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Nishi-Tokyo-shi, Japan

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 2 more authors.
Marine and Petroleum Geology

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. Source

Anderson B.J.,U.S. National Energy Technology Laboratory | Anderson B.J.,West Virginia University | Kurihara M.,Japan Oil Engineering Co. | White M.D.,Pacific Northwest National Laboratory | And 11 more authors.
Marine and Petroleum Geology

Following the results from the open-hole formation pressure response test in the BPXA-DOE-USGS Mount Elbert Gas Hydrate Stratigraphic Test Well (Mount Elbert well) using Schlumberger's Modular Dynamics Formation Tester (MDT) wireline tool, the International Methane Hydrate Reservoir Simulator Code Comparison project performed long-term reservoir simulations on three different model reservoirs. These descriptions were based on 1) the Mount Elbert gas hydrate accumulation as delineated by an extensive history-matching exercise, 2) an estimation of the hydrate accumulation near the Prudhoe Bay L-pad, and 3) a reservoir that would be down-dip of the Prudhoe Bay L-pad and therefore warmer and deeper. All of these simulations were based, in part, on the results of the MDT results from the Mount Elbert Well. The comparison group's consensus value for the initial permeability of the hydrate-filled reservoir (k = 0.12 mD) and the permeability model based on the MDT history match were used as the basis for subsequent simulations on the three regional scenarios. The simulation results of the five different simulation codes, CMG STARS, HydrateResSim, MH-21 HYDRES, STOMP-HYD, and TOUGH+HYDRATE exhibit good qualitative agreement and the variability of potential methane production rates from gas hydrate reservoirs is illustrated. As expected, the predicted methane production rate increased with increasing in situ reservoir temperature; however, a significant delay in the onset of rapid hydrate dissociation is observed for a cold, homogeneous reservoir and it is found to be repeatable. The inclusion of reservoir heterogeneity in the description of this cold reservoir is shown to eliminate this delayed production. Overall, simulations utilized detailed information collected across the Mount Elbert reservoir either obtained or determined from geophysical well logs, including thickness (37 ft), porosity (35%), hydrate saturation (65%), intrinsic permeability (1000 mD), pore water salinity (5 ppt), and formation temperature (3.3-3.9 °C). This paper presents the approach and results of extrapolating regional forward production modeling from history-matching efforts on the results from a single well test. © 2010 Elsevier Ltd. Source

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

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. Source

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

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. Source

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

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. Source

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