The Surat Basin is a significant geological and hydrogeological basin located primarily in south-east Queensland, Australia, with a minor extension into northern New South Wales. It is a major petroleum and coal-producing region, particularly known for its extensive coal seam gas (CSG) reserves and steaming coal deposits.
Geography and Geology
Geologically, the Surat Basin is a large intracratonic sedimentary basin covering an area of approximately 280,000 square kilometers. It forms the south-eastern portion of the larger Great Australian Basin (GAB) system. The basin overlies the Permian Bowen Basin to the east and south, and its sediments are predominantly of Jurassic and Cretaceous age. Key geological formations include:
- Walloon Coal Measures: A sequence of Jurassic age interbedded coal, carbonaceous mudstone, siltstone, and sandstone, which are a primary source of both thermal coal and coal seam gas.
- Gubberamunda Sandstone and Hutton Sandstone: Important aquifer units within the Great Artesian Basin.
- Injune Creek Group: A succession of mostly continental sediments.
The basin's landscape is characterized by flat to gently undulating plains, supporting significant agricultural activities alongside resource extraction. Major towns within the basin include Dalby, Chinchilla, Roma, and Miles.
Natural Resources
The Surat Basin is rich in several natural resources:
- Coal: Large deposits of thermal coal (steaming coal) are found within the Walloon Coal Measures and other Jurassic units. While some open-cut and underground mines operate, coal seam gas extraction has become a more prominent industry.
- Coal Seam Gas (CSG): This is the most economically significant resource in the basin. The Walloon Coal Measures are particularly productive for CSG, which is extracted for both domestic supply and export as liquefied natural gas (LNG) from facilities on Queensland's coast.
- Conventional Oil and Gas: Smaller fields of conventional oil and gas exist, contributing to the basin's overall hydrocarbon production.
- Groundwater: The basin forms a crucial part of the Great Artesian Basin, providing vital groundwater resources for agriculture, livestock, and communities across inland Queensland. Managing the interaction between CSG extraction and these significant groundwater resources is a key environmental and social consideration.
Economic Significance and Industry
The Surat Basin plays a vital role in Australia's energy sector and the Queensland economy. It is a major hub for the coal seam gas industry, with extensive infrastructure including thousands of wells, gas processing plants, and a vast network of pipelines. Gas from the basin is transported via major pipelines to coastal LNG facilities (e.g., at Curtis Island, Gladstone) for export to international markets, and also supplies domestic gas markets in eastern Australia.
While coal mining is present, the gas industry dominates resource extraction in the region. The basin's agricultural sector, particularly cropping (e.g., cotton, sorghum, wheat) and grazing, remains highly significant. The coexistence of agriculture and resource development leads to complexities in land use planning, water management, and community engagement. Environmental management, particularly concerning groundwater impacts and surface land disturbance from CSG operations, is a key focus for regulatory bodies and industry.