Goldwyer Formation Research Articles

New heat flow data aids exploration in the Canning Basin, Western Australia

The Geological Survey of Western Australia (GSWA) is providing new heat flow data and continuing studies in subsurface temperatures to understand the origin, migration and accumulation of geofluids in petroleum and geothermal systems of the Canning Basin. The study includes an investigation of subsurface temperatures from 274 wells, thermal conductivity measurement of 50 core samples from 22 wells, and single-dimensional (1D) heat-flow modelling of 101 wells. Thermal conductivity measurement of Canning Basin formations range from 1.06–5.83 W/mºC and modelled surface heat-flow ranges from 20–160 mW/m². The lowest measured thermal conductivity is in the Ordovician Goldwyer Formation at 1.06± 0.28 W/mºC, and the highest values are in the Upper Carboniferous Reeves Formation at 5.83 ± 0.22 W/mºC. Generally, estimated heat-flow values are lower where thick sedimentary deposits are present such as the Fitzroy Trough, Lennard Shelf, and Kidson Sub-basin, with values less than 65 mW/m². The heat flow values increase to over 80 mW/m² on the Broome Platform and Jurgurra, Mowla and Barbwire terraces. Lower heat-flow values have been modelled in West Blackstone–1 (47 mW/m²), Curringa–1 (52 mW/m²), Kennedia–1, Napier–2 and Pearl–1 (55–52 mW/m²). Higher heat-flow values have been modelled in Goodenia–1, Lovells Pocket–1, Kanak–1, Cudalgarra North–1, and Cudalgarra–1, where heat-flow values are over 100 mW/m². These new thermal conductivities, corrected temperatures, and heat-flow values support improved modelling of the Canning Basin petroleum and geothermal systems.

Stratigraphic distribution of selected acritarchs in the Ordovician subsurface, Canning Basin, Western Australia

Palynological investigation of 80 core samples from four boreholes, drilled through the Lower to Middle Ordovician marine sections of the central-northeastern Canning Basin, northwestern Australia, reveals diverse acritarch associations including a number of stratigraphically significant species. The stratigraphic succession studied, embracing the Willara Formation and conformably overlying Goldwyer Formation, has been independently dated as early Arenig to Llanvirn by conodont faunas ( Oepikodus communis through Phragmodus- Plectodina zonal interval). Nine morphologically distinctive acritarch species have relatively narrow vertical ranges within the study interval and likely constitute serviceable palynostratigraphic indices for the Ordovician in and possibly beyond the Western Australian study area. Three new species, Comasphaeridium setaricum, Polyancistrodorus kunzeanensis, and Stelomorpha calix, are established; and one new combination, Baltisphaeridium variocavatum (Playford and Martin, 1984), is proposed. Other stratigraphically significant species include Petaloferidium comptum Playford and Martin, 1984 and Peteinosphaeridium sp. cf. P. exornatum Tongiorgi et al., 1995; together with Dorsennidium symmetricum (Lu, 1987) Sarjeant and Stancliffe, 1994, Peteinosphaeridium coronula Yin et al., 1998, and Striatotheca rarirrugulata (Cramer et al., 1974) Eisenack et al., 1976, which are found for the first time in Australia. The vertical distribution, and hence the stratigraphic utility, of each of the above species is documented through the studied sections.

Logiciels qualité et systèmes d'information dans les éttablissements de santé

Pyrolysis and bulk kinetic studies were used to investigate the hydrocarbon generation potential and source rock organofacies variability of marine organic-rich rocks from the Middle Ordovician (Darriwilian) Goldwyer Formation in the Canning Basin, Western Australia. Rock-Eval pyrolysis results for the analysed immature to mid-mature calcareous mudstones imply that the upper Goldwyer Sequence I contains oil-prone type I kerogen, while the lower Goldwyer Sequence III contains type II/III oil- and gas-prone kerogen. This is supported by pyrolysis gas chromatography (Py-GC) results that show the presence of homogenous organofacies in the Goldwyer Sequence I having aliphatic molecular signatures, possibly due to selective preservation of lipids derived from Gloeocapsomorpha prisca (G. prisca). The heterogeneous organofacies of the Goldwyer Sequence III contain aromatic moieties in similar abundance to the aliphatic compounds. The calcareous claystones of the Goldwyer Sequence I have the capacity to generate low wax paraffinic oil, whereas the Goldwyer Sequence III has potential for paraffinic-naphthenic-aromatic (P-N-A) low wax oils, gas, and condensate.The temperature for hydrocarbon generation for the type I kerogen, assuming a constant geological heating rate of 3 °C/my, is estimated to occur over a narrow interval between 145 °C and 170 °C for the Goldwyer Sequence I samples. Generation from the type II/III kerogen occurs from 100 °C to 160 °C in the Goldwyer Sequence III samples which are significantly less thermally stable than the Goldwyer Sequence I samples. The kinetic results for both sequences were used in standard thermal and burial history plots to evaluate their transformation ratio and hydrocarbon generative potential. This provided basin-specific kinetic inputs for burial history modelling and better constraint on kerogen transformation and hydrocarbon generation on the Broome Platform.

GEOCHEMICAL CHARACTERISTICS OF PALAEOZOIC PETROLEUM SYSTEMS IN NORTHWESTERN AUSTRALIA

Isotopic and biomarker analyses carried out on Cambrian to Permian oils and source rocks in the Arafura, Bonaparte (Petrel Sub-basin) and Canning Basins have been used to geochemically characterise five distinct petroleum systems within the Larapintine and Gondwanan Petroleum Supersystems. The Larapintine 1 Petroleum System is characterised by isotopically light, free hydrocarbons in the Arafura Basin (613Csat = −32 %o Arafura-1) which have been correlated to kerogens of similar isotopic signature within the Middle Cambrian Jigaimara Formation. The richness and maturity of these source rocks indicate that an effective Larapintine 1 Petroleum System may exist in the northern parts of the Arafura Basin. Larapintine 2 oils, with Gloeocapsomorpha prisca-type signatures, are found on the Barbwire- Dampier Terraces and Admiral Bay Fault Zone in the Canning Basin. These oils can be correlated to source rocks in the Lower Ordovician Goldwyer Formation on the Barbwire Terrace and the Bongabinni Formation in the Admiral Bay Fault Zone by their diagnostic odd- carbon-number preference in the C15—CJ9 n-alkanes. Larapintine 3 oils are derived from Upper Devonian marine carbonates in the Canning Basin and Petrel Sub- basin and have a diagnostic biomarker signature which includes a predominance of steranes relative to diasteranes and abundant gammacerane and 30- norhopanes, similar to those observed in the Upper Devonian Gogo and Pillara Formations. Larapintine 4 oils are derived from Lower Carboniferous marine, clay- rich mudstones in both the Petrel Sub-basin and Canning Basin. They are isotopically light (mean δ13C sat = −28 %o) and have a unique terpane signature which has been identified within the Milligans Formation. Gondwanan 1 Petroleum System hydrocarbons, represented here by the Petrel-4 condensate, have a heavy isotopic signature (δ13C sat = −24 %o) which, coupled with an abundance of the diasterane and diahopane biomarkers, indicates derivation from Permian deltaic source facies. Recognition of the diagnostic geochemical components of each Palaeozoic petroleum system has led to the identification of Permian-like isotopic signatres in some hydrocabon accumulations in the Timor Sea that were previously attributed to Mesozoic sources.

HYDROCARBON SOURCE POTENTIAL OF THE GOLDWYER FORMATION, BARBWIRE TERRACE, CANNING BASIN, WESTERN AUSTRALIA

The Goldwyer Formation is widely known from the subsurface Canning Basin, Western Australia. Microfossils of acritarchs, chitinozoans, and conodonts, and macrofossil remains, indicate it was deposited in a normal marine environment in late Early to Middle Ordovician times (Late Arenig to Llanvirn). In Exploration Permit areas 143 and 225, the Formation is subdivided into four lithologic members, informally designated Units 1 to 4 in ascending stratigraphic order. Horizons within Unit 4, immediately underlying the prospective reservoir dolostones of the Nita Formation, are organic rich with between 0.5 and 6 per cent total organic carbon. Generative potential of these horizons, determined by Rock-Eval, averages 13 litres of hydrocarbon per tonne. A conservative estimate of the cumulative thickness of source rock with hydrogen index (HI) values of 300-900, using whole core fluorescence intensity, is 10 m. Thus, under optimum maturation conditions there is potential for generation of an estimated 61 × 109 barrels of liquids from Unit 4 within EP 143 and EP 225. These figures are based on an integrated analysis of 44 core samples from four fully cored 'slim holes' and cores from one conventional oil well. Kero-gen types and measures of organic maturity cannot be determined accurately from the standard Rock-Eval HI/Tmax crossplot. The dominant oil-prone kerogen in Unit 4 is Gloeocapsamorpha prisca Zalessky 1917 and palynological and gas chromatographic/mass spectrometric studies correlate it with Ordovician kerogens from the Baltic Basin, Michigan and Illinois basins, and Amadeus Basin. Gas chromatographic/mass spectrometric source rock-oil correlations show that oils from the Williston Basin (USA), Canning Basin, and Amadeus Basin are derived predominantly from G. prisca. Palaeogeographic reconstructions suggest that these areas lay within 5° north and south of an Ordovician equator and so provide data for further prediction of possible rich hydrocarbon source areas.

Ordovician acritarchs from the Canning Basin, Western Australia

Core samples from four marine Ordovician sections in the Canning Basin, Western Australia, have yielded an acritarch assemblage of moderate abundance and diversity and of varying preservation. The bulk of the palynologically productive samples represents the Goldwyer Formation and the remainder is from the conformably succeeding or laterally contiguous Nita Formation; these units have previously been regarded as datable within the late Arenigian to Llanvirnian (or ?Llandeilian) interval; i.e., late Early to Middle Ordovician. Newly instituted acritarch taxa comprise one new genus, Dasydorus, and 16 species, viz. Ammonidium aduncum, A. furtivum, A. macilentum, Baltisphaerosum pugiatum, B. variocavatum, Buedingiisphaeridium disgregum, Cymatiosphaera notialis, Dasydorus cirritus (type species), Elektoriskos pilulifera, Gorgonisphaeridium miculum, Lophosphaeridium aequicuspidatum, L. disparipelliculum, Micrhystridium goldwyerense, Multiplicisphaeridium acaciaense, Petaloferidium comptum, and Solisphaeridium c...

Chitinozoaires du Llanvirn (formation de Table Head) de la partie occidentale de Terre-Neuve, Canada

A chitinozoan microfauna is described from the middle part of the Table Head Formation (Diplograptus decoratus Zone, Llanvirn age). It includes Fustichitina langei, Conochitina poumoti, Conochitina pirum, Conochitina subcylindrica, Conochitina cf. C. bulmani, and Desmochitina cf. D. lata. Considering the proposed synonymy, this microfauna appears to be similar to that previously described and assigned to the Caradoc by Neville. This resemblance suggests that Neville's microfauna is also of Llanvirn age. The absence of Lagenochitina baltica in both assemblages confirms the value of this species as a guide fossil for the late Caradoc – early Ashgill.The relationship between the Table Head microfauna and those of the upper Arenig (Zone D) Levis Formation and of the Llanvirn Goldwyer Formation of the Canning Basin of Australia is documented.