Exploring New Zealand's marine territory

2011 ◽  
Vol 51 (1) ◽  
pp. 549 ◽  
Author(s):  
Chris Uruski
Keyword(s):  
New Zealand ◽  
Deep Water ◽  
Seismic Data ◽  
East Coast ◽  
Sedimentary Basins ◽  
Petroleum Exploration ◽  
Seismic Survey ◽  
Data Set ◽  
Eastern Australia ◽  
Deep Water Part

Around the end of the twentieth century, awareness grew that, in addition to the Taranaki Basin, other unexplored basins in New Zealand’s large exclusive economic zone (EEZ) and extended continental shelf (ECS) may contain petroleum. GNS Science initiated a program to assess the prospectivity of more than 1 million square kilometres of sedimentary basins in New Zealand’s marine territories. The first project in 2001 acquired, with TGS-NOPEC, a 6,200 km reconnaissance 2D seismic survey in deep-water Taranaki. This showed a large Late Cretaceous delta built out into a northwest-trending basin above a thick succession of older rocks. Many deltas around the world are petroleum provinces and the new data showed that the deep-water part of Taranaki Basin may also be prospective. Since the 2001 survey a further 9,000 km of infill 2D seismic data has been acquired and exploration continues. The New Zealand government recognised the potential of its frontier basins and, in 2005 Crown Minerals acquired a 2D survey in the East Coast Basin, North Island. This was followed by surveys in the Great South, Raukumara and Reinga basins. Petroleum Exploration Permits were awarded in most of these and licence rounds in the Northland/Reinga Basin closed recently. New data have since been acquired from the Pegasus, Great South and Canterbury basins. The New Zealand government, through Crown Minerals, funds all or part of a survey. GNS Science interprets the new data set and the data along with reports are packaged for free dissemination prior to a licensing round. The strategy has worked well, as indicated by the entry of ExxonMobil, OMV and Petrobras into New Zealand. Anadarko, another new entry, farmed into the previously licensed Canterbury and deep-water Taranaki basins. One of the main results of the surveys has been to show that geology and prospectivity of New Zealand’s frontier basins may be similar to eastern Australia, as older apparently unmetamophosed successions are preserved. By extrapolating from the results in the Taranaki Basin, ultimate prospectivity is likely to be a resource of some tens of billions of barrels of oil equivalent. New Zealand’s largely submerged continent may yield continent-sized resources.

scholarly journals Late Neogene Radiolaria from the East Coast Deformed Belt, New Zealand

2021 ◽  
Author(s):  
◽  
Jeffrey Noel Ashby
Keyword(s):  
New Zealand ◽  
Southern Ocean ◽  
Ocean Circulation ◽  
Deep Water ◽  
East Coast ◽  
Sedimentary Basins ◽  
Early Pleistocene ◽  
Time Segment ◽  
Shelf Slope ◽  
Late Neogene

<p>Within the East Coast Deformed Belt there are a number of Late Neogene sedimentary basins with relatively deep-water sediments which, at places, contain abundant radiolarian skeletons. The region was subject to relatively open ocean circulation patterns during the Neogene which, combined with the input of rhyolitic glass shards, has enhanced the siliceous microfossil preservation. A short review of the silica budget is presented and discussed in relation to the preservation of siliceous microfossils in the New Zealand sequences. Techniques were developed to extract and quantitatively study fossil Radiolaria from some of the relatively barren shelf/slope sediments. One hundred and thirty-eight radiolarian taxa are described, most of which can be assigned at the generic level, but thirty-one of which can not be assigned specific names and may eventually prove to be new species. The radiolarian zonation presented is based on detailed analysis of 155 samples from 26 sections and sites ranging in age from basal Tongaporutuan (early Late Miocene) to middle Nukumaruan (early Pleistocene). Sediments of the Kapitean (uppermost Miocene) were generally deposited in shallow water environments or are missing in unconformities in the East Coast Deformed Belt, consequently the radiolarian zonation is based on very poor data in this time segment. Also upper Opoitian and Waipipian (middle Pliocene) sediments, although at places deposited in relatively deep water, generally lack siliceous tuffs, and radiolarian preservation is poor. Five major radiolarian zones can be recognised: Diartus hughesi Zone, Didymocyrtis sp. A Zone, Didymocyrtis sp. A Zone, Didymocyrtis tetrathalmus tetrathalmus Zone, Lamprocyrtis heteroporos Zone, and Lamprocyclas gamphonycha Zone. In samples with good radiolarian preservation six subzones can be identified. The Diartus hughesi Zone can be divided into the Heliodiscus umbonatum Subzone, Didymocyrtis laticonus Subzone, Heliodiscus asteriscus forma large pores Subzone, and Anthocyrtidium ehrenbergi pliocenica Subzone. Additionally the Didymocyrtis tetrathalmus tetrathalmus Zone can be divided into the Lychnocanium sp. aff. grande Subzone and Lamprocyrtis hannai Subzone. The bioevents that define the zonal boundaries are discussed along with other biostratigraphically useful radiolarian datums. These zones and zubzones are correlated to the foraminiferal zonation which in turn has been related, in part, to the paleomagnetic time scale. Correlation are then made with other radiolarian zonations in the north Pacific, tropics, and southern ocean. Points to emerge from these correlations include the apparent provincialism in the transition from Stichocorys delmontense to Stichocorys peregrine in the tropical Pacific. This transition has been reported to occur during approximately 1.5Ma but in New Zealand occurs over a time segment of at least 5.5Ma. The first appearance of Lamprocyclas gamphonycha appears to be an isochronous datum level in temperate radiolarian faunas of the northern and southern Pacific. The last appearance datum of Diartus hughesi at about 7.5Ma is in good agreement with its level in the tropics. The presence of this taxon in lower Gilbert Antarctic cores suggests either a grossly diachronous event between tropical/temperate areas and the southern ocean or, more probably, a misinterpretation of the paleomagnetic signature from key southern ocean piston cores. If the latter situation is the case then the real age estimates on the "Pre middle Gilbert" southern ocean diatom and silicoflagellate stratigraphies are questionable because they are based on the same key cores. Statistical faunal analysis shows that during the Miocene there was not much change in the radiolarian faunas with time and a major change, probably climatically controlled, took place across the Miocene/Pliocene boundary. Variability in preservation has probably affected the faunas to obscure more precise time variation although post-Miocene faunas indicate that some is present. In conclusion, the Radiolaria, although not as common in the fossil record as the foraminifera, definitely contribute to New Zealand Late Neogene integrated stratigraphy and suggest that our knowledge could be greatly enhanced by the study of other siliceous microfossil groups.</p>

EXPLORATION OPPORTUNITIES, EAST COAST BASIN, NEW ZEALAND

2000 ◽  
Vol 40 (1) ◽  
pp. 39
Author(s):  
J.B. Frederick ◽  
E.J. Davies ◽  
P.G. Smith ◽  
D. Spancers ◽  
T.J. Williams
Keyword(s):  
New Zealand ◽  
Late Miocene ◽  
Joint Venture ◽  
East Coast ◽  
High Amplitude ◽  
Petroleum Exploration ◽  
Early Miocene ◽  
Seismic Survey ◽  
Seismic Events ◽  
Submarine Fan

The Westech-Orion Joint Venture holds onshore Petroleum Exploration Permit 38329 and offshore PEPs 38325, 38326 and 38333 in the East Coast Basin, New Zealand. The Joint Venture holds 24,117 km2 covering Hawkes Bay and the Wairarapa shelf.The Westech-Orion Joint Venture has drilled six exploratory wells and five appraisal wells in the onshore East Coast Basin over a two year period. All wells encountered significant gas shows, with two wells discovering hydrocarbons in potentially commercial volumes. Each well was drilled on the crest of a seismically mapped structure, characterised by asymmetric folding over a northwest dipping thrust fault.Prior to this drilling program, the reservoir potential of the Wairoa area was inferred to be dominated by turbidite sandstones of the Tunanui and Makaretu formations (Mid-Late Miocene). The new wells show that the Mid Miocene and parts of the Early and Late Miocene pinch out across the 'Wairoa High'.One of the primary onshore reservoirs is the Kauhauroa Limestone (Early Miocene), a bryozoan-dominated, tightly packed and cemented limestone with dominantly fracture porosity. The other primary reservoir is the Tunanui Sandstone (Mid Miocene), which in well intersections to date comprises medium-thickly bedded sandstone, with net sand typically 40%. The sands have high lithic content, and are moderately sorted and subangular-subrounded.Abnormally high formation pressures were encountered in all wells, ranging up to 3,400 psi at 1,000 m. Crestal pressure gradients commonly exceed 70% of the lithostatic pressure gradient, despite the relative proximity to outcrop. The overpressure may reflect relatively young uplift of fossil pressures, with insufficient time for pressure equilibration within a generally overpressured system.The prospectivity of the area has been highgraded by recent maturation and reservoir studies in Hawkes Bay and by gas discoveries in Westech-Orion wells onshore northern Hawkes Bay. Maturation studies identified nine kitchen areas with oil migration commencing in the Late Miocene. Seismic stratigraphy and correlation with onshore wells identified offshore submarine fan deposits of Eocene, Early Miocene, Mid Miocene and Pliocene age.A 594 km2 exploration 3D seismic survey was acquired in Hawke Bay in April 1999, and 685 km of 2D seismic were acquired in March 2000. Preliminary interpretation of the 3D survey has yielded five prospects, each covering 20–90 km2. One prospect is a lowstand fan identified by stacked mounding and bidirectional downlap, correlated with the onshore Mid Miocene Tunanui Sandstone. High amplitude seismic events of Mid-Late Miocene ages are inferred to be pulses of submarine fan development, in places associated with direct hydrocarbon indicators (DHIs). High amplitude seismic events in the Pliocene include a package of high amplitude seismic reflectors interpreted as structurally trapped DHI truncated by a major unconformity.

Accelerating seismic fault and stratigraphy interpretation with deep CNNs: A case study of the Taranaki Basin, New Zealand

2020 ◽  
Vol 39 (10) ◽  
pp. 727-733
Author(s):  
Haibin Di ◽  
Leigh Truelove ◽  
Cen Li ◽  
Aria Abubakar
Keyword(s):  
New Zealand ◽  
Seismic Data ◽  
Reservoir Characterization ◽  
Seismic Survey ◽  
Deep Convolutional Neural Networks ◽  
Seismic Attribute ◽  
Data Set ◽  
Seismic Fault ◽  
Attribute Analysis ◽  
Specific Implementation

Accurate mapping of structural faults and stratigraphic sequences is essential to the success of subsurface interpretation, geologic modeling, reservoir characterization, stress history analysis, and resource recovery estimation. In the past decades, manual interpretation assisted by computational tools — i.e., seismic attribute analysis — has been commonly used to deliver the most reliable seismic interpretation. Because of the dramatic increase in seismic data size, the efficiency of this process is challenged. The process has also become overly time-intensive and subject to bias from seismic interpreters. In this study, we implement deep convolutional neural networks (CNNs) for automating the interpretation of faults and stratigraphies on the Opunake-3D seismic data set over the Taranaki Basin of New Zealand. In general, both the fault and stratigraphy interpretation are formulated as problems of image segmentation, and each workflow integrates two deep CNNs. Their specific implementation varies in the following three aspects. First, the fault detection is binary, whereas the stratigraphy interpretation targets multiple classes depending on the sequences of interest to seismic interpreters. Second, while the fault CNN utilizes only the seismic amplitude for its learning, the stratigraphy CNN additionally utilizes the fault probability to serve as a structural constraint on the near-fault zones. Third and more innovatively, for enhancing the lateral consistency and reducing artifacts of machine prediction, the fault workflow incorporates a component of horizontal fault grouping, while the stratigraphy workflow incorporates a component of feature self-learning of a seismic data set. With seven of 765 inlines and 23 of 2233 crosslines manually annotated, which is only about 1% of the available seismic data, the fault and four sequences are well interpreted throughout the entire seismic survey. The results not only match the seismic images, but more importantly they support the graben structure as documented in the Taranaki Basin.

THE EAST COAST BASIN OF NEW ZEALAND, AN EMERGING PETROLEUM PROVINCE

2005 ◽  
Vol 45 (1) ◽  
pp. 563 ◽  
Author(s):  
C.I. Uruski ◽  
B.D. Field ◽  
R. Funnell
Keyword(s):  
New Zealand ◽  
Seismic Data ◽  
Oil And Gas ◽  
East Coast ◽  
Data Set ◽  
Sequence Stratigraphic ◽  
Large Structures ◽  
Oil Generation ◽  
Wide Range ◽  
Reservoir Facies

More than 300 oil and gas seeps are known in the onshore East Coast Basin of North Island, New Zealand. Spectacular geological structures have been explored by more than 40 wells, only three of which have been offshore. Results are tantalising, with 70% of wells yielding oil or gas shows. Westech’s two gas discoveries onshore at Kauhauroa and Tuhara in northern Hawkes Bay remain un-developed at present.Strong gas shows were encountered in both open-file wells drilled offshore and elevated gas readings were recorded in the recent Tawatawa–1 well, but reservoir quality was poor.Nevertheless, good reservoir facies are abundant in the East Coast Basin. A wide range of Miocene and Pliocene sands and limestones, with porosities of 20% and above are known from outcrop and wells. But, modern, good quality seismic data are essential to allow sequence stratigraphic interpretation and a reasonable likelihood of predicting the distribution of reservoir facies. As part of its program to stimulate exploration in New Zealand, the NZ government is commissioning a new 4,000 km, highquality 2D seismic data set with the intention of making it freely available to interested exploration companies by mid-2005.The very thick sedimentary succession, the presence of direct hydrocarbon indicators on seismic data, the strong gas shows in wells drilled offshore and the reasonable expectation of oil generation and expulsion into numerous large structures with good reservoir facies combine to make the offshore East Coast Basin an attractive exploration venue.

scholarly journals Late Neogene Radiolaria from the East Coast Deformed Belt, New Zealand

2021 ◽  
Author(s):  
◽  
Jeffrey Noel Ashby
Keyword(s):  
New Zealand ◽  
Southern Ocean ◽  
Ocean Circulation ◽  
Deep Water ◽  
East Coast ◽  
Sedimentary Basins ◽  
Early Pleistocene ◽  
Time Segment ◽  
Shelf Slope ◽  
Late Neogene

<p>Within the East Coast Deformed Belt there are a number of Late Neogene sedimentary basins with relatively deep-water sediments which, at places, contain abundant radiolarian skeletons. The region was subject to relatively open ocean circulation patterns during the Neogene which, combined with the input of rhyolitic glass shards, has enhanced the siliceous microfossil preservation. A short review of the silica budget is presented and discussed in relation to the preservation of siliceous microfossils in the New Zealand sequences. Techniques were developed to extract and quantitatively study fossil Radiolaria from some of the relatively barren shelf/slope sediments. One hundred and thirty-eight radiolarian taxa are described, most of which can be assigned at the generic level, but thirty-one of which can not be assigned specific names and may eventually prove to be new species. The radiolarian zonation presented is based on detailed analysis of 155 samples from 26 sections and sites ranging in age from basal Tongaporutuan (early Late Miocene) to middle Nukumaruan (early Pleistocene). Sediments of the Kapitean (uppermost Miocene) were generally deposited in shallow water environments or are missing in unconformities in the East Coast Deformed Belt, consequently the radiolarian zonation is based on very poor data in this time segment. Also upper Opoitian and Waipipian (middle Pliocene) sediments, although at places deposited in relatively deep water, generally lack siliceous tuffs, and radiolarian preservation is poor. Five major radiolarian zones can be recognised: Diartus hughesi Zone, Didymocyrtis sp. A Zone, Didymocyrtis sp. A Zone, Didymocyrtis tetrathalmus tetrathalmus Zone, Lamprocyrtis heteroporos Zone, and Lamprocyclas gamphonycha Zone. In samples with good radiolarian preservation six subzones can be identified. The Diartus hughesi Zone can be divided into the Heliodiscus umbonatum Subzone, Didymocyrtis laticonus Subzone, Heliodiscus asteriscus forma large pores Subzone, and Anthocyrtidium ehrenbergi pliocenica Subzone. Additionally the Didymocyrtis tetrathalmus tetrathalmus Zone can be divided into the Lychnocanium sp. aff. grande Subzone and Lamprocyrtis hannai Subzone. The bioevents that define the zonal boundaries are discussed along with other biostratigraphically useful radiolarian datums. These zones and zubzones are correlated to the foraminiferal zonation which in turn has been related, in part, to the paleomagnetic time scale. Correlation are then made with other radiolarian zonations in the north Pacific, tropics, and southern ocean. Points to emerge from these correlations include the apparent provincialism in the transition from Stichocorys delmontense to Stichocorys peregrine in the tropical Pacific. This transition has been reported to occur during approximately 1.5Ma but in New Zealand occurs over a time segment of at least 5.5Ma. The first appearance of Lamprocyclas gamphonycha appears to be an isochronous datum level in temperate radiolarian faunas of the northern and southern Pacific. The last appearance datum of Diartus hughesi at about 7.5Ma is in good agreement with its level in the tropics. The presence of this taxon in lower Gilbert Antarctic cores suggests either a grossly diachronous event between tropical/temperate areas and the southern ocean or, more probably, a misinterpretation of the paleomagnetic signature from key southern ocean piston cores. If the latter situation is the case then the real age estimates on the "Pre middle Gilbert" southern ocean diatom and silicoflagellate stratigraphies are questionable because they are based on the same key cores. Statistical faunal analysis shows that during the Miocene there was not much change in the radiolarian faunas with time and a major change, probably climatically controlled, took place across the Miocene/Pliocene boundary. Variability in preservation has probably affected the faunas to obscure more precise time variation although post-Miocene faunas indicate that some is present. In conclusion, the Radiolaria, although not as common in the fossil record as the foraminifera, definitely contribute to New Zealand Late Neogene integrated stratigraphy and suggest that our knowledge could be greatly enhanced by the study of other siliceous microfossil groups.</p>

scholarly journals Time-Lapse Seismic Monitoring of Onshore Reservoirs in Niger Delta, Field ‘K’ as a Case Study

2017 ◽  
Vol 1 (1) ◽  
pp. 23-27 ◽  
Author(s):  
A. Ogbamikhumi ◽  
T. Tralagba ◽  
E. E. Osagiede
Keyword(s):  
Seismic Data ◽  
Acoustic Impedance ◽  
Niger Delta ◽  
Rock Physics ◽  
Time Lapse ◽  
Seismic Survey ◽  
Impedance Change ◽  
Data Set ◽  
Reservoir Fluid ◽  
4D Seismic

Field ‘K’ is a mature field in the coastal swamp onshore Niger delta, which has been producing since 1960. As a huge producing field with some potential for further sustainable production, field monitoring is therefore important in the identification of areas of unproduced hydrocarbon. This can be achieved by comparing production data with the corresponding changes in acoustic impedance observed in the maps generated from base survey (initial 3D seismic) and monitor seismic survey (4D seismic) across the field. This will enable the 4D seismic data set to be used for mapping reservoir details such as advancing water front and un-swept zones. The availability of good quality onshore time-lapse seismic data for Field ‘K’ acquired in 1987 and 2002 provided the opportunity to evaluate the effect of changes in reservoir fluid saturations on time-lapse amplitudes. Rock physics modelling and fluid substitution studies on well logs were carried out, and acoustic impedance change in the reservoir was estimated to be in the range of 0.25% to about 8%. Changes in reservoir fluid saturations were confirmed with time-lapse amplitudes within the crest area of the reservoir structure where reservoir porosity is 0.25%. In this paper, we demonstrated the use of repeat Seismic to delineate swept zones and areas hit with water override in a producing onshore reservoir.

THE EVOLUTION OF THE BERNIER RIDGE, SOUTHERN CARNARVON BASIN, WESTERN AUSTRALIA:IMPLICATIONS FOR PETROLEUM PROSPECTIVITY

2004 ◽  
Vol 44 (1) ◽  
pp. 241 ◽  
Author(s):  
A.M. Lockwood ◽  
C. D’Ercole
Keyword(s):  
Seismic Data ◽  
Large Scale ◽  
Sedimentary Basins ◽  
Early Carboniferous ◽  
Source Rocks ◽  
Petroleum Exploration ◽  
Large Igneous Province ◽  
Satellite Gravity ◽  
Tectonic Events ◽  
Carnarvon Basin

The basement topography of the Gascoyne Platform and adjoining areas in the Southern Carnarvon Basin was investigated using satellite gravity and seismic data, assisted by a depth to crystalline basement map derived from modelling the isostatic residual gravity anomaly. The resulting enhanced view of the basement topography reveals that the Gascoyne Platform extends further westward than previously indicated, and is bounded by a northerly trending ridge of shallow basement, named the Bernier Ridge.The Bernier Ridge is a product of rift-flank uplift prior to the Valanginian breakup of Gondwana, and lies east of a series of small Mesozoic syn-rift sedimentary basins. Extensive magmatic underplating of the continental margin associated with this event, and a large igneous province is inferred west of the ridge from potential field and seismic data. Significant tectonic events that contributed to the present form of the Bernier Ridge include the creation of the basement material during the Proterozoic assembly of Rodinia, large-scale faulting during the ?Cambrian, uplift and associated glaciation during the early Carboniferous, and rifting of Gondwana during the Late Jurassic. The depositional history and maturity of the Gascoyne Platform and Bernier Ridge show that these terrains have been structurally elevated since the mid-Carboniferous.No wells have been drilled on the Bernier Ridge. The main source rocks within the sedimentary basins west of the Bernier Ridge are probably Jurassic, similar to those in the better-known Abrolhos–Houtman and Exmouth Sub-basins, where they are mostly early mature to mature and within the oil window respectively. Within the Bernier Ridge area, prospective plays for petroleum exploration in the Jurassic succession include truncation at the breakup unconformity sealed by post-breakup shale, and tilted fault blocks sealed by intraformational shale. Plays in the post-breakup succession include stratigraphic traps and minor rollover structures.

The 2017 offshore acreage release areas: petroleum geological overview

2017 ◽  
Vol 57 (2) ◽  
pp. 304
Author(s):  
Thomas Bernecker ◽  
Steve Abbott ◽  
George Bernardel ◽  
Megan Lech ◽  
Ryan Owens ◽  
...  
Keyword(s):  
Information Management System ◽  
Petroleum Exploration ◽  
Seismic Survey ◽  
Data Repository ◽  
Technical Program ◽  
North East ◽  
The North ◽  
Eastern Australia ◽  
Northern Carnarvon Basin ◽  
Offshore Petroleum

In 2017, 21 new offshore petroleum exploration areas have been released. The majority of the areas are located along the North West Shelf spanning the Westralian Superbasin from the Bonaparte Basin in the north-east to the Northern Carnarvon Basin in the south-west. New areas have been released in offshore south-eastern Australia with new opportunities provided in the Otway, Bass and Gippsland basins. Two large areas in the northern Perth Basin, an offshore frontier, complete the 2017 Acreage Release. All Release Areas are supported by industry nominations and one new cash bid area has been offered in the Dampier Sub-basin. Geoscience Australia continues to support industry activities by acquiring, interpreting and integrating pre-competitive datasets that are made freely available as part of the agency’s regional petroleum geological studies. A new regional 2D seismic survey was acquired in the Houtman Sub-basin of the Perth Basin, forming the basis of the latest prospectivity study carried out by Geoscience Australia. The results of the study are presented in the technical program of the 2017 APPEA conference. A wealth of seismic and well data, submitted under the Offshore Petroleum and Greenhouse Gas Storage Act 2006 (OPGSSA) are made available through the National Offshore Petroleum Information Management System (NOPIMS). Additional datasets are accessible through Geoscience Australia’s data repository.

Discovery of a 400 km2 honeycomb structure mimicking a regional unconformity on three-dimensional seismic data

Geology ◽  
2019 ◽  
Vol 47 (12) ◽  
pp. 1181-1184 ◽  
Author(s):  
Rosine Riera ◽  
Julien Bourget ◽  
Victorien Paumard ◽  
Moyra E.J. Wilson ◽  
Jeffrey Shragge ◽  
...  
Keyword(s):  
Seismic Data ◽  
Three Dimensional ◽  
Honeycomb Structure ◽  
Petroleum Exploration ◽  
Negative Consequences ◽  
Burial Diagenesis ◽  
Data Set ◽  
Seismic Reflection Data ◽  
Diagenetic Alteration ◽  
Basin Scale

Abstract Recognition of seismic unconformities is crucial for interpreting basin history from seismic reflection data sets in both siliciclastic and carbonate settings. While it is well established that non-erosional changes in sedimentary facies can create seismic reflections that mimic seismic unconformities (i.e., pseudo-unconformities), these features are generally considered to be localized and uncommon, and, therefore, are largely overlooked during interpretation. Diagenetic alteration of strata can also affect the morphology of seismic reflectors and mislead seismic interpreters. This study is based on a three-dimensional (3-D) seismic data set and documents a 400 km2 honeycomb structure (HS) masquerading as a regional erosional unconformity in the Oligocene–Miocene carbonate strata of Australia’s North West Shelf. This HS is located at the transition between the topsets and the foresets of clinoforms of carbonate to marly composition. The HS expression in 3-D seismic data cross sections is irregular, giving the HS the appearance of a truncated surface that could erroneously be interpreted as a regional seismic unconformity. Closer examination reveals that the HS crosscuts chronostratigraphic clinoform reflectors, and frequency extraction processing shows that the HS dominantly falls within a lower-frequency band than the clinoform reflectors. The morphology of the HS (i.e., continuous with densely packed cells) and its time-transgressive nature suggest that it has a burial diagenetic origin. This suggests that creation of pseudo-unconformities at basin scale by burial diagenesis may lead to surface misidentification, with negative consequences for paleoenvironmental studies and petroleum exploration activities.

The Reinga Basin, North Island, New Zealand

2010 ◽  
Vol 50 (1) ◽  
pp. 287 ◽  
Author(s):  
Chris Uruski ◽  
Eva Reid ◽  
Vaughan Stagpoole ◽  
Rick Herzer ◽  
Angela Griffin ◽  
...  
Keyword(s):  
New Zealand ◽  
Early Stage ◽  
Plate Boundary ◽  
Source Rocks ◽  
Seismic Survey ◽  
Quality Data ◽  
Data Set ◽  
Regional Tectonic ◽  
Sedimentary Succession ◽  
Sedimentary Fill

In early 2009, CGGVeritas, supported by the Crown Minerals Group of New Zealand’s Ministry of Economic Development, undertook a 5,900 km reconnaissance 2D seismic survey of the Reinga Basin, which is located to the northwest of the Northland Peninsula and Basin, New Zealand. Although very little data previously existed across this basin apart from low-fold reconnaissance seismic data, it was suspected of being an extension of the Northland Basin and to contain a thick sedimentary succession. It was thought to have formed as a rift basin near the Gondwana margin and to have been inverted during Neogene evolution of the present plate boundary. This paper is the result of the first interpretation of this new, high-quality data set. It confirms the presence of the basin and its sedimentary succession. Up to 9,000 m of sedimentary fill is imaged. The presence of coaly early rift packages and extensions of the Waipawa Formation black marine shale suggest that the basin contains voluminous source rocks. The basin appears to be more deformed in the northwest where large inversion structures are imaged. The northeastern margin is underlain by an extension of the Northland Allochthon which was obducted onto the New Zealand margin during initiation of the present plate boundary around 25 million years ago (Ma). The basin may also have been affected by strike-slip faulting associated with the Vening-Meinesz fracture zone, which developed during the Miocene. Several volcanic bodies are recognised, but in contrast to the adjacent Northland Basin where many large Miocene shield volcanos erupted, volcanic extrusions are rare in the Reinga region. Thermal modelling suggests that the basal source rocks are mature and expelling hydrocarbons and many direct hydrocarbon anomalies are present. Large trapping structures are apparent throughout the basin and even at this early stage of knowledge it appears that the region may have significant hydrocarbon potential. This paper will discuss the evolution of the basin in the regional tectonic context and summarise its petroleum prospectivity.

Sign in / Sign up

Export Citation Format

Share Document