Higher-resolution palynostratigraphy of the Norian-Carnian (Triassic) Upper Mungaroo Formation, offshore Carnarvon Basin

Palynostratigraphic correlations within the Triassic fluvio-deltaic upper Mungaroo Formation (M. crenulatus and upper S. speciosus zones) of the Carnarvon Basin have proven to be difficult. Although two reliable pollen extinction datums have long been established in the uppermost 200 m of the formation, correlations within the sector below (up to 1,500 m) have had to rely on broad algael and pollen acmes, with variable results. A revised palynostratigraphic scheme is presented in this extended abstract, which has been largely in use within Shell and Morgan-Goodall Palaeo Associates since mid/late 2010, and which has not been previously published in detail. For consistency, the subzone names remain the same as those in previous use; however, crucially, a framework for their reliable identification in more recently-analysed wells is provided by several Morgan gradational sub-types of key pollen species (viz. of Cycadopites stonei, Ephedripites macistriatus and Samaropollenites speciosus). Within this robust framework that is based on top-ranges, base-ranges and rapid switches in the ratios of gradational and related morphotypes, numerous thin marine incursions and regional to sub-regional swampy phases are evidenced. Lateral and vertical relationships between marine incursions and swampy phases are sometimes apparent, and clustering of a few of the above pollen events at these levels hints at condensation. The revised framework has been successfully used in the high-resolution, regional-stratigraphic interpretation of both seismic and well data and is contributing to an increasing understanding of the variability of the Upper Mungaroo depositional system in the Greater Carnarvon Basin.

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Unconformities on the Scotian Shelf

Canadian Journal of Earth Sciences ◽

10.1139/e74-008 ◽

1974 ◽

Vol 11 (1) ◽

pp. 89-100 ◽

Cited By ~ 15

Author(s):

Lewis H. King ◽

Brian MacLean ◽

Gordon B. Fader

Keyword(s):

High Resolution ◽

Seismic Reflection ◽

Upper Cretaceous ◽

Scotian Shelf ◽

Early Tertiary ◽

Late Tertiary ◽

Glacial Processes ◽

Well Data ◽

Seismic Reflection Profiles ◽

Cut And Fill

Four erosional unconformities have been recognized within the Mesozoic-Cenozoic succession on the Scotian Shelf, on the basis of data from high resolution seismic reflection profiles. Older unconformities are known from well data and others may be revealed by detailed biostratigraphic studies.The oldest of the four unconformities discussed in this paper is of Early Cretaceous age and appears to mark, with discordance, the boundary between Jurassic and Cretaceous strata on the western part of the shelf. A second angular unconformity, of Late Cretaceous age, has been recognized on the central part of the shelf where the basal part of the Banquereau Formation (Tertiary and uppermost Cretaceous) oversteps the zero-edge of the Wyandot Formation (Upper Cretaceous) and lies upon truncated beds of the Dawson Canyon Formation (Upper Cretaceous). Cut-and-fill relationships characterize a third unconformity developed during Early Tertiary time. A fourth unconformity was developed in Late Tertiary – Pleistocene time by fluvial processes and later by glacial processes. Although in many areas the latest unconformity appears to be the most conspicuous one on the shelf, its configuration closely follows the geomorphic expression developed during the previous period of erosion. The regional extent of the Cretaceous unconformities is not known, and they might only occur near basin margins and on structural and basement highs.

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Fluid migration and fluid seepage in the Connemara Field, Porcupine Basin interpreted from industrial 3D seismic and well data combined with high-resolution site survey data

International Journal of Earth Sciences ◽

10.1007/s00531-005-0021-2 ◽

2005 ◽

Vol 96 (1) ◽

pp. 185-197 ◽

Cited By ~ 38

Author(s):

P. Van Rensbergen ◽

A. Rabaute ◽

A. Colpaert ◽

T. St. Ghislain ◽

M. Mathijs ◽

...

Keyword(s):

High Resolution ◽

Survey Data ◽

Fluid Migration ◽

3D Seismic ◽

Site Survey ◽

Porcupine Basin ◽

Fluid Seepage ◽

Well Data

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A REVISED DEPOSITIONAL MODEL FOR EAST SPAR AND ITS IMPACT ON FIELD PERFORMANCE

The APPEA Journal ◽

10.1071/aj01025 ◽

2002 ◽

Vol 42 (1) ◽

pp. 461 ◽

Cited By ~ 1

Author(s):

N.P. Tupper ◽

E.F. Tadiar ◽

D.L. Price ◽

J.D.S. Goodall

Keyword(s):

Bottom Water ◽

Field Performance ◽

Depositional Model ◽

Incised Valley ◽

Water Influx ◽

Lateral Extent ◽

Well Data ◽

Multi Phase ◽

Regional Aquifer ◽

Carnarvon Basin

The East Spar gas condensate field is located in production licence WA-13-L in the offshore Carnarvon Basin. Production commenced in 1996 with two subsea wells linked to processing facilities on Varanus Island via a multi-phase pipeline. The pressure performance of the field has been significantly different to predevelopment expectations. This prompted a reexamination of the seismic and well data to investigate the potential for alternative reservoir models.Integrated stratigraphic and seismic interpretation reveals that the Barrow Group reservoir sands were deposited within an incised valley of limited lateral extent. Sea level fall instigated erosion of a valley that on transgression was filled with successive fluvial, estuarine and marine sediments. Good quality sands are expected to be limited to this valley, the upper part of which can be mapped on seismic. Poor sand development in East Spar–2ST is consistent with its location at the edge of the incised valley.Before development, the primary production mechanism was expected to be a strong bottom water drive comparable with other Barrow Group fields in the Carnarvon Basin. The revised depositional model, however, and the observed decline in reservoir pressure, indicate that connection to this regional aquifer is limited. This implies that water influx will probably be later, and ultimate recovery higher, than previously anticipated.

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