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New NTGS Record released PDF Print E-mail
Friday, 16 November 2007

Beardsmore G, 2007.
Geothermal energy potential of the Northern Territory.
Northern Territory Geological Survey, Record 2007-004.

Abstract

The Northern Territory is part of the Central Australian Heat Flow Province andpossesses all the fundamental requirements for geothermal systems that could beused for hot rock or deep hot aquifer geothermal electricity generation.Crystalline basement rocks beneath the NT’s basins are capable of generatinghigh surface heat flows in many areas and adequate thermal insulation isprovided by appropriate rock types in overlying sedimentary successions in anumber of basins. 

The whole of the NT is currently in a compressive stress regime, making it attractive for the hydraulic stimulation of hot basement rocks, and basement is at a drillable depth in many areas. Sedimentary formations at depth may also be suitable drill targets, provided they are naturally permeable or susceptible to permeability enhancement. The NT’s onshore sedimentary basins are individually assessed for their hot fractured rock geothermal energy potential. The McArthur Basin, Beetaloo Sub-basin and Dunmarra Basin are prospective for geothermal systems in areas where there is high heat flow and significant insulating sedimentary layers. Basement is deeply buried beneath these basins, but there is potential for in situ permeability, or layers that can have their permeability artificially enhanced. The Victoria–Birrindudu basins are likely to have high heat flows, but may lack adequate insulating sedimentary layers, reducing the potential for good geothermal systems at drillable depths. Except for northern areas of the Victoria Basin, these basins are also relatively remote from infrastructure. The Daly Basin may host areas of elevated heat flow and is also relatively close to infrastructure and markets. However, sedimentary thicknesses may be insufficient to provide the required thermal insulation, except in parts of the basin that overlap other sedimentary successions. The coastal Bonaparte, Money Shoal and Arafura basins are attractive for exploration because they are underlain by basement with demonstrated high heat flow, they contain potentially insulating intervals of fine-grained sedimentary rocks, and they are also relatively close to infrastructure and/or markets.

The Amadeus Basin contains a thick, but mostly conductive sedimentary succession. However, local areas of basement have exceptionally high heat-generating properties that could elevate surface heat flow to reasonable levels. Thick basement sections occur in shallower portions of the basin on the central ridge and in southern areas; these areas are within drillable depths and are relatively close to infrastructure. The Ngalia Basin has potential for elevated heat flow in areas where basement has high heat-generating properties and the succession has a high proportion of fine-grained sedimentary rocks. This basin is distant from markets, but has relatively good road access. The Georgina Basin contains some areas where crystalline basement rocks are at relatively shallow depths and heat flow is likely to be high. However, the sedimentary fill may not provide adequate thermal insulation and this basin is remote from potential markets. The Pedirka and Eromanga basins are underlain by crystalline basement rocks with high heat-generating potential and the sedimentary succession has excellent potential for thermal insulation. Geothermal targets may be present within drillable depths in some areas, either in basement rocks, or in strata that are naturally permeable or susceptible to permeability enhancement. However, these basins are also distant from potential markets and have limited infrastructure. The Wiso Basin (Lander Trough) is distant from infrastructure and is poorly explored; deeper parts of the basin have not been drilled and its geothermal potential is therefore difficult to assess. However, underlying crystalline basement rocks may provide adequate heat flow and parts of the sedimentary succession may have good thermal insulation properties.

Basins in the north of the NT are relatively close to population centres and electricity power lines from Katherine to Darwin, whereas basins in the south are close to Alice Springs and to north–south rail and road arteries. Remote communities and mining operations in all parts of the Territory could benefit from the development of sustainable geothermal power.

 
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