Time series video analysis of bubble release processes at natural hydrocarbon seeps in the Northern Gulf of Mexico

Johansen, C.; Todd, Austin C.; MacDonald, Ian R.

doi:10.1016/j.marpetgeo.2017.01.014

Cited by 43 publications

(45 citation statements)

References 61 publications

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“…In the northern GOM, gas seeping from the seafloor quantified by use of video time-lapse cameras (Johansen et al, 2017) and stereoscopic high-speed cameras (Wang et al, 2016) revealed gas bubble volume rates similar to those determined for the TYK in this study. Estimated gas bubble volume flows at four emission sites in the northern GOM ranged between 13 and 300 mL/min (Wang et al, 2016).…”

Section: Amounts Of Hydrocarbons Released At Tyksupporting

confidence: 80%

Amount and Fate of Gas and Oil Discharged at 3400 m Water Depth From a Natural Seep Site in the Southern Gulf of Mexico

et al. 2019

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This multidisciplinary study of the hydrocarbon seepage system at Tsanyao Yang Knoll (TYK) in the southern Gulf of Mexico illustrates the amount and fate of hydrocarbons (mainly oil and methane) emanating from the seafloor structure and rising through a 3400 m water column. TYK forms part of the Campeche Knolls and was found to be one of the most active seepage structures at such an exceptional depth. Combining ship-based and AUV-based hydroacoustic mapping with direct seafloor observations and investigations, which used a TV-sled and a remotely operated vehicle with gas and water sampling devices provided an integrated view for the various transport pathways of hydrocarbons from the seafloor to the sea surface. In total, 32 acoustic 'flares,' indicative of gas bubble emission sites, were detected emanating from depressions on top of the knoll. Most of the emission sites were concentrated in two depressions that comprised a main seep field. An estimated volume of 550-4650 L of hydrocarbons per hour (or 8300-70,600 mol CH 4 per hour) are released in the form of gas bubbles, which dissolve almost entirely during their rise in the water column. However, echograms showed gas anomalies to about 500 m below sea surface and some bubbles were seen to burst at the sea surface. Concentrations of dissolved methane were highly elevated (∼30,000 nmol/L) directly above the seafloor emission site, but decreased to background concentrations (3-5 nmol/L) within the lowermost 100 m. Smaller volume flow rates of oil also escaped from the seafloor, rose to the sea surface and generated natural oil slicks visible from the ship and in satellite images. This study shows that hydrocarbon seepage at ∼3400 m water depth can be followed to the sea surface. However, most of the methane dissolves in deeper waters, whereas oil reaches the sea surface.

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Section: Amounts Of Hydrocarbons Released At Tyksupporting

confidence: 80%

Amount and Fate of Gas and Oil Discharged at 3400 m Water Depth From a Natural Seep Site in the Southern Gulf of Mexico

et al. 2019

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“…• Even if pockmarks corresponds to the seafloor expression of a focused fluid flow (King and MacLean, 1970), oil can emit from discrete sources outwards of the main fluid conduit Gay et al, 2007;Johansen et al, 2017). Moreover, seafloor emission outlets are subjected to spatio-temporal evolution within seafloor seeps features (Gay et al, 2006a).…”

Section: Accuracy Of the Modelmentioning

confidence: 99%

Deflection of natural oil droplets through the water column in deep-water environments: The case of the Lower Congo Basin

Jatiault

Dhont

Loncke

et al. 2018

Deep Sea Research Part I: Oceanographic Research Papers

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A B S T R A C TNumerous recurrent seep sites were identified in the deep-water environment of the Lower Congo Basin from the analysis of an extensive dataset of satellite-based synthetic-aperture radar images. The integration of current data was used to link natural oil slicks with active seep-related seafloor features. Acoustic Doppler current profiler measurements across the water column provided an efficient means to evaluate the horizontal deflection of oil droplets rising through the water column. Eulerian propagation model based on a range of potential ascension velocities helped to approximate the path for rising oil plume through the water column using two complementary methods. The first method consisted in simulating the reversed trajectory of oil droplets between sea-surface oil slick locations observed during current measurements and seep-related seafloor features while considering a range of ascension velocities. The second method compared the spatial spreading of natural oil slicks from 21 years of satellite monitoring observations for water depths ranging from 1200 to 2700 m against the modeled deflections during the current measurement period. The mapped oil slick origins are restricted to a 2.5 km radius circle from associated seep-related seafloor features. The two methods converge towards a range of ascension velocities for oil droplets through the water column, estimated between 3 and 8 cm s −1 . The low deflection values validate that the sub-vertical projection of the average surface area of oil slicks at the sea surface can be used to identify the origin of expelled hydrocarbon from the seafloor, which expresses as specific seafloor disturbances (i.e. pockmarks or mounds) known to expel fluids. standing the hydrocarbon plumbing system (Serié et al., 2016). Pockmarks, which are local depressions on the seafloor associated with contemporary focused fluid flow (e.g. King and MacLean, 1970;Hovland and Judd, 1988), are widely recognized as the seafloor outlet of expelled fluids. Even if hydrocarbon migration across the water

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“…Regarding their activities and fluxes, compared with hydrothermal vents that vigorously eject high flux of "focused flow," macro-seeps are less active but efflux similarly focused flow of seep fluids via subsurface channels. Bubbles of methane gas are occasionally visible in water columns, for example, in the Eel River Basin, off northern California [36] and Northern Gulf of Mexico [37]. By contrast, mini-and micro-seeps slowly exhale "diffuse flow" through sediment matrix pores, and the slow flows are virtually invisible and not readily detectable.…”

Section: Migration and Seepage Of Methanementioning

confidence: 99%

Geo-Biological Coupling of Authigenic Carbonate Formation and Autotrophic Faunal Colonization at Deep-Sea Methane Seeps I: Geo-Biological Settings

Naganuma¹

2018

Marine Ecology - Biotic and Abiotic Interactions

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Methane (CH 4) in sub-seafloor sediment is generated both biologically and non-biologically from organic and inorganic sources. A major part of the sub-seafloor methane is oxidized before leakage via "anaerobic oxidation of methane" (AOM) in the subsurface. The AOM-survivor methane, which is relatively minor part of the subsurface methane, leaches to the overlying water column and is eventually subject to thorough anaerobic and aerobic oxidation in the water column. The AOM with sulfate results in the generation of carbon dioxide and sulfide; the former (CO 2) is incorporated into authigenic carbonate and autotrophic biomass, and the autotrophy is energetically driven by oxidation of the latter (H 2 S). These processes are typically observed at focused sites that are generally known as "methane seeps" or hydrocarbon seeps, or occasionally called as cold seeps in comparison with hydrothermal vents. Methane seeps are typically formed in passive and active continental margins, occasionally with unique features such as exposed methane hydrates, mud volcanoes, asphalt volcanoes, salt diapirs, and brine pools. Accordingly, authigenic carbonates and unique biological communities are shaped at respective methane seeps. This chapter overviews geological and biological setting for the formation of methane seeps associated with unique landscapes of carbonates and biomes.

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Time series video analysis of bubble release processes at natural hydrocarbon seeps in the Northern Gulf of Mexico

Cited by 43 publications

References 61 publications

Amount and Fate of Gas and Oil Discharged at 3400 m Water Depth From a Natural Seep Site in the Southern Gulf of Mexico

Amount and Fate of Gas and Oil Discharged at 3400 m Water Depth From a Natural Seep Site in the Southern Gulf of Mexico

Deflection of natural oil droplets through the water column in deep-water environments: The case of the Lower Congo Basin

Geo-Biological Coupling of Authigenic Carbonate Formation and Autotrophic Faunal Colonization at Deep-Sea Methane Seeps I: Geo-Biological Settings

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