Petroleum potential of the offshore southern Carnarvon Basin—insights from new Geoscience Australia data

2011 ◽  
Vol 51 (2) ◽  
pp. 746
Author(s):  
Irina Borissova ◽  
Gabriel Nelson
Keyword(s):  
Seismic Data ◽  
Source Rocks ◽  
Magnetic Data ◽  
Long Distance ◽  
Potential Field Data ◽  
Petroleum Potential ◽  
Gravity And Magnetic ◽  
Gravity And Magnetic Data ◽  
Insight Into ◽  
Carnarvon Basin

In 2008–9, under the Offshore Energy Security Program, Geoscience Australia (GA) acquired 650 km of seismic data, more than 3,000 km of gravity and magnetic data, and, dredge samples in the southern Carnarvon Basin. This area comprises the Paleozoic Bernier Platform and southern part of the Mesozoic Exmouth Sub-basin. The new seismic and potential field data provide a new insight into the structure and sediment thickness of the deepwater southernmost part of the Exmouth Sub-basin. Mesozoic depocentres correspond to a linear gravity low, in water depths between 1,000–2,000 m and contain between 2–3 sec (TWT) of sediments. They form a string of en-echelon northeast-southwest oriented depressions bounded by shallow-dipping faults. Seismic data indicates that these depocentres extend south to at least 24°S, where they become more shallow and overprinted by volcanics. Potential plays in this part of the Exmouth Sub-basin may include fluvio-deltaic Triassic sandstone and Lower–Middle Jurassic claystone source rocks sealed by the regional Early Cretaceous Muderong shale. On the adjoining Bernier Platform, minor oil shows in the Silurian and Devonian intervals at Pendock–1a indicate the presence of a Paleozoic petroleum system. Ordovician fluvio-deltaic sandstones sealed by the Silurian age marine shales, Devonian reef complexes and Miocene inversion anticlines are identified as potential plays. Long-distance migration may contribute to the formation of additional plays close to the boundary between the two provinces. With a range of both Mesozoic and Paleozoic plays, this under-explored region may have a significant hydrocarbon potential.

Automatic 3-D interpretation of potential field data using analytic signal derivatives

Geophysics ◽  
1997 ◽  
Vol 62 (1) ◽  
pp. 87-96 ◽  
Author(s):  
Nicole Debeglia ◽  
Jacques Corpel
Keyword(s):  
Signal Amplitude ◽  
Vertical Gradient ◽  
Analytic Signal ◽  
Magnetic Data ◽  
Practical Implementation ◽  
Potential Field Data ◽  
Gravity And Magnetic ◽  
Second Derivatives ◽  
Gravity And Magnetic Data ◽  
Derivatives Of

A new method has been developed for the automatic and general interpretation of gravity and magnetic data. This technique, based on the analysis of 3-D analytic signal derivatives, involves as few assumptions as possible on the magnetization or density properties and on the geometry of the structures. It is therefore particularly well suited to preliminary interpretation and model initialization. Processing the derivatives of the analytic signal amplitude, instead of the original analytic signal amplitude, gives a more efficient separation of anomalies caused by close structures. Moreover, gravity and magnetic data can be taken into account by the same procedure merely through using the gravity vertical gradient. The main advantage of derivatives, however, is that any source geometry can be considered as the sum of only two types of model: contact and thin‐dike models. In a first step, depths are estimated using a double interpretation of the analytic signal amplitude function for these two basic models. Second, the most suitable solution is defined at each estimation location through analysis of the vertical and horizontal gradients. Practical implementation of the method involves accurate frequency‐domain algorithms for computing derivatives with an automatic control of noise effects by appropriate filtering and upward continuation operations. Tests on theoretical magnetic fields give good depth evaluations for derivative orders ranging from 0 to 3. For actual magnetic data with borehole controls, the first and second derivatives seem to provide the most satisfactory depth estimations.

scholarly journals Crustal structure in the Campanian region (Southern Apennines, Italy) from potential field modelling

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Y. Kelemework ◽  
M. Milano ◽  
M. La Manna ◽  
G. de Alteriis ◽  
M. Iorio ◽  
...  
Keyword(s):  
Potential Field ◽  
Carbonate Platform ◽  
Vertical Gradient ◽  
Magnetic Data ◽  
Potential Field Data ◽  
Gravity And Magnetic ◽  
Significant Depression ◽  
Mountain Chain ◽  
Surrounding Areas ◽  
Gravity And Magnetic Data

AbstractWe present a 3D model of the main crustal boundaries beneath the Campanian region and the onshore and offshore surrounding areas, based on high-resolution potential field data. Our main objective is the definition of the main structural interfaces in the whole Campanian region from gravity and magnetic data, thanks to their ability to define them on a regional and continuous way. The complex morphology of the Mesozoic carbonate platform, which is fundamental to constrain the top of geothermal reservoir, was reconstructed by inverting the vertical gradient of gravity. We assumed local information from seismic models and boreholes to improve the model. We modeled the deep crustal structures by spectral analysis of Bouguer gravity and magnetic data. The inferred depth estimates indicate a shallow crystalline basement below the Tyrrhenian crust and the Apulian foreland and a significant depression beneath the Bradanic foredeep. The map of the Moho boundary shows a NE-SE verging trough below the Southern Apennine chain and two pronounced uplifts beneath the foreland and the Tyrrhenian crust. We also estimated the depth to the magnetic bottom, showing a thick magnetic crust below the mountain chain and shallow depths where the crustal heat flow is high. The models were compared with seismic sections along selected profiles; a good agreement was observed, despite of some inherent lower resolution for the gravity modelling from spectral methods. The regional covering and the continuity of our estimated crustal interfaces make it a new and valid reference for further geological, geophysical and geothermal studies, especially in areas such as northern and eastern Campania, where there is an incomplete geophysical and geological information.

Gravity and magnetic data analysis based on Poisson wavelet-transforms

2020 ◽  
Author(s):  
Kirill Kuznetsov ◽  
Bulychev Andrey ◽  
Ivan Lygin
Keyword(s):  
Data Analysis ◽  
Magnetic Fields ◽  
Potential Field ◽  
Wavelet Transforms ◽  
Geophysical Methods ◽  
Magnetic Data ◽  
Potential Field Data ◽  
Gravity And Magnetic ◽  
Gravity And Magnetic Data ◽  
Poisson Wavelets

<p>Studies of the Earth’s interior structure are one of the most complex topics in modern science. Integration of different geophysical methods plays a key role in effectively tackling the problem. In the last decade capabilities of potential field geophysical methods have been increasing due to development of advanced digital technologies. Improved resolution and accuracy of gravity and magnetic fields measurements made by modern equipment makes it possible to build more detailed geological models. Different tectonic and structural elements being interpreted in such models produce potential field signals with different spectral characteristics. Like any geophysical signals, potential fields can be described as a spatially non-stationary signal. This means its frequency content may change depending on a given signal sample, in particular with different spatial location of a sample. In this case, approaches of gravity and magnetic fields analysis based on Fourier transform or signal decomposition into a number of harmonic functions can lead to incorrect results. One of the ways to solve this challenge involves using wavelet transform based algorithms, since these transforms do not assume stationary signals and each function of a wavelet-based basis is localized in space domain.</p><p>In gravity and magnetic data analysis it is beneficial to use wavelets based on partial derivatives of the Poisson kernel, which correspond to derivatives of a point source gravity potential. Application of Poisson wavelets in potential field data analysis has begun in the 1990's and is predominantly aimed at studying gravity and magnetic fields singularity points during data interpretation.</p><p>Similar to Fourier-based potential field techniques, it is possible to construct a number of data filtering algorithms based on Poisson wavelets. Current work demonstrates that it is possible to construct algorithms based on Poisson wavelets for transforming profile and spatially gridded gravity and magnetic data, e.g. for calculation of equivalent density and magnetization distributions, upward and downward continuations, reduction to pole and many other filters that take into account spatial distribution of the signal.</p><p>Wavelet-transforms allow to account for spatially non-stationary nature of geophysical signals. Use of wavelet based techniques allows to effectively carry out potential field data interpretation in a variety of different geologic and tectonic settings in a consistent fashion.</p>

Bright spots, milligals, and gammas

Geophysics ◽  
1982 ◽  
Vol 47 (12) ◽  
pp. 1693-1705
Author(s):  
Alan O. Ramo ◽  
James W. Bradley
Keyword(s):  
Seismic Data ◽  
Magnetic Data ◽  
Amplitude Analysis ◽  
Seismic Amplitude ◽  
The North ◽  
Gravity And Magnetic ◽  
Amplitude Anomaly ◽  
North Edge ◽  
Gravity And Magnetic Data ◽  
Seismic Anomaly

Spatially discontinuous high‐amplitude seismic reflections were encountered in seismic data acquired in the early 1970s in northeast Louisiana and southwest Arkansas. Large acoustic impedance contrasts are known to result from gaseous hydrocarbon accumulations. However, amplitude anomalies may also result from large density and velocity contrasts which are geologically unrelated to hydrocarbon entrapment. A well drilled on the northeast Louisiana amplitude anomaly encountered 300 ft of rhyolite at a depth of 6170 ft. Subsequent gravity and total field magnetic profiles across the feature revealed the presence of 0.2 mgal and 17 gamma anomalies, respectively. The measured magnetic susceptibility of the rhyolite was 0.0035 emu and the measured density contrast was [Formula: see text]. Model studies based on the seismically determined areal extent of the anomaly and the measured thickness of rhyolite accounted for the observed gravity and magnetic anomalies. The southwest Arkansas amplitude anomaly was a sheet‐like reflection which terminated to the north and west within the survey area. Two north‐south gravity profiles exhibited a negative character over the sheet‐like reflector but did not exhibit a clear spatial correlation with the north limit of the seismic anomaly. Two north‐south magnetic profiles exhibited tenuous 4 gamma anomalies which appeared to be spatially correlated with the interpreted north edge of the seismic anomaly. A subsequent wildcat well encountered no igneous material but did penetrate 200 ft of salt at about 7500 ft. Reassessment of the gravity and magnetic data indicated that this seismic amplitude anomaly is not attributable to an intrasedimentary igneous source; it suggested a salt‐related 0.2 to 0.3 mgal minimum coextensive with the observed seismic amplitude anomaly. Present amplitude analysis technology would treat these seismic data with suspicion. However, gravity and magnetic data acquisition can provide a relatively inexpensive means for evaluation and verification of amplitude anomalies and thus should be an adjunct for land seismic exploration utilizing amplitude analysis.

scholarly journals Marine geophysical investigations offshore East Greenland

1983 ◽  
Vol 115 ◽  
pp. 93-100
Author(s):  
H.C Larsen
Keyword(s):  
Seismic Data ◽  
Seismic Refraction ◽  
Magnetic Data ◽  
Seismic Profiles ◽  
East Greenland ◽  
Gravity And Magnetic ◽  
Marine Gravity ◽  
Refraction Seismic ◽  
Regional Project ◽  
Gravity And Magnetic Data

During August and September 1982 a marine geophysical survey was conducted on the East Greenland Shelf. The survey was part of the ongoing regional project NAD (Larsen & Andersen, 1982; Andersen et al., 1981; Risum, 1980; Larsen & Thorning, 1980). In all 2794 km of 30-fold multi-channel seismic data and marine gravity and magnetic data were acquired (fig. 33). The object of the NAD programme is to acquire regional coverage of aeromagnetic, multichannel seismic refiection, seismic refraction (sonobuoy), marine gravity and magnetic data of the East Greenland Shelf between latitudes 60° N and 78°N. Aeromagnetic data comprising 63000 line kilometres were acquired in 1979 (Larsen & Thorning, 1980) and 5000 km of marine geophysical data were acquired in 1980 and 1981 (Larsen & Andersen, 1982; Andersen et al., 1981). This year the final data for the project were collected. Thus, a total of 7800 km of multi-channel refiection seismic data and 50 sonobuoy refraction seismic profiles of 20 to 70 km length have been acquired (fig. 33). In addition, marine gravity and magnetics were run at most lines.

STRUCTURE AND STRATIGRAPHY OF THE CEDUNA TERRACE REGION, GREAT AUSTRALIAN BIGHT BASIN

1979 ◽  
Vol 19 (1) ◽  
pp. 53 ◽  
Author(s):  
A. R. Fraser ◽  
L. A. Tilbury
Keyword(s):  
Upper Cretaceous ◽  
Single Channel ◽  
South Australia ◽  
Magnetic Data ◽  
The West ◽  
Petroleum Potential ◽  
Northern Margin ◽  
Gravity And Magnetic ◽  
Gravity And Magnetic Data ◽  
Great Australian Bight

The Ceduna Terrace is a bathymetric feature covering some 70,000 sq km, in the continental slope of South Australia. Its most gently sloping part lies between the 500 and 2500m isobaths, and is underlain by the main depocentre of the Great Australian Bight Basin.A systematic interpretation of the region has been made, based on 17,000 km of multi-channel seismic data from Shell surveys, 8000 km of single-channel seismic, gravity and magnetic data from the BMR Continental Margins Survey, and 6000 km of gravity and magnetic data from surveys by Lamont-Doherty Geological Observatory. Seismic ties were made to the wells Potoroo-1 and Platypus-1.Mapping of the key seismic horizons confirms the picture of the basin as a sedimentary wedge, more than 10 km thick, extending from the edge of the shelf to the continental rise. Three important unconformities can be mapped over a wide area and tied to Potoroo-1 well-a basement reflector separating Lower Proterozoic crystalline rocks of the Gawler Craton from an overlying, block-faulted sequence of mainly Lower to mid-Cretaceaus sediments; an unconformity at the base of an Upper Cretaceous sequence which includes a major prograded unit in the west; and a break-up unconformity at the base of a Tertiary marine transgressive sequence, that, in turn, is overlain by marine carbonate deposits. Widespread shallow marine sediments are believed to exist in the west of the basin, in both the Lower and Upper Cretaceous sequences.Structure is dominated by normal, west to NW trending, down-to-the-south faults, many of which are synsedimentary. Fault displacements are greatest beneath the shelf-break, where basement has been downthrown 5 to 6 km. Farther south, synsedimentary faulting has resulted in a marked thickening of both Upper and Lower Cretaceous sequences.The basin has been barely explored for hydrocarbons. Regional seismic coverage is good, but drilling in the main part of the basin is limited to one well on the northern margin. The petroleum potential of the western half of the basin is rated as good, in view of the interpreted existence of abundant marine source beds and the recognition of situations favourable for generation, migration and entrapment of hydrocarbons.

ACLAS — A method to define geologically significant lineaments from potential-field data

Geophysics ◽  
2017 ◽  
Vol 82 (4) ◽  
pp. G87-G100 ◽  
Author(s):  
Lorenzo Cascone ◽  
Chris Green ◽  
Simon Campbell ◽  
Ahmed Salem ◽  
Derek Fairhead
Keyword(s):  
Large Scale ◽  
Magnetic Data ◽  
Data Set ◽  
New Approach ◽  
Potential Field Data ◽  
North West ◽  
Gravity And Magnetic ◽  
Lineament Analysis ◽  
The Individual ◽  
Gravity And Magnetic Data

Geologic features, such as faults, dikes, and contacts appear as lineaments in gravity and magnetic data. The automated coherent lineament analysis and selection (ACLAS) method is a new approach to automatically compare and combine sets of lineaments or edges derived from two or more existing enhancement techniques applied to the same gravity or magnetic data set. ACLAS can be applied to the results of any edge-detection algorithms and overcomes discrepancies between techniques to generate a coherent set of detected lineaments, which can be more reliably incorporated into geologic interpretation. We have determined that the method increases spatial accuracy, removes artifacts not related to real edges, increases stability, and is quick to implement and execute. The direction of lower density or susceptibility can also be automatically determined, representing, for example, the downthrown side of a fault. We have evaluated ACLAS on magnetic anomalies calculated from a simple slab model and from a synthetic continental margin model with noise added to the result. The approach helps us to identify and discount artifacts of the different techniques, although the success of the combination is limited by the appropriateness of the individual techniques and their inherent assumptions. ACLAS has been applied separately to gravity and magnetic data from the Australian North West Shelf; displaying results from the two data sets together helps in the appreciation of similarities and differences between gravity and magnetic results and indicates the application of the new approach to large-scale structural mapping. Future developments could include refinement of depth estimates for ACLAS lineaments.

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