Development of High Temperature Telemetry Systems for Long Term Borehole Monitoring Systems in Riser Holes

Abstract

In the present study, some component evaluation tests, unit integration tests, system integration tests, environmental life tests and land tests have done with using the experimental prototype (EXP) mockups of the telemetry system for the long term borehole observatory system (LTBMS). This paper describes some issues on the development of telemetry system and reports some test results. The telemetry system being developed in the present study is intended to apply especially for the deep riser holes in Nankai, Japan. Analog to Digital Converters (ADCs), voltage controlled crystal oscillators (VCXOs), and the other major components in the telemetry systems have been evaluated and their life-times have been estimated as more than five years in 125 °C. The life time of the EXP itself has been estimated as five years in the environment of 100 °C. The case study about the power distribution in the EXP of 8 downhole modules and 1 subsea module has shown that the assumed power supply of total 45 Watts from a submarine cable network, so-called DONET, can't maintain the versatile power supply for the sensors. This means we need to consider more specified power supply for the sensors after defining the sensor configuration. The shock and vibration tests on the telemetry system have shown some of modules being failed. Some anti-vibration measures have been conducted. The present study identified some issues to be resolved to realize the deep riser hole long term observations.