TY - JOUR
T1 - Drilling and logging results of USDP-4 - Penetration into the volcanic conduit of Unzen Volcano, Japan
AU - Sakuma, Sumio
AU - Kajiwara, Tatsuya
AU - Nakada, Setsuya
AU - Uto, Kozo
AU - Shimizu, Hiroshi
N1 - Funding Information:
Drilling operations succeeded only through cooperation with JMC Geothermal Engineering Co., Ltd. and Teiseki Drilling Co., Ltd. The borehole logging was conducted by Schlumberger K.K. The project was supported by the Ministry of Education, Culture, Sport and Science (MEXT), and the International Continental Scientific Drilling (ICDP) to whom we give sincere thanks. We would like to dedicate results from this drilling project to Seiji Saito who organized the drilling international workshop for this project in 2000 and died without witnessing its successful completion. We also thank Tom Wright, Mineyuki Hanano, A. C Skinner and Dennis Nielsen for their useful suggestions and comments.
PY - 2008/7/30
Y1 - 2008/7/30
N2 - Borehole USDP-4 was drilled into the Unzen volcanic conduit 9 years after its last eruption. The sub-surface mechanism of eruption at Unzen Volcano was investigated by taking cores and by geophysical logging. The drilling operations were carried out in 2003-04, as a joint research program sponsored by the Japanese Government and the International Continental Scientific Drilling Program (ICDP). Borehole USDP-4 was a directional 6-1/4 in. (158.8 mm) borehole drilled from a site located on the northern slope of the volcano at 840 m above sea level, and was designed to penetrate into the conduit at sea level with a final deviation angle of over 70° from vertical and a borehole depth of 1800 m. An igneous dyke with a high likelihood of being the Unzen conduit was encountered at 1996 m depth and core samples were taken from that location. Chemical analysis of drill cores confirmed the identification of the conduit. Geophysical logging, including recording of gamma ray, resistivity, self-potential, density, neutron porosity, sonic velocity, and temperature suggested an alternation of dykes and flows in rock penetrated during the drilling, and in-hole pictures confirmed the lithologic identifications. Although borehole collapse and high temperature had been expected in the conduit, the actual drilling and logging into the conduit experienced no gas or fluid kick, and the measured temperatures within the dyke were below 200 °C.
AB - Borehole USDP-4 was drilled into the Unzen volcanic conduit 9 years after its last eruption. The sub-surface mechanism of eruption at Unzen Volcano was investigated by taking cores and by geophysical logging. The drilling operations were carried out in 2003-04, as a joint research program sponsored by the Japanese Government and the International Continental Scientific Drilling Program (ICDP). Borehole USDP-4 was a directional 6-1/4 in. (158.8 mm) borehole drilled from a site located on the northern slope of the volcano at 840 m above sea level, and was designed to penetrate into the conduit at sea level with a final deviation angle of over 70° from vertical and a borehole depth of 1800 m. An igneous dyke with a high likelihood of being the Unzen conduit was encountered at 1996 m depth and core samples were taken from that location. Chemical analysis of drill cores confirmed the identification of the conduit. Geophysical logging, including recording of gamma ray, resistivity, self-potential, density, neutron porosity, sonic velocity, and temperature suggested an alternation of dykes and flows in rock penetrated during the drilling, and in-hole pictures confirmed the lithologic identifications. Although borehole collapse and high temperature had been expected in the conduit, the actual drilling and logging into the conduit experienced no gas or fluid kick, and the measured temperatures within the dyke were below 200 °C.
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U2 - 10.1016/j.jvolgeores.2008.03.039
DO - 10.1016/j.jvolgeores.2008.03.039
M3 - Article
AN - SCOPUS:50049107821
VL - 175
SP - 1
EP - 12
JO - Journal of Volcanology and Geothermal Research
JF - Journal of Volcanology and Geothermal Research
SN - 0377-0273
IS - 1-2
ER -