The Petroleum program has provided the petroleum industry with new geophysical and geological coverages in order to promote and foster petroleum exploration. Comprehensive geoscience investigations have been undertaken over the major sedimentary basins to appraise their petroleum prospectivity.

Petroleum Systems of the Sedimentary Basins of New South Wales

Presenting a series of petroleum system events chart (after Magoon and Dow) of the major sedimentary troughs in New South Wales highlighting the favourable and highly prospective elements and processes associated with these lightly explored basins.

Positive generation of hydrocarbons is indicated by the presence of several oil and gas shows and surface seeps particularly for Sydney-Gunnedah-Bowen, Clarence-Moreton and Eromanga Basins. The sporadic and cyclic exploration for petroleum and the new focus on coal seam methane have contributed to a negative perception of the conventional plays for these basins.

The petroleum systems approach is being applied to address the risks and put a positive view on the ultimate potential of the petroleum resource of the State. Results will be published soon.

Griffith-Murrumbidgee (northern Oaklands) Seismic Surveys

As part of the Exploration NSW initiative, the Department has acquired a 50-km regional reconnaissance seismic survey near Griffith. This survey aims to validate the previous magnetic and gravity interpretation and modelling around the Oaklands Basin, which indicate a structural discontinuity (graben) located north of the basin. The model suggests a possible large elongated Permo-Triassic depocentre capable of hosting thick sedimentary section and sourcing petroleum. Depths to magnetic sources (+ 1000m) imply that the thick sections are located west of a major fault and the seismic lines are likely to establish a significant fairway that may open up large frontier areas for petroleum exploration in southern central NSW. The data is currently being processed and will soon be released.

Oaklands Basin (northern extension) Passive Soil Gas Geochemical Survey

Based on the successful trial of the Gore-Sober® geochemical survey technique, a large grid sampling was undertaken for the northern Oaklands in conjunction with the geophysical survey acquired in the same region. The sampling and analytical technique was employed to test the generative potential of the Permo-Triassic strata and positive results will establish the presence of petroleum accumulations and generation of hydrocarbons from the deep source sequences deposited in the Basin. Report will be in DIGS® soon.

Sydney-Gunnedah Basin Coal Seam Methane Modelling Project

As an emerging and State-significant energy resource, the enormous coal seam methane (CSM) potential in the Sydney-Gunnedah Basin deserves a closer evaluation. A detailed assessment of the resource has been completed, delineating exploration fairways and 'sweet spots' based on the popular and tested coalbed methane exploration modelling approach by Altuda Energy (USA). CSM resource estimates for the basin based on this study range from 58 to 248 TCF. The report from this project is available free from NSW DPI Maitland sales counter.

Eromanga Basin Soil Gas Microseep Survey

As a follow-up to the successful results of the Darling Basin soil-gas microseep detection project, a similar sampling and analytical program was undertaken for the Mesozoic Eromanga Basin. This project aims to establish the presence of petroleum accumulations and identify the positive generation of thermogenic hydrocarbons in this relatively unexplored portion of northern NSW. This geochemical technique is a continuation of the previous surveys in the Darling Basin, which successfully established positive generation of gaseous hydrocarbons. For this recent survey, there are several anomalous concentrations of ethane, butane and propane, which suggest subsurface source of thermogenic hydrocarbons. Report is available from NSW DPI (contact petroleum@dpi.nsw.gov.au).

Murray-Darling-Eromanga Basins SEEBASE™ Project

In conjunction with the recent acquisition of high-resolution aeromagnetic and radiometric data at the Murray and Eromanga Basins, an infill SEEBASE™ (Structurally Enhanced View of Economic Basement) and structural GIS project was undertaken by FrogTech P/L. The study was meant to investigate the effects of tectonics, basement geology and architecture on basin evolution and petroleum systems in these areas. This interpretation of the potential field data will serve as an initial guide to designing a cost-effective exploration in frontier areas. The results of this project are available on DVD-ROM. Please contact petroleum@dpi.nsw.gov.au to order.

Eromanga and Murray Basins Aeromagnetic and Radiometric Surveys

These two major geophysical surveys in NSW occurred in May 2006. Together, the survey data represent the largest airborne geophysical program ever conducted in NSW - a program made possible by the NSW government's seven-year $30 million Exploration NSW initiative. The surveys , which cover a vast area of 80,800 sq km and produced over 262,600 line kilometres of data, completes the high-resolution aeromagnetic coverage of the southwest portion of NSW. The Eromanga and Murray Basins Aeromagnetic and Radiometric Surveys data sets are available on DVD-ROM from the NSW Department of Primary Industries for $110 each, and at a later date will be available online via Geoscience Australia's geophysical archive data delivery site.

DPI-ANSIR-GA Deep Crustal Seismic Survey

This joint-venture project by NSW DPI, ANSIR and Geoscience Australia to acquire deep crustal-regional seismic data in NSW. The Thomson-Lachlan project acquired approximately 300 km of high resolution 2D data down to 12 secs. The seismic survey examined and made significant impact on our understanding of the crustal geometry of the Thomson-Lachlan boundary. The seismic data enabled the constraining of the basement structure of this region and provided implications for possible mineralisation styles and petroleum opportunities along this convergent boundary. The structural interpretation of the deep crustal events have given new light in the evolution and structural deformation of the Nelyambo and Wilcannia Troughs which could have major impact on the petroleum potential of the Darling Basin. Data will be released in March 2007.

Darling Basin Petroleum Data Package

The Darling Basin Petroleum Data Package is a comprehensive compilation of geological, geophysical, seismic, well, petrophysical, geochemical and cultural data, presented as a digital geospatial data product, and in a format that is ready for use by petroleum exploration companies. It is an update of the 1993 Darling Basin Petroleum Data Package (Department of Mineral Resources, 1993) and includes recently collected and processed data, and the latest interpretations of geology and petroleum prospectivity of the Basin. A new feature of the Data Package is the presentation of spatial data as interactive GIS maps, shape and georeferenced raster images. The data package is available on DVD-ROM.

Darling Basin Seismic Surveys

The Darling Basin has good regional to semi-regional gravity and magnetic coverage and survey interpretations have confirmed the existence of infra-basins within the Darling Basin in which substantial thicknesses of Palaeozoic sediments are preserved. Estimates from potential field data interpretations indicate thicknesses compatible with hydrocarbon generation.

Despite its acknowledged potential, the basin is under-explored with only 20 wells, mostly drilled in the 60's and 70's and less than 1600 km of modern multi-fold seismic data. Virtually none of the wells drilled to date can be considered a valid test of targeted structures. This is mainly due to inadequate seismic coverage, very poor seismic resolution across fault zones and steeply dipping strata, and/or limited well depth penetration.

To provide new information for explorers, the Exploration NSW petroleum program has conducted two seismic surveys using new acquisition and processing parameters to define the sedimentary thickness and basement relief of the Darling Basin.

• Wilcannia seismic survey 2003 - consisting of approximately 170 kms of new seismic reflection data, acquired in March 2003. The survey, which was of generally good quality, tied into existing surveys and wells. It provided modern reflection data in areas where there was no existing coverage and investigated newly postulated plays. The existence of large simple structures and thick sedimentary sections in the areas surveyed was confirmed. The results of this survey are available on CD-ROM.
• Wilcannia seismic survey 2004 - consisting of 134 kms of seismic reflection data recorded in June 2004. The objective of this survey was to establish closure on previously defined structures and to image the faulted basin boundaries. Data quality was excellent and results are available on CD-ROM. Please contact petroleum@dpi.nsw.gov.au to order.

Darling Basin SEEBASE™ Project

In July 2003, an integrated study of the existing gravity, magnetic and seismic data was carried out by SRK Energy Services (now FrOG Tech). Together with the depth to basement maps generated by SEEBASE™, a tectonic history of the Darling Basin was developed which highlighted basinal areas and troughs considered most prospective. The results of the study are available on CD-ROM. This information forms an important part of the Darling Basin Petroleum Data Package.

Mapping of Devonian Sequences in the Darling Basin

The purpose of this field investigation was to measure sections through the Mid to Upper Devonian rocks of the Manara Range, and the Neckarbo Range in the Darling Basin and to make notes on the nature of the sediments with reference to their potential as reservoir, seal and source for hydrocarbons.

Mapping was undertaken by John Connolly with DPI assistance in June 2004. The report "Devonian Sequences in the Darling Basin NSW" is available free from NSW DPI (contact petroleum@dpi.nsw.gov.au) and will soon be available in the DIGS® system.

Darling Basin Geochemical Study

Two soil geochemistry surveys were undertaken in the Darling Basin, first in March 2004 and the second in Feb 2005. The surveys conducted along existing seismic lines revealed anomalous high amounts of ethane and propane above background levels, which suggest the thermogenic origin of hydrocarbons vis-à-vis the positive generation of hydrocarbons. A total of 1300 samples were collected at 500m intervals. On-site gas analysis was used to determine the composition of alkanes up to C₅+. Additional samples were collected at closer intervals over identified anomalous areas. Post survey activities include an analysis of any correlations between anomalous gas zones and potential petroleum traps. The report no. GS2004/216 is available in the DIGS® system.

Murray-Darling Basin Water Bore Analysis

This ongoing program is an extension of the successful Eromanga and Surat Basins artesian waterbore sampling programme, and is aimed at developing a widespread database of bore water hydrocarbon geochemistry. Bore water data from the Eromanga and Surat Basins (report no. GS2001/203) has been instrumental in defining zones of anomalous hydrocarbons. These anomalies are thought to reflect subsurface hydrocarbon generation or migration, and therefore bore water sampling provides a relatively inexpensive exploration technique.

In the Murray and Darling Basins, waterbores are typically sub-artesian and require mechanical collection of water using a downhole submersible pump. Although present in trace amounts only, the hydrocarbon components (up to and including C₇+) present suggest the possibility of petroleum sources at depth. These and future analyses results will help assess the petroleum potential of infrabasins underlying the Murray Basin. The report no. GS2003/242 is available in the DIGS® system.

Oaklands Basin Petroleum Data Package

Despite the large number of coal exploration boreholes in the basin targeting Permian coals and the presence of Tertiary coal, lignite and peat in the overlying Murray Basin sequence there has been little, if any, direct coal seam methane exploration within the Basin. There have been only two wells drilled for petroleum exploration purpose within basin and both of these are stratigraphic tests.

Although conventional petroleum potential is largely unknown in the Oaklands Basin, the presence of Permian coals and carbonaceous sediments overlain by the numerous good sand reservoirs and clay seals of the Murray Basin strongly suggests potential for conventional gas and to a lesser extent oil accumulations.

The Oaklands Basin petroleum data package reviews and re-evaluates the coal seam methane and conventional petroleum prospectivity of the Oaklands Basin. The data package was released at a Petroleum Exploration Society of Australia (PESA) NSW technical meeting in Sydney on the 9th December 2003. The data package is available on CD-ROM.

Gore-Sorber® Hydrocarbon Detection Trials

The Department has just completed a joint bore water and soil geochemistry trial with the Survey Products Group of W. L. Gore & Associates, Inc. The Gore-Sorber® technique extends the use of passive soil gas and bore water sampling to oil and gas exploration through surface geochemical techniques.

The technique follows from the theory that hydrocarbons preferentially move vertically through microstructures in the rocks and therefore can be detected in minute concentrations in the subsoil. This technique has been used for several decades in environmental investigation and monitoring (including water quality monitoring). Data from the trial shows that hydrocarbon compounds, in the range of carbon numbers from C₂ to C₁₈, were clearly detected at significant levels in the surface sample data from both the water bore and in-ground sample locations. The results also hint that the technique can be utilised in petroleum system studies and will provide a cost effective geochemistry tool for future petroleum exploration. The analytical results and interpretative report are available on request (contact petroleum@dpi.nsw.gov.au).

Bowen and Surat Basins Petroleum Data Package

The Bowen and Surat Basins Petroleum Data Package on CD-ROM was released in September 2002. The Bowen and Surat Basins host significant oil and gas fields in Queensland, however these basins have largely been ignored in New South Wales since the 1960's. The data package outlines new leads, that may, in time, result in discoveries similar to the Coonarah gas field in the nearby Gunnedah Basin area to the southeast.

For more information, please contact petroleum@dpi.nsw.gov.au.