Matthews C.,Monash University |
Beardsmore G.,University of Adelaide |
Driscoll J.,Panax Geothermal Ltd |
Pollington N.,Hot Dry Rocks Pty Ltd
Exploration Geophysics | Year: 2013
This paper presents the results of 34 new heat flow estimates taken in 2004 from 16 water bores and 18 petroleum exploration wells in the western Otway Basin. The average estimated heat flow measured across the study area is 65.6±9.4mW/m2, with a range of 42-90mW/m2. There are three recognisable sectors within the study area where heat flow is slightly elevated relative to the background levels. These sectors can be broadly classified as Mount Schank (73.5±0.5mW/m2), Mount Burr (71.2±7.6mW/m2) and Beachport (78.3±10.4mW/m2). Thermal conductivity values for each unit involved in heat flow estimation were determined from laboratory measurements on representative core using a divided bar apparatus. Borehole thermal conductivity profiles were then developed in this study by assigning a constant value of conductivity to each geological formation. The process of collecting temperature data involved measuring temperature profiles for 16 water bores using a cable, winch and thermistor, and compiling well completion temperature data from 18 petroleum wells. The precision of temperature data was higher in the water bores (continuous logs) than in the petroleum wells (largely bottom-of-hole temperature estimates). Inversion heat flow modelling suggests heterogeneous heat flow at 6000m depth, with two zones where vertical heat flow might exceed 90mW/m2, and several zones where vertical heat flow might be as low as 40mW/m2. Therefore, while slightly higher surface heat flow does coincide with some of the volcanic centres, heterogeneous basement heat production is a more likely explanation, as there are no heat flow anomalies greater than 5-10mW/m2 associated with the Pleistocene-Recent Newer Volcanics Province. The distribution of heat flow in south-east South Australia is most simply explained by non-volcanic phenomena. © 2013 ASEG.
Siegel C.,Queensland University of Technology |
Siegel C.,University of Queensland |
Schrank C.E.,Queensland University of Technology |
Schrank C.E.,University of Western Australia |
And 4 more authors.
Geothermics | Year: 2014
A large subsurface, elevated temperature anomaly is well documented in Central Australia. High heat producing granites (HHPGs) intersected by drilling at Innamincka are often assumed to be the dominant cause of the elevated subsurface temperatures, although their presence in other parts of the temperature anomaly has not been confirmed. Geological controls on the temperature anomaly remain poorly understood. Additionally, methods previously used to predict temperature at 5. km depth in this area are simplistic and possibly do not give an accurate representation of the true distribution and magnitude of the temperature anomaly. Here we re-evaluate the geological controls on geothermal potential in the Queensland part of the temperature anomaly using a stochastic thermal model. The results illustrate that the temperature distribution is most sensitive to the thermal conductivity structure of the top 5. km. Furthermore, the results indicate the presence of silicic crust enriched in heat producing elements between 5 and 40. km. © 2014 Elsevier Ltd.
Antriasian A.,Hot Dry Rocks Pty Ltd |
Beardsmore G.,Hot Dry Rocks Pty Ltd
Geotechnical Testing Journal | Year: 2014
We present a method for measuring the heat capacity of a rock specimen using a divided bar apparatus in a "transient" mode. The specific heat capacity can be derived if the mass of the specimen is known. Thermal conductivity can be measured during a steady-state phase of the measurement process, and longitudinal thermal diffusivity can also be derived if the specimen volume (and hence density) is measured. A divided bar delivers a longitudinal flow of heat through a rock specimen and is conventionally used only in a steady-state mode for thermal conductivity measurements. Our method employs a time-series record of temperature changes at four points along the divided bar assembly to compare the net thermal energy absorbed by a specimen to its change in temperature during thermal re-equilibration from one steady-state temperature to another. The technique is calibrated using a set of analytical standards of known heat capacity. Our method yields mean values of specific heat capacity within 61 % of published values for cultured quartz. Repeated measurements on the same specimens also give consistent results within approximately 61 %. A combined thermal conductivity and heat capacity measurement takes less than one hour per specimen. Our method can be replicated with any divided bar apparatus employing a precise electronic temperature control system capable of switching between two steady-state mean temperatures, along with a digital data-logging system capable of recording and displaying data at a rate of one record per second. Copyright © 2014 by ASTM International.
Mortimer L.,Hot Dry Rocks Pty Ltd. |
Cooper G.,Hot Dry Rocks Pty Ltd.
AusIMM Bulletin | Year: 2011
The article outlines a concept developed by geothermal consultants, Hot Dry Rocks Pty Ltd, of how these issues may in part be addressed through the syngenetic development of geothermal power plants that utilize co-produced CSG water as their cooling fluid agent. While there is no technical lower temperature limit for geothermal power conversion, practical economic constraints typically result in a minimum reservoir temperature requirement well above 100°C. The Queensland Department of Infrastructure and Planning recently estimated that an annual average of 25 GL of CSG water would be produced for the next 25 years from the Surat Basin to supply the domestic gas market. Plant scaling due to poor CSG water quality is a potential operational issue. However, although some CSG water is considered too saline and sodic for most domestic and agricultural purposes, it is relatively benign when compared to fluids that power existing conventional geothermal operations around the world.