Journal of the Japanese Association for Petroleum Technology
Online ISSN : 1881-4131
Print ISSN : 0370-9868
ISSN-L : 0370-9868
Volume 62, Issue 1
Displaying 1-8 of 8 articles from this issue
  • Yoshikazu Yaguchi, Keiichi Kimura, Takao Asaki
    1997 Volume 62 Issue 1 Pages 3-12
    Published: 1997
    Released on J-STAGE: March 27, 2008
    JOURNAL FREE ACCESS
    The MITT (Ministry of International Trade and Industry) has been encouraging oil and gas exploration in domestic areas. In line with this policy, a “Five Year Plan for Domestic Oil and Natural Gas Resources Development” was set up in 1995 and has been renewed every five years to meet the current situation respectively. The plan comprises of both reconnaissance geophysical surveys (mainly on seismic fields) and exploratory test drillings.
    During the period from 1955 through to 1994, a total of seventy-two wells were drilled by MITI for structural, stratigraphic and exploratory tests. As a result, samples, geological data and imformative knowledge, acquired from these tests, were utilized for plannning exploration by the private sector, as well as for studies and research in academic institutes of Japan.
    Some highlights of MITI exploratory test wells drilled include:
    1. Five wells out of a total of seventy-two resulted in success. One of them (MITI Yoshida well) could be developed for commercial production.
    2. Deep seated crystalline basement rocks were found in six wells. These rocks are of mostly Cretaceous granites or metamorphics.
    3. Stratigraphy and sedimentary facies were recognized in some unexplored areas.
    4. Potential source rocks were discovered in some areas in Hokkaido.
    5. Much information and data on Green Tuff volcanic rocks were gathered for their distribution, stratigraphy, facies changes, fracture development, reservoir properties, and rock alteration enhancing reservoir quality.
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  • Hiroshi Kurita, Akiko Obuse
    1997 Volume 62 Issue 1 Pages 13-24
    Published: 1997
    Released on J-STAGE: March 27, 2008
    JOURNAL FREE ACCESS
    A Miocene-Upper Cretaceous section of the MITI Tempoku borehole, northern Hokkaido, was subdivided into seven dinoflagellate cyst assemblage zones. Biostratigraphically useful pollen and spore assemblages were also recorded from the lower Paleogene-upper Upper Cretaceous part of the section which is mostly nonmarine or deltaic. The combination of these organic microfossils established a fundamental biostratigraphic-chronostratigraphic framework in the section, where the recovery of other calcareous and siliceous microfossils was not very significant. The case study demonstrates the practical application of palynology to Cenozoic-Mesozoic sections particularly in the higher latitudes in Japan and its surrounding areas.
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  • Tohru Danhara
    1997 Volume 62 Issue 1 Pages 25-34
    Published: 1997
    Released on J-STAGE: March 27, 2008
    JOURNAL FREE ACCESS
    Zircon Fission-Track Analysis (ZFTA) as a geological clock is based on zeta age calibration and track length measurements. Fission-track dating samples are classified into four types according to combination of two factors of 1) homogeneity in fission track age and 2) heating effect to fission track age. The four types of samples are (a) homogeneous and unheated, (b) heterogeneous and unheated, (c) homogeneous and heated and (d) heterogeneous and heated. As an example of ZFTA applied to the four-type samples, the author reviewed recent fission track dating studies in Japan as follows: (a) volcanic ash layers of the Kazusa Group in the Boso Peninsula, (b) the Pliocene Hirosegawa Tuff Member of the Sendai Group in Northeast Honshu, (c) the MITI “Honjo-oki” well and (d) the MITI “Mishima” well, respectively. Studies on the two exploratory test wells show ZFTA is a useful tool for petroleum exploration in Japan.
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  • Masaaki Tateishi, Osamu Takano, Tsukasa Takashima, Katsuki Kurokawa
    1997 Volume 62 Issue 1 Pages 35-44
    Published: 1997
    Released on J-STAGE: March 27, 2008
    JOURNAL FREE ACCESS
    Studies of stratigraphy and sedimentary system for Cenozoic sequence in the Northern Fossa Magna have progressed in these two decades. Especially a regional stratigraphical correlation using volcanic ash markers has remarkably progressed, and contributed markedly in the geological studies of the Northern Fossa Magna. The Upper Miocene to Pliocene sequence has been so far correlated on the basis of zoning of benthonic foraminifera in the petroleum geology. However, the stratigraphic correlation on the basis of this paleontological zoning is not consistent with the stratigraphical correlation using the volocanic ash markers. The contradiction between these stratigraphic correlations was examined in this study.
    The geohistorical change of depositional system and tectonic evolution of the Northern Fossa Magna were discussed on the basis of sedimentary facies analysis and sedimentary petrography. Five geohistorical stages, namely pre-rift, rift, stable, conversion, and deformation stages, were consequently distinguished in the Cenozoic of the Northern Fossa Magna.
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  • With special reference to the spreading of the back-arc basin
    Kenji Shuto, Susumu Kato, Jun'ichi Ohki, Hiroo Kagami, Hiroyuki Arato, ...
    1997 Volume 62 Issue 1 Pages 45-58
    Published: 1997
    Released on J-STAGE: March 27, 2008
    JOURNAL FREE ACCESS
    The underground volcanic activity before middle Miocene in the Niigata oil and gas fields are divided into three periods; late Oligocene (27-23Ma), early Miocene (19-16Ma) and middle Miocene (16-13Ma).
    These volcanism might have taken place in close association with multiple formations of NS-trending grabens. The rifting of the Japan Sea might have caused the formation of the first stage graben of late Oligocene to early Miocene. During the spreading of the Japan Sea, the second stage graben has been formed in submarine environments. Within this submarine deep graben, middle Miocene basaltic and rhyolitic rocks were extensively accumulated and they have been buried in the level deeper than 5, 000-000m since middle Miocene.
    The deep seated early to middle Miocene basatts can be divided into three different groups based on initial Sr isotopic ratios (Sri) and εNd values. Sri and εNd values expected for unaltered samples of each group are as follows; Sri=0.7032-0.7033 and εNd=+6-+8 for group I, Sri=0.7038-0.7040 and εNd=+4-+5 for group II, Sri=0.7045-0.7050 and εNd=0-+2 for group III. Middle Miocene rhyolites from the Tsugawa and Tadami areas show significantly higher Sri ratios (0.7055-0.7080) and lower εNd values (-8-0) than the basaltic rocks.
    Basaltic magmas of group III are considered to have formed from the sub-island arc lithospheric mantle with an undepleted isotope signature, while those of groups I and II are from the hot mantle with a depleted isotope signature, upwelling from the athenosphere to the sub-island arc lithospheric mantle during the spreading of the Japan Sea. Genesis of rhyolitic rocks from the underground and surface outcrops in the Tsugawa and Tadami areas may be ascribed to the partial melting of the lower crust.
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  • Shinichi Takakura, Koichi Nakagami, Yuji Mitsuhata, Ryuhei Murayama
    1997 Volume 62 Issue 1 Pages 59-68
    Published: 1997
    Released on J-STAGE: March 27, 2008
    JOURNAL FREE ACCESS
    Magnetotelluric (MT) data were obtained along a line which is almost perpendicular to the strike of the geologic structure in the Higashi-Kubiki area, Niigata prefecture, Japan. The resistivity structure analyzed from a two dimensional inversion of the MT data is consistent with the geologic structure estimated from other survey results. We interpreted the resistivity structure in comparison with the MITI Higashi-Kubiki well data such as resistivity, porosity, temperature, vitrinite reflectance and altered-mineral contents. The results are as follows.
    (1) Resistive layers at or near surface correspond to the Uonuma formations, which were not altered.
    (2) Very conductive layers of about 1 to 3Ωm at a depth range from 1 to 3km correspond to the Nishiyama and the Shiiya formations. The low resistivity is primarily due to high contents of smectites which were produced by diagenesis. Because the permeability of rocks containing plenty of smectites is generally low, the conductive layers may form cap rocks.
    (3) Below the conductive layers, resistivity increases with depth. The relatively resistive zone of about 3 to 100Ωm corresponds to the Upper Teradomari, the Lower Teradomari, the Nanatani formations and the Green Tuffs. According to the logging data of some nearby wells, this resistivity range agrees with a vitrinite reflectance range from 0.5 to 1.2%. Therefore the resistive zone is interpreted as source rocks of this area.
    (4) Very resistive layers of more than 300Ωm at deeper than about 10km are probably pre-Tertiary basement rocks or intrusive rocks, which contain probably no oil and gas.
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  • Masahiko Akiyama, Akio Hirai
    1997 Volume 62 Issue 1 Pages 69-79
    Published: 1997
    Released on J-STAGE: March 27, 2008
    JOURNAL FREE ACCESS
    The following four conclusions were deduced particularly from the examination of vitrinite reflectance (Ro) data from MITI exploratory test wells conducted by the Ministry of International Trade and Industry together with some other data from Japanese oil companies.
    (1) The regression equation between Ro and maximum burial temperature formulated by disregarding the effective heating time (Barker and Pawlewicz, 1994) is not applicable to the estimation of the temperature gradient of the Tertiary and Quaternary Systems in Japan, because there is significance change of Ro with time within 20-30m.y.
    (2) Correlation between Ro and maximum paleotemperature was estimated by isomerization of sterane and hopane biomarkers in the MITI Hamayuchi well core (Sakata and Akiyama, 1989). Maximum paleotemperature gradients of 23 wells in Japan were calculated based on the above correlation data. All of the calculated gradient values are much higher than the measured present temperature gradient values (Table 1). This result suggests that the poor correlation is due to too few Ro measurements in the MITI Hamayuchi core, while the estimation method of maximum paleotemperature using isomerization of sterane and hopane biomarkers is reliable.
    (3) The maximum paleotemperatures estimated from the nomogram of the MITI Shimoigarashi well of Niigata Prefecture (Sekiguchi and Hirai, 1980) show good agreement with the measured present temperature gradient in many wells drilled in the Niigata plain. The area around Mt. Yoneyama in the central part of Niigata Prefecture, which shows marked igneous activity in the Pliocene has a high paleotemperature gradient suggesting much higher heat flow than at the present.
    (4) The kink in a two-segment vitrinite reflectance profile in MITI Takadaheiya, MITI Kubiki and many other wells in Niigata Oil Field is restricted to the Middle Miocene Nambayama Formation, suggesting perturbation in the thermal gradient caused by heat transfer processes associated with abnormal high-pressures as was discussed by Law et al. (1989) and Hunt (1995).
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  • Itsuro Kita, Hideo Takizawa, Hidenao Hasegawa, Ryuichi Arayashiki, Kei ...
    1997 Volume 62 Issue 1 Pages 80-89
    Published: 1997
    Released on J-STAGE: March 27, 2008
    JOURNAL FREE ACCESS
    He isotopic ratios of gas samples from exploration and production wells of oils and natural gases in the northeast Japan were measured for discussing the migration of He gas between the formations in the Green Tuff region. In Niigata and Akita Prefectures, He gases from the Green Tuff formations give the highest 3He/4He ratios, indicating magmatic origins. It is noted that both radiogenic and magmatic He gases were found from the different depths of the same formation in Niigata Prefecture. This feature strongly indicates that the magmatic He is not originated from volcanic rock, although volcanic rocks homogeneously distributes in the formation. In Akita Prefecture, He gases in the formation containing little volcanic rocks have the large proportion of magmatic He. Therefore, it can be inferred that magmatic He migrates from the Green Tuff formation to upper formations through faults or cracks.
    δ13C value of CH4 gas coexisting with radiogenic He found in the Niigata Green Tuff region was -28.1‰, indicating the thermogenic origin. The same feature was observed in the natural gases from the Iwaki-oki production wells located in the Pacific ocean. In contrast, in the Akita area, He and CH4 gases from the formation containing little volcanic rocks give magmatic 3He/4He ratios and biogenic δ13C values. These gases deviate from the positive correlation between the 3He/4He ratios and δ13C values of CH4 which have been reported for natural gases from Japanese island arcs. Therefore, the relation demonstrated previously has no meaning for discussing the origin of CH4 in natural gases. These results seem to support that the origins of CH4 having high δ13C values from the Green Tuff region in Japan are mainly not magmatic but thermogenic.
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