FIELD INVESTIGATIONS FOR NORTH WEST SHELF DESIGN CRITERIA

1975 ◽  
Vol 15 (1) ◽  
pp. 133
Author(s):  
S. A. Stroud ◽  
R. W. King
Keyword(s):  
Data Collection ◽  
Water Movement ◽  
Environmental Data ◽  
Design Criteria ◽  
Published Data ◽  
Shelf Area ◽  
Offshore Area ◽  
North West ◽  
The North ◽  
Sea Bed

Since 1971, when major gas discoveries on the North West Continental Shelf were confirmed, B.O.C. of Australia Limited (BOCAL), as operator for the Northwest Shelf Consortium, has carried out a major programme of environmental data collection. The purpose of the data collection programmes and follow-up studies has been to define engineering design criteria for evaluation of offshore production structures and pipelines.Prior to the commencement of exploration drilling, little was known of the meteorological/oceanographic regimes of this vast offshore area and no published data existed on the sea bed topography or composition. During the past 3½ years a substantial library of environmental information has been assembled using both conventional and the most modern techniques available. Acquisition of field data has been mainly concentrated in the southwestern portion of the Consortium's lease area where the major exploration effort was maintained.During the course of the programme, weather instrumentation on all exploration rigs was upgraded. Wave measurement and current metering programmes were also carried out to ascertain the modes of water movement at various offshore discovery locations. To assess the foundation materials and qualities, test borings were carried out at 6 exploration well sites, including a series of in-situ pile load tests at the North Rankin location. Preliminary surveys over possible offshore pipeline routes were carried out to assess the nature and topography of the sea bed.Information gained from the programme of field-collected data and related environmental studies has enabled BOCAL to proceed confidently with platform design for the production of gas from the North Rankin Field.Work is continuing on the acquisition of further field environmental data in order to improve the understanding of the meteorology and oceanography of the North West Shelf area. This will assist in further evaluation of offshore design criteria for the North West Shelf of Australia.

REASSESSING POTENTIAL ORIGINS OF SYNTHETIC APERTURE RADAR (SAR) SLICKS FROM THE TIMOR SEA REGION OF THE NORTH WEST SHELF ON THE BASIS OF FIELD AND ANCILLARY DATA

2005 ◽  
Vol 45 (1) ◽  
pp. 311 ◽  
Author(s):  
A.T. Jones ◽  
G.A. Logan ◽  
J.M. Kennard ◽  
N. Rollet
Keyword(s):  
Synthetic Aperture Radar ◽  
Transition Zone ◽  
Environmental Data ◽  
Synthetic Aperture ◽  
Shelf Area ◽  
North West ◽  
The North ◽  
Timor Sea ◽  
Natural Hydrocarbon ◽  
Aperture Radar

The Timor Sea region of the North West Shelf is one of natural hydrocarbon accumulation and seepage, which has been investigated by integrated remote sensing studies in the past 10 years. One of the primary tools incorporated in these studies has been Synthetic Aperture Radar (SAR). During a recent Geoscience Australia marine survey to the Yampi Shelf area, active hydrocarbon seepage was directly observed in the form of gas plumes rising from the sea-floor. Active seepage was not observed in areas associated with dense clusters of elongated to irregularshaped features in the SAR data, which have previously been interpreted as natural hydrocarbon seepage slicks. These slicks, and another dense cluster of slicks across the Browse–Bonaparte Basin Transition Zone, are reassessed in the context of alternative formational processes.Mapping of bathymetric channels directly beneath the SAR slicks using multi-beam swath bathymetry and measurement of tidal currents using an acoustic doppler current profiler indicates that tidal current flows may have contributed to slick formation over the Yampi Shelf headland. In contrast, coral spawning may have contributed to the formation of annular to crescent-shaped SAR slicks associated with submerged reefs and shoals over the nearby transition zone. Subsequent to identifying potential alternative origins for these two types of SAR features, the remaining slicks across the area were re-categorised on the basis of their size and shape in the context of ancillary hydrographic and environmental data. An alternative nonseepage origin was established for most of the 381 SAR slicks previously identified as being related to natural hydrocarbon seepage. This may necessitate a significant downgrading of the extent and frequency of active hydrocarbon (particularly oil) seepage in the region.

GEOLOGICAL FRAMEWORK OF THE GREAT AUSTRALIAN BIGHT

1969 ◽  
Vol 9 (1) ◽  
pp. 60
Author(s):  
R. Smith ◽  
P. Kamerling
Keyword(s):  
Middle Eocene ◽  
Early Stage ◽  
Upper Jurassic ◽  
The South ◽  
The West ◽  
Offshore Area ◽  
North West ◽  
Carbonate Sedimentation ◽  
The North ◽  
Great Australian Bight

Geophysical exploration carried out in the Great Australian Bight since 1966, combined with geological fieldwork in the adjacent land areas, has made it possible to outline the broad geological framework of the area.The "basement" consists of two major units, an offshore extension of the locally metamorphic Cambrian Kanmantoo Group in the south-east and the extension of the West Australian Archaean shield in the north-west. The boundary is thought to follow a trend extending westerly from the Cygnet-Snelling fault zone on Kangaroo Island.In two areas the basement has been downfaulted, thus creating depositional areas for thick sequences of sediments, namely the Elliston trough to the west of Eyre Peninsula and the Duntroon basin, south of Eyre Peninsula and west of Kangaroo Island.The geological setting of the Duntroon basin appears to be comparable with the Otway basin and a Jurassic- Cretaceous age is assumed for the folded sequence of sediments overlying the basement and underlying the Tertiary with angular unconformity. The basin was possibly partially and temporarily closed to the south and open to marine influences from the west.In the Elliston trough the lower part of the section which has low to medium velocity seismic character, is probably Mesozoic, as is evidenced by the Upper Jurassic encountered in its onshore extension. Proterozoic-Cambrian sediments may overlie the basement in the eastern part of the trough. Deformation of the Mesozoic is limited to the mouth of the trough where there is indication of a base- Tertiary unconformity. This trough was probably also open to marine influences to the west.Along the continental margin between the basins and also south of the Eucla basin a thin Mesozoic section, conformably underlying the Tertiary, is probably present, gradually thickening towards the continental slope.In the onshore area Tertiary sedimentation started with local deposition of clastics during the Middle Eocene, which also may have been the case off the Eucla basin, in the Elliston trough and in the Duntroon basin. Carbonate sedimentation took place from the Middle-Upper Eocene onwards, to reach its widest areal extent during the Lower Miocene. A hiatus during the Oligocene may have occurred in the western part of the Bight as is the case in the Eucla basin.Only weak deformation of the Tertiary in the offshore area has been observed. This generally occurs over Mesozoic structures in the Duntroon basin and as draping over topographic basement highs at the mouth of the Elliston trough.No significant hydrocarbon indications are known from the surrounding land areas, but the well-documented bitumen strandings along the coast point to offshore seepages indicating generation of hydrocarbons in the general area.At this stage prospects must be regarded as speculative.although a folded probable Mesozoic sequence forms an objective in the Duntroon basin while prospective Mesozoic-Tertiary section appears to be present in the Elliston trough, where structural evaluation is still at a relatively early stage.

The Sustainable Grazing Systems National Experiment. 1. Introduction and methods

2003 ◽  
Vol 43 (8) ◽  
pp. 695 ◽  
Author(s):  
M. H. Andrew ◽  
G. M. Lodge
Keyword(s):  
Data Collection ◽  
Western Australia ◽  
Annual Rainfall ◽  
Single Experiment ◽  
Data Set ◽  
North West ◽  
North East ◽  
The North ◽  
Grazing Systems ◽  
Sustainable Grazing

This paper outlines the development and design of the Sustainable Grazing Systems (SGS) National Experiment from the initial call for expressions of interest, through several workshop processes to the final selection and implementation of its 6 component sites, and the general methodology used at each. Sites were located in Western Australia, western Victoria, north-east Victoria, and on the Central Tablelands, North West Slopes, and the eastern Riverina of New South Wales. Sites in Western Australia, north-east Victoria, the North West Slopes, and the eastern Riverina also had subsites. Methods for the sites and subsites (data collection for pastures, livestock, weather, soils and site characterisation) are presented to provide a central reference, and to save duplication in subsequent papers. Descriptions are provided of the location, average annual rainfall, major pasture, soil and stock types, design and number of treatments, and initial soil levels (0–10 cm) of phosphorus, electrical conductivity, and pH for sites and subsites. Also outlined is the major focus of the research undertaken at each site. While sites studied regionally relevant issues, they operated under a common protocol for data collection with a minimum data set being specified for each of 5 unifying themes: pastures, animal production, water, nutrients, and biodiversity. Economic analyses were also undertaken at the macro- and micro-level, and a procedural tool developed for appraising the on- and off-farm impacts of different systems. To give effect to the themes, common database and modelling tools were developed specifically for the national experiment, so that collectively sites comprised a single experiment.

scholarly journals High prevalence of SARS-CoV-2 swab positivity in England during September 2020: interim report of round 5 of REACT-1 study

2020 ◽  
Author(s):  
Steven Riley ◽  
Kylie E. C. Ainslie ◽  
Oliver Eales ◽  
Caroline E. Walters ◽  
Haowei Wang ◽  
...  
Keyword(s):  
Data Collection ◽  
Reproduction Number ◽  
Age Groups ◽  
Model Assessment ◽  
Interim Report ◽  
North West ◽  
The North ◽  
Random Samples ◽  
High Prevalence ◽  
Using Data

AbstractBackgroundREACT-1 is a community survey of PCR confirmed swab-positivity for SARS-CoV-2 among random samples of the population in England. This interim report includes data from the fifth round of data collection currently underway for swabs sampled from the 18th to 26th September 2020.MethodsRepeated cross-sectional surveys of random samples of the population aged 5 years and over in England with sample size ranging from 120,000 to 160,000 people in each round of data collection. Collection of self-administered nose and throat swab for PCR and questionnaire data. Prevalence of swab-positivity by round and by demographic variables including age, sex, region, ethnicity. Estimation of reproduction number (R) between and within rounds, and time trends using exponential growth or decay model. Assessment of geographical clustering based on boundary-free spatial model.ResultsOver the 9 days for which data are available, we find 363 positives from 84,610 samples giving a weighted prevalence to date of 0.55% (0.47%, 0.64%) in round 5. This implies that 411,000 (351,000, 478,000) people in England are virus-positive under the assumption that the swab assay is 75% sensitive. Using data from the most recent two rounds, we estimate a doubling time of 10.6 (9.4, 12.0) days covering the period 20th August to 26th September, corresponding to a reproduction number R of 1.47 (1.40, 1.53). Using data only from round 5 we estimate a reproduction number of 1.06 (0.74, 1.46) with probability of 63% that R is greater than 1. Between rounds 4 and 5 there was a marked increase in unweighted prevalence at all ages. In the most recent data, prevalence was highest in the 18 to 24 yrs age group at 0.96% (0.68%, 1.36%). At 65+ yrs prevalence increased ∼7-fold between rounds 4 and 5 from 0.04% (0.03%, 0.07%) to 0.29% (0.23%, 0.37%). Prevalence increased in all regions between rounds 4 and 5, giving the highest unweighted prevalence in round 5 in the North West at 0.86% (0.69%, 1.06%). In London, prevalence increased ∼5-fold from 0.10% (0.06%, 0.17%) to 0.49% (0.36%, 0.68%). Regional R values ranged from 1.32 (1.16,1.50) in Yorkshire and the Humber to 1.63 (1.42, 1.88) in the East Midlands over the same period. In the most recent data, there was extensive clustering in the North West, Midlands and in and around London with pockets of clustering in other regions including the South West, North East and East of England. Odds of swab-positivity were ∼2-fold higher in people of Asian and Black ethnicity compared with white participants.ConclusionRapid growth has led to high prevalence of SARS-CoV-2 virus in England among all regions and age groups, including those age groups at highest risk. Although there is evidence of a recent deceleration in the epidemic, current levels of prevalence will inevitably result in additional hospitalisations and mortality in coming weeks. A re-doubling of public health efforts is needed to return to a declining phase of the epidemic.

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