Seafloor geomorphology and submarine landslide hazards along the continental slope in the Carnarvon Basin, Exmouth Plateau, North West Shelf, Australia

2012 ◽  
Vol 52 (1) ◽  
pp. 493 ◽  
Author(s):  
James Hengesh ◽  
James K. Dirstein ◽  
Alistair J. Stanley
Keyword(s):  
Continental Slope ◽  
Seismic Data ◽  
Slope Failure ◽  
Sediment Accumulation ◽  
Infrastructure Development ◽  
Slope Failures ◽  
North West ◽  
Exmouth Plateau ◽  
Submarine Slope ◽  
Carnarvon Basin

3D exploration seismic data were interpreted to investigate the locations and characteristics of submarine slope failures along the continental slope in the offshore Carnarvon Basin on Australia’s North West Shelf. Seisnetics™, a patented genetic algorithm was used to process the 3D seismic data to extract virtually all trough and peak surfaces in an unbiased and automated manner. The extracted surfaces were combined in the 3D visual database to develop a seafloor digital terrain model that extends from the continental slope to the Exmouth Plateau. The 3D data were used to map the subsurface extent and geometry of landslide failure planes, as well as to estimate the thickness and volumes of slide deposits. This paper describes the geomorphic characteristics of five of the survey areas. Geomorphic mapping shows the presence of slope failures ranging from small (20 km across) mass transport complexes (MTC). The features are associated with debris flow chutes, turbidity flow channels, and debris fields. Analysis of failure planes show prominent grooves or striations related to the mobilisation of slide material down both the continental slope and Exmouth Plateau and into the Kangaroo Syncline. Submarine slope failures can occur at the continental shelf break in about 200–300 m of water and run out to the Exmouth Plateau surface in about 1,100–1,400 m water depths. The largest individual slides in the survey areas have widths of 30 km and minimum run-out lengths of 75 km, though associated turbidity flow deposits likely extend much further. The subsurface expression of the large MTCs illustrates a history of sediment accumulation along the mid-slope followed by repeated slope failure and debris run-out. Sediment accumulation and slope failure processes are actively occurring along the continental slope and submarine landslides thus are a major driver of hazard to subsea infrastructure development. Smaller more frequent slides may pose a greater hazard than large infrequent MTCs.

Investigating the controls of submarine landslides and associated hazards in Pangnirtung Fiord, Eastern Baffin Island (Nunavut)

2021 ◽  
Author(s):  
Philip Sedore ◽  
Alexandre Normandeau ◽  
Vittorio Maselli
Keyword(s):  
High Latitude ◽  
Debris Flows ◽  
Slope Failure ◽  
Recurrence Time ◽  
High Recurrence Rate ◽  
Baffin Island ◽  
Submarine Landslides ◽  
Slope Failures ◽  
Near Surface ◽  
Submarine Slope

<p>High-latitude fiords are susceptible to hazardous subaerial and submarine slope failures. Recent investigations have shown that past slope failures in fiords of Greenland and Alaska have generated devastating landslide induced tsunamis. Since coastal communities inhabit these high-latitude fiords, it is critical to understand the slope failure recurrence time, their distribution, potential triggers, and ability to generate tsunamis. In this study, we identified > 50 near-surface submarine landslides in Pangnirtung Fiord, eastern Baffin Island, Nunavut, using multibeam bathymetric and sub-bottom profiler data, along with sediment gravity-cores collected in 2019. Morphometric and morphological analyses, along with sedimentological analyses, were carried out on submarine landslide deposits to quantify their spatial and temporal distribution throughout the fiord and to evaluate the factors that may have triggered the slope failures.</p><p>Combining bathymetric with topographic data from unmanned aerial vehicle imagery, we found that most of these landslide deposits are relatively small (~ 0.08 km<sup>2</sup>) and are associated with outwash fans and steep fiord sidewalls. However, since most slope failure head scarps lie between the intertidal zone and ~30 m water depth, they could not be mapped, which makes it challenging to determine the triggers of the submarine slope failures. Radiocarbon dating reveals that most of these surficial landslide deposits are younger than 500 years old and that they were most likely triggered at different times. This finding highlights a high recurrence rate of slope failures within the fiord, suggesting that localised triggers are responsible for slope failures within the fiord, as opposed to widespread, seismically induced triggers which do not occur as frequently in the study area. In addition, the elongated morphology of the landslide deposits and the varying degrees of landslide deposit surface roughness supports localised point-source triggers. Since most landslides are associated with subaerial outwash fans and deltas, we suggest that triggers of these relatively frequent submarine landslides within Pangnirtung Fiord include rapid floodwater input, subaerial debris flows, and sea-ice loading during low tide.</p><p>This research shows that slope failures in a high-latitude fiord are affected by the interaction of numerous subaerial and submarine processes, leading us to speculate that a potential increase in the frequency of subaerial debris flows and river floods due to climate change may increase the recurrence of submarine landslides.<strong> </strong></p>

scholarly journals The influence of clay content on submarine slope failure: insights from laboratory experiments and numerical models

2020 ◽  
Vol 500 (1) ◽  
pp. 301-309 ◽  
Author(s):  
M. M. W. Silver ◽  
B. Dugan
Keyword(s):  
Pore Pressure ◽  
Slope Failure ◽  
Failure Modes ◽  
Initial Conditions ◽  
Numerical Models ◽  
Clay Content ◽  
Passive Margin ◽  
Slope Failures ◽  
Submarine Slope ◽  
Failure Evolution

AbstractSubmarine slope failures pose risks to coastlines because they can damage infrastructure and generate tsunamis. Passive margin slope failures represent the largest mass failures on Earth, yet we know little about their dynamics. While numerous studies characterize the lithology, structure, seismic attributes and geometry of failure deposits, we lack direct observations of failure evolution. Thus, we lack insight into the relationships between initial conditions, slope failure initiation and evolution, and final deposits. To investigate submarine slope failure dynamics in relation to initial conditions and to observe failure processes we performed physical experiments in a benchtop flume and produced numerical models. Submarine slope failures were induced under controlled pore pressure within sand–clay mixtures (0–5 wt% clay). Increased clay content corresponded to increased cohesion and pore pressure required for failure. Subsurface fractures and tensile cracks were only generated in experiments containing clay. Falling head tests showed a log-linear relation between hydraulic conductivity and clay content, which we used in our numerical models. Models of our experiments effectively simulate overpressure (pressure in excess of hydrostatic) and failure potential for (non)cohesive sediment mixtures. Overall our work shows the importance of clay in reducing permeability and increasing cohesion to create different failure modes due to overpressure.

A re-evaluation of the Lower to Middle Triassic on the Candace Terrace, Northern Carnarvon Basin

2017 ◽  
Vol 57 (1) ◽  
pp. 263 ◽  
Author(s):  
Roisin McGee ◽  
Jeff Goodall ◽  
Stephen Molyneux
Keyword(s):  
Seismic Data ◽  
Middle Triassic ◽  
Submarine Canyon ◽  
North West ◽  
Northern Carnarvon Basin ◽  
3D Seismic Data ◽  
Southern Flank ◽  
Opening Up ◽  
Mixed Carbonate ◽  
Carnarvon Basin

The Lower to Middle Triassic mixed carbonate–clastic system in the Northern Carnarvon Basin is poorly understood relative to the stratigraphically younger Jurassic play systems. Few well penetrations and a lack of quality seismic data have deterred exploration of this interval for many years. In recent times, the Lower to Middle Triassic source potential has been comprehensively de-risked within the Roebuck Basin, with subsequent implications across the entire North West Shelf of Australia, opening up the possibility of an entirely new regional play fairway. This paper focuses on the Candace Terrace, on the southern flank of the Carnarvon Basin, where seismic observations and interpretations of Lower to Middle Triassic submarine canyon systems have been made. The stratigraphic elements of this play interval can now be more clearly observed with the aid of 3D seismic data. Amplitude extractions show the internal geometries of these highly erosive systems are sinuous, compensating flows. The aims of this paper are to postulate the stratigraphy of the Lower to Middle Triassic on the Candace Terrace, highlight the tectonic cause of the canyon systems and discuss the prospectivity of the observed turbidite features.

scholarly journals On the potential of gassy marine soils triggering submarine slope instabilities

2020 ◽  
Vol 205 ◽  
pp. 12006
Author(s):  
Pauline Kaminski ◽  
Jürgen Grabe
Keyword(s):  
Slope Failure ◽  
Turbidity Currents ◽  
Continental Margins ◽  
Extensive Literature ◽  
Slope Failures ◽  
Free Gas ◽  
Submarine Slope ◽  
Failure Event ◽  
Liquefaction Failure ◽  
Excess Pore Pressures

The development of debris flows and turbidity currents in the course of a submarine slope failure event can cause major damage in offshore infrastructure. Additionally, the tsunamogenic potential of large slope failures at continental margins poses a direct threat to coastal communities. Therefore, the trigger mechanisms of submarine slope failures have been thoroughly investigated in the past. However, the influence of free gas in the sediment, which has been observed close to several slide events, remains unexplained. In order to evaluate the potential of gassy marine soils to precondition or trigger slope failure the mechanical behaviour of gassy soils is assessed based on an extensive literature review. It is found that gas-induced excess pore pressures can lead to liquefaction failure in sands, while cohesive, gassy soils show a less conclusive response. Hence, fine-grained soils and approaches to implement the gas impact into relevant existing constitutive soil models are assessed in greater detail. Concludingly, based on the predominant boundary conditions in failure prone regions at the continental margins, free gas occurrence can be defined as a preconditioning factor rather than as a definite trigger mechanism.

CARNARVON BASIN ARCHITECTURE AND STRUCTURE DEFINED BY THE INTEGRATION OF MINERAL AND PETROLEUM EXPLORATION TOOLS AND TECHNIQUES

2002 ◽  
Vol 42 (1) ◽  
pp. 287 ◽  
Author(s):  
L.L. Pryer ◽  
K.K. Romine ◽  
T.S. Loutit ◽  
R.G. Barnes
Keyword(s):  
Seismic Data ◽  
Structural Model ◽  
Mineral Exploration ◽  
Petroleum Exploration ◽  
Block Rotation ◽  
North West ◽  
The North ◽  
Northern Carnarvon Basin ◽  
Migration Pathways ◽  
Carnarvon Basin

The Barrow and Dampier Sub-basins of the Northern Carnarvon Basin developed by repeated reactivation of long-lived basement structures during Palaeozoic and Mesozoic tectonism. Inherited basement fabric specific to the terranes and mobile belts in the region comprise northwest, northeast, and north–south-trending Archaean and Proterozoic structures. Reactivation of these structures controlled the shape of the sub-basin depocentres and basement topography, and determined the orientation and style of structures in the sediments.The Lewis Trough is localised over a reactivated NEtrending former strike-slip zone, the North West Shelf (NWS) Megashear. The inboard Dampier Sub-basin reflects the influence of the fabric of the underlying Pilbara Craton. Proterozoic mobile belts underlie the Barrow Sub-basin where basement fabric is dominated by two structural trends, NE-trending Megashear structures offset sinistrally by NS-trending Pinjarra structures.The present-day geometry and basement topography of the basins is the result of accumulated deformation produced by three main tectonic phases. Regional NESW extension in the Devonian produced sinistral strikeslip on NE-trending Megashear structures. Large Devonian-Carboniferous pull-apart basins were introduced in the Barrow Sub-basin where Megashear structures stepped to the left and are responsible for the major structural differences between the Barrow and Dampier Sub-basins. Northwest extension in the Late Carboniferous to Early Permian marks the main extensional phase with extreme crustal attenuation. The majority of the Northern Carnarvon basin sediments were deposited during this extensional basin phase and the subsequent Triassic sag phase. Jurassic extension reactivated Permian faults during renewed NW extension. A change in extension direction occurred prior to Cretaceous sea floor spreading, manifest in basement block rotation concentrated in the Tithonian. This event changed the shape and size of basin compartments and altered fluid migration pathways.The currently mapped structural trends, compartment size and shape of the Barrow and Dampier Sub-basins of the Northern Carnarvon Basin reflect the “character” of the basement beneath and surrounding each of the subbasins.Basement character is defined by the composition, lithology, structure, grain, fabric, rheology and regolith of each basement terrane beneath or surrounding the target basins. Basement character can be discriminated and mapped with mineral exploration methods that use non-seismic data such as gravity, magnetics and bathymetry, and then calibrated with available seismic and well datasets. A range of remote sensing and geophysical datasets were systematically calibrated, integrated and interpreted starting at a scale of about 1:1.5 million (covering much of Western Australia) and progressing to scales of about 1:250,000 in the sub-basins. The interpretation produced a new view of the basement geology of the region and its influence on basin architecture and fill history. The bottom-up or basement-first interpretation process complements the more traditional top-down seismic and well-driven exploration methods, providing a consistent map-based regional structural model that constrains structural interpretation of seismic data.The combination of non-seismic and seismic data provides a powerful tool for mapping basement architecture (SEEBASE™: Structurally Enhanced view of Economic Basement); basement-involved faults (trap type and size); intra-sedimentary geology (igneous bodies, basement-detached faults, basin floor fans); primary fluid focussing and migration pathways and paleo-river drainage patterns, sediment composition and lithology.

IDENTIFICATION AND INTERPRETATION OF LEAKING HYDROCARBONS USING SEISMIC DATA:A COMPARATIVE MONTAGE OF EXAMPLES FROM THE MAJOR FIELDS IN AUSTRALIA'S NORTHWEST SHELF AND GIPPSLAND BASIN

2000 ◽  
Vol 40 (1) ◽  
pp. 119 ◽  
Author(s):  
R. Cowley ◽  
G.W. O'Brien
Keyword(s):  
Seismic Data ◽  
Oil And Gas ◽  
Hydrocarbon Migration ◽  
North West ◽  
Seal Integrity ◽  
Seismic Amplitudes ◽  
Gas Chimneys ◽  
Hydrocarbon Charge ◽  
Gippsland Basin ◽  
Carnarvon Basin

An extensive volume of 3D seismic data over a number of oil and gas fields in Australia's North West Shelf and Gippsland Basin has been examined for evidence of the effects of hydrocarbon migration and/or leakage. For comparative purposes, 2D and 3D data have also been studied over a number of adjacent traps, including dry traps and partially to completely breached accumulations. Fields and traps investigated include Bayu-Undan, Jabiru, Skua, Swift and Tahbilk in the Bonaparte Basin, Cornea in the Browse Basin, North Rankin, Chinook, Macedon, Enfield and Zeewulf in the Carnarvon Basin, and Kingfish in the Gippsland Basin. The principal goal of the study is to provide representative case studies from known fields so that, in undrilled regions, the exploration uncertainties associated with the issues of hydrocarbon charge and trap integrity might be reduced.Direct indicators of hydrocarbon migration and/or leakage are relatively rare throughout the basins studied, though the discoveries themselves characteristically show seismic anomalies attributable to hydrocarbon leakage. The nature and intensity of these hydrocarbon-related seismic effects do, however, vary dramatically between the fields. Over traps such as Skua, Swift, Tahbilk and Macedon, they are intense, whereas over others, for example Chinook and North Rankin, they are quite subtle. Hydrocarbon-related diagenetic zones (HRDZs), which had been identified previously above the reservoir zones of leaky traps within the Bonaparte Basin, have also been recognised within the Browse, Carnarvon, Otway and Gippsland Basins. HRDZs are the most common leakage indicators found and are identified easily via a combination of high seismic amplitudes through the affected zone, time pull-up and degraded stack response of underlying reflectors. In some cases (the Skua and Macedon Fields), the HRDZs actually define the extent of the accumulations at depth.Anomalous, subtle to strong, seismic amplitude anomalies are associated with the majority of the major fields within the Carnarvon Basin. The strength and location of the anomalies are related to a complex interplay between trap type (in particular four-way dip-closed versus fault dependent), top seal capacity, fault seal integrity, and charge history. In some areas within the Carnarvon, Browse and Bonaparte Basins, shallow amplitude anomalies can be related directly to gas chimneys emanating from the reservoir zone itself. In other instances, the continuous migration of gas from the reservoir has produced an assortment of pockmarks, mounds and amplitude anomalies on the present day sea floor, which all provide evidence of hydrocarbon seepage. In the Browse Basin, strong evidence has been found that many of the modern carbonate banks and reefs in the region were initially located over hydrocarbon seeps on the palaeo-seafloor.The examples and processes presented demonstrate that the analysis of hydrocarbon leakage indicators on seismic data can help to better understand exploration risk and locate subtle hydrocarbon accumulations. In mature exploration provinces, this methodology may lead to the identification of subtle accumulations previously left undetected by more conventional methods. In frontier regions, it can help to identify the presence of a viable petroleum system, typically the principal exploration uncertainty in undrilled regions.

Estimating smectite content from seismic data

2019 ◽  
Vol 59 (2) ◽  
pp. 851
Author(s):  
Roman Beloborodov ◽  
Marina Pervukhina ◽  
Valeriya Shulakova ◽  
Dimitri Chagalov ◽  
Matthew Josh ◽  
...  
Keyword(s):  
Seismic Data ◽  
Oil And Gas ◽  
Clay Mineralogy ◽  
Mineralogical Composition ◽  
Hydrocarbon Exploration ◽  
Seismic Survey ◽  
Maximum Deviation ◽  
North West ◽  
Northern Carnarvon Basin ◽  
Carnarvon Basin

Predicting the mineralogical composition of shales is crucial for drilling operations related to hydrocarbon exploration/production as well as for the assessment of their sealing capacity as hydrocarbon or CO2 barriers. For example, hydrocarbon exploration in the Northern Carnarvon Basin, North-West Shelf, Australia is hindered by the presence of a thick (up to 1 km) smectite-rich shale seal that spreads regionally. Complex structures of the channelised oil and gas fields in the area make it necessary to drill deviated wells through that seal. The maximum deviation angle at which successful drilling is possible depends strongly on the clay mineralogy and, in particular, on the smectite content in the shale. Here, we introduce a novel workflow combining seismic data, well logs and laboratory measurements to infer shale composition at the reservoir scale. It is applied to the Duyfken 3D seismic survey in the central part of the Northern Carnarvon Basin. Interpretation results are verified against the laboratory X-ray diffraction measurements from the test well that was not used for the interpretation. The results match the test data well within the determined uncertainty bounds.

Shell's integrated quantitative interpretation workflow

2011 ◽  
Vol 51 (2) ◽  
pp. 681
Author(s):  
Frank Glass ◽  
Stephan Gelinsky ◽  
Irene Espejo ◽  
Teresa Santana ◽  
Gareth Yardley
Keyword(s):  
Seismic Data ◽  
Rock Properties ◽  
Well Log ◽  
Reservoir Properties ◽  
North West ◽  
The North ◽  
Fluid Properties ◽  
Well Data ◽  
Acoustic Responses ◽  
Carnarvon Basin

Shell Development Australia is a major asset holder in the Browse Basin and the Carnarvon Basin in the North West Shelf of Australia. In 2007, Shell Development Australia embarked on an integrated quantitative seismic interpretation project related to the Triassic Mungaroo Formation in the Carnarvon Basin. The main objective was to constrain the uncertainties in using seismic data as a predictor for rock and fluid properties of fields and prospects in the basin. This project followed a workflow that has been proven in other basins around the world, whereby the vertical and lateral variability of rock properties of both reservoir and non-reservoir lithologies are captured in general trends. The calculated trends are based on well log extractions of end member lithologies and the input of petrographic information and forward modelling. In combination with a regionally consistent 3D burial model for the estimation of remaining porosity, these established rock trends then allow for a prediction of various acoustic responses of reservoir and pore fill properties. The comparisons between the pre-drill predicted rock properties and the properties encountered after drilling at different reservoir levels have lead to a general confidence that the reservoir properties can be derived from seismic data where well data are not abundant. This increased confidence will play a major part in Shell’s attitude towards appraisal activities and decisions on various development options.

Some features of the northwest African margin and magnetic quiet zone

1980 ◽  
Vol 294 (1409) ◽  
pp. 87-96 ◽  
Keyword(s):  
West Africa ◽  
Continental Slope ◽  
Oceanic Crust ◽  
Seismic Data ◽  
Cape Verde ◽  
Sharp Boundary ◽  
North West ◽  
Continental Rise ◽  
Layered Rock ◽  
Seismic Lines

A smooth basement reflector drilled in D.S.D.P. / IPOD Site 367 as basalt extends throughout much of the magnetic quiet zone off North West Africa. Multichannel seismic lines show structures and layered rock complexes locally beneath this basalt reflector. Under the continental slope of Senegal and Mauritania, the basement reflexion is no longer distinguished beneath a Cretaceous carbonate front. Refraction profiles between the Cape Verde Rise and Mauritania and from Conception Bank to Morocco establish the existence of a 7.1 km/s layer at a depth of 14 km. Off Mauritania the smooth basement seems to merge with this layer. Diapiric salt basins existing under the continental rise are only resolved as velocity layers off Mauritania. No sharp boundary from continental to oceanic crust was deduced from the seismic data.

Sign in / Sign up

Export Citation Format

Share Document