The continuous monitoring of onsen (hot springs) is important for assessing the quality and sustainability of the onsen, and for evaluating the effects of geothermal energy developments on the onsen’s water supply. Due to the complexity of the data, automated monitoring once a week or less is insufficient to detect changes in the quality of the onsen due to natural variability or scaling in a pipeline, and other factors such as the weather and maintenance operations. In this study, the effects of scaling and other site-specific factors on the performance of the monitoring sensors were revealed by field experiments at the Obama and Kakkonda sites. The sensors considered in the experiment measured the flowrate, temperature, electric conductivity (EC) and fluid pressure. The sampling rate of each sensor was 1 measurement per second. The analysis of scale samples using X-Ray diffraction and energy dispersive X-ray spectroscopy revealed that the main components of the scales were aragonite at the Obama site and amorphous silica at the Kakkonda site. At both sites, the scaling reduced the accuracy of the observations of EC, although its effect was negligible for the other variables being monitored. The daily averages derived from the 1/sec observations were almost the same as those derived from the 1/hour observations. However, there were differences in the results for the daily observations when measured at noon and midnight. Site-specific maintenance operations correlated with pressure change, and fluid temperature decreased with increased precipitation. These results suggested that the onsen monitoring device can be constructed with the sensors used in this study, except for EC. In addition, a sampling rate of one measurement per hour, along with information about regional phenomena, are needed for the accurate evaluation of the onsen quality.
A new, portable, and desk-top type of thermoluminescence (TL) measurement system has been developed for mineral analysis in geothermal exploration. The equipment consists of a heater and extremely sensitive photon-detecting and control/recording (PC) units, which can be operated with an ordinary electric current source. A liberated and grained mineral (eg. quartz) without surface removal by HF treatment is put on the heating pan in a dark box and heated from ambient temperature to 400°C at a constant rate. The TL signal is then detected by the photomultiplier. After detecting the TL, the sample is air-cooled and then continuously re-heated to detect the background luminescence. The glow curve of the sample is obtained by subtracting the background from the original signal. This newly developed TL measurement system makes it possible to measure the TL of minerals in a field-based camp. This development could allow researchers to further evaluate geothermal activity in the field on the basis of TL behaviors of minerals.
Nittetsu Mining Consultants Co., Ltd. (hereinafter referred to as NMCC) purchased an AC electric-drive rig “ZJ50DBST” for geothermal drilling manufactured by HONGHUA, China in 2013. This rig includes 1,600HP drawworks, top drive system and two mud pumps which develop 1,300HP and is capable of drilling a largediameter hole at shallow depths using a mud motor and running 9-5/8”CSG string to 2,500m. Furthermore, most of the components can be transported by 15-ton trucks and the mast doesn’t need to be raised because it can be assembled stacking up each section of it with a crane. It allows the rig to be rigged up even at a narrow site. On the other hand, some of the components such as small motors and a centrifuge are of poor quality. Therefore it is necessary to replace whole of those components or some parts of the components with products made in Japan or the USA.
There are some concerns about sustaining the performance of the rig such as parts procurement, how to do periodic maintenance, theft and trouble in transit. NMCC has considered solutions regarding these concerns.
This rig has a good reputation for usability from the drilling crews. NMCC plans to modify it to be easier to use. It cost approximately 1 billion yen to purchase the rig, excluding the expenses for meetings and inspection.