Torrens Energy Limited (Torrens Energy), an Australia-based company, has reported the results from heat flow drilling completed in late 2008. Final heat flows calculated from two diamond drill holes (Raitaro 1 and TKHD1A) recorded 75 and 96mW/m2, at the Adelaide Plains and Port Augusta projects respectively. The Port Augusta result is highly significant, and above the company’s target of 90mW/m2.
Modelled temperature estimates from this hole are approximately 200°C at 4600m depth, well above the temperatures required for geothermal power production.
In addition TKHD1A is located 6 kilometres from the National Power Grid and 53 kilometres from the town of Port Augusta, highlighting the potential for the Company to establish a new “geothermal field” in this key location.
Ongoing exploration activity is supported by a matching $3 million Federal Government grant under the Federal Government REDI programme.
Torrens Energy continues to bring the search for ‘hot rocks’ to the Port Augusta and Adelaide Regions – the hub of power infrastructure and markets in South zustralia.
Shared Drilling 2008
Results were recorded from two diamond drill holes completed from September to November 2008, at the Adelaide Plains and Port Augusta Projects, South Australia.
A combination of rotary mud and diamond core drilling was undertaken at Raitaro 1 and TKHD1A, for a total depth of 403 and 1002m respectively, to enable ‘clean’ temperature measurements to be taken.
Both holes were operated by explorers targeting minerals on coincident Licence Areas. Torrens was able to gain access to the holes for heat flow testing by contributing to drilling costs.
Heat Flow Data
At Raitaro 1 continuous temperature logging was conducted at 2m intervals using the Company’s vehicle mounted thermistor probe and motorised cable winch.
For the deeper hole TKHD1A, temperature was directly measured at 0.05m intervals by a SA Government contract well logging equipment.
For Raitaro 1 resistance was measured downhole and then converted to temperature using a standard calibration. Temperature recordings were taken from holes that had been allowed to equilibrate for approximately 5–8 weeks after drilling.
Preliminary Heat Flow Modelling
Heat flow modelling is a standard method for projecting temperatures down to target reservoir depth (3500-5500m). Rock units that act as insulating layers above the target reservoir must be assigned thermal conductivity values.
The sub-surface geology for the Port Augusta area was inferred from regional geological maps form PIRSA. Thermal conductivities for 14 interpreted geological formations are based on either direct measurement from core samples, or estimations using textbook values.
By assigning these values and applying a heat flow of 96mWm2 at TKHD1A, modelling was completed to 5000m, resulting in a predicted target temperature of approximately 200°C at 4600m depth.
The result at TKHD1A is highly significant, in that ‘hot rock’ geothermal power production in a similar geological environment in Europe utilises reservoir temperatures in the order of 150°C.
Furthermore TKHD1A is located just 6 kilometres from the 132kV Port Augusta – Leigh Creek transmission line, representing a considerable commercial advantage in comparison to remotely located ‘hot rock’ plays in South Australia.
Executive Director John Canaris commented; “The result at TKHD1A marks an exciting start to 2009, and is a good indicator of the excellent geothermal potential of the Port Augusta area. As always the prospect of defining a large ‘geothermal field’ proximal to existing power infrastructure continues to be our primary goal, with each exploration success moving the Company a step closer”.
Further interpretation of this excellent result is in progress, and follow-up exploration drilling is planned near Port Augusta for 2009.