Geological setting and characterization of a methane hydrate reservoir distributed at the first offshore production test site on the Daini-Atsumi Knoll in the eastern Nankai Trough, Japan

Fujii, Tetsuya; Suzuki, Kiyofumi; Takayama, Tokujiro; Tamaki, Machiko; Komatsu, Yuhei; Konno, Yoshihiro; Yoneda, Jun; Yamamoto, Koji; Nagao, Jiro

doi:10.1016/j.marpetgeo.2015.02.037

Cited by 330 publications

(217 citation statements)

References 18 publications

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“…Cores 8P and 10P were taken from the upper third of the methane hydrate concentration zone (MHCZ), while core 20P was from the lower third of the MHCZ (see Fujii et al, 2015, andYamamoto, 2015, for additional coring interval information). Testing locations along each pressure core for all PCCT devices are shown in Figure 2.…”

Section: Resultsmentioning

confidence: 99%

“…The study utilizes pressure cores recovered from hydrate-bearing sediments in hole AT1-C, on the north slope of Daini Atsumi Knoll off the Atsumi and Shima peninsulas. A location overview is provided by Yamamoto (2015), and a more precise location map is given by Fujii et al (2015). Pressure cores were collected during the third hydrate drilling program at Nankai Trough from June 29th to July 4th of 2012 (Yamamoto et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

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Hydro-bio-geomechanical properties of hydrate-bearing sediments from Nankai Trough

Santamarina

Dai

Terzariol

et al. 2015

Marine and Petroleum Geology

204

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a b s t r a c tNatural hydrate-bearing sediments from the Nankai Trough, offshore Japan, were studied using the Pressure Core Characterization Tools (PCCTs) to obtain geomechanical, hydrological, electrical, and biological properties under in situ pressure, temperature, and restored effective stress conditions. Measurement results, combined with index-property data and analytical physics-based models, provide unique insight into hydrate-bearing sediments in situ. Tested cores contain some silty-sands, but are predominantly sandy-and clayey-silts. Hydrate saturations S h range from 0.15 to 0.74, with significant concentrations in the silty-sands. Wave velocity and flexible-wall permeameter measurements on neverdepressurized pressure-core sediments suggest hydrates in the coarser-grained zones, the silty-sands where S h exceeds 0.4, contribute to soil-skeletal stability and are load-bearing. In the sandy-and clayey-silts, where S h < 0.4, the state of effective stress and stress history are significant factors determining sediment stiffness. Controlled depressurization tests show that hydrate dissociation occurs too quickly to maintain thermodynamic equilibrium, and pressureetemperature conditions track the hydrate stability boundary in pure-water, rather than that in seawater, in spite of both the in situ pore water and the water used to maintain specimen pore pressure prior to dissociation being saline. Hydrate dissociation accompanied with fines migration caused up to 2.4% vertical strain contraction. The firstever direct shear measurements on never-depressurized pressure-core specimens show hydratebearing sediments have higher sediment strength and peak friction angle than post-dissociation sediments, but the residual friction angle remains the same in both cases. Permeability measurements made before and after hydrate dissociation demonstrate that water permeability increases after dissociation, but the gain is limited by the transition from hydrate saturation before dissociation to gas saturation after dissociation. In a proof-of-concept study, sediment microbial communities were successfully extracted and stored under high-pressure, anoxic conditions. Depressurized samples of these extractions were incubated in air, where microbes exhibited temperature-dependent growth rates.Published by Elsevier Ltd.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Hydro-bio-geomechanical properties of hydrate-bearing sediments from Nankai Trough

Santamarina

Dai

Terzariol

et al. 2015

Marine and Petroleum Geology

204

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“…The Eastern Nankai Trough is the most potential resource-rich area of gas hydrates in Japan [22,27]. In this area, the total amount of CH 4 gas contained in HBS was estimated at an average value of 1.1 × 10 12 m 3 , most of which was reserved in the 16 methane hydrate concentrated zones (MHCZs) [4,22,28].…”

Section: Site Conditionsmentioning

confidence: 99%

“…In fact, the marine gas hydrate drilling explorations at the Eastern Nankai Trough of Japan and in Shenhu area of the South China Sea revealed the variable distribution of hydrate deposits. Gas hydrate reservoirs are composed of alternating beds of sand and clay in sediments with various conditions of permeability, porosity, and hydrate saturation [22,25]. Consequently, the development of suitable geological model is critical to identify the dissociation layers and dissociation front induced by depressurization, which are key factors to ensure the success of the next long-term offshore production test [3,4,19,22].…”

Section: Introductionmentioning

confidence: 99%

“…Gas hydrate reservoirs are composed of alternating beds of sand and clay in sediments with various conditions of permeability, porosity, and hydrate saturation [22,25]. Consequently, the development of suitable geological model is critical to identify the dissociation layers and dissociation front induced by depressurization, which are key factors to ensure the success of the next long-term offshore production test [3,4,19,22]. Additionally, the sensitivity analyses of gas production potential in previous studies were concentrated on production pressure, reservoir permeability, porosity, hydrate saturation, thickness, and initial temperature and pressure of HBS [11,12,14,15,26], whereas comprehensive studies related to the effects of well production interval on gas recovery have been reported sparsely, which are important for the optimization of gas production and reducing the water production rate.…”

Section: Introductionmentioning

confidence: 99%

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Multiphase Flow Behavior of Layered Methane Hydrate Reservoir Induced by Gas Production

Yuan¹,

Xu²,

Xin³

et al. 2017

Geofluids

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Gas hydrates are expected to be a potential energy resource with extensive distribution in the permafrost and in deep ocean sediments. The marine gas hydrate drilling explorations at the Eastern Nankai Trough of Japan revealed the variable distribution of hydrate deposits. Gas hydrate reservoirs are composed of alternating beds of sand and clay, with various conditions of permeability, porosity, and hydrate saturation. This study looks into the multiphase flow behaviors of layered methane hydrate reservoirs induced by gas production. Firstly, a history matching model by incorporating the available geological data at the test site of the Eastern Nankai Trough, which considers the layered heterogeneous structure of hydrate saturation, permeability, and porosity simultaneously, was constructed to investigate the production characteristics from layered hydrate reservoirs. Based on the validated model, the effects of the placement of production interval on production performance were investigated. The modeling results indicate that the dissociation zone is strongly affected by the vertical reservoir's heterogeneous structure and shows a unique dissociation front. The beneficial production interval scheme should consider the reservoir conditions with high permeability and high hydrate saturation. Consequently, the identification of the favorable hydrate deposits is significantly important to realize commercial production in the future.

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Simulation of gas hydrate dissociation caused by repeated tectonic uplift events

2016

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Gas hydrate dissociation by tectonic uplift is often used to explain geologic and geophysical phenomena, such as hydrate accumulation probably caused by hydrate recycling and the occurrence of double bottom‐simulating reflectors in tectonically active areas. However, little is known of gas hydrate dissociation resulting from tectonic uplift. This study investigates gas hydrate dissociation in marine sediments caused by repeated tectonic uplift events using a numerical model incorporating the latent heat of gas hydrate dissociation. The simulations showed that tectonic uplift causes upward movement of some depth interval of hydrate‐bearing sediment immediately above the base of gas hydrate stability (BGHS) to the gas hydrate instability zone because the sediment initially maintains its temperature: in that interval, gas hydrate dissociates while absorbing heat; consequently, the temperature of the interval decreases to that of the hydrate stability boundary at that depth. Until the next uplift event, endothermic gas hydrate dissociation proceeds at the BGHS using heat mainly supplied from the sediment around the BGHS, lowering the temperature of that sediment. The cumulative effects of these two endothermic gas hydrate dissociations caused by repeated uplift events lower the sediment temperature around the BGHS, suggesting that in a marine area in which sediment with a highly concentrated hydrate‐bearing layer just above the BGHS has been frequently uplifted, the endothermic gas hydrate dissociation produces a gradual decrease in thermal gradient from the seafloor to the BGHS. Sensitivity analysis for model parameters showed that water depth, amount of uplift, gas hydrate saturation, and basal heat flow strongly influence the gas hydrate dissociation rate and sediment temperature around the BGHS.

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Geological setting and characterization of a methane hydrate reservoir distributed at the first offshore production test site on the Daini-Atsumi Knoll in the eastern Nankai Trough, Japan

Cited by 330 publications

References 18 publications

Hydro-bio-geomechanical properties of hydrate-bearing sediments from Nankai Trough

Hydro-bio-geomechanical properties of hydrate-bearing sediments from Nankai Trough

Multiphase Flow Behavior of Layered Methane Hydrate Reservoir Induced by Gas Production

Simulation of gas hydrate dissociation caused by repeated tectonic uplift events

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