The discovery of a new sedimentary basin: offshore Raukumara, East Coast, North Island, New Zealand

2008 ◽  
Vol 48 (1) ◽  
pp. 53 ◽  
Author(s):  
Chris Uruski ◽  
Callum Kennedy ◽  
Rupert Sutherland ◽  
Vaughan Stagpoole ◽  
Stuart Henrys
Keyword(s):  
New Zealand ◽  
Oil And Gas ◽  
East Coast ◽  
Plate Boundary ◽  
Source Rocks ◽  
Fault System ◽  
Northern Coast ◽  
The South ◽  
Petroleum Potential ◽  
The North

The East Coast of North Island, New Zealand, is the site of subduction of the Pacific below the Australian plate, and, consequently, much of the basin is highly deformed. An exception is the Raukumara Sub-basin, which forms the northern end of the East Coast Basin and is relatively undeformed. It occupies a marine plain that extends to the north-northeast from the northern coast of the Raukumara Peninsula, reaching water depths of about 3,000 m, although much of the sub-basin lies within the 2,000 m isobath. The sub-basin is about 100 km across and has a roughly triangular plan, bounded by an east-west fault system in the south. It extends about 300 km to the northeast and is bounded to the east by the East Cape subduction ridge and to the west by the volcanic Kermadec Ridge. The northern seismic lines reveal a thickness of around 8 km increasing to 12–13 km in the south. Its stratigraphy consists of a fairly uniformly bedded basal section and an upper, more variable unit separated by a wedge of chaotically bedded material. In the absence of direct evidence from wells and samples, analogies are drawn with onshore geology, where older marine Cretaceous and Paleogene units are separated from a Neogene succession by an allochthonous series of thrust slices emplaced around the time of initiation of the modern plate boundary. The Raukumara Sub-basin is not easily classified. Its location is apparently that of a fore-arc basin along an ocean-to-ocean collision zone, although its sedimentary fill must have been derived chiefly from erosion of the New Zealand land mass. Its relative lack of deformation introduces questions about basin formation and petroleum potential. Although no commercial discoveries have been made in the East Coast Basin, known source rocks are of marine origin and are commonly oil prone, so there is good potential for oil as well as gas in the basin. New seismic data confirm the extent of the sub-basin and its considerable sedimentary thickness. The presence of potential trapping structures and direct hydrocarbon indicators suggest that the Raukumara Sub-basin may contain large volumes of oil and gas.

DEVELOPMENTS IN THE CENTRAL AND NORTHEASTERN EAST COAST BASIN, NORTH ISLAND, NEW ZEALAND

2006 ◽  
Vol 46 (1) ◽  
pp. 215 ◽  
Author(s):  
C.I. Uruski ◽  
B.D. Field ◽  
R. Funnell ◽  
C. Hollis ◽  
A. Nicol ◽  
...  
Keyword(s):  
New Zealand ◽  
20Th Century ◽  
Oil And Gas ◽  
East Coast ◽  
Source Rocks ◽  
Late 20Th Century ◽  
Data Set ◽  
General Sequence ◽  
Thermal Models ◽  
The North

Oil production in the East Coast Basin began in the late 19th century from wildcat wells near oil seeps. By the mid-20th century, geology was being applied to oil exploration, but with little success. In the late 20th century, seismic techniques were added to the exploration arsenal and several gas discoveries were made. At each stage it was recognised that exploration in this difficult but tantalising basin required more information than was available. Continuing work by exploration companies, as well as by the Institute of Geological & Nuclear Sciences (GNS), has begun to reduce the risk of exploration. Source rocks have been identified and sophisticated thermal models show that petroleum is being generated and expelled from them as shown by numerous oil and gas seeps onshore. Many potential reservoir sequences have been recognised from outcrop studies and depositional models are being refined. All components of petroleum systems have been demonstrated to be present. The most important deficiency to date is the general lack of high-quality seismic data which would allow recognition of reservoir facies in the subsurface.During early 2005, Crown Minerals, the New Zealand government group charged with promoting and regulating oil and gas exploration, commissioned a high specification regional 2D survey intended to address some of the main data gaps in the offshore East Coast Basin. A broad grid was planned with several regional lines to be acquired with a 12,000 m streamer and infill lines to be acquired with a streamer 8,000 m long. It was expected that the long streamer would increase resolution of Paleogene and Cretaceous units. Several of the lines were actually acquired with a 4,000 m streamer due to unexpectedly high rates of unserviceability. The resulting 2,800 km data set consists of a series of northwest–southeast lines approximately orthogonal to the coast at a spacing of about 10 km as well as several long strike lines.GNS was contracted to produce a series of reports covering source rock distribution, a catalogue of reservoir rocks, a regional seismic interpretation, thermal models and structural reconstruction. The data package and reports are available free of charge to any interested exploration company to accompany the licensing round that was announced on 1 September 2005. The new data set has confirmed the existence of a large, little-deformed basin to the north of North Island and the Bay of Plenty; it has elucidated the complex structure of a large part of the East Coast Basin and has enabled generation of a general sequence stratigraphic model which assists in delineating reservoir targets. On 1 September 2005, the New Zealand government launched a licensing round covering about 43,000 km2 of the East Coast Basin, from the far offshore East Cape Ridge in the north to the northern Wairarapa coast in the south. Four blocks (I, J, K and L) were on offer for a competitive staged work programme bid, closing on 17 February 2006.

Geodetic strain and the deformational history of the North Island of New Zealand during the late Cainozoic

1987 ◽  
Vol 321 (1557) ◽  
pp. 163-181 ◽  
Keyword(s):  
New Zealand ◽  
Subduction Zone ◽  
East Coast ◽  
Late Quaternary ◽  
Plate Boundary ◽  
Boundary Zone ◽  
Metamorphic Belt ◽  
Volcanic Region ◽  
The North ◽  
Plate Boundary Zone

The subduction zone under the east coast of the North Island of New Zealand comprises, from east to west, a frontal wedge, a fore-arc basin, uplifted basement forming the arc and the Central Volcanic Region. Reconstructions of the plate boundary zone for the Cainozoic from seafloor spreading data require the fore-arc basin to have rotated through 60° in the last 20 Ma which is confirmed by palaeomagnetic declination studies. Estimates of shear strain from geodetic data show that the fore-arc basin is rotating today and that it is under extension in the direction normal to the trend of the plate boundary zone. The extension is apparently achieved by normal faulting. Estimates of the amount of sediments accreted to the subduction zone exceed the volume of the frontal wedge: underplating by the excess sediments is suggested to be the cause of late Quaternary uplift of the fore-arc basin. Low-temperature—high-pressure metamorphism may therefore be occurring at depth on the east coast and high-temperature—low-pressure metamorphism is probable in the Central Volcanic Region. The North Island of New Zealand is therefore a likely setting for a paired metamorphic belt in the making.

scholarly journals Adjoint tomography of the Hikurangi subduction zone and the North Island of New Zealand

2021 ◽  
Author(s):  
Bryant Chow
Keyword(s):  
New Zealand ◽  
Subduction Zone ◽  
East Coast ◽  
Plate Boundary ◽  
Velocity Model ◽  
Seismic Velocities ◽  
Low Velocity ◽  
Velocity Models ◽  
The North ◽  
Adjoint Tomography

<p><b>Seismic tomography is a powerful tool for understanding Earth structure. In New Zealand, velocity models derived using ray-based tomography have been used extensively to characterize the complex plate boundary between the Australian and Pacific plates. Advances in computational capabilities now allow us to improve these velocity models using adjoint tomography, an imaging method which minimizes differences between observed and simulated seismic waveforms. We undertake the first application of adjoint tomography in New Zealand to improve a ray-based New Zealand velocity model containing the Hikurangi subduction zone and the North Island of New Zealand.</b></p> <p>In support of this work we deployed the Broadband East Coast Network (BEACON), a temporary seismic network aimed at improving coverage of the New Zealand permanent network, along the east coast of the North Island. We concurrently develop an automated, open-source workflow for full-waveform inversion using spectral element and adjoint methods. We employ this tool to assess a candidate velocity model’s suitability for adjoint tomography. Using a 3D ray-based traveltime tomography model of New Zealand, we generate synthetic seismic waveforms for more than 10 000 source–receiver pairs and evaluate waveform misfits. We subsequently perform synthetic checkerboard inversions with a realistic New Zealand source–receiver distribution. Reasonable systematic time shifts and satisfactory checkerboard resolution in synthetic inversions indicate that the candidate model is appropriate as an initial model for adjoint tomography. This assessment also demonstrates the relative ease of use and reliability of the automated tools.</p> <p>We then undertake a large-scale adjoint tomography inversion for the North Island of New Zealand using up to 1 800 unique source–receiver pairs to fit waveforms with periods 4–30 s, relating to minimum waveform sensitivities on the order of 5 km. Overall, 60 geographically well-distributed earthquakes and as many as 88 broadband station locations are included. Using a nonlinear optimization algorithm, we undertake 28 model updates of Vp and Vs over six distinct inversion legs which progressively increase resolution. The total inversion incurred a computational cost of approximately 500 000 CPU-hours. The overall time shift between observed and synthetic seismograms is reduced, and updated velocities show as much as ±30% change with respect to initial values. A formal resolution analysis using point spread tests highlights that velocity changes are strongly resolved onland and directly offshore, at depths above 30 km, with low-amplitude changes (> 1%) observed down to 100 km depth. The most striking velocity changes coincide with areas related to the active Hikurangi subduction zone.</p> <p>We interpret the updated velocity model in terms of New Zealand tectonics and geology, and observe good agreement with known basement terranes, and major structural elements such as faults, sedimentary basins, broad-scale subduction related features. We recover increased spatial heterogeneity in seismic velocities along the strike of the Hikurangi subduction zone with respect to the initial model. Below the East Coast, we interpret two localized high-velocity anomalies as previously unidentified subducted seamounts. We corroborate this interpretation with other work, and discuss the implications of deeply subducted seamounts on slip behavior along the Hikurangi margin. In the Cook Strait we observe a low-velocity zone that we interpret as a deep sedimentary basin. Strong velocity gradients bounding this low-velocity zone support hypotheses of a structural boundary here separating the North and South Islands of New Zealand. In the central North Island, low-velocity anomalies are linked to surface geology, and we relate seismic velocities at depth to crustal magmatic activity below the Taupo Volcanic Zone.</p> <p>This new velocity model provides more accurate synthetic seismograms and additional constraints on enigmatic tectonic processes related to the North Island of New Zealand. Both the velocity model itself, and the underpinning methodological contributions, improve our ever-expanding understanding of the North Island of New Zealand, the Hikurangi subduction zone, and the broader Australian-Pacific plate boundary.</p>

scholarly journals Geological structure and petroleum potential of the Kara Sea shelf

2019 ◽  
Vol 489 (3) ◽  
pp. 272-276
Author(s):  
V. A. Kontorovich ◽  
A. E. Kontorovich
Keyword(s):  
Oil And Gas ◽  
Sedimentary Basins ◽  
Geological Structure ◽  
Water Area ◽  
Kara Sea ◽  
Gas Content ◽  
Liquid Hydrocarbons ◽  
The South ◽  
Petroleum Potential ◽  
The North

On the Kara Sea shelf, there are two sedimentary basins separated by the North-Siberian sill. Tectonically the southern part of the Kara Sea covers the South Kara regional depression, which is the northern end of the West Siberian geosyncline. This part of the water area is identified as part of the South Kara oil and gas region, within which the Aptian-Albian-Senomanian sedimentary complex is of greatest interest in terms of gas content, in terms of liquid hydrocarbons - Neocomian and Jurassic deposits. The northern part of the Kara Sea is an independent North Kara province, for the most part of which the prospects of petroleum potential are associated with Paleozoic sedimentary complexes. Oil and gas perspective objects of this basin may be associated with anticlinal, non-structural traps and reef structures.

scholarly journals Petroleum Potential of the Deep Ordovician- Lower Devonian Oil and Gas Complex in the South-East of the Timan-Pechora Petroleum Province

2021 ◽  
Vol 20 (3) ◽  
pp. 274-283
Author(s):  
E.A. Kuznetsovа ◽  
Keyword(s):  
Lower Devonian ◽  
Oil And Gas ◽  
Source Rocks ◽  
Hydrocarbon Generation ◽  
The South ◽  
Reservoir Properties ◽  
Lower Paleozoic ◽  
Petroleum Potential ◽  
Middle Paleozoic ◽  
Gas Potential

The article is devoted to the assessment of the oil and gas potential of the deep Ordovician-Lower Devonian oil and gas complex in the south-east of the Timan-Pechora oil and gas province. Within the Upper Pechora Basin of the Pre-Ural trough and in the south of the Pechora-Kolva aulacogen, several wells were drilled with a depth of more than 5 km, some of which entered the Lower Paleozoic deposits. These strata are difficult to access and poorly studied, and the prospects for their oil and gas potential are unclear. The article describes the composition of the complex, gives geochemical characteristics, describes reservoir properties, and presents the results of 1D and 2D basin modeling. Models of the zoning of catagenesis are presented. The oil and gas complex includes a variety of oil and gas source rocks. It is possible to allocate collectors, as well as the seals. In the Lower Paleozoic sediments, the processes of oil, gas and gas condensate generation took place, which could ensure the formation of deposits both in the deep strata of the Lower and Middle Paleozoic, and in the overlying horizons. The generation and accumulation of hydrocarbons in deep-buried sediments occurred at a favorable time for the formation of deposits. However, it is considered that the scale of hydrocarbon generation for the Lower Paleozoic deposits is not high.

PETROLEUM POTENTIAL OF THE GREAT SOUTH BASIN, NEW ZEALAND—NEW SEISMIC DATA IMPROVES IMAGING

2007 ◽  
Vol 47 (1) ◽  
pp. 145 ◽  
Author(s):  
C. Uruski ◽  
C. Kennedy ◽  
T. Harrison ◽  
G. Maslen ◽  
R.A. Cook ◽  
...  
Keyword(s):  
New Zealand ◽  
Seismic Data ◽  
Oil And Gas ◽  
Petroleum Industry ◽  
Source Rocks ◽  
Seismic Survey ◽  
Recording Time ◽  
Petroleum Potential ◽  
South Basin ◽  
Time Migration

Much of the Great South Basin is covered by a 30,000 km grid of old seismic data, dating from the 1970s. This early exploration activity resulted in drilling eight wells, one of which, Kawau–1a, was a 461 Bcf gas-condensate discovery. Three other wells had significant oil and gas shows; in particular, Toroa–1 had extensive gas shows and 300 m oil shows. Cuttings are described in the geological logs as dripping with oil. The well was never tested due to engineering difficulties, meaning that much of the bore was accidentally filled with cement while setting casing.In early 2006, Crown Minerals, New Zealand’s petroleum industry regulating body, conducted a new 2D seismic survey in a previously lightly surveyed region across the northern part of the Great South Basin. While previous surveys were generally recorded for five seconds, sometimes six, with up to a 2,500-metre-long cable, the new survey, acquired by CGG Multiwave’s Pacific Titan, employed a 6,000-metre-long streamer and recorded for eight seconds.The dataset was processed to pre-stack time migration (PreSTM) by the GNS Science group using its access to the New Zealand Supercomputer. Increasing the recording time yielded dividends by more fully imaging, for the first time, the nature of rift faulting in the basin. Previous data showed only the tops of many fault blocks. The new data show a system of listric extensional faults, presumably soling out onto a mid-crust detachment. Sedimentary reflectors are observed to seven seconds, implying a thickness of up to 6,000 m of section, probably containing source rock units. The rotated fault blocks provide focal points for large compaction structures. The new data show amplitude anomalies and other features possibly indicating hydrocarbons associated with many of these structures. The region around the Toroa–1 well was typified by anomalously low velocities, which created a vertical zone of heavily attenuated reflections, particularly on intermediate processing products. The new data also show an amplitude anomaly at the well’s total depth (TD) which gives rise to a velocity push-down.Santonian age coaly source rocks are widespread and several reservoir units are recognised. The reservoir at Kawau–1a is the extensive Kawau Sandstone, an Early Maastrichtian transgressive unit sealed by a thick carbonate-cemented mudstone. In addition to the transgressive sandstone target, the basin also contains sandy Eocene facies, and Paleogene turbidite targets may also be attractive. Closed structures are numerous and many are very large with potential to contain billion barrel oil fields or multi-Tcf gas fields.

THE GEOLOGY AND EVOLUTION OF THE SOUTH PEPPER HYDROCARBON ACCUMULATION

1985 ◽  
Vol 25 (1) ◽  
pp. 235 ◽  
Author(s):  
A.F. Williams ◽  
D.J. Poynton
Keyword(s):  
Middle Miocene ◽  
Oil And Gas ◽  
Upper Jurassic ◽  
Lower Jurassic ◽  
Source Rocks ◽  
The South ◽  
Hydrocarbon Migration ◽  
Tectonic Event ◽  
The North ◽  
Migration History

The South Pepper field, discovered in 1982, is located 30 km southwest of Barrow Island in the offshore portion of the Barrow Sub-basin, Western Australia. The oil and gas accumulation occurs in the uppermost sands of the Lower Cretaceous Barrow Group and the overlying low permeability Mardie Greensand Member of the Muderong Shale.The hydrocarbons are trapped in one of several fault closed anticlines which lie on a high trend that includes the North Herald, Pepper and Barrow Island structures. This trend is postulated to have formed during the late Valanginian as the result of differential compaction and drape over a buried submarine fan sequence. During the Turonian the trend acted as a locus for folding induced by right-lateral wrenching along the sub-basin edge. Concurrent normal faulting dissected the fold into a number of smaller anticlines. This essentially compressional tectonic phase contrasted with the earlier extensional regime which was associated with rift development during the Callovian. A compressional tectonic event in the Middle Miocene produced apparent reverse movement on the South Pepper Fault but only minor changes to the structural closure.Geochemical and structural evidence indicates at least two periods of hydrocarbon migration into the top Barrow Group - Mardie Greensand reservoir. The earlier occurred in the Turonian subsequent to the period of wrench tectonics and involved the migration of oil from Lower Jurassic Dingo Claystone source rocks up the South Pepper Fault. This oil was biodegraded before the second episode of migration occurred after the Middle Miocene tectonism. The later oil is believed to have been sourced by the Middle to Upper Jurassic Dingo Claystone. Biodegradation at this stage ceased or became insignificant due to temperature increase and reduction of meteoric water flow. Gas-condensate, sourced from Triassic or Lower Jurassic sediments may have migrated into the structure with this second oil although a more recent migration cannot be ruled out.The proposed structural and hydrocarbon migration history fits regional as well as local geological observations for the Barrow Sub-basin. Further data particularly from older sections of the stratigraphic column within the area are needed to refine the interpretation.

scholarly journals Strike-Slip Enables Subduction Initiation Beneath a Failed Rift: New Seismic Constraints from Puysegur Margin, New Zealand

2020 ◽  
Author(s):  
Brandon Shuck ◽  
Harm Van Avendonk ◽  
Sean Gulick ◽  
Michael Gurnis ◽  
Rupert Sutherland ◽  
...  
Keyword(s):  
New Zealand ◽  
Subduction Zone ◽  
Plate Boundary ◽  
Strike Slip ◽  
Rift Basin ◽  
The South ◽  
Subduction Initiation ◽  
The North ◽  
Collision Zone ◽  
Seismic Images

&lt;p&gt;Critical ingredients and conditions necessary to initiate a new subduction zone are debated. General agreement is that subduction initiation likely takes advantage of previously weakened lithosphere and may prefer to nucleate along pre-existing plate boundaries. To evaluate how past tectonic regimes and lithospheric structures might facilitate underthrusting and lead to self-sustaining subduction, we present an analysis of the Puysegur Margin, a young subduction zone with a rapidly evolving tectonic history.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;The Puysegur Margin, south of New Zealand, currently accommodates convergence between the Australian and Pacific plates, exhibits an active seismic Benioff zone, a deep ocean trench, and young adakitic volcanism on the overriding plate. Tectonic plate reconstructions show that the margin experienced a complicated transformation from rifting to seafloor spreading, to strike-slip motion, and most recently to incipient subduction, all in the last ~45 million years. Details of this tectonic record remained incomplete due to the lack of high-quality seismic data throughout much of the margin.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;Here we present seismic images from the South Island Subduction Initiation Experiment (SISIE) which surveyed the Puysegur region February-March, 2018. SISIE acquired 1252 km of deep-penetrating multichannel seismic (MCS) data on 7 transects, including 2 regional dip lines coincident with Ocean Bottom Seismometers (OBS) deployments which extend (west to east) from the incoming Australian plate, across the Puysegur Trench and Puysegur Ridge, over the Solander Basin and onto the continental Campbell Plateau margin.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;We integrate pre-stack depth migrated MCS profiles with OBS tomography models to constrain the tectonic development of the Puysegur Margin. Based on our results we propose the following Cenozoic evolution: (1) The entire Solander Basin contains thinned continental crust which formed from orthogonal stretching between the Campbell and Challenger plateaus during the Eocene-Oligocene. This phase of rifting was more pronounced to the south, producing thinner crust with abundant syn-rift volcanism across a wider rift-basin, in contrast to the relatively thicker crust, moderate syn-rift volcanism and narrower rift basin in the north. (2) Strike-slip deformation subsequently developed along Puysegur Ridge, west of the locus of rifting and within relatively unstretched continental lithosphere. This young strike-slip plate boundary translated unstretched crust northward causing an oblique continent-collision zone, which led to a transpressional pattern of distributed left-stepping, right-lateral faults. (3) Subduction initiation was aided by large density contrasts as oceanic lithosphere translated from the south was forcibly underthrust beneath the continent-collision zone. Early development of oblique subduction generated modest and widespread reactivation of faults in the upper plate. (4) Present-day, the Puysegur Trench shows a spatiotemporal transition from nearly mature subduction in the north to a recently initiated stage along the southernmost margin, requiring a southward propagation of subduction through time.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;Our new seismic images suggest subduction initiation at the Puysegur Margin was assisted by inherited buoyancy contrasts and structural weaknesses that were imprinted into the lithosphere during earlier phases of continental rifting and strike-slip along the developing plate boundary. The Puysegur Margin demonstrates that forced nucleation along a strike-slip boundary is a viable subduction initiation model and should be considered throughout Earth&amp;#8217;s history.&lt;/p&gt;

THE GEOLOGY AND PETROLEUM POTENTIAL OF THE WESTERN ARAFURA SEA

1990 ◽  
Vol 30 (1) ◽  
pp. 91 ◽  
Author(s):  
Jeanette M. McLennan ◽  
John S. Rasidi ◽  
Richard L. Holmes ◽  
Greg C. Smith
Keyword(s):  
Oil And Gas ◽  
Source Rocks ◽  
Petroleum Potential ◽  
Northern Margin ◽  
The North ◽  
Australian Plate ◽  
North Eastern ◽  
Arafura Sea ◽  
Good Potential ◽  
Reservoir Potential

The northern Bonaparte Basin and the Arafura-Money Shoal Basins lie along Australia's offshore northern margin and offer significantly different exploration prospects resulting from their differing tectonic and burial histories. The Arafura Basin is dominated by a deep, faulted and folded, NW-SE orientated Palaeozoic graben overlain by the relatively flat-lying Jurassic-Tertiary Money Shoal Basin. The north-eastern Bonaparte Basin is dominated by the deep NE-SW orientated Malita Graben with mainly Jurassic to Recent basin-fill.A variety of potential structural and stratigraphic traps occur in the region especially associated with the grabens. They include tilted or horst fault blocks and large compressional, drape and rollover anticlines. Some inversion and possibly interference anticlines result from late Cenozoic collision between the Australian plate and Timor and the Banda Arc.In the Arafura-Money Shoal Basins, good petroleum source rocks occur in the Cambrian, Carboniferous and Jurassic-Cretaceous sequences although maturation is biassed towards early graben development. Jurassic-Neocomian sandstones have the best reservoir potential, Carboniferous clastics offer moderate prospects, and Palaeozoic carbonates require porosity enhancement.The Malita Graben probably contains good potential Jurassic source rocks which commenced generation in the Late Cretaceous. Deep burial in the graben has decreased porosity of the Jurassic-Neocomian sandstones significantly but potential reservoirs may occur on the shallower flanks.The region is sparsely explored and no commercial discoveries exist. However, oil and gas indications are common in a variety of Palaeozoic and Mesozoic sequences and structural settings. These provide sufficient encouragement for a new round of exploration.

OIL EXPLORATION IN NEW ZEALAND—PAST AND FUTURE TRENDS

1971 ◽  
Vol 11 (1) ◽  
pp. 35
Author(s):  
H. R. Katz
Keyword(s):  
New Zealand ◽  
Oil And Gas ◽  
East Coast ◽  
Small Scale ◽  
Expiry Date ◽  
Seismic Surveys ◽  
The North ◽  
Geophysical Surveys ◽  
Increased Activity ◽  
Commercial Field

The earliest lease for oil prospecting was granted in 1865, and the first bore went down in 1866. Since then and up to 1936, 130 wells were drilled mainly in Taranaki, the East Coast of the North Island and the West Coast of the South Island. No commercial field was discovered, but some oil and gas was found sporadically — sometimes enough for local small-scale consumption — which kept interests alive.The Petroleum Act in 1937 vested all petroleum prospecting and mining rights in the Crown; with minor modification, it has regulated exploration to the present day. The war-time years saw renewed activity by several major companies; the first seismic surveys were undertaken, and some 20 holes were drilled. But except intermittent, small production from the Moturoa field in New Plymouth (the she of the first well of 1866), no further success was achieved and exploration ceased after 1944. The present period of activity started in 1955. On land the Kapuni gas-condensate field was discovered in 1959, and offshore the much larger Maui field in 1969. Both are in the Taranaki Basin which, having the best prospects in the country, has also received far more attention than other areas.Land operations sharply decreased after 1965 when Shell and BP, the only majors with on-land interests, began concentrating on new offshore holdings while still retaining their original big land concessions. Amongst the increasing number of independents continued regrouping of interests, farm deals, etc., have become common, and these companies account for nearly all activity on land during more recent years. Practically all drilling after 1965, which from a 5,686 ft. low in 1966 increased to 28,741 ft. in 1969 and 16,952 ft. in 1970 (the smaller 1970 figure is mainly due to rig shortage), was done by companies other than Shell-BP, many of them newcomers. Since to these the more promising prospects have been unavailable, exploration has noticeably shifted to areas of lesser and even marginal prospects.Concessions have for a number of years covered all lands of even remotest possibilities; the total area leased is around 50,000 sq. miles.Offshore the first concessions were granted in 1965; in 1970 they covered 384,547 sq. miles. Extensive geophysical surveys followed nearly immediately, and the first well was spudded by Esso in October, 1968. The second well, by Shell in March, 1969, discovered the large Maui field, later confirmed by two step-outs. Up to November 1970, 10 offshore wells with an aggregate footage of 101,181 ft. were drilled.I he only offshore rig now has left but additional targets are already established, and more will undoubtedly be after seismic surveys presently in course. Offshore drilling is expected to resume as soon as possible, particularly in concessions soon to expire. In large areas only recently granted, however, excessive water depth of up to 1000 m will prevent drilling for probably many years.On land, the tendency for wider participation in joint ventures is likely to continue. Increased activity by small operators is expected, as domestic rig availability has improved and many concessions are nearing expiry date. New licences to be granted over Greymouth and Canterbury areas which have drawn many competing applications should further stimulate the picture. Since Shell-BP in 1970 finally farmed out their large block in Taranaki which still holds the best prospects and many unexplored features, new operations are expected also there before expiry in 1973; BP-Shell's East Coast holdings expire in 1972 and the future of these two blocks which since 1955 have been in the hands of the same consortium, will probably be most important to further developments in New Zealand.

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