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Coastal Ocean Natural Gas Hydrate 2014

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A special issue of Energies (ISSN 1996-1073).

Deadline for manuscript submissions: closed (31 January 2015) | Viewed by 110554

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Prof. Dr. Richard Coffin

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Department of Physical & Environmental Sciences, Texas A&M University, Corpus Christi, TX 78412, USA
Interests: methane; isotope geochemistry; carbon cycling; climate change; ocean models
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Dear Colleagues,

Gas hydrates are recognized an opportunity for new energy, a contribution to climate change, a significant factor in coastal stability and a potential approach to reduce carbon dioxide emissions. State of the art field and laboratory research requires integration of geophysics, geology, biology and geochemistry in field and laboratory to assess sediment methane hydrate loadings, predict carbon dioxide and methane hydrate stability, understand the hydrate role in ocean cycles, global economy, and reducing greenhouse gas emissions. Over the past years publications in this special issue have presented science on key issues lead by world leaders in gas hydrate research.

Recent studies show a strong potential of future energy for many nations. Ongoing climate change studies in the Arctic are working for a better understanding of the relative methane contribution from permafrost and coastal regions to the atmosphere. Initial experiments show the potential to exchange hydrate methane with carbon dioxide to address the anthropogenic influence on climate change and lower the risk of coastal and platform stability that results from mining. This Special Issue invites papers on methane hydrate exploration and methane — carbon dioxide hydrate exchange related to alternate energy, carbon sequestration and climate change.

Dr. Richard B. Coffin
Guest Editor

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Keywords

gas hydrates
coastal
formation
stability
mining
energy
climate change

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Published Papers (10 papers)

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644 KiB

Open AccessArticle

Stability Analysis of Methane Hydrate-Bearing Soils Considering Dissociation

by Hiromasa Iwai, Sayuri Kimoto, Toshifumi Akaki and Fusao Oka

Energies 2015, 8(6), 5381-5412; https://doi.org/10.3390/en8065381 - 5 Jun 2015

Cited by 9 | Viewed by 6638

Abstract

It is well known that the methane hydrate dissociation process may lead to unstable behavior such as large ground deformations, uncontrollable gas production, etc. A linear instability analysis was performed in order to investigate which variables have a significant effect on the onset of the instability behavior of methane hydrate-bearing soils subjected to dissociation. In the analysis a simplified viscoplastic constitutive equation is used for the soil sediment. The stability analysis shows that the onset of instability of the material system mainly depends on the strain hardening-softening parameter, the degree of strain, and the permeability for water and gas. Then, we conducted a numerical analysis of gas hydrate-bearing soil considering hydrate dissociation in order to investigate the effect of the parameters on the system. The simulation method used in the present study can describe the chemo-thermo-mechanically coupled behaviors such as phase changes from hydrates to water and gas, temperature changes and ground deformation. From the numerical results, we found that basically the larger the permeability for water and gas is, the more stable the simulation results are. These results are consistent with those obtained from the linear stability analysis. Full article

(This article belongs to the Special Issue Coastal Ocean Natural Gas Hydrate 2014)

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2603 KiB

Open AccessFeature PaperArticle

Molecular and Isotopic Composition of Volatiles in Gas Hydrates and in Sediment from the Joetsu Basin, Eastern Margin of the Japan Sea

by Akihiro Hachikubo, Katsunori Yanagawa, Hitoshi Tomaru, Hailong Lu and Ryo Matsumoto

Energies 2015, 8(6), 4647-4666; https://doi.org/10.3390/en8064647 - 25 May 2015

Cited by 28 | Viewed by 6897

Abstract

Hydrate-bearing sediment cores were retrieved from the Joetsu Basin (off Joetsu city, Niigata Prefecture) at the eastern margin of the Japan Sea during the MD179 gas hydrates cruise onboard R/V Marion Dufresne in June 2010. We measured molecular and stable isotope compositions of volatiles bound in the gas hydrates and headspace gases obtained from sediments to clarify how the minor components of hydrocarbons affects to gas hydrate crystals. The hydrate-bound hydrocarbons at Umitaka Spur (southwestern Joetsu Basin) primarily consisted of thermogenic methane, whereas those at Joetsu Knoll (northwestern Joetsu Basin, about 15 km from Umitaka Spur) contained both thermogenic methane and a mixture of thermogenic and microbial methane. The depth concentration profiles of methane, ethane, propane, CO₂, and H₂S in the sediments from the Joetsu Basin area showed shallow sulfate–methane interface (SMI) and high microbial methane production beneath the SMI depth. Relatively high concentrations of propane and neopentane (2,2-dimethylpropane) were detected in the headspace gases of the hydrate-bearing sediment cores obtained at Umitaka Spur and Joetsu Knoll. Propane and neopentane cannot be encaged in the structure I hydrate; therefore, they were probably excluded from the hydrate crystals during the structure I formation process and thus remained in the sediment and/or released from the small amounts of structure II hydrate that can host such large gas molecules. The lower concentrations of ethane and propane in the sediment, high δ¹³C of propane and isobutane, and below-detection normal butane and normal pentane at Umitaka Spur and Joetsu Knoll suggest biodegradation in the sediment layers. Full article

(This article belongs to the Special Issue Coastal Ocean Natural Gas Hydrate 2014)

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2020 KiB

Open AccessArticle

Transport Mechanisms for CO₂-CH₄ Exchange and Safe CO₂ Storage in Hydrate-Bearing Sandstone

by Knut Arne Birkedal, Lars Petter Hauge, Arne Graue and Geir Ersland

Energies 2015, 8(5), 4073-4095; https://doi.org/10.3390/en8054073 - 8 May 2015

Cited by 45 | Viewed by 7750

Abstract

CO₂ injection in hydrate-bearing sediments induces methane (CH₄) production while benefitting from CO₂ storage, as demonstrated in both core and field scale studies. CH₄ hydrates have been formed repeatedly in partially water saturated Bentheim sandstones. Magnetic Resonance Imaging (MRI) and CH₄ consumption from pump logs have been used to verify final CH₄ hydrate saturation. Gas Chromatography (GC) in combination with a Mass Flow Meter was used to quantify CH₄ recovery during CO₂ injection. The overall aim has been to study the impact of CO₂ in fractured and non-fractured samples to determine the performance of CO₂-induced CH₄ hydrate production. Previous efforts focused on diffusion-driven exchange from a fracture volume. This approach was limited by gas dilution, where free and produced CH₄ reduced the CO₂ concentration and subsequent driving force for both diffusion and exchange. This limitation was targeted by performing experiments where CO₂ was injected continuously into the spacer volume to maintain a high driving force. To evaluate the effect of diffusion length multi-fractured core samples were used, which demonstrated that length was not the dominating effect on core scale. An additional set of experiments is presented on non-fractured samples, where diffusion-limited transportation was assisted by continuous CO₂ injection and CH₄ displacement. Loss of permeability was addressed through binary gas (N₂/CO₂) injection, which regained injectivity and sustained CO₂-CH₄ exchange. Full article

(This article belongs to the Special Issue Coastal Ocean Natural Gas Hydrate 2014)

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2484 KiB

Open AccessArticle

Deep Sediment-Sourced Methane Contribution to Shallow Sediment Organic Carbon: Atwater Valley, Texas-Louisiana Shelf, Gulf of Mexico

by Richard B. Coffin, Christopher L. Osburn, Rebecca E. Plummer, Joseph P. Smith, Paula S. Rose and Kenneth S. Grabowski

Energies 2015, 8(3), 1561-1583; https://doi.org/10.3390/en8031561 - 18 Feb 2015

Cited by 21 | Viewed by 7522

Abstract

Coastal methane hydrate deposits are globally abundant. There is a need to understand the deep sediment sourced methane energy contribution to shallow sediment carbon relative to terrestrial sources and phytoplankton. Shallow sediment and porewater samples were collected from Atwater Valley, Texas-Louisiana Shelf, Gulf of Mexico near a seafloor mound feature identified in geophysical surveys as an elevated bottom seismic reflection. Geochemical data revealed off-mound methane diffusion and active fluid advection on-mound. Gas composition (average methane/ethane ratio ~11,000) and isotope ratios of methane on the mound (average δ¹³C_CH4(g) = −71.2‰; D¹⁴C_CH4(g) = −961‰) indicate a deep sediment, microbial source. Depleted sediment organic carbon values on mound (δ¹³C_SOC = −25.8‰; D¹⁴C_SOC = −930‰) relative to off-mound (δ¹³C_SOC = −22.5‰; D¹⁴C_SOC = −629‰) suggest deep sourced ancient carbon is incorporated into shallow sediment organic matter. Porewater and sediment data indicate inorganic carbon fixed during anaerobic oxidation of methane is a dominant contributor to on-mound shallow sediment organic carbon cycling. A simple stable carbon isotope mass balance suggests carbon fixation of dissolved inorganic carbon (DIC) associated with anaerobic oxidation of hydrate-sourced CH₄ contributes up to 85% of shallow sediment organic carbon. Full article

(This article belongs to the Special Issue Coastal Ocean Natural Gas Hydrate 2014)

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1233 KiB

Open AccessArticle

Experimental Investigation into the Combustion Characteristics of Propane Hydrates in Porous Media

by Xiang-Ru Chen, Xiao-Sen Li, Zhao-Yang Chen, Yu Zhang, Ke-Feng Yan and Qiu-Nan Lv

Energies 2015, 8(2), 1242-1255; https://doi.org/10.3390/en8021242 - 5 Feb 2015

Cited by 36 | Viewed by 7107

Abstract

The combustion characteristics of both pure propane hydrates and the mixtures of hydrates and quartz sands were investigated by combustion experiments. The flame propagation, flame appearance, burning time and temperature in different hydrate layers were studied. For pure propane hydrate combustion, the initial flame falls in the “premixed” category. The flame propagates very rapidly, mainly as a result of burnt gas expansion. The flame finally self-extinguishes with some proportion of hydrates remaining unburned. For the hydrate-sand mixture combustion, the flame takes the form of many tiny discontinuous flames appearing and disappearing at different locations. The burn lasts for a much shorter amount of time than pure hydrate combustion. High porosity and high hydrate saturation is beneficial to the combustion. The hydrate combustion is the combustion of propane gas resulting from the dissociation of the hydrates. In both combustion test scenarios, the hydrate-dissociated water plays a key role in the fire extinction, because it is the main resistance that restrains the heat transfer from the flame to the hydrates and that prevents the hydrate-dissociated gas from releasing into the combustion zone. Full article

(This article belongs to the Special Issue Coastal Ocean Natural Gas Hydrate 2014)

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4789 KiB

Open AccessArticle

Methane Flux and Authigenic Carbonate in Shallow Sediments Overlying Methane Hydrate Bearing Strata in Alaminos Canyon, Gulf of Mexico

by Joseph P. Smith and Richard B. Coffin

Energies 2014, 7(9), 6118-6141; https://doi.org/10.3390/en7096118 - 23 Sep 2014

Cited by 14 | Viewed by 7576

Abstract

In June 2007 sediment cores were collected in Alaminos Canyon, Gulf of Mexico across a series of seismic data profiles indicating rapid transitions between the presence of methane hydrates and vertical gas flux. Vertical profiles of dissolved sulfate, chloride, calcium, magnesium, and dissolved inorganic carbon (DIC) concentrations in porewaters, headspace methane, and solid phase carbonate concentrations were measured at each core location to investigate the cycling of methane-derived carbon in shallow sediments overlying the hydrate bearing strata. When integrated with stable carbon isotope ratios of DIC, geochemical results suggest a significant fraction of the methane flux at this site is cycled into the inorganic carbon pool. The incorporation of methane-derived carbon into dissolved and solid inorganic carbon phases represents a significant sink in local carbon cycling and plays a role in regulating the flux of methane to the overlying water column at Alaminos Canyon. Targeted, high-resolution geochemical characterization of the biogeochemical cycling of methane-derived carbon in shallow sediments overlying hydrate bearing strata like those in Alaminos Canyon is critical to quantifying methane flux and estimating methane hydrate distributions in gas hydrate bearing marine sediments. Full article

(This article belongs to the Special Issue Coastal Ocean Natural Gas Hydrate 2014)

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1493 KiB

Open AccessArticle

Contribution of Vertical Methane Flux to Shallow Sediment Carbon Pools across Porangahau Ridge, New Zealand

by Richard B. Coffin, Leila J. Hamdan, Joseph P. Smith, Paula S. Rose, Rebecca E. Plummer, Brandon Yoza, Ingo Pecher and Michael T. Montgomery

Energies 2014, 7(8), 5332-5356; https://doi.org/10.3390/en7085332 - 18 Aug 2014

Cited by 28 | Viewed by 8896

Abstract

Moderate elevated vertical methane (CH₄) flux is associated with sediment accretion and raised fluid expulsion at the Hikurangi subduction margin, located along the northeast coast of New Zealand. This focused CH₄ flux contributes to the cycling of inorganic and organic carbon in solid phase sediment and pore water. Along a 7 km offshore transect across the Porangahau Ridge, vertical CH₄ flux rates range from 11.4 mmol·m⁻²·a⁻¹ off the ridge to 82.6 mmol·m⁻²·a⁻¹ at the ridge base. Stable carbon isotope ratios (δ¹³C) in pore water and sediment were variable across the ridge suggesting close proximity of heterogeneous carbon sources. Methane stable carbon isotope ratios ranging from −107.9‰ to −60.5‰ and a C1:C2 of 3000 indicate a microbial, or biogenic, source. Near ridge, average δ¹³C for pore water and sediment inorganic carbon were ¹³C-depleted (−28.7‰ and −7.9‰, respectively) relative to all core subsamples (−19.9‰ and −2.4‰, respectively) suggesting localized anaerobic CH₄ oxidation and precipitation of authigenic carbonates. Through the transect there was low contribution from anaerobic oxidation of CH₄ to organic carbon pools; for all cores δ¹³C values of pore water dissolved organic carbon and sediment organic carbon averaged −24.4‰ and −22.1‰, respectively. Anaerobic oxidation of CH₄ contributed to pore water and sediment organic carbon near the ridge as evidenced by carbon isotope values as low as to −42.8‰ and −24.7‰, respectively. Carbon concentration and isotope analyses distinguished contributions from CH₄ and phytodetrital carbon sources across the ridge and show a low methane contribution to organic carbon. Full article

(This article belongs to the Special Issue Coastal Ocean Natural Gas Hydrate 2014)

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2515 KiB

Open AccessArticle

Numerical Investigation of Hydrate Dissociation Performance in the South China Sea with Different Horizontal Well Configurations

by Jing-Chun Feng, Xiao-Sen Li, Gang Li, Bo Li, Zhao-Yang Chen and Yi Wang

Energies 2014, 7(8), 4813-4834; https://doi.org/10.3390/en7084813 - 28 Jul 2014

Cited by 53 | Viewed by 8737

Abstract

Based on the available measurement data and literature on the hydrate deposits of the South China Sea, a numerical simulation with a new dual horizontal well system has been carried out. Warm brine stimulation combined with depressurization is employed as the production method. Two horizontal wells were situated in the same horizontal plane and they were placed in the middle of the Hydrate-Bearing Layer (HBL). The warm brine is injected from the left well (LW) into the reservoir, and the right well (RW) acted as the producer under constant pressure. The simulation results show that the effects of hydrate dissociation rate, gas to water ratio, and energy ratio are all better than the previous work in which the dual horizontal wells are placed in the same vertical plane. In addition, the sensitivity analysis indicates that a higher injection rate can enhance the hydrate dissociation rate and gas production rate, while a lower injection rate gives a more favorable gas to water ratio and energy ratio. Full article

(This article belongs to the Special Issue Coastal Ocean Natural Gas Hydrate 2014)

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832 KiB

Open AccessArticle

Gas Hydrate Occurrence Inferred from Dissolved Cl⁻ Concentrations and δ¹⁸O Values of Pore Water and Dissolved Sulfate in the Shallow Sediments of the Pockmark Field in Southwestern Xisha Uplift, Northern South China Sea

by Min Luo, Linying Chen, Hongpeng Tong, Wen Yan and Duofu Chen

Energies 2014, 7(6), 3886-3899; https://doi.org/10.3390/en7063886 - 20 Jun 2014

Cited by 16 | Viewed by 42198

Abstract

Deep-water pockmarks are frequently accompanied by the occurrence of massive gas hydrates in shallow sediments. A decline in pore-water Cl⁻ concentration and rise in δ¹⁸O value provide compelling evidence for the gas hydrate dissociation. Mega-pockmarks are widely scattered in the southwestern Xisha Uplift, northern South China Sea (SCS). Pore water collected from a gravity-core inside of a mega-pockmark exhibits a downward Cl⁻ concentration decrease concomitant with an increase in δ¹⁸O value at the interval of 5.7–6.7 mbsf. Concentrations of Cl⁻, Na⁺, and K⁺ mainly cluster along the seawater freshening line without distinct Na⁺ enrichment and K⁺ depletion. Thus, we infer that the pore water anomalies of Cl⁻ concentrations and δ¹⁸O values are attributed to gas hydrate dissociation instead of clay mineral dehydration. Moreover, the lower δ¹⁸O values of sulfate in the target core (C14) than those in the reference core (C9) may be associated with the equilibrium oxygen fractionation during sulfate reduction between sulfate and the relatively ¹⁸O-depleted ambient water resulting from gas hydrate formation. The gas hydrate contents are estimated to be 6%–10% and 7%–15%, respectively, according to the offset of Cl⁻ concentrations and δ¹⁸O values from the baselines. This pockmark field in southwestern Xisha Uplift is likely to be a good prospective area for the occurrence of gas hydrate in shallow sediments. Full article

(This article belongs to the Special Issue Coastal Ocean Natural Gas Hydrate 2014)

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Review

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351 KiB

Open AccessReview

Is the Surface of Gas Hydrates Dry?

by Nobuo Maeda

Energies 2015, 8(6), 5361-5369; https://doi.org/10.3390/en8065361 - 4 Jun 2015

Cited by 18 | Viewed by 5591

Abstract

Adhesion (cohesion) and agglomeration properties of gas hydrate particles have been a key to hydrate management in flow assurance in natural gas pipelines. Despite its importance, the relevant data in the area, such as the surface energy and the interfacial energy of gas hydrates with gas and/or water, are scarce; presumably due to the experimental difficulties involved in the measurements. Here we review what is known about the surface energy and the interfacial energy of gas hydrates to date. In particular, we ask a question as to whether pre-melting can occur on the surface of gas hydrates. Surface thermodynamic analyses show that pre-melting is favoured to occur on the surface of gas hydrates, however, not sufficient data are available to assess its thickness. The effects of the existence of pre-melting layers on the cohesion and friction forces between gas hydrate particles are also discussed. Full article

(This article belongs to the Special Issue Coastal Ocean Natural Gas Hydrate 2014)

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