Japan Oil Engineering Co.

Tokyo, Japan

Japan Oil Engineering Co.

Tokyo, Japan
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Uchida N.,Tohoku University | Shimamura K.,Tohoku University | Shimamura K.,Japan Oil Engineering Co. | Matsuzawa T.,Tohoku University | Okada T.,Tohoku University
Journal of Geophysical Research B: Solid Earth | Year: 2015

We examined the temporal variation of the size of repeating earthquakes related to the 2011 Tohoku-oki earthquake (M9.0) in the northeastern Japan subduction zone for the period from July 1984 to the end of 2011. The repeaters (M2.5-6.1) show postseismic magnitude increases for most sequences located in the area of large postseismic slip at the downdip extension of the M9 source region. The magnitudes of the first events after the M9 earthquake increased by an average of about 0.3 for sequences having three or more earthquakes over the 9 months following it. We also examined the slip area in detail for Kamaishi repeaters whose magnitudes had been M4.9 ± 0.2 but which increased by about 1 after the M9 earthquake. Waveform modeling shows that the slip area for the post-M9 Kamaishi earthquakes overlaps with that before the Tohoku-oki earthquake but enlarged by about 6 times. Until the occurrence time of the last event (September 2011) in the analysis period, the rupture area remained larger than before but appeared to shrink over time. The enlargement of the rupture area suggests that an aseismic-to-seismic transition occurred in the region surrounding the pre-M9 repeaters and is most likely related to fast loading of the repeaters due to rapid postseismic slip estimated to have occurred in the area. The existence of conditionally stable regions around the repeating earthquakes and/or patches slightly larger than the earthquake nucleation sizes may explain such behavior. The temporal change of loading rate is an important factor in determining earthquake size in this case. ©2014. American Geophysical Union. All Rights Reserved.


Kurihara M.,Japan Oil Engineering Co. | Sato A.,Japan Oil Engineering Co. | Funatsu K.,Japan Oil Engineering Co. | Ouchi H.,Japan Oil Engineering Co. | And 3 more authors.
Marine and Petroleum Geology | Year: 2011

Targeting the methane hydrate (MH) bearing units C and D at the Mount Elbert prospect on the Alaska North Slope, four MDT (Modular Dynamic Formation Tester) tests were conducted in February 2007. The C2 MDT test was selected for history matching simulation in the MH Simulator Code Comparison Study. Through history matching simulation, the physical and chemical properties of the unit C were adjusted, which suggested the most likely reservoir properties of this unit. Based on these properties thus tuned, the numerical models replicating "Mount Elbert C2 zone like reservoir" "PBU L-Pad like reservoir" and "PBU L-Pad down dip like reservoir" were constructed. The long term production performances of wells in these reservoirs were then forecasted assuming the MH dissociation and production by the methods of depressurization, combination of depressurization and wellbore heating, and hot water huff and puff. The predicted cumulative gas production ranges from 2.16×106m3/well to 8.22×108m3/well depending mainly on the initial temperature of the reservoir and on the production method.This paper describes the details of modeling and history matching simulation. This paper also presents the results of the examinations on the effects of reservoir properties on MH dissociation and production performances under the application of the depressurization and thermal methods. © 2010 Elsevier Ltd.


Tamaki M.,Japan Oil Engineering Co. | Kusumoto S.,University of Toyama | Itoh Y.,Osaka Prefecture University
Island Arc | Year: 2010

Formation and deformation processes of the late Paleogene sedimentary basins related to a strike-slip fault system in southern central Hokkaido are described by a combination of paleomagnetic study and numerical analysis. After correction of the Miocene counter-clockwise rotation associated with back-arc opening of the Japan Sea, paleomagnetic declination data obtained from surface outcrops in the Umaoi and Yubari areas show significant easterly deflections. Although complicated differential rotation is anticipated as a result of recent thrust movements, clockwise rotation in the study areas is closely linked with development of the Paleogene Minami-naganuma Basin as a pull-apart depression along the north-south fault system. Numerical modeling suggests that 30 km of strike-slip is required to restore the distribution and volume of the Minami-naganuma Basin. The relative slip rate on the long-standing fault system is about 10 mm/yr, which corresponds to global-scale plate motion. It has inevitably caused regional rearrangement of the eastern Eurasian margin. A rotation field simulated by simplified dextral motion using dislocation modeling basically accords with the paleomagnetic data around the pull-apart basin. © 2009 Blackwell Publishing Asia Pty Ltd.


Konno Y.,Japan National Institute of Advanced Industrial Science and Technology | Oyama H.,Japan National Institute of Advanced Industrial Science and Technology | Nagao J.,Japan National Institute of Advanced Industrial Science and Technology | Masuda Y.,University of Tokyo | Kurihara M.,Japan Oil Engineering Co.
Energy and Fuels | Year: 2010

Oceanic gas hydrate deposits at high saturations have been found within continuous thick sands in areas such as the Eastern Nankai Trough and the Gulf of Mexico. The recent discovery of these deposits has stimulated research and development programs exploring the use of gas hydrates as energy resources. Because the permeability of hydrate-bearing sediments is a crucial factor for successful gas production from oceanic hydrate reservoirs, the permeability of these sediments and the dissociation process of hydrates should be investigated using hydrate cores obtained at these oceanic hydrate reservoirs. In this study, to investigate the permeability of actual hydrate-bearing sediments and the dissociation process of hydrates by a depressurization method, a numerical simulation was conducted using a state-of-the-art hydrate reservoir simulator. A dissociation experiment of hydrate-bearing sandy cores obtained from turbidite sediments at the Eastern Nankai Trough was analyzed. By choosing appropriate model parameters, the simulator precisely reproduces the dissociation behavior such as cumulative gas production, cumulative water production, and pressure change. The model parameters associated with permeability indicate a pore-filling tendency rather than a coating tendency of the hydrate in the pore space. Although the permeability of the hydrate-bearing cores obtained at hydrate reservoirs in nature was relatively low, the effective water permeability obtained in this study seems promising for achieving depressurization-induced hydrate dissociation. It has been found that the pressure reduction propagates deeply into the hydrate-bearing zone and the hydrate is spatially dissociated. Also, the permeability is beyond the lower limit of threshold permeability, which is absolutely necessary for successful gas production by depressurization. This study confirms the advantage of employing depressurization as a gas production method, using the hydrate in sandy turbidite sediments at the Eastern Nankai Trough as our test sample. The numerical analysis method used is effective to analyze the dissociation behavior of hydrate-bearing cores obtained at natural hydrate reservoirs, and it enables evaluation of gas productivity in those reservoirs. © 2010 American Chemical Society.


Konno Y.,Japan National Institute of Advanced Industrial Science and Technology | Masuda Y.,University of Tokyo | Akamine K.,Japan Oil Engineering Co. | Naiki M.,Japan Oil Engineering Co. | Nagao J.,Japan National Institute of Advanced Industrial Science and Technology
Energy Conversion and Management | Year: 2016

The cyclic depressurization method, which uses alternating depressurization and shut-in periods over decades, has been proposed to achieve sustainable gas production from methane hydrate reservoirs. Numerical simulations were conducted to investigate the dissociation and reformation behaviors of methane hydrate during depressurization and shut-in periods. A high gas production rate was obtained for a few years after primary depressurization; however, the production rate drastically decreased because the sensible heat of the reservoir was exhausted owing to hydrate dissociation. During the shut-in period after 10 years of production, methane hydrate continued to dissociate owing to the geothermal heat flow for a few decades and then started to reform in accordance with pressure recovery. Case studies with shut-in periods of 10-30 years showed that 20 years of shut-in was the most effective period before the next depressurization. A conceptual operation plan for a hypothetical field showed that the production time increased to 120 years from 70 years when the cyclic depressurization method was considered. The recovery factor increased from 42.4% to 71.5%. The number of operating wells was reduced to less than one-third compared with the operation with normal depressurization method only. The results suggest that the cyclic depressurization method is a sustainable heat supply method driven by the geothermal heat flow and is both economically and environmentally sound. © 2015 Elsevier Ltd.


Fujii T.,Japan Oil, Gas and Metals National Corporation | Suzuki K.,Japan Oil, Gas and Metals National Corporation | Takayama T.,Japan Oil, Gas and Metals National Corporation | Tamaki M.,Japan Oil Engineering Co. | And 5 more authors.
Marine and Petroleum Geology | Year: 2015

To obtain basic information for methane hydrate (MH) reservoir characterization at the first offshore production test site (AT1) located on the northwestern slope of the Daini-Atsumi Knoll in the eastern Nankai Trough, extensive geophysical logging and pressure coring using a hybrid pressure coring system were conducted in 2012 at a monitoring well (AT1-MC) and a coring well (AT1-C). The MH-concentrated zone (MHCZ), which was confirmed by geophysical logging at AT1-MC, has a 60-m-thick turbidite assemblage with sublayers ranging from a few tens to hundreds of centimeters thickness. The turbidite assemblage is composed of lobe/sheet-type sequences in the upper part and relatively thick channel-sand sequences in the lower part. Well-to-well correlations of sandy layers between two monitoring wells within 40 m of one another exhibited fairly good lateral continuity of sand layers in the upper part of the reservoir. This suggests an ideal reservoir for the production test.The validity of MH pore saturation (Sh) evaluated from geophysical logging data were confirmed by comparing with those evaluated by pressure core analysis. In the upper part of the MHCZ, Sh values estimated from resistivity logs showed distinct differences between the sand and mud layers, compared with Sh values from nuclear magnetic resonance (NMR) logs. Resistivity logs have higher vertical resolution than NMR logs; therefore, they are favorable for these types of thin-bed evaluations. In the upper part, Sh values of 50%-80% were observed in sandy layers, which is in fairly good agreement with core-derived Sh values. In the lower part of the MHCZ, Sh values estimated from both resistivity and NMR logs showed higher background values and relatively smoother curves than those for the upper part. In the lower part, Sh values of 50%-80% were also observed in sandy layers, and they showed good agreement with the core-derived Sh values. © 2015 The Authors.


Tamaki M.,Japan Oil Engineering Co. | Suzuki K.,Japan Oil, Gas and Metals National Corporation | Fujii T.,Japan Oil, Gas and Metals National Corporation
Marine and Petroleum Geology | Year: 2015

To understand the paleocurrent directions and depositional processes in the forearc basin along the active convergent margin of the eastern Nankai Trough, analysis of the anisotropy of magnetic susceptibility (AMS) has been applied to Pleistocene turbidite sediments in a borehole core obtained in the vicinity of the gas hydrate production test site. Sixty-one core specimens mainly sampled from silty and sandy sediments were measured, and the AMS results show generally oblate magnetic fabrics characterized by girdle-distributed weakly-clustered maximum and intermediate susceptibility axes. Diagnostic magnetic fabric parameters show that the sediments generally preserve primary sedimentary structures without significant sediment disturbance due to events such as coring and bioturbation. The characteristic remanent magnetization was also measured to determine the reorientation of each core. Paleocurrent directions estimated from the offset of the minimum susceptibility axes in the stratigraphic coordinates show two predominant directions: one toward the southwest (SW) and the other toward the northwest (NW). On the basis of the interpretations of 3D seismic data, the principal SW direction is generally parallel to the trough-shaped basin axis; this suggests that the sediments were carried by axial turbidity currents within the channel. The subordinate NW direction corresponds to the downslope direction of the Daini-Atsumi Knoll; this may be due to a sediment supply from the southeast associated with a submarine slope failure and landslide evolution or it may be due to flow reflections from the slope toward the basin center. The results of the paleocurrent analysis suggest that the Pleistocene depositional system around the Daini-Atsumi Knoll is affected by the basin configuration. These results are in good agreement with previous studies of the coeval depositional system for the adjacent forearc minibasin around the eastern Nankai Trough. © 2015 Elsevier Ltd.


Konno Y.,Japan National Institute of Advanced Industrial Science and Technology | Konno Y.,University of Tokyo | Masuda Y.,Japan National Institute of Advanced Industrial Science and Technology | Masuda Y.,University of Tokyo | And 4 more authors.
Energy and Fuels | Year: 2010

Oceanic methane hydrate (MH)depositshave been found at high saturations within reservoir-quality sands in the EasternNankai Trough and theGulf ofMexico. This study investigates the key factors for the success of depressurization- induced gas production from such oceanicMH deposits. A numerical simulator (MH21-HYDRES: MH21 Hydrate Reservoir Simulator) was used to study the performance of gas production fromMH deposits. We calculated the hydrate dissociation behavior and gas/water production performance during depressurization for a hypothetical MH well. Simulation runs were conducted under various initial reservoir conditions of MH saturation, temperature, and absolute permeability.Aproductivity function (PF) was introduced as an indicator of gas productivity, which is a function of gas production rate, water production rate, and discount rate. The simulations showed that recovery factors over 36%andmaximumgas production rates over 450 000 Sm3/d were expected for the most suitable conditions of a class 3 deposit (i.e., an isolated MH deposit that is not in contact with any hydrate-free zone of mobile fluids). However, gas productivity was affected by formation temperature and initial effective permeability. The values of PF increased with increasing formation temperature when the initial permeability of the deposit was higher than a threshold value (the threshold permeability); however, it decreased for the deposit below the threshold permeability. The threshold permeability was estimated to be between 1 and 10 mD in the class 3 deposit. These results suggest that key factors for the success of depressurization- induced gas production from oceanicMH are as follows: (1) The initial effective permeability of the MHdeposit is higher than the threshold value, and (2) the temperature of the MH deposit is as high as possible. © 2010 American Chemical Society.


Konno Y.,Japan National Institute of Advanced Industrial Science and Technology | Masuda Y.,University of Tokyo | Hariguchi Y.,University of Tokyo | Kurihara M.,Japan Oil Engineering Co. | Ouchi H.,Japan Oil Engineering Co.
Energy and Fuels | Year: 2010

Oceanicmethane hydrate (MH)depositshave been found at high saturations within reservoir-quality sands in the EasternNankai Trough and theGulf ofMexico. This study investigates the key factors for the success of depressurization- induced gas production from such oceanicMH deposits. A numerical simulator (MH21-HYDRES: MH21 Hydrate Reservoir Simulator) was used to study the performance of gas production fromMH deposits. We calculated the hydrate dissociation behavior and gas/water production performance during depressurization for a hypothetical MH well. Simulation runs were conducted under various initial reservoir conditions of MH saturation, temperature, and absolute permeability.Aproductivity function (PF) was introduced as an indicator of gas productivity, which is a function of gas production rate, water production rate, and discount rate. The simulations showed that recovery factors over 36%andmaximumgas production rates over 450 000 Sm3/d were expected for the most suitable conditions of a class 3 deposit (i.e., an isolated MH deposit that is not in contact with any hydrate-free zone of mobile fluids). However, gas productivity was affected by formation temperature and initial effective permeability. The values of PF increased with increasing formation temperature when the initial permeability of the deposit was higher than a threshold value (the threshold permeability); however, it decreased for the deposit below the threshold permeability. The threshold permeability was estimated to be between 1 and 10 mD in the class 3 deposit. These results suggest that key factors for the success of depressurization- induced gas production from oceanicMH are as follows: (1) The initial effective permeability of the MHdeposit is higher than the threshold value, and (2) the temperature of theMHdeposit is as high as possible. © 2010 American Chemical Society.


Konno Y.,Japan National Institute of Advanced Industrial Science and Technology | Uchiumi T.,Japan National Institute of Advanced Industrial Science and Technology | Oyama H.,Japan National Institute of Advanced Industrial Science and Technology | Jin Y.,Japan National Institute of Advanced Industrial Science and Technology | And 3 more authors.
Energy and Fuels | Year: 2012

To investigate the effect of ice formation on gas production from gas-hydrate-bearing sandy porous media, we conducted dissociation experiments using artificial methane hydrate cores by depressurizing them to below the quadruple point. We prepared water- and gas-saturated hydrate cores to evaluate the influence of water content on ice formation. The experiments showed that gas production under the ice formation regime had a unique high-rate period in the early stage of production, whereas under the water generation regime, the high-rate period was not observed. During ice formation, the gas production rates of the water-saturated cores exhibited greater acceleration than those of the gas-saturated cores. We conducted numerical simulations using the hydrate reservoir simulator MH21-HYDRES for quantitative analyses. The results showed that ice forms faster in a water-saturated core because of the availability of pore water for ice formation. This further enhances the gas production rate of a water-saturated core. Sensitivity analyses indicated that the rate of ice formation and the permeability reduction by ice formation are key model parameters affecting gas production behavior. From the experimental and numerical investigations, we conclude that depressurization-induced gas production can be accelerated by ice formation during hydrate dissociation at a pressure below the quadruple point. © 2012 American Chemical Society.

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