Developing a Geothermal TEM System Using Squid Magnetometer

Abstract

Since the Fukushima nuclear accident in March 2011, a geothermal power generation is increasingly attracting attention in Japan as it produces less CO2 than other power generation styles and it is capable of supplying a baseload electricity for a long term. Although many geothermal development companies or municipality are beginning to investigate for new geothermal resources, relatively high initial survey costs and long lead times are one of the major problems, especially for new geothermal developers. Therefore, JOGMEC which is a Japanese government independent administrative institution has been subsidizing the initial costs and researching and developing technologies aiming to reduce the costs and shorten the survey period. As part of R&D of the technologies, JOGMEC has developed an electromagnetic (EM) exploration system named SQUITEM, which aims to more efficient in term of the measurement including its preparation with equal or higher resolution than the conventional ones. The SQUITEM is a kind of a transient-EM (TEM) exploration system using a SQUID (Super-conducting QUantum Interference Device) magnetometer which has a high resolution compared to the other ones. As the SQUITEM was originally developed by JOGMEC metal/mineral resource exploration team for shallow explorations, we JOGMEC geothermal team improved it suitable for deep geothermal exploration and the survey in the Japanese geothermal fields. We tested our new SQUITEM system at some geothermal fields in Japan to confirm its measurement efficiency and its exploration performance. The results showed that our new system can explore an underground resistivity structure up to more than 2 km depth with the high measurement efficiency.