BROWSE BASIN A joint study by Geotrack International and AGSO of the thermal history of the basin using AFTA, FAMM and VR data Regional thermal history investigation constraining the timing and magnitude of multiple thermal episodes affecting the basin

New thermal history data will be collected from selected wells in the basin in order to identify, quantify and characterise major events affecting the basinal sediments.

The THR approach (Thermal History Reconstruction) will provide the necessary hard constraints to rigorously assess the timing of maturation of key source rock horizons, to identify thermal mechanisms other than burial (e.g. fluid effects), and to evaluate VR suppression. New AFTA results will be used to allow a direct and quantitative assessment of the thermal history. These constraints are important for any rigorous assessment of the hydrocarbon potential of the area.

We invite early participation from sponsoring companies as the final well selection is made. Sampling is in progress with the final report scheduled for December 1997.

Comprehensive Report: $20,500 (prior to June 30th 1997)

Project background and objectives

Exploration activity in the Browse Basin began in 1963, with interest increasing significantly in the past five years owing to recent drilling success in the region. The Browse Basin is believed to have experienced a complex geological history consisting of several episodes of heating related to Paleozoic and Mesozoic rifting, pre- and post-breakup volcanism, possible Triassic and Miocene inversion, and tectonics related to salt movement. The relative significance and influence of these events on hydrocarbon generation and migration are not well understood. A rigorous assessment of the thermal history, the timing of maturity development, and the reliability of existing VR data is a vital part of prospect evaluation in this region.

The project aims to resolve these problems by direct assessment of the timing and magnitude of paleo-thermal effects in the Carboniferous to Tertiary section. Rather than relying on theoretical models of basin evolution, use of AFTA and VR data in selected wells will allow direct measurement of the various thermal episodes and their variation across the basin.

The objectives of this joint Geotrack-AGSO study include:

• identification of the major thermal episodes affecting the drilled section,
• quantification of the timing and magnitude of multiple(?) thermal episodes,
• characterisation of the processes responsible for each episode,
• measurement of the paleogeothermal gradient during each recognised episode,
• quantitative assessment of timing of maturation of key source rock horizons,
• estimation of the timing and amount of uplift and erosion at each studied location,
• recognition of any non-burial related thermal effects, caused for example by heatflow variation or fluid movement,
• to assess existing VR data which in many places appears less than expected, and
• provision of a regional thermal history synthesis, with implications for oil and gas generation based on new thermal history results and AGSO's understanding of the regional development of the area.

The combination of Geotrack's thermal history methods with AGSO's experience and knowledge base provides a unique and reliable basis for developing well-constrained thermal histories in the Browse Basin. These histories will allow new insight to the maturation history and hydrocarbon potential in the area.

Proposed work program

The project will be based on ~30+ new AFTA analyses and ~100+ new VR analyses from 10-12 wells in the Browse Basin. In addition, new FAMM analyses will be included where appropriate. Sample collection will commence in June 1997 and sample analyses are expected to be completed by September with the final report complete by December 1997. The preliminary work program includes the following wells, although suggestions from early subscribers are sought and additional wells may be included: Bassett-1A, Brecknock-1, Brewster-1, Buffon-1, Caswell-2, Kalyptea-1, Leveque-1, Lombardina-1, Londonderry-1, Rob Roy-1 and Yampi-1.

Prices

After December 30th:

$25,600

Group discounts available:  2 companies: price x 1.6  3 companies: price x 2.0  4 companies: price x 2.4

For further information, please contact:

Paul F. Green Geotrack International phone: 03-9380-1077 fax: 03-9380-1477 e-mail

Jane E. Blevin AGSO phone: 06-249-9818 fax: 06-249-9980 e-mail: jblevin@agso.gov.au