Super-High-Temperature Geothermal Well Logging Tools (450°C) and Log Interpretation

Abstract

The development of high temperature well logging tools in Japan started in 1978 with the sponsorship of the Japanese government. This endeavor was named the "Sunshine Project". Engineers in diverse fields such as oil well logging, electronics, mechanics, electrical cables and computer software teamed up on this project. The project was successfully concluded in 1983 with the establishment of logging systems that can be used at temperatures up to 320°C. With the advancement of geothermal activities in JAPAX's Satsunan field in the southern part of Kyushu, Japan, bottom hole temperature over 375°C have been recorded in several wells. Therefore, the development of super high temperature logging tools that can be used at temperatures up to 450°C became an urgent problem for JAPEX. The project team to achieve this was formed in 1982. The super high temperature tools developed up to 1984 are as follows: logging unit (truck mounted), logging cable, high temperature wire line lubricator, temperature log, pressure log, caliper log (4 arms), borehole fluid sampler, sonic log, latero logo, and continuous flow meter. These tools are now used in well tests routinely, and all the tools except the sonic log and the latero log have been successfully operated in geothermal wells. The sonic log and the latero log have been undergoing field tests since January 1985. This paper briefly describes the principle features of the logging unit and logging tools, and gives examples of log interpretation using field data.