Mesozoic rift onset and its impact on the sequence stratigraphic architecture of the Northern Carnarvon Basin

2016 ◽  
Vol 56 (1) ◽  
pp. 143 ◽  
Author(s):  
Anthony Gartrell ◽  
Jose Torres ◽  
Matt Dixon ◽  
Myra Keep
Keyword(s):  
Marked Change ◽  
Middle Part ◽  
Late Triassic ◽  
Normal Faults ◽  
Rift Basins ◽  
Tectonic Event ◽  
Growth Strata ◽  
Stratigraphic Architecture ◽  
Northern Carnarvon Basin ◽  
Carnarvon Basin

Ages varying from Late Triassic to Early Jurassic have been proposed by different authors for the onset of rifting in the Northern Carnarvon Basin. Seismic sections from the Exmouth Sub-basin and outer Exmouth Plateau demonstrate significant growth strata associated with displacement on normal faults starting at least at the base of the R. rhaetica zone (Rhaetian). This tectonic event coincides with a marked change in sequence architecture and a large landward shift (~300 km) of the paleo-shoreline to the vicinity of the Rankin and Alpha Arch trends. Rapid creation of accommodation in the inboard narrow rift basins (Exmouth, Barrow and Dampier sub-basins) is suggested to be the most likely cause of this major transgression. The preferential development of associated carbonate build-ups during the Rhaetian on the footwall side of active tilted fault blocks provides additional evidence for the onset of significant extensional faulting occurring during this time. An earlier more subtle initiation phase of rifting, however, is interpreted during the Norian, from around the middle part of the H. balmei biozone time, above which a change in stratigraphic architecture from aggrading to retrograding occurs. The observed structural and stratigraphic transitions can be related to typical phases of evolution described in many rift basins around the world. The work highlights the importance of integrating regional structural geology, sequence stratigraphy and depositional systems observations to provide robust constraints for basin evolutions.

Synsedimentary collapse of portions of the lower Blomidon Formation (Late Triassic), Fundy rift basin, Nova Scotia

1995 ◽  
Vol 32 (11) ◽  
pp. 1965-1976 ◽  
Author(s):  
Rolf V. Ackermann ◽  
Roy W. Schlische ◽  
Paul E. Olsen
Keyword(s):  
Nova Scotia ◽  
Late Triassic ◽  
Normal Faults ◽  
Rift Basin ◽  
Rift Basins ◽  
Kink Bands ◽  
Deformation Features ◽  
Terrestrial Environments ◽  
Sediment Deformation ◽  
Fluvial Sandstone

A chaotic mudstone unit within the lower Blomidon Formation (Late Triassic) has been traced for 35 km in the Mesozoic Fundy rift basin of Nova Scotia. This unit is characterized by highly disrupted bedding that is commonly cut by small (<0.5 m) domino-style synsedimentary normal faults, downward movement of material, geopetal structures, variable thickness, and an irregular, partially faulted contact with the overlying unit. The chaotic unit is locally overlain by a fluvial sandstone, which is overlain conformably by mudstone. Although the thickness of the sandstone is highly variable, the overlying mudstone unit exhibits only gentle regional dip. The sandstone unit exhibits numerous soft-sediment deformation features, including dewatering structures, convoluted bedding, kink bands, and convergent fault fans. The frequency and intensity of these features increase dramatically above low points at the base of the sandstone unit. These stratigraphic relations suggest buried interstratal karst, the subsurface dissolution of evaporites bounded by insoluble sediments. We infer that the chaotic unit was formed by subsidence and collapse resulting from the dissolution of an evaporite bed or evaporite-rich unit by groundwater, producing dewatering and synsedimentary deformation structures in the overlying sandstone unit, which infilled surface depressions resulting from collapse. In coeval Moroccan rift basins, facies similar to the Blomidon Formation are associated with halite and gypsum beds. The regional extent of the chaotic unit indicates a marked period of desiccation of a playa lake of the appropriate water chemistry. The sedimentary features described here may be useful for inferring the former existence of evaporites or evaporite-rich units in predominantly clastic terrestrial environments.

Extending interpretations of natural fractures from the wellbore using 3D attributes: The Carnarvon Basin, Australia

2016 ◽  
Vol 4 (1) ◽  
pp. SB107-SB129 ◽  
Author(s):  
Adam H. E. Bailey ◽  
Rosalind C. King ◽  
Simon P. Holford ◽  
Martin Hand
Keyword(s):  
Fluid Flow ◽  
Integrated Approach ◽  
Horizontal Stress ◽  
Electric Resistivity ◽  
Normal Faults ◽  
Data Sets ◽  
Natural Fractures ◽  
Northern Carnarvon Basin ◽  
Resistivity Image ◽  
Carnarvon Basin

Natural fractures can be identified in wellbores using electric resistivity image logs; however, the challenge of predicting fracture orientations, densities, and probable contribution to subsurface fluid flow away from the wellbore remains. Regional interpretations of fracture sets are generally confined to areas featuring an extensive reservoir analog outcrop. We have made use of extensive data sets available in Western Australia’s Northern Carnarvon Basin to map subsurface natural fractures, contributing to a regional understanding of fracture sets that can be applied to broader parts of the basin. The Northern Carnarvon Basin is composed of distinct structural domains that have experienced differing tectonic histories. Interpretation of regional fractures was achieved through an integrated approach, incorporating electric resistivity image logs from 52 Carnarvon Basin wells and seismic attribute analysis of two 3D seismic data sets: Bonaventure_3D ([Formula: see text]) and HC_93_3D ([Formula: see text]). Integration of these two data sets allows for a regionally extensive identification of natural fractures away from well control. Fractures of differing age and character are identified within the basin: Outboard areas are dominated by fractures likely to be open to fluid flow that are parallel to subparallel to the approximately east–west present-day maximum horizontal stress, providing possible flow conduits between potential damage zones identified alongside the north–northeast/south–southwest-striking faults that constitute the major structural trend of the basin, and inboard areas dominated by northeast–southwest to north–northeast/south–southeast fractures formed in fault damage-zones alongside normal, and inverted-normal, faults at those orientations. Finally, fractures observed in wells from the Rankin Platform and Dampier Subbasin occur at neither of these orientations; rather, they closely parallel the strikes of local faults. Additionally, variation is seen in fracture strikes due to isotropic present-day stress magnitudes. This methodology extends fracture interpretations from the wellbore and throughout the region of interest, constituting a regional understanding of fracture sets that can be applied to broader parts of the basin.

GEOLOGICAL CONTROLS ON OVERPRESSURE IN THE NORTHERN CARNARVON BASIN

2001 ◽  
Vol 41 (1) ◽  
pp. 573 ◽  
Author(s):  
P.R. Tingate ◽  
A. Khaksar ◽  
P. van Ruth ◽  
D. Dewhurst ◽  
M. Raven ◽  
...  
Keyword(s):  
Pore Pressure ◽  
Late Triassic ◽  
Research Centre ◽  
Hydrocarbon Generation ◽  
Depth Range ◽  
Cooperative Research ◽  
Well Completion ◽  
Pore Pressure Prediction ◽  
Northern Carnarvon Basin ◽  
Carnarvon Basin

A small, but significant fraction of wells drilled in the Northern Carnarvon Basin have encountered problems with overpressure: better pore pressure prediction would improve safety and economy for drilling operations. In the Northern Carnarvon Basin the occurrence of overpressure and likely mechanisms are under investigation as part of the Australian Petroleum Cooperative Research Centre (APCRC) Research Program on Pore Pressure Prediction. Previous workers have proposed a number of mechanisms as the main cause of overpressure including undercompaction, hydrocarbon generation, horizontal stress and clay reactions.A preliminary regional study was undertaken incorporating over 400 well completion reports which identified approximately 60 wells with mud weights greater than 1.25 S.G. A subset of these wells was investigated and more reliable but much scarcer pressure indicators such as kicks or direct pressure measurements were examined. Depth-pressure profiles of wells across the region are variable and commonly show pressure compartmentalisation. Using a range of indicators, it was observed that overpressured strata in the Barrow Subbasin:occur over a wide depth range (2,500 to 4,000+ mbsl);occur over a wide stratigraphic range (Late Triassic to Late Cretaceous);are not regionally limited by major structural boundaries;are associated with sequences dominated by finegrained sediments with variable clay mineralogy; and in depositionally, or structurally, isolated sandstones; andmainly to the west of the Barrow and Dampier Subbasins around the Alpha Arch and Rankin Trend, coinciding with thickest Tertiary deposition.Previous published work in the study area has tended to support hydrocarbon generation as the primary cause of overpressure, though more recent publications have emphasised compaction disequilibrium. The log response (DT, RHOB and NPHI) of overpressured clay-rich strata has been investigated to constrain the type of overpressure mechanism. A normal compaction trend has been derived for four stratigraphic groupings; Muderong Shale, Barrow Group, Jurassic and Triassic. All overpressure occurrences were accompanied by an increase in sonic transit time. Not all wells have suitable log data for evaluation, but all stratigraphic groups show some evidence of elevated porosity associated with overpressure consistent with disequillibrium compaction as a dominant mechanism. Overpressures in the Barrow Group in Minden-1 and the Jurassic section within Zeepaard–1 do not have accompanying porosity anomalies suggesting a different overpressure mechanism model is needed.

Analysis of overpressure and its generating mechanisms in the northern Carnarvon Basin from drilling data

2012 ◽  
Vol 52 (1) ◽  
pp. 375
Author(s):  
Iko Sagala ◽  
Mark Tingay
Keyword(s):  
Pore Pressure ◽  
Effective Stress ◽  
Late Triassic ◽  
Effective Stress Analysis ◽  
Pore Pressure Prediction ◽  
Pressure Indicators ◽  
Northern Carnarvon Basin ◽  
Vertical Effective Stress ◽  
Prediction Techniques ◽  
Carnarvon Basin

The Northern Carnarvon Basin is one of Australia’s most prolific hydrocarbon basins. Overpressure has been encountered in numerous wells drilled in the Northern Carnarvon Basin. Knowledge of overpressure distribution is important for drilling and exploration strategies, and understanding the origin of overpressure is essential for applying reliable pore pressure prediction techniques. Unconventional pore pressure indicators—primarily drilling kicks and the presence of connection gas—were used to improve an updated distribution of overpressure and to investigate the origin of overpressure in the Northern Carnarvon Basin. This unconventional dataset was compiled from 45 wells. Overpressures are observed in 40 wells and tend to occur near, or on, the Rankin Platform, Alpha Arch, and Barrow Trend. The presence of overpressure in this area coincides with the region of maximum Cenozoic deposition. Overpressured strata in the Northern Carnarvon Basin occurs through a wide stratigraphic range, from Late Triassic to Paleocene sequences. Generally, post Paleocene sequences in the Northern Carnarvon Basin are considered to be normally pressured. Porosity-vertical effective stress analysis in shale lithologies was used to investigate the origin of overpressure in the Northern Carnarvon Basin. Porosity-vertical effective stress plots from 28 wells in the Northern Carnarvon Basin identified 20 wells where the overpressure appears to be generated by disequilibrium compaction, and eight wells where the overpressure appears to be generated by a component of fluid expansion. Disequilibrium compaction mechanisms were the predominant cause of overpressure in wells around the Rankin Platform and areas located further away from the coast. Conversely, fluid expansion mechanisms were the predominant cause of overpressure in wells around the Alpha Arch and Bambra Trend, and an area located closer to the coast. These results broadly confirm those obtained from earlier studies and highlight the usefulness of kick and connection gas data in overpressure analysis.

scholarly journals Unravelling the Triassic Mungaroo Formation within North Carnarvon Basin using Regional Stratal Slice Volumes

2018 ◽  
Vol 58 (2) ◽  
pp. 833 ◽  
Author(s):  
Tony Marsh ◽  
Bill Kowalik ◽  
Rhonda Welch ◽  
Anne Powell ◽  
Heidi Howe ◽  
...  
Keyword(s):  
Regional Scale ◽  
Depositional Environments ◽  
Late Triassic ◽  
Seismic Surveys ◽  
Marine Deposits ◽  
Northern Carnarvon Basin ◽  
Stratal Slice ◽  
Well Data ◽  
Vertical Spacing ◽  
Carnarvon Basin

Chevron has developed a new method for viewing, rendering and interpreting multiple, proportionally-flattened seismic surveys (US patent). The products of this method are referred to as Regional Stratal Slice Volumes (RSSVs). Within the Northern Carnarvon Basin (NCB), local RSSVs contain a patchwork of 22 3D seismic surveys covering an area of approximately 68 000 km2 and comprising a 4+ km-thick succession of alluvial to shallow-marine deposits of the Late Triassic Mungaroo Formation. Seismic slices for each constituent volume were spliced together, correlated with adjacent volumes and combined with supporting structural, cultural and well-based data. This has created a temporal series of unbroken, regionally-extensive, seismic snapshots which, when viewed successively, capture the evolving geomorphology and palaeogeography of the basin from east of Gorgon and Wheatstone out to the Exmouth Plateau. Through the integration of the RSSVs and well data, the shoreline and marginal marine to non-marine transitions were identified and accurately mapped at an approximately 20 m vertical spacing throughout the Mungaroo Formation. This work resulted in an in-depth understanding of changing depositional environments at a regional scale. Observed, temporally-systematic fluctuations of the shoreline on the RSSVs provide a highly predictive stratigraphic framework for the basin. Additionally, RSSVs have been used to provide insight into regional NCB studies and to support localised prospect and field scale evaluations. Over the past three years, RSSVs combined with automatically generated closures have been used to identify significant additions to Chevron’s prospect portfolio.

The paleogeography of the Beagle Sub-basin, northern Carnarvon Basin, Australia

1998 ◽  
Vol 68 (6) ◽  
pp. 1131-1145
Author(s):  
A. E. Stephenson ◽  
J. E. Blevin ◽  
B. G. West
Keyword(s):  
Northern Carnarvon Basin ◽  
Carnarvon Basin

POST-RIFT TECTONIC SUBSIDENCE AND PALAEO-WATER DEPTHS IN THE NORTHERN CARNARVON BASIN, WESTERN AUSTRALIA

2001 ◽  
Vol 41 (1) ◽  
pp. 367 ◽  
Author(s):  
A.R. Kaiko ◽  
A.M. Tait
Keyword(s):  
Vitrinite Reflectance ◽  
Tectonic Subsidence ◽  
Hydrocarbon Generation ◽  
Basin Inversion ◽  
Sedimentary Architecture ◽  
History Of ◽  
Northern Carnarvon Basin ◽  
Migration Pathways ◽  
Water Depths ◽  
Carnarvon Basin

The subsidence history of the Northern Carnarvon Basin has been dominated by simple thermal sag following the creation of the Exmouth, Barrow and Dampier Sub-basins by Early to Middle Jurassic rifting. This conclusion follows from the recognition of vitrinite reflectance suppression, which removes the need for recent heating events, and from the use of seismic stratigraphy, rather than only palynology and micro-palaeontology, to determine palaeo-water depths.The simple thermal-sag model, related to Jurassic rifting, accounts for the post-rift sedimentary architecture of the Northern Carnarvon Basin, especially in areas of sediment starvation. It also has implications for the timing of hydrocarbon generation and the reconstruction of migration pathways. This work has re-emphasised the theoretical possibility of determining palaeo-water depths by adjusting one-dimensional basin models to fit simple thermal sag tectonic subsidence curves.Miocene uplift, in the order of several hundred metres, has caused local basin inversion, accentuated some preexisting structures and re-activated some faults causing hydrocarbon remigration, but has otherwise not affected the thermal history of the sediments.

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