Permafrost-associated natural gas hydrate occurrences on the Alaska North Slope

Collett, Timothy S.; Lee, Myung W.; Agena, W.F.; Miller, John J.; Lewis, Kristen A.; Zyrianova, Margarita V.; Boswell, Ray; Inks, Tanya L.

doi:10.1016/j.marpetgeo.2009.12.001

Cited by 221 publications

(208 citation statements)

References 24 publications

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“…These estimates agree with the final calculated S h values (65-75%) from well logs in the Mount Elbert well (Collett et al, 2011a;. Another ''B'' sand unit, located from 756.2 m to 810.7 m was successfully predicted to be completely waterbearing, containing no gas hydrate.…”

Section: Geologic Setting and Gas Hydrate Presencesupporting

confidence: 76%

“…However, the condition of the borehole greatly affects log quality. A number of excellent well logs were obtained as part of the Mount Elbert field program due in part to the use of chilled drilling mud Collett et al, 2011a). Gas-hydrate saturation levels are consistent between different logs, indicating that hydrate saturation reaches about 65% to 75% in the hydrate reservoirs (Collett et al, 2011a;.…”

Section: Introductionmentioning

confidence: 99%

“…A number of excellent well logs were obtained as part of the Mount Elbert field program due in part to the use of chilled drilling mud Collett et al, 2011a). Gas-hydrate saturation levels are consistent between different logs, indicating that hydrate saturation reaches about 65% to 75% in the hydrate reservoirs (Collett et al, 2011a;. Although indirect well-log surveys provide valuable information, actual minimally disturbed physical specimens are required to provide quantifiable assessment of many reservoir properties (Dandekar, 2006).…”

Section: Introductionmentioning

confidence: 99%

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Physical properties of sediment from the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope

Winters

Walker

Hunter

et al. 2011

Marine and Petroleum Geology

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a b s t r a c tThis study characterizes cored and logged sedimentary strata from the February 2007 BP Exploration Alaska, Department of Energy, U.S. Geological Survey (BPXA-DOE-USGS) Mount Elbert Gas Hydrate Stratigraphic Test Well on the Alaska North Slope (ANS). The physical-properties program analyzed core samples recovered from the well, and in conjunction with downhole geophysical logs, produced an extensive dataset including grain size, water content, porosity, grain density, bulk density, permeability, X-ray diffraction (XRD) mineralogy, nuclear magnetic resonance (NMR), and petrography.This study documents the physical property interrelationships in the well and demonstrates their correlation with the occurrence of gas hydrate. Gas hydrate (GH) occurs in three unconsolidated, coarse silt to fine sand intervals within the Paleocene and Eocene beds of the Sagavanirktok Formation: Unit D-GH (614.4 m-627.9 m); unit C-GH1 (649.8 m-660.8 m); and unit C-GH2 (663.2 m-666.3 m). These intervals are overlain by fine to coarse silt intervals with greater clay content. A deeper interval (unit B) is similar lithologically to the gas-hydrate-bearing strata; however, it is water-saturated and contains no hydrate.In this system it appears that high sediment permeability (k) is critical to the formation of concentrated hydrate deposits. Intervals D-GH and C-GH1 have average ''plug'' intrinsic permeability to nitrogen values of 1700 mD and 675 mD, respectively. These values are in strong contrast with those of the overlying, gas-hydrate-free sediments, which have k values of 5.7 mD and 49 mD, respectively, and thus would have provided effective seals to trap free gas. The relation between permeability and porosity critically influences the occurrence of GH. For example, an average increase of 4% in porosity increases permeability by an order of magnitude, but the presence of a second fluid (e.g., methane from dissociating gas hydrate) in the reservoir reduces permeability by more than an order of magnitude.Published by Elsevier Ltd.

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Section: Geologic Setting and Gas Hydrate Presencesupporting

confidence: 76%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Physical properties of sediment from the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope

Winters

Walker

Hunter

et al. 2011

Marine and Petroleum Geology

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“…Bottom-simulating reflectors (BSRs) on seismic profiles generally mark the transition between overlying gas hydrate and underlying free gas (Holbrook et al, 1996;Pecher et al, 2001) and thereby imply high quantities of CH 4 in pore space (Dickens et al, 1997;Pecher et al, 2001). Such BSRs have been documented along the Alaska North Slope (Collett et al, 2010), within the Beaufort Sea (Grantz et al, 1976(Grantz et al, , 1982Weaver and Stewart, 1982;Hart et al, 2011;Phrampus et al, 2014), around Canadian Arctic islands (Hyndman and Dallimore, 2001;Majorowicz and Osadetz, 2001;Yamamoto and Dallimore, 2008), adjacent to Svalbard (Posewang and Mienert, 1999;Hustoft et al, 2009;Petersen et al, 2010), and within the Barents Sea (Løvø et al, 1990;Laberg and Andreassen, 1996;Laberg et al, 1998;Ostanin et al, 2013). Furthermore, Lorenson and Kvenvolden (1995) observed high CH 4 concentrations in shelf waters of the Beaufort Sea, and Shakhova et al (2010a, b) have documented CH 4 escape to the water column above the East Siberian shelf.…”

Section: Introductionmentioning

confidence: 90%

Pore water geochemistry along continental slopes north of the East Siberian Sea: inference of low methane concentrations

et al. 2017

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Abstract. Continental slopes north of the East Siberian Sea potentially hold large amounts of methane (CH 4 ) in sediments as gas hydrate and free gas. Although release of this CH 4 to the ocean and atmosphere has become a topic of discussion, the region remains sparingly explored. Here we present pore water chemistry results from 32 sediment cores taken during Leg 2 of the 2014 joint Swedish-Russian-US Arctic Ocean Investigation of Climate-Cryosphere-Carbon Interactions (SWERUS-C3) expedition. The cores come from depth transects across the slope and rise extending between the Mendeleev and the Lomonosov ridges, north of Wrangel Island and the New Siberian Islands, respectively. Upward CH 4 flux towards the seafloor, as inferred from profiles of dissolved sulfate (SO 2− 4 ), alkalinity, and the δ 13 C of dissolved inorganic carbon (DIC), is negligible at all stations east of 143 • E longitude. In the upper 8 m of these cores, downward SO 2− 4 flux never exceeds 6.2 mol m −2 kyr −1 , the upward alkalinity flux never exceeds 6.8 mol m −2 kyr −1 , and δ 13 C composition of DIC (δ 13 C-DIC) only moderately decreases with depth (−3.6 ‰ m −1 on average). Moreover, upon addition of Zn acetate to pore water samples, ZnS did not precipitate, indicating a lack of dissolved H 2 S. Phosphate, ammonium, and metal profiles reveal that metal oxide reduction by organic carbon dominates the geochemical environment and supports very low organic carbon turnover rates. A single core on the Lomonosov Ridge differs, as diffusive fluxes for SO 2− 4 and alkalinity were 13.9 and 11.3 mol m −2 kyr −1 , respectively, the δ 13 C-DIC gradient was 5.6 ‰ m −1 , and Mn 2+ reduction terminated within 1.3 m of the seafloor. These are among the first pore water results generated from this vast climatically sensitive region, and they imply that abundant CH 4 , including gas hydrates, do not characterize the East Siberian Sea slope or rise along the investigated depth transects. This contradicts previous modeling and discussions, which due to the lack of data are almost entirely based on assumption.

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“…4 On Earth today, permafrost covers a large proportion of highaltitude and high-latitude land in both hemispheres. 5 Gas hydrate is known to have accumulated in Arctic regions in association with the permafrost in western Siberia, Russia, 3 the Alaskan North Slope, the United States, 6 and the Mackenzie Delta, Canada. 7,8 In addition, gas hydrates have been found in the permafrost of the Qilian Mountains in the The gas hydrate system in the permafrost of the Qilian Mountains is considered an epigenetic hydrocarbon reservoir situated over a deep-seated hydrocarbon reservoir.…”

Section: Introductionmentioning

confidence: 99%

Effect of permafrost properties on gas hydrate petroleum system in the Qilian Mountains, Qinghai, Northwest China

Wang

Zhang

Zhu

et al. 2014

Environ. Sci.: Processes Impacts

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The gas hydrate petroleum system in the permafrost of the Qilian Mountains, which exists as an epigenetic hydrocarbon reservoir above a deep-seated hydrocarbon reservoir, has been dynamic since the end of the Late Pleistocene because of climate change. The permafrost limits the occurrence of gas hydrate reservoirs by changing the pressure-temperature (P-T) conditions, and it affects the migration of the underlying hydrocarbon gas because of its strong sealing ability. In this study, we reconstructed the permafrost structure of the Qilian Mountains using a combination of methods and measured methane permeability in ice-bearing sediment permafrost. A relationship between the ice saturation of permafrost and methane permeability was established, which permitted the quantitative evaluation of the sealing ability of permafrost with regard to methane migration. The test results showed that when ice saturation is >80%, methane gas can be completely sealed within the permafrost. Based on the permafrost properties and genesis of shallow gas, we suggest that a shallow "gas pool" occurred in the gas hydrate petroleum system in the Qilian Mountains. Its formation was related to a metastable gas hydrate reservoir controlled by the P-T conditions, sealing ability of the permafrost, fault system, and climatic warming.From an energy perspective, the increasing volume of the gas pool means that it will likely become a shallow gas resource available for exploitation; however, for the environment, the gas pool is an underground "time bomb" that is a potential source of greenhouse gas. Environmental impactThe gas hydrate petroleum system in the Qilian Mountains permafrost is an epigenetic hydrocarbon reservoir situated over a deep-seated hydrocarbon reservoir, which has been dynamic since the end of the Late Pleistocene because of climatic changes. The permafrost not only limits the occurrence of the gas hydrate reservoir by changing the P-T conditions, but also affects the migration of underlying hydrocarbon gas because of its strong sealing ability. This study established the relationship between permafrost ice saturation and methane permeability, which suggests that under the inuence of a warming climate, a shallow gas pool has formed in the Qilian Mountains gas hydrate petroleum system, because of the P-T conditions, sealing ability of permafrost, and the fault system.

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Permafrost-associated natural gas hydrate occurrences on the Alaska North Slope

Cited by 221 publications

References 24 publications

Physical properties of sediment from the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope

Physical properties of sediment from the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope

Pore water geochemistry along continental slopes north of the East Siberian Sea: inference of low methane concentrations

Effect of permafrost properties on gas hydrate petroleum system in the Qilian Mountains, Qinghai, Northwest China

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