Natural gas hydrates in the Rio Grande Cone (Brazil): A new province in the western South Atlantic

Miller, Dennis J.; Ketzer, João Marcelo Medina; Viana, Adriano R.; Kowsmann, Renato Oscar; Freire, Antônio Fernando Menezes; Oreiro, Sérgio Goulart; Augustin, Adolpho Herbert; Lourega, Rogério V.; Rodrigues, Luiz Frederico; Heemann, Roberto; Preissler, Adriane G.; Machado, Claudia Xavier; Sbrissa, Gesiane Fraga

doi:10.1016/j.marpetgeo.2015.05.012

Cited by 53 publications

(82 citation statements)

References 40 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Numerical methods for predicting future ocean warminginduced methane release from the marine hydrate reservoir span a wide range of complexities, from the simplest approaches where gas escape from the seafloor is estimated as a function of temperature change (Biastoch et al, 2011;Hunter et al, 2013;Kretschmer et al, 2015) to more sophisticated models that include coupled hydraulic-thermodynamic behaviour of multiphase fluid flow in hydrate-bearing porous media (Darnell and Flemings, 2015;Reagan et al, 2011;Reagan and Moridis, 2008;Stranne et al, 2016a;Thatcher et al, 2013). One example of the latter is the TOUGH+HYDRATE (T+H) model which predicts the evolution of pressure, temperature, salinity and the phase saturation distributions in hydrate-bearing systems (Moridis, 2014). Stranne et al (2017) integrated a geomechanical coupling into the T+H model (referred to as T+H-GeoMech in the text) and showed that such coupling is critical since dissociation of methane increases pore pressure and leads to hydraulic fracturing.…”

Section: Introductionmentioning

confidence: 99%

Can anaerobic oxidation of methane prevent seafloor gas escape in a warming climate?

et al. 2019

View full text Add to dashboard Cite

Abstract. Assessments of future climate-warming-induced seafloor methane (CH4) release rarely include anaerobic oxidation of methane (AOM) within the sediments. Considering that more than 90 % of the CH4 produced in ocean sediments today is consumed by AOM, this may result in substantial overestimations of future seafloor CH4 release. Here, we integrate a fully coupled AOM module with a numerical hydrate model to investigate under what conditions rapid release of CH4 can bypass AOM and result in significant fluxes to the ocean and atmosphere. We run a number of different model simulations for different permeabilities and maximum AOM rates. In all simulations, a future climate warming scenario is simulated by imposing a linear seafloor temperature increase of 3 ∘C over the first 100 years. The results presented in this study should be seen as a first step towards understanding AOM dynamics in relation to climate change and hydrate dissociation. Although the model is somewhat poorly constrained, our results indicate that vertical CH4 migration through hydraulic fractures can result in low AOM efficiencies. Fracture flow is the predicted mode of methane transport under warming-induced dissociation of hydrates on upper continental slopes. Therefore, in a future climate warming scenario, AOM might not significantly reduce methane release from marine sediments.

show abstract

Section: Introductionmentioning

confidence: 99%

Can anaerobic oxidation of methane prevent seafloor gas escape in a warming climate?

et al. 2019

View full text Add to dashboard Cite

show abstract

“…Several locations indicates a relationship and co-occurrence between venting of methane-rich fluids, gas hydrate and the formation of authigenic carbonates at the seafloor -e.g., the Sea of Okhotsk (Soloviev &Ginsburg 1997), the Cascadia Margin (Bohrmann et al 1998) and the Blake Ridge (Paull et al 1995), Rio Grande Cone (Miller et al 2015). Besides the authigenic carbonates have been shown to occur in sediments containing CH 4 hydrates, they are often associated with faults that act as conduits for the upward migration of fluids and CH 4 (Bohrmann et al 1998).…”

Section: Discussionmentioning

confidence: 99%

“…The Pelotas Basin has an area of approximately 250,000 km 2 resulted from the rifting of Gondwana and the drifting of the South American plate, having accumulated a thick sedimentary package (up to 12 km) from the Barremian to the Recent. The main structures present in the basin are normal faults in the proximal extensional domain and folds and thrust faults in the distal compressional domain (Silveira &Machado 2004).Distinct bottom simulating reflectors (BSRs) are ubiquitous in the Rio Grande Cone, and have been used as the main evidence for the occurrence of large gas hydrate deposits in the Pelotas Basin in Brazil (Sad et al 1998, Fontana & Mussumeci 1994, Clennell 2000,Oliveira et al 2010, Miller et al 2015 and in Uruguay (Tomasini et al 2011).…”

Section: Study Area and Geological Settingmentioning

confidence: 99%

The influence of methane fluxes on the sulfate/methane interface in sediments from the Rio Grande Cone Gas Hydrate Province, southern Brazil

et al. 2017

Self Cite

View full text Add to dashboard Cite

Much research has been published regarding the relation between major gas hydrate accumulations and the global carbon cycle. In this context, the determination of the sulfate/methane interface (SMI) depth is of primary importance in order to understand the dynamics of methane flux in the shallow section. This paper identifies the depth of the SMI in sediments based on sulfate and methane concentration profiles in cores recovered in the Rio Grande Cone Gas Hydrate Province, Pelotas Basin, southern Brazil. The shape of methane and sulfate concentration profiles in the sediments can be linked to the local methane flux rate as follows: (i) near linear, high upward-diffusing methane flux coupled with high sulfate diffusion from seawater; (ii) irregular, variable methane flux rates; and (iii) kink-type profile, which is indicative of variable rather than strictly high upward methane flux. The areas in which a high methane flux was identified are spatially associated with gas chimneys in sediments within pockmarks, whereas profiles with low methane flux are present in adjacent areas. These chimneys appear as acoustic blankings in seismic records and can therefore be mapped in subsurface. The wavy-like seismic reflection following the SMI coincides with the occurrence of authigenic carbonate nodules and concretions. In addition, high methane fluxes and the occurrence of concretions and nodules carbonates were correlated by stratigraphic position of the concretions bearing intervals and sulfate profiles. KEYWORDS: gas hydrate; methane flux; Rio Grande Cone; Brazil. RESUMO: Muitas pesquisas têm sido publicadas relacionando elevadas acumulações de hidrato de gás e o ciclo global do carbono. Nesse contexto, a determinação da profundidade da interface sulfato/metano (SMI) é importante para entender a dinâmica do fluxo de metano em locais rasos. Este artigo científico identifica a profundidade da SMI em sedimentos com base em perfis de concentração de sulfato e metano em testemunhos recuperados na Província do Hidrato de Gás do

show abstract

“…in pockmarks or crater fields (Ginsburg, 1998;Miller et al, 2015), or by more focused escapes along shallow faults (Freire et al, 2011;Mienert & Posewang, 1999;Suess et al, 1999).…”

Section: Gas Hydrates Backgroundmentioning

confidence: 99%

Fluid escape structures as possible indicators of past gas hydrate dissociation during the deposition of the Barremian sediments in the Recôncavo Basin, NE, Brazil

et al. 2017

View full text Add to dashboard Cite

Empty elliptical vesicles are observed in outcrops of Barremian very fine clayey sandstone to siltstone lacustrine slurry deposits of the Pitanga Member (Maracangalha Formation), exposed in the Maré Island, Southern Recôncavo Basin, Brazil. These sedimentary features have been traditionally interpreted as water escape structures triggered by the diapirism of the underlying shales of the Candeias Formation. This work proposes that vesicles were generated during massive gas hydrate dissociation as a result of tectonic activity in a paleolake system. Tectonic uplift would have triggered both the reduction of the confining pressure as well as an increase in lake bottom temperature, resulting in the instability of gas hydrate and causing intense release of both methane -or carbon dioxide (CO 2 ) -and water. On one hand, this proposal has a strong impact on paleoenvironmental interpretations, giving support to the current hypothesis that rocks related to the Pitanga Member would have been deposited under water columns deep enough for gas hydrate formation and subsequent dissociation. On the other hand, it provides new insights on the genesis of fluid escape structures in sedimentary rocks, both lacustrine and marine, providing a paleobathymetric indicator.KEYWORDS: Fluidization; Gas hydrates; Maracangalha Formation; Pitanga Member; Recôncavo Basin; Vesicles. Recôn-cavo, uma RESUMO: Vesículas elípticas ocas são observadas em afloramentos de arenitos argilosos muito finos e siltitos lacustrinos do Membro Pitanga da Formação Maracangalha, expostos na Ilha de Maré, sudeste da Bacia do Recôncavo, Estado da Bahia, Brasil. Essas rochas foram depositadas em condições subaquosas e são consideradas depósitos gravitacionais do tipo slurry. Essas feições têm sido tradicionalmente interpretadas como sendo estruturas de escape de água, resultado da ação do diapismo de folhelhos sotopostos da Formação Candeias. Este trabalho propõe que as vesículas foram geradas durante uma intensa dissociação de hidratos de gás em resposta à atividade tectônica existente naquele sistema lacustre. O soerguimento tectônico do fundo do lago teria propiciado a redução da pressão confinante nos poros sedimentares, bem como o aumento de temperatura nas águas de fundo, resultando na instabilidade dos hidratos de gás contidos nas porções rasas dos sedimentos e causando uma violenta liberação de metano -ou gás carbônico (CO 2 ) -e água. Se correta, esta proposta tem um grande impacto na interpretação paleoambiental da Bacia do INTRODUCTIONDiscussions regarding the formation and dissociation of gas hydrates in oceans, seas and permafrost environments are widely described in the literature (Collett, 2002;Freire, 2010;Haacke et al., 2009;Hyndman & Davis, 1992;Matsumoto, 2005;Matsumoto et al., 2009). However, studies concerning fossil gas hydrate formation and dissociation in both marine and lacustrine environments are rare, since the evidences of such processes are not based on direct observations, as those of present day gas hydrate occurrences. ...

show abstract

Natural gas hydrates in the Rio Grande Cone (Brazil): A new province in the western South Atlantic

Cited by 53 publications

References 40 publications

Can anaerobic oxidation of methane prevent seafloor gas escape in a warming climate?

Can anaerobic oxidation of methane prevent seafloor gas escape in a warming climate?

The influence of methane fluxes on the sulfate/methane interface in sediments from the Rio Grande Cone Gas Hydrate Province, southern Brazil

Fluid escape structures as possible indicators of past gas hydrate dissociation during the deposition of the Barremian sediments in the Recôncavo Basin, NE, Brazil

Contact Info

Product

Resources

About