Multiple resolution seismic imaging of a shallow hydrocarbon plumbing system, Woolsey Mound, Northern Gulf of Mexico

Macelloni, Leonardo; Simonetti, Antonello; Knapp, J. H.; Knapp, C. C.; Lutken, Carol; Lapham, L.

doi:10.1016/j.marpetgeo.2012.06.010

Cited by 41 publications

(59 citation statements)

References 14 publications

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“…Combining evidence from subsurface studies with seafloor surface observations, Macelloni et al, (2013) developed the conceptual model of the Woolsey Mound shown in Figure 3; this graphic portrays a multi-attributes (geology, biology, geochemistry, etc.) transect through the mound, and includes the three crater complexes.…”

Section: Previous Work At Woolsey Moundmentioning

confidence: 99%

“…The shallower, BS-2, may mark the base of the HSZ and be directly related to the seafloor venting which varies at each complex. Differences in the spatial distribution of bio-geological processes reflect the responses of the biota to different fluid flux regimes [after Lutken et al, 2011b;Macelloni et al, 2013]. Three mechanisms have been recognized: gas dominated fluid flux at the NW Complex, steady fluid flux at the SW Complex, and hydrate dominated fluid flux at the SE Complex [modified from Macelloni et al, 2013].…”

Section: Heat-flow Surveymentioning

confidence: 99%

“…Smith et al, 2014) flow from depth up the master faults, progressing through secondary and tertiary faults and fault zones and eventually through the overlying, surficial sediments. Vertical flow is more easily accomplished than lateral and the many small vertical and near-vertical faults in the vicinity of the Woolsey Mound that are clearly imaged on multiple resolution data datasets Macelloni et al, 2012;Simonetti et al, 2013] provide accessible pathways for fluids to migrate vertically. In the case of the heat-flow measured across the magenta fault (see Fig.…”

Section: Woolsey Mound Heat-flowmentioning

confidence: 99%

“…In Figure 7, the subsurface model of Woolsey Mound, as presented by Macelloni et al, [2013], has been integrated with the depth of the base of the hydrate stability zone for cases 3, and 6 as calculated in the section, Computation of BHSZ. The two depths represent, respectively, the base of the stability zone assuming pure methane and Woolsey Mound solid hydrates compositions from a sample recovered during a dive of the Johnson SeaLink in 2002 (Sassen et al, 2006).…”

Section: Dynamics Of the Hydrate Stability Zonementioning

confidence: 99%

“…We have computed the base of the hydrates stability field integrating the results from a high resolution in situ heat-flow survey that was specifically designed to investigate the geothermal regime along active fault zones where previous studies have recognized different fluid flux regimes [Lapham et al, 2008;Macelloni et al, 2013]. Furthermore, a "compositional" simulator, was developed especially to model the hydrate formation/dissociation of Structure II hydrates (formed by molecules heavier than methane).…”

Section: Introductionmentioning

confidence: 99%

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Heat-flow regimes and the hydrate stability zone of a transient, thermogenic, fault-controlled hydrate system (Woolsey Mound northern Gulf of Mexico)

Macelloni

Lutken

Garg

et al. 2015

Marine and Petroleum Geology

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a b s t r a c tThis study aims to constrain the base of the hydrates stability field in structurally complexsites using the case of Woolsey Mound, a fault-controlled, transient, thermogenic hydrates system, in Mississippi Canyon Block 118, northern Gulf of Mexico. We have computed the base of the hydrates stability field integrating results from a recent heat-flow survey, designed to investigate geothermal anomalies along fault zones which exhibit different fluid flux regimes. An advanced "compositional" simulator was used to model hydrate formation and dissociation at Woolsey Mound and addresses the following hypotheses:1. Migrating thermogenic fluids alter thermal conditions of the Hydrate Stability Zone (HSZ), so heat-flow reflects fault activity; 2. Gas hydrate formation and dissociation vary temporally at active faults, temporarily sealing conduits for migration of thermogenic fluids; 3. High salinity and inclusion of thermogenic gases with higher molecular weight than methane produce opposite effects on the depth to the bottom of the hydrate stability zone.Applications of results include identifying and quantifying hydrate deposits in shallow sediments using an interdisciplinary approach that includes multiple resolution seismic data evaluation, geological and geochemical groundtruthing and heat-flow analyses as a proxy for activity along faults.

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Section: Previous Work At Woolsey Moundmentioning

confidence: 99%

Section: Heat-flow Surveymentioning

confidence: 99%

Section: Woolsey Mound Heat-flowmentioning

confidence: 99%

Section: Dynamics Of the Hydrate Stability Zonementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Heat-flow regimes and the hydrate stability zone of a transient, thermogenic, fault-controlled hydrate system (Woolsey Mound northern Gulf of Mexico)

Macelloni

Lutken

Garg

et al. 2015

Marine and Petroleum Geology

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Subsurface methane sources and migration pathways within a gas hydrate mound system, Gulf of Mexico

Wilson

Macelloni

Simonetti

et al. 2014

Geochem Geophys Geosyst

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[1] Geochemical profiles were coupled with seismic information to examine subsurface hydrocarbon source, migration, and fate at a Gulf of Mexico carbonate-gas hydrate mound (Woolsey Mound). Three seafloor features were investigated in detail: (1) major faults resulting from a rising salt body, (2) an acoustic backscatter anomaly, and (3) a pockmark associated with a major fault. We analyzed sulfate, chloride, dissolved inorganic carbon, and hydrocarbon concentrations, and carbon isotopes in pore water extracted from 20 m piston cores to characterize gas source and calculate methane flux. Dissolved biogenic methane dominated the off-fault sites, while the contribution of thermogenic methane increased near a major fault where thermogenic gas hydrates were recovered. Within the pockmark, methane concentrations were low and isotopes indicated a biogenic source. Since pockmarks are typically formed from expulsive fluid flow, this suggests that either the pockmark is the legacy of a conduit that has become plugged or that the expulsed fluid is confined within the fault walls. At the acoustic anomaly,

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Focused hydrocarbon‐migration in shallow sediments of a pockmark cluster in the Niger Delta (Off Nigeria)

Prunelé

Ruffine

Riboulot

et al. 2017

Geochem Geophys Geosyst

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The Niger Delta is one of the largest hydrocarbon basin offshore Africa and it is well known for the presence of active pockmarks on the seabed. During the Guineco-MeBo cruise in 2011, long cores were taken from a pockmark cluster in order to investigate the state of its current activity. Gas hydrates, oil, and pore-water were sampled for geochemical studies. The resulting dataset combined with seismic data reveal that shallow hydrocarbon migration in the upper sedimentary section was focused exclusively within the pockmarks. There is a clear tendency for gas migration within the hydrate-bearing pockmarks, and oil migration within the carbonate-rich one. This trend is interpreted as a consequence of hydrate dissolution followed by carbonate precipitation in the course of the evolution of these pockmarks. We also demonstrate that Anaerobic Oxidation of Methane (AOM) is the main process responsible for the depletion of pore-water sulfate, with depths of the Sulfate-Methane Transition Zone (SMTZ) ranging between 1.8 and 33.4 m. In addition, a numerical transport-reaction model was used to estimate the age of hydrate-layer formation from the present-day sulfate profiles. The results show that the sampled hydrate-layers were formed between 21 and 3750 years before present. Overall, this work shows the importance of fluid flow on the dynamics of pockmarks, and the investigated cluster offers new opportunities for future cross-site comparison studies. Our results imply that sudden discharges of gas can create hydrate layers within the upper sedimentary column which can affect the seafloor morphology over few decades. Key Points:Seismic surveys and geochemical analyses were combined to study a cluster of hydrate-bearing pockmarks The pockmark dynamics is governed by fluid flow Sulfate-profile simulation allowed estimating the formation age of four selected hydrate layers Supporting Information:Supporting Information S1Correspondence to: L. Ruffine, livio.ruffine@ifremer.fr Citation:de Prunel e, A., et al. (2017), Focused hydrocarbon-migration in shallow sediments of a pockmark cluster in the

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Multiple resolution seismic imaging of a shallow hydrocarbon plumbing system, Woolsey Mound, Northern Gulf of Mexico

Cited by 41 publications

References 14 publications

Heat-flow regimes and the hydrate stability zone of a transient, thermogenic, fault-controlled hydrate system (Woolsey Mound northern Gulf of Mexico)

Heat-flow regimes and the hydrate stability zone of a transient, thermogenic, fault-controlled hydrate system (Woolsey Mound northern Gulf of Mexico)

Subsurface methane sources and migration pathways within a gas hydrate mound system, Gulf of Mexico

Focused hydrocarbon‐migration in shallow sediments of a pockmark cluster in the Niger Delta (Off Nigeria)

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