Tuesday, February 12, 1:00pm

Professor Simon Lang

Associate Professor, Sedimentology and Stratigraphy, NCPGG, Adelaide University
 

Analogues for fluvial reservoirs from the West Siberian peat mires  
 

Abstract

The Permian coal measures of Eastern Australia (Bowen-Sydney-Cooper-Galillee basin system) were deposited in a vast foreland and intracratonic basin setting in a cool-temperate paleoclimate that steadlily warmed through the late Permian, terminating at the Permo-Triassic boundary. Significant gas and oil is reservoired in fluvial channel and crevasse splay sandstones, as well fluvial-glacial outwash, and seals include extensive lacustrine and floodplain intervals in the Cooper, passing into more marine rocks in the Bowen-Sydney basins. To further understand reservoir geometry, interconnectivity, and relationship with the coal, it is useful insighsts can be gained from modern analogues, including the modern rivers of Canada, Alaska, and especially Siberia.

The West Siberian lowlands contain the world's most extensive cool temperate peat mires, and also hosts the Ob River that flows north for over 4000 from the Altai Mountains near the Russian/Chinese border. The gradient is very low, with the last 2900 km of the Ob River dropping only 91 m, and it is dominantly meandering and anastomosing in the middle reaches, with splay belts in the lower reaches. The Ob River is frozen about 220 days of the year but thaws in May and June, usually accompanied by ice jams and flooding. The Western Siberian Lowland is a structural basin with more than 1000 m of Tertiary cover overlying several thousand meters of Mesozoic and Paleozoic rocks that host the largest gas province and second largest oil province in the World (especially the Jurassic sand-prone coastal and shelf systems). Basement structure controls the present day channel belt orientation, and the peat mires become more extensive on the interfluves where peat sits directly on sandy, fluvio-glacial outwash. Drilling in the middle Ob shows an extensive sheet of amalgamated fluvial channel sands over 100m thick, extending up to 100km wide, overlying extensive lacustrine sediments. Peats mainly form as raised mires (up to 40m above the river) but also infill abandoned channels along with organic silts, providing food for thought about stratigraphic traps and ideas for interpreting 3Dseismic.

This talk will present the results of a field visit by Drs Lang, Kassan and Esterle in August 2001 to the region as part of a pilot project on reservoir analogues co-funded by Santos Ltd, and the APCRC Reservoir Characterisation Program at the NCPGG. It will include lots of spectacular helicopter and ground-based images of the Ob River meander belt and floodplain as well as the drainage divide between the Ob and the Arctic where vast peat mires are drained by sand-prone meandering rivers. We will show images raised mires, forest mires, permafrost features, peat-filled sandy channels in meanders ranging from a few hundreds of metres to several kilometres.

Implications for reservoir geometry, connectivity and stratigraphic traps will be breifly outlined, as well as some mention of interesting features of the oil and gas industry and living conditions in this formerly closed region of Russia.

Acknowledgements

Kassan, J., Whistler Research Ltd, Spring Mountain and Research Associate, NCPGG, Esterle, J., CSIRO, Centre for Advanced Technologies, Pinjarra Hills.

Biography of the Speaker

Simon Lang graduated from the University of Queensland in 1985 with a BSc (Hons) in Geology and Mineralogy, and later obtained his PhD (part-time) also from University of Queensland in 1994. From 1979 to 1992 he worked as a geological technician and geologist for the Geological Survey of Queensland in the Palaeontology, and Regional Mapping Sections mainly in central and northern Queensland. Simon joined Queensland University of Technology in 1992 as a lecturer in sedimentology and stratigraphy during which time he supervised petroleum and mineral related postgraduate projects in a range of basins in Australia, Indonesia, PNG, and Venezuela. In addition he developed a reservoir analogues research program based on sedimentology and seismic/sequence stratigraphy of Moreton Bay and the SE Queensland continental shelf, as well as working on other modern depositional environments in Lake Eyre and Hervey Bay. Simon joined the National Centre for Petroleum Geology and Geophysics as Associate Professor in sedimentology and sequence stratigraphy in 1999. Simon is currently the Project leader on reservoir characterization for the APCRC and co-leading reservoir characterisation research programs, in addition to leading the Sedimentology and Sequence Stratigraphy research program at the NCPGG. Simon is a member of PESA, GSA, AAPG, SEPM, IAS and IPA.