Hydrophobic Dielectric Sealing Material Enabled Highly Reliable Electrical Connectors for Downhole Data and Power Transmission Application

Abstract

A high-strength dielectric sealing material has been developed for sealing electrical connectors, feedthroughs, bulkheads, and interconnectors. X-ray diffraction analyses have identified that the microstructures of the sealing material could be of amorphous and α-phase mixed morphology, α+β mixed phase, and β-phase dominated tetrahedral microstructure, which primarily depend upon the material processing temperature. The electrical insulation resistance of the β-phase dominated sealing material have nearly two times higher than that of α+β mixed phase sealing material. Both β-phase dominated and α+β mixed phase sealing materials have shown water repelling properties, while amorphous glass phase has shown hydrophilic properties. If a 5,000MΩ insulation resistance is also regarded as baseline for a downhole electrical connector, the maximum operation temperature of α+β mixed phase sealing materials is around 240°C while that of the β-phase dominated sealing material can be up to 300°C. Furthermore, a thermo-mechanical modeling has been developed to quantify if a designed electrical connector has sufficient reliability in the hostile wellbore or downhole environments. The temperature- and pressure-dependent seal compression have suggested that the temperature-related safety factor should be chosen in the range from 2.0 to 5.0 while the pressure-related safety factor should be chosen in the range from 1.5 to 2.0 to ensure 10-20 years electrical connector downhole operating reliability. The qualification tests from prototyped electrical connectors, under 260°C/32,000PSI simulated water-fluid based conditions, have demonstrated that such high-strength sealing material sealed electrical connector could be integrated with logging while drilling (LWD) or/and measurement while drilling (MWD) tools for providing long-term reliable signal, data, and electrical power transmission services, regardless of a water-based or moisture-rich wellbore or/and downhole environment.