Thermo-physical rock properties and the impact of advancing hydrothermal alteration — A case study from the Tauhara geothermal field, New Zealand

摘要: Abstract The thermo-physical rock properties density, porosity, matrix permeability, thermal conductivity and specific heat capacity of 418 orientated plugs cut from 233 cores recovered geothermal investigation wells THM12, THM13, THM14, THM17, THM18, THM19, TH18 at the Tauhara field, New Zealand were measured a statistical database was set up. lithotype each sample classified, hydrothermal alteration rank intensity determined by optical microscopy. clays (typically smectite, smectite–illite, illite) analysed methylene blue dye adsorption test short wave infrared spectroscopy. Investigated stratigraphic units are Huka Falls Formation with its sub members upper, middle lower Formation, Wairora Spa Andesite associated breccias, Racetrack rhyolite breccias. Lithotypes clay-altered tuff intercalated mudstone/siltstone (cap for system); tuffaceous sandstones, sedimentary pyroclastic breccias pumiceous ash (reservoir-hosting units); rhyolitic andesitic lavas, their obtained property data indicate common porosity range 30% to 45% sediments, volcaniclastics lava an average 10% andesite lava, 39% lava. Matrix permeability mudstone, siltstone, lavas is commonly − 1  K 1 W m ), while have higher values (0.9 W m 1.4 W m ). Specific similar all lithotypes (0.6 kJ kg 0.8 kJ kg Advancing decreases sandstone tuff, but has contrasting effects on permeability. Permeability increases few millidarcy, it up multiple orders magnitude advancing alteration. Thermal about 25% triples sandstone, remains rather stable.