scholarly journals Characterization and Distribution of Cenozoic Polygonal Fault: Case Studies in West Africa and Vietnam Continental Margins

2021 ◽  
Vol 54 (1E) ◽  
pp. 19-28
Author(s):  
Anh Ngoc Le
Keyword(s):  
Seismic Data ◽  
Normal Faults ◽  
Continental Margins ◽  
Fine Grained ◽  
Passive Margins ◽  
Gradient Slope ◽  
Polygonal Pattern ◽  
Low Amplitude ◽  
3D Seismic Data ◽  
Polygonal Fault

The Cenozoic sequence of offshore Cameroon and Vietnam has been analysed based on newly 1500 km2 3D seismic data (Kribi-Campo basin) and 75 km 2D seismic data (Hoang Sa basin). Polygonal faults are widely developed in both passive margins and have relatively similar characteristics. These highly faulted intervals are up to c. 1000 m, characterized by normal faults with a throw of 10-20 ms TWT and 100 m - 1000 m spacing, displaying a polygonal pattern in the map view. Polygonal faults in the Kribi-Campo basin developed almost in the entire Cenozoic sequence mainly in two sets, one in deep section and one in shallow section whereas the Hoang Sa basin developed the polygonal fault only in the shallow section up to the seafloor corresponding to the Pliocene- Pleistocene sequence. In the Kribi-Campo basin, polygonal faults are developed extensively in the high gradient slope (3.4o) which is relatively rare in the low gradient slope (0.7o). Hoang Sa basin shows the widespread polygonal fault except for the area of canyon occurrence. The occurrence of thick and widespread polygonal fault formations associated with the low amplitude reflections suggests the interpretation of fine-grained sediments, thus possibly great seal potential for the study areas.

Extensive, Gas-charged Quaternary Sand Accumulations of the Northern North Sea and North Sea Fan

2020 ◽  
Author(s):  
Benjamin Bellwald ◽  
Sverre Planke ◽  
Sunil Vadakkepuliyambatta ◽  
Stefan Buenz ◽  
Christine Batchelor ◽  
...  
Keyword(s):  
North Sea ◽  
Seismic Data ◽  
Data Sets ◽  
3D Seismic ◽  
Fine Grained ◽  
The North ◽  
Northern North Sea ◽  
Well Data ◽  
Sea Fan ◽  
3D Seismic Data

<p>Sediments deposited by marine-based ice sheets are dominantly fine-grained glacial muds, which are commonly known for their sealing properties for migrating fluids. However, the Peon and Aviat hydrocarbon discoveries in the North Sea show that coarse-grained glacial sands can occur over large areas in formerly glaciated continental shelves. In this study, we use conventional and high-resolution 2D and 3D seismic data combined with well information to present new models for large-scale fluid accumulations within the shallow subsurface of the Norwegian Continental Shelf. The data include 48,000 km<sup>2</sup> of high-quality 3D seismic data and 150 km<sup>2</sup> of high-resolution P-Cable 3D seismic data, with a vertical resolution of 2 m and a horizontal resolution of 6 to 10 m in these data sets. We conducted horizon picking, gridding and attribute extractions as well as seismic geomorphological interpretation, and integrated the results obtained from the seismic interpretation with existing well data.</p><p>The thicknesses of the Quaternary deposits vary from hundreds of meters of subglacial till in the Northern North Sea to several kilometers of glacigenic sediments in the North Sea Fan. Gas-charged, sandy accumulations are characterized by phase-reserved reflections with anomalously high amplitudes in the seismic data as well as density and velocity decreases in the well data. Extensive (>10 km<sup>2</sup>) Quaternary sand accumulations within this package include (i) glacial sands in an ice-marginal outwash fan, sealed by stiff glacial tills deposited by repeated glaciations (the Peon discovery in the Northern North Sea), (ii) sandy channel-levee systems sealed by fine-grained mud within sequences of glacigenic debris flows, formed during shelf-edge glaciations, (iii) fine-grained glacimarine sands of contouritic origin sealed by gas hydrates, and (iv) remobilized oozes above large evacuation craters and sealed by megaslides and glacial muds. The development of the Fennoscandian Ice Sheet resulted in a rich variety of depositional environments with frequently changing types and patterns of glacial sedimentation. Extensive new 3D seismic data sets are crucial to correctly interpret glacial processes and to analyze the grain sizes of the related deposits. Furthermore, these data sets allow the identification of localized extensive fluid accumulations within the Quaternary succession and distinguish stratigraphic levels favorable for fluid accumulations from layers acting as fluid barriers.</p>

Identification of polygonal faulting from legacy 3D seismic data in vintage Gulf of Mexico data using seismic attributes

2021 ◽  
pp. 1-17
Author(s):  
Karen M. Leopoldino Oliveira ◽  
Heather Bedle ◽  
Karelia La Marca Molina
Keyword(s):  
Seismic Data ◽  
Seismic Attributes ◽  
Fault System ◽  
3D Seismic ◽  
Seismic Attribute ◽  
Variable Amplitude ◽  
Attribute Analysis ◽  
Amplitude Data ◽  
3D Seismic Data ◽  
Polygonal Fault

We analyzed a 1991 3D seismic data located offshore Florida and applied seismic attribute analysis to identify geological structures. Initially, the seismic data appears to have a high signal-to-noise-ratio, being of an older vintage of quality, and appears to reveal variable amplitude subparallel horizons. Additional geophysical analysis, including seismic attribute analysis, reveals that the data has excessive denoising, and that the continuous features are actually a network of polygonal faults. The polygonal faults were identified in two tiers using variance, curvature, dip magnitude, and dip azimuth seismic attributes. Inline and crossline sections show continuous reflectors with a noisy appearance, where the polygonal faults are suppressed. In the variance time slices, the polygonal fault system forms a complex network that is not clearly imaged in the seismic amplitude data. The patterns of polygonal fault systems in this legacy dataset are compared to more recently acquired 3D seismic data from Australia and New Zealand. It is relevant to emphasize the importance of seismic attribute analysis to improve accuracy of interpretations, and also to not dismiss older seismic data that has low accurate imaging, as the variable amplitude subparallel horizons might have a geologic origin.

scholarly journals Ultra-slow throw rates of polygonal fault systems

Geology ◽  
2020 ◽  
Vol 48 (5) ◽  
pp. 473-477
Author(s):  
James J. King ◽  
Joe A. Cartwright
Keyword(s):  
Three Dimensional ◽  
Volumetric Strain ◽  
Time Frame ◽  
Normal Faults ◽  
Seismic Reflection Data ◽  
Fine Grained ◽  
Fault Systems ◽  
Reflection Data ◽  
Gravity Driven ◽  
Polygonal Fault

Abstract Polygonal fault systems (PFSs) are an enigmatic class of small nontectonic extensional faults. PFSs are predominantly hosted in fine-grained sedimentary tiers and are prevalent along many continental margin basins. The genesis of PFSs is widely debated, and little is known about the time frame for polygonal fault growth. We present the first measurements of throw rates for polygonal faults by measuring the vertical offset of seven age-calibrated horizons mapped using three-dimensional seismic reflection data from the Norwegian Sea. Individual polygonal faults exhibit a range of throw rate profiles through time, ranging from near linear to singly or multiply stepped. The stepped profiles have short-term throw rates ranging from 0 to 18 m/m.y. Time-averaged throw rates of 180 polygonal faults over the entire 2.61–0 Ma interval are normally distributed and range between 1.4 and 10.9 m/m.y. We convert our PFS throw rates to displacement rates and compare these to published displacement rates for gravity-driven and tectonic normal faults. We find that the displacement rates of polygonal faults mark the lower limit of a continuous spectrum of extensional fault displacement rates; they are as much as two orders of magnitude slower than those of gravity-driven faults, and as much as three orders of magnitude slower than those of the fastest-growing tectonic faults. We attribute the ultra-slow kinematic behavior to the nontectonic nature of polygonal faults, where throw accumulates primarily through dewatering of the largely fine-grained sediments composing the host layers for the PFSs, and through differential volumetric strain between the fault footwalls and hanging walls.

High-resolution architecture of a polygonal fault interval inferred from geomodel applied to 3D seismic data from the Gjallar Ridge, Vøring Basin, Offshore Norway

2012 ◽  
Vol 332-334 ◽  
pp. 134-151 ◽  
Author(s):  
Dimitri Laurent ◽  
Aurélien Gay ◽  
Catherine Baudon ◽  
Christian Berndt ◽  
Roger Soliva ◽  
...  
Keyword(s):  
High Resolution ◽  
Seismic Data ◽  
3D Seismic ◽  
3D Seismic Data ◽  
Vøring Basin ◽  
Polygonal Fault

Fault System Study in South Beir Sag

2014 ◽  
Vol 508 ◽  
pp. 177-180
Author(s):  
Yan Huo ◽  
Zheng He Zhang
Keyword(s):  
Seismic Data ◽  
Oil And Gas ◽  
Fault System ◽  
Normal Faults ◽  
Oil And Gas Exploration ◽  
Positive Guidance ◽  
Complex Process ◽  
Formation And Evolution ◽  
3D Seismic Data

The Tamt basin is a Mesozoic-Cenozoic rift basin. Strongly influenced by the late tectonism, the basin structure and evolution has a very complex process. Based on Interpretation of 3D seismic data, the faults are divided into four categories in the system, that is, extensional normal faults, shear or torsional tensional normal faults, shear compression thrust faults and reversible faults. Major faults in the evolutionary sequence are divided into early development, late development, and long-term development, with good correlation between the formation and evolution of the basin. On the surface, the fault strike shift from NNE and NE to SN-trending and NNW. For the sector, fault system can be divided into the lower stretch fault system and the upper strike-slip fault system by the T22 seismic reflection layer. The structure style in South Beir Sag can be summed up as rift style, transtension style, transpression reverse style into three categories, and the different structural styles play an important role in the distribution of oil and gas. The results have positive guidance to oil and gas exploration in South Beir sag.

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