDTHROUGH PACKAGE|
|Keywords: HPHT electrical feedthru, moisture resistant & high insulation resistance, hydrophobic ceramic sealing material|
|High-insulation-strength sealing materials are a critical element for making a downhole electrical feedthrough performing reliably in water-based or moisture-rich wellbores. In most of applications today, a hydrophilic ceramic or glass sealing material may exhibit high mechanical strength that enables an electrical feedthrough package to survive downhole harsh condition, but it is limited in use to oil-based wellbores. Downhole wireline tools, logging while drilling (LWD), and measurement while drilling (MWD) tools often fail as a result of the electrical insulation loss when exposed to a moisture-rich oil or water-based wellbore at 30,000 PSI and 300oC harsh conditions. It is desirable to have moisture-resistant sealing materials to solve problems related to moisture ingress in water-based or moisture-rich oil-based wellbores. This presentation will report on a new-generation sealing material that provides not only high mechanical strengths but also high moisture-resistance or hydrophobicity to mitigate any potential failure modes from a downhole electrical feedthrough.
A bismuth oxide based sealing material has been designed with xH3BO3-yBi2O3-(1-x-y-z-e)MO-zSiO2-eREO multi-composition platform with MO=TiO2, BaO, ZnO, Fe2O3 etc., and rare earth oxides [1-3]. It has been demonstrated that a sealing material is very likely of hydrophilic properties in its amorphous phase, while a sealing material is very likely of hydrophobic properties if it has covalent bond tetragonal phase, and a mixed phase consisting of monoclinic and tetragonal structures may show moisture-resistant properties.
To prove the moisture-resistance and hydrophobicity of the designed sealing materials, the prototyped electrical feedthroughs have been exposed to a simulated water-fluid downhole harsh condition. The experimental data have demonstrated that this new sealing material can sustain its hydrophobicity with greater than 300,000Mohm insulation resistance, even after 100 hours soaking in 30,000PSI/200℃ water/steam environment, as shown in FIG.1, where the moisture-resistant materials have positive resistance response as a function of measurement time, while the hydrophilic material shows negative resistance decrease because of leaky currents. Further insulation resistance test under elevated temperatures verified that the electric feedthrough prototypes still have 5,000Mohm insulation resistance at 300oC
|Hua Xia, Chief Scientist
Hermetic Solutions Group, LLC (USA)
Tinton Falls, NJ