Identification of Structural Hydrocarbon Traps in the Amadeus Basin

Identification of Structural Hydrocarbon Traps in the Amadeus Basin

Skills

This research project provides the opportunities for research students to obtain skills and experience in the enhancement and interpretation geophysical data an its integration with geological information, skills highly regarded in resource exploration companies, as well as forming a firm basis for a research or academic career.

Project Description

The Amadeus Basin, one of the major basins of central Australia, is the least explored onshore petroleum-bearing basin with proven reserves in Australia. It is located in the southern part of the Northern Territory and extends westward into Western Australia (Fig. 1).

The Amadeus Basin comprises rocks recording nearly 500 million years of Earth history ranging from the latest part of the Precambrian into the Mid-Paleozoic (~800 to 300 Ma; Lindsay et al., 2005). The sedimentary fill in the basin is at least 10 km thick. The Basin has a complicated depositional history and structural complexity caused by the upward movement of salt bodies during burial compaction and subsequent phases of tectonic deformation (e.g. Lindsay & Korsch, 1991; Shaw et al., 1991; Haines et al. 2001; Dyson & Marshall, 2005);

Figure 1 Map of Amadeus Basin showing location, main features and wells.

The Amadeus Basin hosts two producing petroleum fields (Fig.1), both fields are in structural traps. Mereenie contains considerable reserves of oil and gas and Palm Valley has gas. Reservoirs not only contain natural gas (methane) but also helium.

High quality modern basin-wide aeromagnetic data have been flown by the Northern Territory Geological Survey (NTGS). A preliminary appraisal of the basin-wide aeromagnetic dataset acquired by the NTGS shows that there are responses which are consistent with potential hydrocarbon trap structures. Initial analysis of the aeromagnetic data shows that most basin-fill responses are caused by tabular sources, which suggests stratigraphically controlled variations in magnetism are responsible for the observed variations in magnetic intensity. Gravity data are also available, most are in the public domain, and additional proprietary data will be made available for the proposed research project. In the Amadeus Basin it is necessary to ascertain how they can be most effectively used to derive structural information about the basin fill, and hence the presence of potential hydrocarbon traps. This will be based on texture-based processing of these data (Fig.2, Dentith et al., 2000), petrophysical data, all available seismic data and modeling of magnetic and gravity responses.

The ‘Noddy’ geology-geophysical modeling package will be used to understand the geological evolution of particular areas (Jessell et al., 1993). This package allows the user to progressively deform (fold, fault, intrude) a geological model with the intention of reproducing the observed cross-sectional and/or geological map patterns. Importantly, the package has the capability to calculate the gravity and magnetic responses of the model at any stage in its development. Seismic data will also modeled, using in-house software.

An innovative aspect of the proposed research is an investigation of whether hydrocarbon-bearing structures have particular geophysical and remote-sensing responses related to seepage. Magnetic anomalies of this kind have been postulated in areas outside Australia but there are no reported studies from this country. The origin of these anomalies is controversial (Liu et al., 2004 and references therein). The most favoured interpretation is that secondary magnetic minerals are created in the rocks overlying the field due to hydrocarbon leakage.

BEFORE

AFTER

Figure 2. Examples of results of novel techniques currently being developed at UWA to enhance the weak magnetic responses from features in sedimentary basins. The two datasets are from geological terrains comparable to the Amadeus Basin. The images on the left are TMI. Those on the right are the equivalent data after enhancement.

Recommended Reading

Dentith, M.C., Cowan, D.R. and Tompkins, L.A., 2000. Enhancement of subtle features in aeromagnetic data. Exploration Geophysics 31, 104-108.

Dyson, I.A. and Marshall, T.R., 2005. The influence of salt tectonics on Neoproterozoic to early Palaeozoic sedimentation, Amadeus Basin. Central Australian Basins Symposium Handbook, 25-27.

Haines, P.W., Hand, M. and Sandiford, M. 2001. Palaeozoic synorogenic sedimentation in central and northern Australia: a review of distribution and timing with implications for the evolution of intracontinental orogens. Australian Journal of Earth Sciences, 48, 911-928.

Jessell, M.W., Valenta, R.K., Jung, G., Cull, J.P. and Geiro, A., 1993. Structural geophysics. Exploration Geophysics 24, 599-602.

Lindsay, J.F. and Korsch, R.J., 1991. The evolution of the Amadeus Basin, central Australia. In, Korsch, R.J. and Kennard, J.M., (Editors), Geological and Geophysical Studies in the Amadeus Basin, Central Australia, BMR Bulletin 236, 7-32.

Lindsay, J.F., Kruse, P.D., and five others, 2005. The Neoproterozoic–Cambrian record in Australia: a stable isotope study. Precambrian Research 143, 113-133.

Liu, Q., Chan, L., Liu, G., Li, H., Wang, F., Zhang, S., Xia, X. and Cheng, T., 2004. Relationship between magnetic anomalies and hydrocarbon microseepage above the Jingbian gas field, Ordos Basin, China. AAPG Bulletin 88, 241-251.

Shaw, R.D., Korsch, R.J., Wright, C. and Goleby, B.R., 1991. Seismic interpretation and thrust tectonics of the Amadeus Basin, central Australia, along the MBR regional seismic line. BMR Bulletin 236, 385-408.