| Title | A Preliminary Study on Na-Cl-H2O-rock Interactions of the Hot Fractured Rock Geothermal System in Cooper Basin, South Australia |
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| Authors | Gideon B. Kuncoro, Yung Ngothai, Brian O’Neill, Allan Pring, Joël Brugger |
| Year | 2010 |
| Conference | Australian Geothermal Energy Conference |
| Keywords | hot fractured rock, fluid-rock interaction, Na-Cl-H2O system, geothermal, Cooper Basin, Habanero, thermosyphon |
| Abstract | A preliminary study was undertaken to observe the fluid-rock interaction in Na-Cl-H2O system. Samples of drill cuttings from a borehole 5 km deep from Habanero 3 well were contacted with 250 ppm sodium chloride solution in a thermosyphon induced loop reactor at 250oC and 40-50 bar. The experiments were carried out in a Titanium flow through cell for 1, 7, and 28 days at 250oC and 40 bars). The fluid was replaced every 24 hours in order to accelerate the dilution rate to observe which minerals are reactive (soluble) and to mimic a condition which uses fresh water or treated water from a precipitation tank that is reinjected to the fracture. Fluid and rock samples were analysed prior to, and after circulation to observe the dissolved minerals and mineralogy. Water analysis was performed using ICP-MS, and rock analyses were conducted using an optical microscope, SEM and XRD. The experimental results indicated that mineral dissolution was more rapid in the early stages of the experiment. This may be a consequence of the dissolution of finer rock particles. SEM observations showed evidence of etching of the mineral surfaces consistent with partial dissolution. XRD results indicated that the feldspars (NaAlSi3O8 and KAlSi3O8) in the rock had completely dissolved and small amount of quartz remained. ICP-MS analysis on the water sample confirmed that some mineral dissolution has occurred. The concentrations of the elements increased with time. |