Academic literature on the topic 'Cadna-owie Formation'

AbstractWater sampling at springs that are a part of the Freeling Spring Group, South Australia, was used along with electrical resistivity imaging (ERI) data to evaluate the sources and pathways for groundwater to the springs and to find evidence of mixing between the Great Artesian Basin (GAB) aquifer system (Algebuckina Sandstone, Cadna-owie Formation and lateral equivalents) and waters from the adjacent mountain block basement (MB) aquifer. Five springs and a well were used to evaluate spring chemistry; multi-electrode resistivity data were collected along three orientations over the Freeling Spring site. The resistivity data indicate three independent electrically conductive curvilinear features connected to the spring. These features are evidence of mixing at the spring vent similar to what would be predicted from traditional hydraulic flownets. The chemistry of the spring water samples indicates that the water emanating from the Freeling Spring Group is a mixture of waters from both the GAB and the MB aquifers, supporting the geophysical evidence. The data suggest mixing occurs along a fracture in the body of the MB and porous media flow in the GAB beds, but the system is dominated by the GAB flow, which provides approximately 90% of the discharge.

Five fully-cored and wire-line logged stratigraphic bores have been drilled by the Queensland Department of Mines, relatively close to producing oil fields in the Eromanga Basin, south-west Queensland. Correlations between the stratigraphic bores and petroleum wells have established lithologic control in an area where lithostratigraphy is interpreted mainly from wire-line logs. The Eromanga Basin sequence below the Wallumbilla Formation has been investigated, and a uniform lithostratigraphic nomenclature has been applied; in the past, an inconsistent nomenclature system was applied in different petroleum wells.Accumulation of the Eromanga Basin sequence was initiated in the early Jurassic by major epeirogenic downwarping; in the investigation area the pre-Eromanga Basin surface consists mainly of rocks comprising the Thargomindah Shelf and the Cooper Basin. The lower Eromanga Basin sequence in the area onlaps the Thargomindah Shelf and thickens relatively uniformly to the north-west. The sequence comprises mainly Jurassic/Cretaceous terrestrial units in which vertical and lateral distribution is predominantly facies-controlled. These are uniformly overlain by the mainly paralic Cadna-owie Formation, signalling the initiation of a major Cretaceous transgression over the basin.The terrestrial sequence over most of the area comprises alternating coarser and finer-grained sedimentary rocks, reflecting major cyclical changes in the energy of the depositional environment. The Hutton Sandstone, Adori Sandstone and 'Namur Sandstone Member' of the Hooray Sandstone comprise mainly sandstone, and reflect high energy fluvial depositional environments. Lower energy fluvial and lacustrine conditions are reflected by the finer-grained sandstone, siltstone and mudstone of the Birkhead and Westbourne Formations, and 'Murta Member' of the Hooray Sandstone. Similar minor cycles are represented in the 'basal Jurassic' unit. The Algebuckina Sandstone, recognised only in the far south-west of the investigation area, comprises mainly fluvial sandstones.

The aim of the National Geoscience Mapping Accord Cooper-Eromanga Basins Project was to develop a quantitative petroleum generation model for the Cooper and Eromanga Basins by delineating basin fill, thermal history and generation potential of key stratigraphic intervals. Bio- and lithostratigraphic frameworks were developed that were uniform across state boundaries. Similarly cross-border seismic horizon maps were prepared for the C horizon (top Cadna-owie Formation), P horizon (top Patchawarra Formation) and Z horizon (base Eromanga/Cooper Basins). Derivative maps, such as isopach maps, were prepared from the seismic horizon maps.Burial geohistory plots were constructed using standard decompaction techniques, a fluctuating sea level and palaeo-waterdepths. Using terrestrial compaction and a palaeo-elevation for the Winton Formation, tectonic subsidence during the Winton Formation deposition and erosion is the same as the background Eromanga Basin trend—this differs significantly from previous studies which attributed apparently rapid deposition of the Winton Formation to basement subsidence. A dynamic topography model explains many of the features of basin history during the Cretaceous. Palaeo-temperature modelling showed a high heatflow peak from 90–85 Ma. The origin of this peak is unknown. There is also a peak over the last two–five million years.Expulsion maps were prepared for the source rock units studied. In preparing these maps the following assumptions were made:expulsion is proportional to maturity and source rock richness;maturity is proportional to peak temperature; andpeak temperature is proportional to palaeo-heatflow and palaeo-burial.The geohistory modelling involved 111 control points. The major expulsion is in the mid-Cretaceous with minor amounts in the late Tertiary. Maturity maps were prepared by draping seismic structure over maturity values at control points. Draping of maturity maps over expulsion values at the control points was used to produce expulsion maps. Hydrocarbon generation was calculated using a composite kerogen kinetic model. Volumes generated are theoretically large, up to 120 BBL m2 of kitchen area at Tirrawarra North. Maps were prepared for the Patchawarra and Toolachee Formations in the Cooper Basin and the Birkhead and Poolowanna Formations in the Eromanga Basins. In addition, maps were prepared for Tertiary expulsion. The Permian units represent the dominant source as Jurassic source rocks have only generated in the deepest parts of the Eromanga Basin.

The general objectives of the study are to assess the applicability of sequence stratigraphic concepts to non-marine deposition in a large intracratonic basin and to determine fundamental controls that affect the stratal architectures of this basin. During the last two decades, sequence stratigraphy has been emerging as a powerful tool to analyze marine sedimentary successions and has been successfully applied in many petroleum exploration programs. However, at present, there is still some debate as to the applicability of sequence stratigraphic concepts to non-marine successions. The early works in sequence stratigraphy (i.e. Vail et. al. 1977; Posamentier and Vail, 1988; Galloway, 1989) focused on passive continental margin settings. In these settings, eustatic change of sea level (such as published by Haq et. al., 1988) is the major factor in determining the facies architecture and stacking patterns of sedimentary rock strata. The model derived from these studies has often been used (or abused!) as a template for exploration works in marginal marine basins (Posamentier and James, 1993). Later it was realized that the concepts of sequence stratigraphy could also be applied to the study of sedimentary strata of non marine basins (e.g. Shanley and McCabe, 1993; Legaretta et al., 1993; Blum, 1993, among others) where global sea level change has little, if any, effect on the processes of sedimentation. Although the basic concepts of sequence stratigraphy, the control of sediment supply and accommodation, are valid in all basin settings, the specific models and schematic sections for marginal marine basins certainly need to be modified before being applied to basins that are isolated from the sea (Weimer, 1992; Posamentier and James, 1993).

Early sequence stratigraphic models emphasised the use of sequence stratigraphic surfaces for identifying and constraining the stratigraphic position of reservoir intervals at large scales (100s-1 000s of metres) using mostly seismic reflection data. In contrast, reservoir development focuses on resolving small­scale, largely lateral changes in reservoir quality and distribution where the stratigraphic position of the reservoir interval is generally already well defined. Also, due to the scale of analysis, the database for reservoir development studies commonly consists exclusively of well data (i.e. fullhole cores, wireline logs and image logs); fluid flow properties can be measured directly using the same data types that are employed to identify and map key surfaces. Despite well documented successes of the sequence stratigraphic approach at exploration scales, little information exists regarding the utility of sequence stratigraphic approach for reservoir development. This study investigates the utility of the sequence stratigraphic approach for aiding reservoir development of the Wyandra Sandstone Member at Tarbat-lpundu Field, Southwest Queensland. A sequence stratigraphic framework was constructed for the Wyandra Sandstone Member using a database of core, wireline suites, image logs, palynological data and modern analogues. The utility of the sequence stratigraphic framework for reservoir development was then evaluated using petrography and measurements of fluid flow properties from conventional core analysis and wireline logs. The Wyandra Sandstone Member is a -20m thick, volcaniclastic sandstone sheet that forms a fining-upward succession. Despite relative lithologic homogeneity, the sandstone sheet is characterised by severe variations in fluid flow properties stemming from complex patterns of diagenetic porosity/permeability occlusion and enhancement. A grain size control on the occurrence and intensity of secondary dissolution suggests that an understanding of grain size distribution within the_ Wyandra Sandstone Member is central to resolving reservoir heterogeneity. Sequence stratigraphic divisions of the Wyandra Sandstone Member indicate that it formed in response to a high-order regressive - transgressive cycle driven by glacio-eustatic fluctuation coupled with variation in the rate of basin subsidence from the Barremian to the Aptian. Seventy-three percent of reservoir rock within the Cadna-owie Formation is confined to the lower, fluvially dominated portion of the Wyandra Sandstone Member that is interpreted to represent a lowstand systems tract. However, the identification of the lowstand systems tract, in itself, is of limited value for reservoir development. Several uneconomic development wells have intersected low permeability sandstone within the lowstand systems tract. The largely lateral variations in reservoir properties within the lowstand systems tract of the Wyandra Sandstone Member stem from the partitioning of medium- to very coarse-grained sandstone to channelised fluvial distributary deposits. Although sandstone of fluvial distributary deposits show a range of fluid flow properties (0.01->1000mD), secondary dissolution of chemically unstable framework grains, authigenic clay and carbonate cement occurs preferentially in areas of intense channel amalgamation. These areas are interpreted as major fluvial axes similar to those that occur at the 'fan apex' of modern depositional systems of the Great Artesian Basin and modern transverse depositional systems occurring along strike-slip faults. The position of the major fluvial axes are interpreted to be controlled by localised changes in the style of basement faulting and related patterns of differential compaction in the overlying cover units. Mapping sequence stratigraphic surfaces, as distinct from lithologic surfaces, in the Cadna-owie Formation defines linkages of contemporaneous depositional systems. Consequently, the sequence stratigraphic divisions are compatible with studies of modern depositional systems, whereas lithologic divisions of the Cadna­owie Formation generally are not. As a result, a variety of analyses conducted with respect to sequence stratigraphic divisions, and particularly the utilisation of modern analogues, improves our understanding of the sedimentological processes operative during deposition of the Wyandra Sandstone Member. It is hoped that the conclusions stemming from this study provide a basis for more accurately accessing the development risk at Tarbat-lpundu Field.

This item is only available electronically.
Regolith and sedimentary material overlying potentially enriched basement, is an ever-present obstacle in the highly prospective Olympic iron-oxide copper gold (IOCG) Province, South Australia. The Eromanga Basin, composed of Mesozoic sediments - Algebuckina Sandstone, Cadna-owie Formation and Bulldog Shale - overlies the northern extent of the Stuart Shelf, including the Olympic Dam IOCG province. The closest surface exposures of these sediments to Olympic Dam, is around the opal mining town of Andamooka. The formation and distribution of the precious opal has been previously linked to fluctuating water tables. However, oxidation of pyrite by fluctuating water table height, caused by intracontinental extensional faulting in the area, provides an enhanced interpretation linking opal distribution with the presence of jasper and silcrete lag. Extensional fault boundaries were identified through contrasting regolith and landform components observed from field mapping and remote sensing imagery. ASTER band ratios and relative absorption-band depth ratios complimented field observations with ratios primarily useful in distinguishing high reflectance homogenous mineral groups e.g. opal diggings and sand dunes. A regolith-landform map and digital elevation model over the area identifies the contrasting units, with opal diggings (digitised from ASTER imagery) strongly associated with higher elevations. The potential for secondary economic mineralisation is proposed for the Andamooka area. A source material (Olympic IOCG Province), transport mechanism (extensional duplex faulting), and potential trap rock (REDOX boundaries and varying permeability of Mesozoic units) all contributed to a prospective exploration model for the area.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Earth and Environmental Sciences, 2011