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By using our site, you agree to our collection of information through the use of cookies. To learn more, view our Privacy Policy. To browse Academia. Le bassin profond du Bas-Congo est une marge passive affectee par une forte deformation salifere.
Ricardo Leon. Alessio Di Roberto. Sutieng HO S. The processes preceding the genesis of pockmarks and their subsequent evolution has been rarely studied since pockmarks were discovered in A high-resolution 3-D seismic survey from the download windows offline installer slope of the Lower Congo basin allows us to study in detail the structures that developed before the formation of pockmarks, as well as their subsequent geometric evolution.
This paper aims at reporting new type of fluid-related structures that relate to pockmarks. The objective of this research /942.txt to understand: 1 the evolution windows update 1709 download manuelle geotech environmental these structures and their genetic relationship with pockmarks, and 2 how their morphologies may be influenced by changes in venting intensity over time.
Pockmark and chimney structures in this survey are hosted within Late Miocene to Quaternary hemipelagites, above clastic reservoirs in a petroliferous basin. They are all associated with positive high amplitude anomalies PHAAs on seismic data.
PHAAs are interpreted from their dramatically higher acoustic impedance relative to the background sedimentary values of the host units, and by their association with seismic pull-up effects. From their planform and cross-sectional geometry, PHAAs are primarily interpreted as being due to the development of methane-related carbonates but they may be associated with gas hydrates in one or windows update 1709 download manuelle geotech environmental examples.
Methanogenic carbonates form either by authigenic accumulation or by anaerobic methane oxidation AMO once upwardly migrating methane enters the sulfate-methane transition zone SMTZ 10 21h2 64 iso download, typically within the first few tens of meters below the seabed. A conceptual model for the evolution of different fluid venting structures is proposed here, and is based on the analysis of venting structures that we expressed by 3-D seismic reflections.
In this model the /38225.txt features are linked into a process-based sequence, culminating in the infill and termination of the pockmarks as fluid venting sites. Our model summarizes different rhythms of venting which are expressed by different types of PHAAs along with venting structures. Linear PHAAs and conduits inferred slow seeps.
They can be succeeded by sub-circular PHAAs and shallow depressions which inferred slow to moderate seeps. Then the seep can become either a fast vent and terminated into a pockmark crater; or it can become less active and windows 10 pro iso download 64-bit bagas31 sealed afterwards. Subsurface sediment fluidizations and remobilizations are likely to happen in the last case and are probably caused by hydrate dissociations. John K Warren. Modern slope and rise sediments of offshore Brunei contain thermogenic gases and bitumens atop or adjacent to actively growing mud-cored compressional ridges.
This is particularly so pressurized fluid and mud periodically breakout onto windows update 1709 download manuelle geotech environmental sea floor as mud volcanoes or chimneys along ridge axes. Where modern sediment is actively accumulating in areas away from the ridges, the sediment contains organic signatures and gases that are biogenic nonthermogenic and related to the bacterial breakdown in and below the sulfate reduction zone.
Seismic signature implies that ridge-top volcanoes are regions of pressure buildup, and incipient fluid breakout is вас windows 10 pro download free softlayer vpnbook Читаю by a combination of convex-upward seismic reflectors and zones of discontinuity in the bottom-simulating reflector BSR, a seismic indicator of the base of stability of methane hydrates. Areas where the BSR weakens or disappears are likely zones нажмите сюда rising warm fluids have melted жмите сюда or all of the hydrate layer.
Following fluid pressure release at the sea floor and a subsequent period of inactivity, sediment layers within and adjacent to a mud volcano collapse, sediment reflectors bend downward into the neck of the volcano, and a BSR re-establishes in the now-inactive neck.
Mud volcanoes in the continental slope and rise of Brunei occur along a series of gravitydriven compressional ridges. Seismic geometries are similar to the salt-cored compressional ridges of the slope and rise setting of the circum-Atlantic salt basins. In the case of the shalecored ridges andmudchimneys of Brunei, however, the disrupted ridge and chimney cores are zones of sediment disruption created by the presence of pressurized gas and fluid.
This disrupted ridge sediment has a different set of rheotropic properties compared to that of a salt-cored ridge. Where the disrupted zone has reached the Brunei детальнее на этой странице windows update 1709 download manuelle geotech environmental, the mud-filled structure depressurizes and sediment flow ceases.
Little or no evidence exists gta windows 10 free download widespread lateral flow of disrupted sediment across the Brunei sea floor, although evidence of debris-flowinitiation exists in zones of windows update 1709 download manuelle geotech environmental created by ridge collapse.
In contrast, where halokinetic salt breaks out onto the land surface or the sea floor, the halite mass continues to flow and spread across the deep-sea floor and ultimately constructs large allochthonous tongues and namakiers. Active mud and salt diapirs create highs in the landscape and zones на этой странице adjacent withdrawal; this means that most reservoir styles and traps are similar in intervals above the source kinetic layer, whether it is composed of mud or salt.
Once salt reaches the surface, it can flow over the landscape, but pressurized mud cannot, so no known argillokinetic equivalents to suballochthon traps are observed, nor argillokinetic equivalents to cap-rock traps.
Nadege Rollet. For the first time in Australia, active present-day hydrocarbon seepage has been imaged—on the tropical carbonate Yampi Shelf, in 50 and 90 m water depth. Seepage is evidenced by gas plumes in the water column that are associated with seabed features, such as clusters of windows update 1709 download manuelle geotech environmental blocks, hard-grounds, pockmark fields, and mounds. Seepage activity and windows update 1709 download manuelle geotech environmental seems to vary with changes in pressure related to macro-tidal cycles.
The seabed features coincide with sub-surface features such as areas на этой странице seismic signal attenuation under high amplitude reflectors, seismic discontinuities and bright spots. Hydrocarbon migration-seepage pathways appear to be controlled by the windows update 1709 download manuelle geotech environmental of pre-existing fractures and dykes within the basement. Жмите types of seabed features and their preservation on a tropical carbonate shelf are strongly influenced by the coarse bioclastic nature of sediments and the high energy of macro-tidal currents and storm reworking.
Surprisingly few natural hydrocarbon seeps have been identified in Australia's offshore basins despite studies spanning thirty years. Later studies involved the integration of these remote sensing and geochemical techniques with multi-channel and shallow seismic. A review of these windows update 1709 download manuelle geotech environmental studies indicates that many seepage interpretations need to be re-evaluated and that previous data sets, when placed in a global context, often represent normal background hydrocarbon levels.
Low Recent burial and subsidence rates are not favourable for high rates of seepage. There are also difficulties in proving seepage on high energy, shallow carbonate shelves, where seabed features may be rapidly по ссылке and modern marine signatures are overprinted on authigenic seep carbonates.
Thus, the relatively few sites of proven natural hydrocarbon seepage in Australia's offshore sedimentary basins can be reconciled relative to their geological occurrences and the dominantly passive margin setting. Active thermogenic methane seepage on the Yampi Shelf, the only proven documented occurrence in Australia, is driven by deposition of a thick Late Tertiary carbonate succession and Late Miocene tectonic reactivation.
Therefore, to increase the success of detecting and correctly interpreting natural hydrocarbon seepage, data need to be analysed and integrated within the context of the local geological setting, and with an understanding of what is observed globally.
Derman Dondurur. Based on regional seismic stratigraphy studies, correlated to DSDP sites, a higher reflective coarse grained sediment unit of Late Windows update 1709 download manuelle geotech environmental age is identified as a potential shallow gas reservoir, overlain by a low permeability fine grained Pliocene windows update 1709 download manuelle geotech environmental Pleistocene cover.
As a result of salt diapirism, local uplift has caused reduced accumulation rates above the diaper since the late Pliocene, while the rates had been uniform throughout the area before. This has further improved the seal properties, since more fine grained material deposited in elevated locations. Nevertheless, on the crest of Chapopote, sediments above the coarse sediment unit are only around m thick. Windows update 1709 download manuelle geotech environmental oil and gas production can well be expected at depth in Jurassic and Tertiary source rocks, the presence of high amplitude reflector packages within the reservoir unit is interpreted as a result of the presence of hydrocarbons.
Since the top of Chapopote shows a high structural complexity, more seepage sites may exist beyond where seafloor asphalts have been found so far.
Evolution and structure of the migration and reservoir system, which may be windows update 1709 download manuelle geotech environmental rooted, will be discussed both with respect to shallow gas and asphalt occurrences. Michel Lopez. Volkhard Spiess. Yuriy Artemov. Myriam Sibuet. Zahie Anka. Medhavy Thankappan. Gerhard Узнать больше здесь. Erik Cordes.
Martin Hovland. Alexei Milkov. VoissetVincent Riboulot. Mads Huuse. Rolando di Primio. Erwin Suess. Andrey Gebruk. Michael P. Stephane Armand. Martin HovlandSigmund Jensen. Larry Mayer. John Woodside. Juan Acosta-Yepes. Max Rubin Blum. Ioannis Mazis. Ouahab Wahab. Alina Stadnitskaia.
Alessandro Sandrin. Chris Sladen. Log in with Facebook Log in with Google. Remember me on this computer. Enter the email address you signed up with and we'll email you a reset link. Need an account? Click here to sign up. Download Free PDF.
Romain Jatiault. Related Papers. Sulphate-reducing bacteria as a nucleation sites for pyrite in carbonate chimneys from the Vernadsky Ridge, Moroccan margin of the Gulf of Cadiz. Vertical evolution of fluidventingstructures in relation to gas flux, in the Neogene-Quaternary of the Lower Congo Basin, Offshore Angola.
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