Cascadia margin gas hydrates

Collett, T. S.; Riedel, Michael; Malone, Mitchell J

doi:10.2204/iodp.sp.311.2005

Cited by 20 publications

(12 citation statements)

References 24 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, shallow (Figure 2). At the same time, like other gas hydrate locations, the increasing ratios of Mg 2+ /Ca 2+ and Sr 2+ /Ca 2+ manifest calcite precipitation is the most important process in shallow sediments [52,53] (Figure 4). SMI depths, relative high sulfate flux and high I flux, and obvious carbonate precipitation within shallow sediments in the Shenhu area indicate intensive microorganism activities in shallow sediments and fluids upwelling from depths.…”

Section: Discussionmentioning

confidence: 80%

“…At the same time, like other gas hydrate locations, the increasing ratios of Mg 2+ /Ca 2+ and Sr 2+ /Ca 2+ manifest calcite precipitation is the most important process in shallow sediments [52,53] (Figure 4). …”

Section: Precipitation Of Authigenic Carbonatesmentioning

confidence: 80%

“…Negative abnormity of Ca 2+ , Mg 2+ and Sr 2+ in pore water has been proved to be caused by carbonate precipitation in sites 995 and 997 of ODP 164 and sites 1325 and 1326 of IODP 311 [52,53]. In the sulfate reduction zone, Ca 2+ , Mg 2+ and Sr 2+ concentrations have similar trend with that of SO 2− 4 , due to carbonate formation caused by reaction between cations and DIC released by AMO process.…”

Section: Precipitation Of Authigenic Carbonatesmentioning

confidence: 92%

See 2 more Smart Citations

Geochemical characteristics of pore water in shallow sediments from Shenhu area of South China Sea and their significance for gas hydrate occurrence

Yang

Jiang

et al. 2009

Chin. Sci. Bull.

View full text Add to dashboard Cite

The Shenhu area is one of the promise target areas for marine gas hydrate exploration in the northern margin of the South China Sea. Pore water samples were collected from two piston cores (8.75 and 8.52 m) in site HS-A and site HS-B in the Shenhu area, and their major anion and cation contents and trace element contents have been analyzed in this study. Cl − concentrations in pore waters are similar to the seawater value and no systematic change along depth profiles has been found for the Cl − content in both sites. In site HS-A, the SO 2− 4 contents show a limited range in pore waters from 0 to 3 m depths, but a dramatic decrease is documented in depth below 3 m. Other elements such as Ca 2+ , Mg 2+ and Sr 2+ show similar variation patterns as the SO 2− 4 , i.e., no variation in 0−3 m, but large decrease in depth below 3 m. In site HS-B, both the SO 4 and Ca 2+ , Mg 2+ and Sr 2+ display a decrease pattern along the depth profile, but in 0−3 m the variation is less significant than those in depth below 3 m. In both sites HS-A and HS-B, I contents show a dramatic increase along depth profiles. Calculations show that the SMI depths are very shallow (10 and 11 m) in both sites, and the sulfate flux and I flux are very high. These geochemical characteristics and anomalies at Shenhu are quite similar to those found in other gas hydrate locations in the world, and a genetic link is suggested to be related to the gas hydrate occurrence at depths in the study area. In summary, we suggest that combined geochemical parameters in shallow sediment pore waters are useful indicators to indicate the gas hydrate occurrence at depths. gas hydrate, pore water, sulfate flux, iodine flux, Shenhu area in South China Sea Citation: Yang T, Jiang S Y, Ge L, et al. Geochemical characteristics of pore water in shallow sediments from Shenhu area of South China Sea and their significance for gas hydrate occurrence.Gas hydrate is an ice-like crystalline substance composed of cages, which are predominantly of water and nature gas. Gas hydrate occurs both in polar region and in offshore deep-water marine sediments under conditions of lowtemperature, high-pressure and adequate methane concentrations [1,2]. Natural gas hydrate was first recognized in the middle 1960s, on land in Arctic conditions [3]. In the early 1970s, natural gas hydrate was drilled on the Blake Ridge [4]. Since then, gas hydrate has received great attention in the international community. Up to now, gas hydrate reserves were found in more than 220 areas in the world. Among them, most of these reserves are recognized by Bottom Simulating Reflector (BSR) and gas hydrates samples were directly sampled from more than 40 locations [5]. Gas hydrate has been identified in nature occurrence generally by inference from the evidence including geological, geophysical, geochemical data, deep-sea video recording and drilling. By geochemical investigation of gas hydrate samples, marine sediments and pore water, we have gained great knowledge in gas hydrate compositions,

show abstract

Section: Discussionmentioning

confidence: 80%

Section: Precipitation Of Authigenic Carbonatesmentioning

confidence: 80%

Section: Precipitation Of Authigenic Carbonatesmentioning

confidence: 92%

See 1 more Smart Citation

Geochemical characteristics of pore water in shallow sediments from Shenhu area of South China Sea and their significance for gas hydrate occurrence

Yang

Jiang

et al. 2009

Chin. Sci. Bull.

View full text Add to dashboard Cite

show abstract

“…The purpose of this newly installed system is to monitor the gas‐hydrate deposits known to be present in the area (see Mir 2011). Collett et al . (2005) and Riedel et al .…”

Section: Introductionmentioning

confidence: 99%

The marine controlled source electromagnetic response of a steel borehole casing: applications for the NEPTUNE Canada gas hydrate observatory

Swidinsky¹,

Edwards²,

Jegen³

2013

Geophysical Prospecting

View full text Add to dashboard Cite

Gas hydrates are a potential energy resource, a possible factor in climate change and an exploration geohazard. The University of Toronto has deployed a permanent seafloor time‐domain controlled source electromagnetic (CSEM) system offshore Vancouver Island, within the framework of the NEPTUNE Canada underwater cabled observatory. Hydrates are known to be present in the area and due to their electrically resistive nature can be monitored by 5 permanent electric field receivers. However, two cased boreholes may be drilled near the CSEM site in the near future. To understand any potential distortions of the electric fields due to the metal, we model the marine electromagnetic response of a conductive steel borehole casing. First, we consider the commonly used canonical model consisting of a 100 Ωm, 100 m thick resistive hydrocarbon layer embedded at a depth of 1000 m in a 1 Ωm conductive host medium, with the addition of a typical steel production casing extending from the seafloor to the resistive zone. Results show that in both the frequency and time domains the distortion produced by the casing occurs at smaller transmitter‐receiver offsets than the offsets required to detect the resistive layer. Second, we consider the experimentally determined model of the offshore Vancouver Island hydrate zone, consisting of a 5.5 Ωm, 36 m thick hydrate layer overlying a 0.7 Ωm sedimentary half‐space, with the addition of two borehole casings extending 300 m into the seafloor. In this case, results show that the distortion produced by casings located within a 100 m safety zone of the CSEM system will be measured at 4 of the 5 receivers. We conclude that the boreholes must be positioned at least 200 m away from the CSEM array so as to minimize the effects of the casings.

show abstract

“…Site U1329 (proposed Site CAS-05D; Collett et al, 2005) is at the easternmost end of the southwest-northeast-trending, marginperpendicular transect of sites drilled during Integrated Ocean Drilling Program (IODP) Expedition 311 and is located closest to shore (65 km) at a water depth of 946 m. Newly acquired bathymetry data showed that this site is located in an area characterized by multiple canyons of various sizes where water depth decreases rapidly from 500 to 1300 m over a distance of only 7.5 km with an average slope of 6° (Figs. F3 and F4 in the "Expedition 311 summary" chapter).…”

Section: Background and Objectivesmentioning

confidence: 99%

Site U1329

2006

Proceedings of the IODP, 311

View full text Add to dashboard Cite

Expedition 311 Scientists Site U1329 We divide the 187.5 m thick sedimentary section recovered at Site U1329 into three lithostratigraphic units (Fig. F7) based on visual inspection of the recovered cores and analysis of smear slides. Other parameters, such as mineralogy data from X-ray diffraction (XRD) analyses, helped to better define the entire stratigraphic section. Results were also compared and correlated with two-dimensional seismic data, downhole LWD/MWD data, physical property measurements, and color reflectance spectrophotometry from the archive multisensor track.

show abstract

Cascadia margin gas hydrates

Cited by 20 publications

References 24 publications

Geochemical characteristics of pore water in shallow sediments from Shenhu area of South China Sea and their significance for gas hydrate occurrence

Geochemical characteristics of pore water in shallow sediments from Shenhu area of South China Sea and their significance for gas hydrate occurrence

The marine controlled source electromagnetic response of a steel borehole casing: applications for the NEPTUNE Canada gas hydrate observatory

Site U1329

Contact Info

Product

Resources

About