scholarly journals Acoustic evidence for shallow gas and seabed classification along selected ship tracks on the deep-water margin of the Grand Banks of Newfoundland

2000 ◽  
Author(s):  
G D M Cameron ◽  
D J W Piper
Keyword(s):  
Deep Water ◽  
Shallow Gas ◽  
Grand Banks ◽  
Seabed Classification ◽  
Ship Tracks ◽  
Water Margin

scholarly journals Logs of short push cores, deep-water margin of Flemish Cap and the eastern Grand Banks of Newfoundland

2014 ◽  
Author(s):  
J Weitzman ◽  
S Ledger ◽  
C D Stacey ◽  
G Strathdee ◽  
D J W Piper ◽  
...  
Keyword(s):  
Deep Water ◽  
Grand Banks ◽  
Water Margin

scholarly journals Distribution of deep-water corals of the Flemish Cap, Flemish Pass, and the Grand Banks of Newfoundland (Northwest Atlantic Ocean): interaction with fishing activities

2010 ◽  
Vol 68 (2) ◽  
pp. 319-332 ◽  
Author(s):  
F. J. Murillo ◽  
P. Durán Muñoz ◽  
A. Altuna ◽  
A. Serrano
Keyword(s):  
Atlantic Ocean ◽  
Continental Slope ◽  
Deep Water ◽  
Coral Species ◽  
Habitat Mapping ◽  
Bottom Trawl ◽  
Soft Corals ◽  
Northwest Atlantic ◽  
Grand Banks ◽  
Black Corals

Abstract Murillo, F. J., Durán Muñoz, P., Altuna, A., and Serrano, A. 2011. Distribution of deep-water corals of the Flemish Cap, Flemish Pass, and the Grand Banks of Newfoundland (Northwest Atlantic Ocean): interaction with fishing activities. – ICES Journal of Marine Science, 68: 319–332. The distribution of deep-water corals of the Flemish Cap, Flemish Pass, and the Grand Banks of Newfoundland is described based on bycatch from Spanish/EU bottom trawl groundfish surveys between 40 and 1500 m depth. In all, 37 taxa of deep-water corals were identified in the study area: 21 alcyonaceans (including the gorgonians), 11 pennatulaceans, 2 solitary scleractinians, and 3 antipatharians. The greatest diversity of coral species was on the Flemish Cap. Corals were most abundant along the continental slope, between 600 and 1300 m depth. Soft corals (alcyonaceans), sea fans (gorgonians), and black corals (antipatharians) were most common on bedrock or gravel, whereas sea pens (pennatulaceans) and cup corals (solitary scleractinians) were found primarily on mud. The biomass of deep-water corals in the bycatches was highest in previously lightly trawled or untrawled areas, and generally low in the regularly fished grounds. The information derived from bottom-trawl bycatch records is not sufficient to map vulnerable marine ecosystems (VMEs) accurately, but pending more detailed habitat mapping, it provides a valuable indication of the presence/absence of VMEs that can be used to propose the candidate areas for bottom fishery closures or other conservation measures.

Geotechnical sampling in deep water using a tensioned conductor pipe-casing and weighted footblock

1984 ◽  
Vol 21 (1) ◽  
pp. 92-99
Author(s):  
H. T. Yan
Keyword(s):  
Deep Water ◽  
Concrete Block ◽  
Vertical Movement ◽  
The Self ◽  
Wave Forces ◽  
Secondary Effects ◽  
Marine Riser ◽  
Grand Banks ◽  
Riser Pipe ◽  
Axial Tension

A drilling system is described for geotechnical exploration and soil sampling in the seabed, modelled after the concept of the marine riser pipe. The system derives its stability from a "tensioning weight," in the form of a cylindrical concrete block at the bottom, which keeps the conductor pipe in tension at all times. The axial tension from the tensioning weight and the self-weight of the conductor pipe substantially reduce the bending effects in the conductor pipe resulting from current and wave forces, as well as from the drift of the drilling vessel. The lateral reaction required to keep the pipe in place at the sea floor is provided by a concrete footblock. The bottom end of the conductor pipe slides into the footblock, which has a doughnut-shaped cross section that allows for the vertical movement or heave of the drilling vessel. The Hermitian equation is used to solve for the secondary effects due to the deformation of the flexible conductor under wave or current forces and the self-weight of the conductor pipe. The system has been used successfully on the Grand Banks in 122 m of water. Keywords: geotechnical exploration, sampling, deep water drilling, marine riser analogy, tensioning weight.

Methane emissions from abandoned offshore wells– First data from a 2019 research cruise to the Dogger Bank, German North Sea

2020 ◽  
Author(s):  
Martin Blumenberg ◽  
Stefan Schlömer ◽  
Miriam Römer ◽  
Katja Heeschen ◽  
Hendrik Müller ◽  
...  
Keyword(s):  
Water Column ◽  
North Sea ◽  
Water Depth ◽  
Deep Water ◽  
Carbon Dioxide Emissions ◽  
Oil And Gas ◽  
Methane Emissions ◽  
Shallow Gas ◽  
Dogger Bank ◽  
Central North Sea

<p>Methane is the second most important greenhouse gas and, considering a period of 100 years, has a more than 30 times higher “global warming potential” than carbon dioxide. Emissions from the production, storage, distribution and use of fossil energy resources in recent years sum up to about 15 % of global methane emissions with numbers still being under discussion and topic of numerous research programs.</p><p>Abandoned oil and gas wells are one of the sources of methane from the oil and gas sector. Recent studies found escaping methane at selected abandoned drill holes in the central North Sea. Assuming this would hold for one third of the ~11.000 wells in the region, the process would introduce significant amounts of methane at shallow water depth. Interestingly, the collected methane was of biogenic rather than thermogenic origin, potentially escaping from shallow gas pockets. Likely, this methane was mobilized by mechanical disturbance of the sediments through the drilling operation and the well section has served as a pathway thereafter. However, little is known about the number of wells affected and the relevance for the amounts of methane realeased.</p><p>During a research cruise with the German research vessel Heincke in July, 2019, we studied seafloor characteristics, water column anomalies and sediment methane geochemistry and further inspected visually nine abandoned well sites at ~40 m water depth in the German sector of the central North Sea (Dogger Bank). The cruise targeted different situations, including known seeps in the Dutch part of the Dogger Bank, well sites of different ages and an area where abandoned wells penetrate shallow gas pockets. First data demonstrate that at none of the studied sites concentrations of dissolved methane were enriched in the upper water column. For most sites, sediment and deep water methane data demonstrate concentrations in the range known as background for that area (i.e., deep water methane close to ~ 10 nM). At one site with high indications for the presence of shallow gas pockets, we observed methane abundances several times enriched compared to background. However, the enrichments also occurred 500 m away from the drill site and did not increase towards the center. Based on our data we argue for an active natural seep situation rather than a leaking well and underline that natural seeps may challenge the identification of potentially leaking wells.</p>

Surficial sediment failures due to the 1929 Grand Banks Earthquake, St Pierre Slope

2018 ◽  
Vol 477 (1) ◽  
pp. 583-596 ◽  
Author(s):  
Irena Schulten ◽  
David C. Mosher ◽  
Sebastian Krastel ◽  
David J. W. Piper ◽  
Markus Kienast
Keyword(s):  
Deep Water ◽  
Slope Failure ◽  
Turbidity Current ◽  
Surficial Sediment ◽  
Grand Banks ◽  
Swath Bathymetry ◽  
Sediment Mass ◽  
Total Failure ◽  
Fault Scarps ◽  
Sediment Failure

AbstractA Mw 7.2 earthquake centred beneath the upper Laurentian Fan of the SW Newfoundland continental slope triggered a damaging turbidity current and tsunami on 18 November 1929. The turbidity current broke telecommunication cables, and the tsunami killed 28 people and caused major infrastructure damage along the south coast of Newfoundland. Both events are believed to have been derived from sediment mass failure as a result of the earthquake. This study aims to identify the volume and kinematics of the 1929 slope failure in order to understand the geohazard potential of this style of sediment failure. Ultra-high-resolution seismic reflection and multibeam swath bathymetry data are used to determine: (1) the dimension of the failure area; (2) the thickness and volume of failed sediment; (3) fault patterns and displacements; and (4) styles of sediment failure. The total failure area at St Pierre Slope is estimated to be 5200 km2, recognized by escarpments, debris fields and eroded zones on the seafloor. Escarpments are typically 20–100 m high, suggesting failed sediment consisted of this uppermost portion of the sediment column. Landslide deposits consist mostly of debris flows with evidence of translational, retrogressive sliding in deeper water (>1700 m) and evidence of instantaneous sediment failure along fault scarps in shallower water (730–1300 m). Two failure mechanisms therefore seem to be involved in the 1929 submarine landslide: faulting and translation. The main surficial sediment failure concentrated along the deep-water escarpments consisted of widely distributed, translational, retrogressive failure that liquefied to become a debris flow and rapidly evolved into a massive channelized turbidity current. Although most of the surficial failures occurred at these deeper head scarps, their deep-water location and retrogressive nature make them an unlikely main contributor to the tsunami generation. The localized fault scarps in shallower water are a more likely candidate for the generation of the tsunami, but further research is needed in order to address the characteristics of these fault scarps.

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