Regional gravity and magnetic data usage for seismic survey planning and the integration of 3‐D gravity and seismic data in the Santos and Campos Basins, Brazil

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.

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Crustal structure of the western Indian shield: Model based on regional gravity and magnetic data

Geoscience Frontiers ◽

10.1016/j.gsf.2013.02.006 ◽

2013 ◽

Vol 4 (6) ◽

pp. 717-728 ◽

Cited By ~ 13

Author(s):

Suman Kilaru ◽

Bandaru Karunakar Goud ◽

Vijay Kumar Rao

Keyword(s):

Crustal Structure ◽

Magnetic Data ◽

Indian Shield ◽

Model Based ◽

Gravity And Magnetic ◽

Regional Gravity ◽

Gravity And Magnetic Data

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Bright spots, milligals, and gammas

Geophysics ◽

10.1190/1.1441319 ◽

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.

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Seismic, gravity and magnetics, a complementary geophysical study of the Paqualin Structure, Timor Sea, Australia

Exploration Geophysics ◽

10.1071/eg989025 ◽

1989 ◽

Vol 20 (2) ◽

pp. 25 ◽

Cited By ~ 2

Author(s):

P.M. Smith ◽

M. Whitehead

Keyword(s):

Seismic Data ◽

Gravity Data ◽

Seismic Survey ◽

Magnetic Data ◽

Data Sets ◽

Intrusive Body ◽

Geophysical Study ◽

Timor Sea ◽

Susceptibility Contrast ◽

Gravity And Magnetic Data

The presence of a large anomalous structure in the northern part of Permit AC/P2 in the Timor Sea has been recognised ever since seismic data were first acquired in the area. Historically, however, sparse seismic coverage has always prevented a detailed and unambiguous interpretation of the complicated structure. In order to overcome this problem, some 2000 km of 3D seismic data were acquired over the feature. In conjunction with this seismic survey, detailed gravity and magnetic data sets were also recorded over the structure.Interpretation of the new seismic data indicated the presence of a piercement structure which is associated with a small negative Bouguer gravity anomaly and a magnetic intensity anomaly resulting from a positive susceptibility contrast. Modelling of the magnetic data indicated that an acidic or intermediate intrusive body was the most likely cause of the piercement structure. The presence of an acidic intrusive body was consistent with the gravity data which indicated that no large density contrast existed between the material of the piercement structure and the surrounding sediments.The combined interpretation of these three data sets was tested by a well, Paqualin-1, drilled on the flank of the piercement structure. The well encountered a thick evaporite sequence with associated thin bands of magnetitie and intermediate igneous rocks. It was logged with a three component downhole magnetic probe and forward magentic modelling work incorporating the results of the magnetic log gave good agreement with the observed aeromagnetic profiles.

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Marine geophysical investigations offshore East Greenland

Rapport Grønlands Geologiske Undersøgelse ◽

10.34194/rapggu.v115.7839 ◽

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.

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