HR: 10:35h
AN: OS12A-02    [Abstracts]
TI: Resource Assessment of Methane Hydrate in the Eastern Nankai Trough, Japan
AU: * Fujii, T
EM: fujii-tetsuya@jogmec.go.jp
AF: Japan Oil, Gas and Metals National Corporation, 1-2-2 Hamada, Mihama-ku, Chiba, 261- 0025, Japan
AU: Saeki, T
EM: saeki-tatsuo@jogmec.go.jp
AF: Japan Oil, Gas and Metals National Corporation, 1-2-2 Hamada, Mihama-ku, Chiba, 261- 0025, Japan
AU: Kobayashi, T
EM: kobayashi-toshiaki@jogmec.go.jp
AF: Japan Oil, Gas and Metals National Corporation, 1-2-2 Hamada, Mihama-ku, Chiba, 261- 0025, Japan
AU: Inamori, T
EM: inamori-takao@jogmec.go.jp
AF: Japan Oil, Gas and Metals National Corporation, 1-2-2 Hamada, Mihama-ku, Chiba, 261- 0025, Japan
AU: Hayashi, M
EM: hayashi-masao@jogmec.go.jp
AF: Japan Oil, Gas and Metals National Corporation, 1-2-2 Hamada, Mihama-ku, Chiba, 261- 0025, Japan
AU: Takano, O
EM: takano-osamu@jogmec.go.jp
AF: Japan Oil, Gas and Metals National Corporation, 1-2-2 Hamada, Mihama-ku, Chiba, 261- 0025, Japan
AB: Resource assessment of methane hydrate (MH) in the eastern Nankai Trough was conducted through probabilistic approach using 2D/3D seismic survey data and drilling survey data from METI exploratory test wells gTokai-oki to Kumano-nadah [1, 2, 3]. We have extracted several prospective gMH concentrated zonesh [4] characterized by high resistivity in well log, strong seismic reflector, seismic high velocity, and turbidite deposit delineated by sedimentary facies analysis. The amount of methane gas contained in MH bearing layers was calculated using volumetric method for each zone. Each parameter, such as Gross Rock Volume (GRV), net-to-gross ratio (N/G), MH pore saturation (Sh), porosity, cage occupancy, and volume ratio was given as probabilistic distribution for Monte Carlo simulation, considering the uncertainly of these values. The GRV for each hydrate bearing zones was calculated from both strong seismic amplitude anomaly and velocity anomaly. Time-to-depth conversion was conducted using interval velocity derived from SVWD (Seismic Vision While Drilling). Risk factor was applied for the estimation of the GRV in 2D seismic area considering the uncertainty of seismic interpretation. The N/G was determined based on the relationship between LWD (Logging While Drilling) resistivity and grain size in zones with existing wells. 3ohm-m was used for typical cut off value to determine net intervals. Seismic facies map created by sequence stratigraphic approach [5] was also used for the determination of the N/G in zone without well controls. Porosity was estimated using density log, together with calibration by core analysis. The Sh was estimated by the combination of density log and NMR log (DMR method), together with the calibration by observed gas volume from onboard MH dissociation tests using PTCS (Pressure Temperature Core Sampler) [6]. The Sh in zone without well control was estimated using relationship between seismic P-wave interval velocity and Sh from NMR log at well location. Cage occupancy was determined to be around 0.95 by refereeing recent field observations. Total amount of methane gas in place contained in MH in the eastern Nankai Trough within survey area was estimated to be 40 tcf as Pmean value (10 tcf as P90 value, 82 tcf as P10 value). Total gas in place for MH concentrated zone was estimated to be 20 tcf (Half of total amount) as Pmean value. Sensitivity analysis indicated that the N/G and Sh have higher sensitivity than other parameters, and they are important for further detail analysis. This study was carried out as a part of Research Consortium for Methane Hydrate Resource in Japan (MH21). [1] Takahashi et al. (2005): Proc. Of 2005 OTC, 2-5 May, Houston, Texas, U.S.A. [2] Fujii et al. (2005): Proc. Of 5th ICGH, Trondheim, Norway, 974-979. [3] Tsuji et al. (2007): AAPG Special Publication (in press). [4] Saeki et al. (2007): Abst. of 2007 Technical Meeting of the JAPT, June 5-7, 2007, Tokyo, p49. [5] Takano et al. (2007): Abst. of 2007 Technical Meeting of the JAPT, June 5-7, 2007, Tokyo, p34. [6] Fujii et al. (2007): AAPG Special Publication (in press).
DE: 3004 Gas and hydrate systems
SC: Ocean Sciences [OS]
MN: 2007 Fall Meeting