A natural gas hydrate system on the Exmouth Plateau (NW shelf of Australia) sourced by thermogenic hydrocarbon leakage

Paganoni, M.; King, James J.; Foschi, Martino; Mellor-Jones, Katy; Cartwright, Joe

doi:10.1016/j.marpetgeo.2018.10.029

Cited by 19 publications

(11 citation statements)

References 108 publications

(75 reference statements)

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“…It should be noted that methane with an inferred biogenic origin was identified in well U1461 (Gallagher et al, 2017), then suggesting that shallow, biogenic methane may have also participated in pockmark and submarine landslide formation in Gorgon area. Additionally, in the deeper Carnarvon area (i.e., water depth of 680 m-930 m), an influence of gas hydrate cannot be totally excluded, as a natural gas hydrate system is reported at slightly deeper water depth in the adjacent Exmouth Plateau (Paganoni et al, 2019). This study, however, has found no specific indication of the presence of gas hydrates in the Carnarvon Pockmark Field area.…”

Section: Influence Of Gas On Landslide and Pockmark Formationcontrasting

confidence: 61%

“…There are, however, multiple indirect indications of the existence of gas seeps. Those indirect markers -identified through geochemistry, remote sensing, seismic interpretation and core description -were observed in the northern and southern part of the NWS (Logan et al, 2010), including, from North to South: (1) the Bonaparte Basin (Bishop et al, 1992); (2) the Browse Basin (O'Brien et al, 2005); and (3) the Northern Carnarvon Basin (Cowley, 2001;Paganoni et al, 2019). However, it is unknown if those seepages are active (i.e., driven by faulting) or passive (i.e., microseepage).…”

Section: Hydrocarbon Seepages and Pockmarks Along The Nwsmentioning

confidence: 99%

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Origin of seafloor pockmarks overlying submarine landslides: Insights from semi-automated mapping of 3D seismic horizons (North West Shelf, Australia)

Riera¹,

Paumard

Gail³

et al. 2022

Marine and Petroleum Geology

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Pockmarks are geohazards that can impact offshore developments, and an understanding of their formation assists in determination of their physical characteristics and in the prediction of their future behaviour. This study documents how the presence of submarine landslides -either on the seafloor or buried -can favour pockmark formation through the characterisation of two pockmark fields from the Australian North West Shelf. Analysis was carried out through an innovative workflow combining full-volume interpretation of exploration 3D seismic data and semi-automated mapping of seismic horizons. The Gorgon Pockmark Field (GPF) extends over ~125 km 2 in water depths ranging from 210 to 480 m. It contains ~500 pockmarks with diameters of ~150-200 m. The pockmark field overlies a submarine landslide and was likely created by the expulsion of fluids and/or liquefied sediment during or after the formation of the landslide. The Carnarvon Pockmark Field (CPF), located 100 km southwest of the GPF, covers around ~150 km 2 in water depth ranging from 680 to 930 m. It contains ~250 pockmarks, each having a diameter of ~250-300 m. The CPF developed on a buried paleo-landslide. While the seafloor pockmarks and the paleo-landslide are physically disconnected by a sedimentary drape, seafloor pockmarks are abundant above the paleo-landslide and present a characteristic morphology, then suggesting that fluids circulating through the paleo-landslide induced the formation of the seafloor pockmarks. Study of the Gorgon and Carnarvon pockmark fields presents new evidence that submarine landslides -either on the seafloor or buried -can control the development of pockmarks over huge areas of the seafloor.

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Section: Influence Of Gas On Landslide and Pockmark Formationcontrasting

confidence: 61%

Section: Hydrocarbon Seepages and Pockmarks Along The Nwsmentioning

confidence: 99%

Origin of seafloor pockmarks overlying submarine landslides: Insights from semi-automated mapping of 3D seismic horizons (North West Shelf, Australia)

Riera¹,

Paumard

Gail³

et al. 2022

Marine and Petroleum Geology

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“…Models suggest that stratal geometries related to anticlinal structures focus migrating gas, resulting in concentrated hydrate deposits (Figure a). Upward migration of gas charging hydrate systems is often associated with faults, fault intersections and associated structural highs that focus gas migration (Barnes et al, ; Freire et al, ; Hustoft et al, ; Paganoni et al, ; Plaza‐Faverola et al, ). Models in the present study were run without considering the influence of faults.…”

Section: Discussionmentioning

confidence: 99%

A 3‐D Model of Gas Generation, Migration, and Gas Hydrate Formation at a Young Convergent Margin (Hikurangi Margin, New Zealand)

Kroeger

Crutchley

Kellett

et al. 2019

Geochem Geophys Geosyst

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We present a three‐dimensional gas hydrate systems model of the southern Hikurangi subduction margin in eastern New Zealand. The model integrates thermal and microbial gas generation, migration, and hydrate formation. Modeling these processes has improved the understanding of factors controlling hydrate distribution. Three spatial trends of concentrated hydrate occurrence are predicted. The first trend (I) is aligned with the principal deformation front in the overriding Australian plate. Concentrated hydrate deposits are predicted at or near the apexes of anticlines and to be mainly sourced from focused migration and recycling of microbial gas generated beneath the hydrate stability zone. A second predicted trend (II) is related to deformation in the subducting Pacific plate associated with former Mesozoic subduction beneath Gondwana and the modern Pacific‐Australian plate boundary. This trend is enhanced by increased advection of thermogenic gas through permeable layers in the subducting plate and focused migration into the Neogene basin fill above Cretaceous‐Paleogene structures. The third trend (III) follows the northern margin of the Hikurangi Channel and is related to the presence of buried strata of the Hikurangi Channel system. The predicted trends are consistent with pronounced seismic reflection anomalies related to free gas in the pore space and strength of the bottom‐simulating reflection. However, only trend I is also associated with clear and widespread seismic indications of concentrated gas hydrate. Total predicted hydrate masses at the southern Hikurangi Margin are between 52,800 and 69,800 Mt. This equates to 3.4–4.5 Mt hydrate/km2, containing 6.33 × 108–8.38 × 108 m3/km2 of methane.

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“…Continental break‐up occurred along the western and southern margin of the Exmouth Plateau in the Valanginian‐to‐Hauterivian (∼135–130 Ma; Figure 2b) (e.g., Direen et al., 2008; Reeve et al., 2021; Robb et al., 2005). Following break‐up, thermal subsidence accommodated deposition of a thick post‐rift succession that hosts several tiers of polygonal faults (e.g., Paganoni et al., 2019; Velayatham et al., 2019).…”

Section: Geological Settingmentioning

confidence: 99%

Seismic Reflection Data Reveal the 3D Subsurface Structure of Pit Craters

et al. 2022

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Pit craters are quasi‐circular depressions observed on rocky and icy planetary bodies, as well as numerous asteroids. Pit craters are thought to form by overburden collapse into a subsurface cavity or volumetrically depleted zone. Importantly, the surface size and distribution of pit craters may provide an important record of otherwise inaccessible subsurface processes. However, because we cannot access the subsurface of many planetary bodies, we rely on physical and numerical models to infer processes linked to pit crater formation. Here, we use 3D seismic reflection data to quantify the palaeosurface and subsurface geometry of 59 Late Jurassic pit craters buried to depths of ∼3 km within a sedimentary basin, offshore NW Australia. The pit craters are typically funnel‐like, with an inverted conical upper section underlain by a pipe. Pit crater depths, that is, the height of inverted cone sections, correlate with their plan‐view length, consistent with observations of pit craters elsewhere; this trend is rendered less apparent by later sediment‐infilling. For the first time, we show some pit crater pipes connect to underlying igneous dikes or steeply dipping, likely dilatational portions of normal faults. Although some pit craters seemed to have formed due to faulting and others to dyking, they cannot be differentiated based on their surface expression. Our data also suggest pit crater size may not relate to the mechanical properties of the host material. Overall, we conclude that the surface expression of pit craters on Earth and other planetary bodies may not be diagnostic of subsurface processes or properties.

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A natural gas hydrate system on the Exmouth Plateau (NW shelf of Australia) sourced by thermogenic hydrocarbon leakage

Cited by 19 publications

References 108 publications

Origin of seafloor pockmarks overlying submarine landslides: Insights from semi-automated mapping of 3D seismic horizons (North West Shelf, Australia)

Origin of seafloor pockmarks overlying submarine landslides: Insights from semi-automated mapping of 3D seismic horizons (North West Shelf, Australia)

A 3‐D Model of Gas Generation, Migration, and Gas Hydrate Formation at a Young Convergent Margin (Hikurangi Margin, New Zealand)

Seismic Reflection Data Reveal the 3D Subsurface Structure of Pit Craters

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