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Volume 69 (2004)
- Issue 6 Pages 602-
- Issue 5 Pages 463-
- Issue 4 Pages 335-
- Issue 3 Pages 255-
- Issue 2 Pages 119-
- Issue 1 Pages 5-
Volume 69, Issue 4
Displaying 1-7 of 7 articles from this issue
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Yuichi Sugai, Chengxie Hong, Tadashi Chida, Heiji Enomoto2004 Volume 69 Issue 4 Pages 335-347
Published: 2004
Released on J-STAGE: March 27, 2008
JOURNAL FREE ACCESSOur research group has carried out experimental studies to analyze the performance and the mechanism of MEOR with TU-15A, a microbe that produces water-soluble polymer. In the previous study, a mathematical model for this MEOR was developed, including almost all important phenomena such as growth and death of microbe, consumption of nutrient, production of water-soluble polymer, increase of water viscosity and the flow of reservoir fluids.
In this study, the validity of the MEOR simulation model was firstly examined by comparison between experimental and computed results. The results of the numerical simulation agreed with the experimental results in terms of oil recovery, injection pressure, oil cut and flow profile of injection water.
Next, numerical simulation was carried out to analyze the performance and mechanism of this MEOR process for five-spot pattern flooding. The procedure and the conditions used are as follows.
Step 1: Conduct water flooding until water cut becomes 90%.
Step 2: Inject microbe and nutrient solution into reservoir up to 0.1 PV.
Step 3: Shut-in and wait for cultivation in the reservoir for 10 days.
Step 4: Conduct postflash until water cut becomes 95%.
The quantitative changes of microbe, nutrient, water viscosity and oil saturation were analyzed. Regarding the alteration of flow pattern in the reservoir, it was found that (1) the water-soluble polymer produced by the microbe flowed into the main flow channel along the shortest way between the injection well and the production well and water viscosity there increased, (2) subsequently more uniform flow profile of injected water for oil recovery was established, and (3) then the residual oil was mobilized to the production well. The more than 10% additional oil recovery was obtained in the early phase of postflash in this MEOR process compared with waterflooding.View full abstractDownload PDF (1592K) -
application to well-site geological survey by using magnetic susceptibility meterMasami Otake, Masahiko Yamashita, Koji Nagashima2004 Volume 69 Issue 4 Pages 348-360
Published: 2004
Released on J-STAGE: March 27, 2008
JOURNAL FREE ACCESSMagnetic susceptibility was measured using portable equipment on cuttings collected at 10 meter intervals from MG-35, MG-36 and MG-37 wells in the Higashi Niigata gas field, Niigata prefecture, Japan. Each of three formations (Kambara Group, Haizume Formation and Nishiyama Formation) has its own characteristic value of magnetic susceptibility. The pattern of its variation often changes at formation boundaries. Major magnetic mineral responsible for the magnetic susceptibility was identified as magnetite by the X-ray diffraction analysis.
Kambara Group has high fluctuations in magnetic susceptibility due to an abundance of lithofacies change. Characteristic patterns of variation are shown in each lithofacies and can be roughly correlated throughout the three wells. As for Haizume Formation of MG-35 and MG-36, the magnetic susceptibility variation is closely related to the resistivity logging data; the intervals of higher and lower amplitude of fluctuations in magnetic susceptibility and resistivity repeatedly occur. The magnetic susceptibility of the Nishiyama Formation has a positive correlation with the content of sand in places, which coincides with the measurement results at an outcrop consisting of turbidite sandstones intercalated with mudstones.
On the basis of the relationship between magnetic susceptibility and lithofacies and the characteristic pattern of magnetic susceptibility in each formations, the measurement of magnetic susceptibility can be efficient means for interpretation and correlation of lithostratigraphy as a part of well-site geological survey.View full abstractDownload PDF (1807K) -
Hiroki Hayashi, Yukito Kurihara, Toyosaburo Sakai2004 Volume 69 Issue 4 Pages 361-373
Published: 2004
Released on J-STAGE: March 27, 2008
JOURNAL FREE ACCESSThe Miocene marine sequence of the upper part of the Nagaoka and Ozo Formations in the Utsunomiya Hills area, Tochigi Prefecture, central Japan, yielded planktonic foraminiferal species Praeorbulina spp. and Orbulina spp. The upper part of the Nagaoka Formation contains a molluscan assemblage including Nanaochlamys notoensis notoensis which characterizes the Moniwa-type molluscan fauna of early middle Miocene age. These foraminiferal and molluscan results indicate that the stratigraphic interval from the upper part of the Nagaoka to Ozo Formations should be correlated with the planktonic foraminferal zones N.8 to N.9 of Blow (1969). This zonal assignment permits to correlate the interval with the lower part of the Kobana Formation in the Motegi-Karasuyama area, in the eastern margin of the central lowland of Tochigi Prefecture.View full abstractDownload PDF (1976K) -
Norihiko Kobayashi, Kazuhiko Kano, Takeshi Ohguchi2004 Volume 69 Issue 4 Pages 374-384
Published: 2004
Released on J-STAGE: March 27, 2008
JOURNAL FREE ACCESSThe Oga Peninsula is famous for the standard locality of the Green Tuff succession in Japan. The stratigraphy of the lower succession, however, remains in debate because of the complicated associations of volcanic rocks and many poor or inaccessible exposures especially in the inland area. This paper proposes a new stratigraphic unit, the Nomuragawa Formation, extensively distributed in the inland area of the west Oga Peninsula where the late Eocene to early Oligocene shallow-water to terrestrial volcanic rocks of the Monzen Formation has been believed to occupy.
The Nomuragawa Formation is unconformably underlain by the Monzen Formation and is onlapped by the late early Miocene to early middle Miocene marine Nishikurosawa Formation. This formation is composed mainly of non- to intensely welded dacite pyroclastic flow deposits and basalt to basaltic andesite lava flows and volcaniclastic deposits. Three radiometric ages determined for this formation range from 19 to 21 Ma, correlative to the Hokakejima Dacite and the Sugoroku and Daijima Basalts, both of the Daijima Formation. Our finding of the Nomuragawa Formation in the west Oga Peninsula raises a doubt on the belief of the well-established lithostratigraphic division of the Daijima Formation. Volcanic products correlative in lithology and age to the Nomuragawa Formation sparsely occur along the Japan Sea coast. They are commonly onlapped by the succeeding marine sediments, and perhaps mark the beginning of rapid opening of the Japan Sea.View full abstractDownload PDF (1538K) -
Susumu Kato, Hiroshi Oda, Tohru Danhara2004 Volume 69 Issue 4 Pages 385-394
Published: 2004
Released on J-STAGE: March 27, 2008
JOURNAL FREE ACCESSTwo important benthonic foraminiferal markers are recognized in the Teradomari Formation, Niigata Prefecture. These markers are the last occurrence of Spirosigmoilinella compressa and the "Blue Zone" (Watanabe, 1976) containing characteristic calcareous species. Three gas reservoirs, 2000m reservoir, 2700m reservoir and 3200m reservoir in descending order, exist above or below these markers in the Katakai gas field.
Fission-track (FT) ages using zircon crystals in tuffaceous sandstone cores collected from these reservoirs are 5.8±0.2Ma, 7.7±0.3Ma and 8.6±0.3Ma respectively. These ages place the following constrains on two markers.
1) Taking into account the revised FT age for the Gtp tuff (5.3±0.2Ma), the last occurrences of Spirosigmoilinella compressa in both Niigata and Akita Prefectures are more or less synchronous.
2) The "Blue Zone", the geologic age of which is estimated to be about 8.2Ma, is probably correlated with the O-1 assemblage in the Onnagawa Formation.
This study shows that FT dating using both internal and external surfaces of zircon crystals is useful for tuffaceous sandstone cores.View full abstractDownload PDF (946K) -
Yuko Suto, Shunsuke Yamazaki, Seiji Saito, Nobuo Hatakeyama, Hiroshi T ...2004 Volume 69 Issue 4 Pages 395-403
Published: 2004
Released on J-STAGE: March 27, 2008
JOURNAL FREE ACCESSRecently, oil wells reach deeper and deeper formations where temperature is higher than temperature ratings of drilling tools. Several deep, high-temperature oil wells, with bottom hole static temperatures ranging from 200 to 230°C have been drilled since 1990 in Japan by MITI. Reports of these wells pointed out the difficulty of downhole works and decreasing drilling time due to high temperature. Therefore, it is becoming very important to know borehole temperature while drilling and to take measures against high temperature.
In this study, a relationship among the borehole temperature around a bit, the damage of O-ring seals in the bit, and drilling time was investigated. Bit performance and dull bit grade records of the MITI-Nishikubiki well showed what caused the reduced bit life was the damage of bearings, rather than wear of teeth or insert. The measurement of mechanical characteristics of O-ring seals after both the thermal damage test and the use in geothermal wells was performed. The results indicated that elasticity of O-ring seal decreased significantly when the O-ring was exposed to 150°C for 25 hours and 170°C for a few hours. Estimating the borehole temperature around a bit while drilling using the borehole temperature simulator, we estimated durations that bits were exposed to temperature higher than 150°C and 170°C. The distribution of damage grade of bearing on a graph of the simulated duration of exposure at high temperature vs. drilling time showed two obvious areas. One is an area of non-useful life, the other is an area of useful life. We suggested the "O-ring life curve" as the boundary of these two areas.View full abstractDownload PDF (1055K) -
Hiroki Hayashi, Seiji Horiuchi, Masaki Takahashi, Keiji Kasahara2004 Volume 69 Issue 4 Pages 404-416
Published: 2004
Released on J-STAGE: March 27, 2008
JOURNAL FREE ACCESSMicrofossil biochronology was examined for sixteen deep observation wells of the National Research Institute for Earth Science and Disaster Prevention (NIED). The subsurface Neogene marine sediments in the Kanto Plain are divided into three stratigraphic units; "N. 8 deposits", "post N. 8 deposits" and Kazusa-Shimousa Groups, in ascending order. Upper two units widely distribute beneath the Kanto Plain. "Post N. 8 deposits" covers the pre-Neogene basement rocks unconformably at most localities. In contrast, the "N. 8 deposits" is recognized from a few sites, which may represent the sporadic distribution of this unit in the Kanto Plain. Microfossil geochronology of subsurface geology suggests that the "post N. 8 deposits" can be divided into the Middle to Late Miocene intra-arc basin fills and overlapping Pliocene fore-arc basin sediments.View full abstractDownload PDF (1774K)
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