A multidisciplinary approach to quantify the permeability of the Whakaari/White Island volcanic hydrothermal system (Taupo Volcanic Zone, New Zealand)

Heap, Michael; Kennedy, Ben; Farquharson, Jamie; Ashworth, James; Mayer, Klaus; Letham-Brake, Mark; Reuschlé, Thierry; Gilg, H. Albert; Scheu, Bettina; Lavallée, Yan; Siratovich, Paul; Cole, Jim; Jolly, Arthur D.; Baud, Patrick; Dingwell, Donald B.

doi:10.1016/j.jvolgeores.2016.12.004

Cited by 107 publications

(100 citation statements)

References 85 publications

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“…The micropore structure, which controls fluid flow Heap et al 2017a), can be modified by post-depositional processes. Intrusive rocks have little initial porosity due to their holocrystalline matrix, but their post-cooling porosity and permeability develops as a result of tectonic and thermal stresses that manifest as macroscopic and microscopic fractures (Géraud 1994;Lane and Gilbert 2008).…”

Section: Microfracture and Pore Analysismentioning

confidence: 99%

“…Intrusive rocks have little initial porosity due to their holocrystalline matrix, but their post-cooling porosity and permeability develops as a result of tectonic and thermal stresses that manifest as macroscopic and microscopic fractures (Géraud 1994;Lane and Gilbert 2008). Volcanic rocks have a wide range of porosities due to variables such as cooling time, transport, gas content, and weathering (e.g., Mueller et al 2011;Olalla et al 2010), while porosity in volcaniclastic and sedimentary rocks is generally controlled by the size and distribution of particles (e.g., Heap et al 2017a;Bai et al 2016).…”

Section: Microfracture and Pore Analysismentioning

confidence: 99%

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Matrix permeability of reservoir rocks, Ngatamariki geothermal field, Taupo Volcanic Zone, New Zealand

et al. 2018

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The Taupo Volcanic Zone (TVZ) hosts 23 geothermal fields, seven of which are currently utilised for power generation. Ngatamariki geothermal field (NGF) is one of the latest geothermal power generation developments in New Zealand (commissioned in 2013), located approximately 15 km north of Taupo. Samples of reservoir rocks were taken from the Tahorakuri Formation and Ngatamariki Intrusive Complex, from five wells at the NGF at depths ranging from 1354 to 3284 m. The samples were categorised according to whether their microstructure was pore or microfracture dominated. Image analysis of thin sections impregnated with an epoxy fluorescent dye was used to characterise and quantify the porosity structures and their physical properties were measured in the laboratory. Our results show that the physical properties of the samples correspond to the relative dominance of microfractures compared to pores. Microfracture-dominated samples have low connected porosity and permeability, and the permeability decreases sharply in response to increasing confining pressure. The pore-dominated samples have high connected porosity and permeability, and lower permeability decrease in response to increasing confining pressure. Samples with both microfractures and pores have a wide range of porosity and relatively high permeability that is moderately sensitive to confining pressure. A general trend of decreasing connected porosity and permeability associated with increasing dry bulk density and sonic velocity occurs with depth; however, variations in these parameters are more closely related to changes in lithology and processes such as dissolution and secondary veining and re-crystallisation. This study provides the first broad matrix permeability characterisation of rocks from depth at Ngatamariki, providing inputs for modelling of the geothermal system. We conclude that the complex response of permeability to confining pressure is in part due to the intricate dissolution, veining, and recrystallization textures of many of these rocks that lead to a wide variety of pore shapes and sizes. While the laboratory results are relevant only to similar rocks in the Taupo Volcanic Zone, the relationships they highlight are applicable to other geothermal fields, as well as rock mechanic applications to, for example, aspects of volcanology, landslide stabilisation, mining, and tunnelling at depth.

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Section: Microfracture and Pore Analysismentioning

confidence: 99%

Section: Microfracture and Pore Analysismentioning

confidence: 99%

Matrix permeability of reservoir rocks, Ngatamariki geothermal field, Taupo Volcanic Zone, New Zealand

et al. 2018

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“…The effects of temperature on the physical, chemical, and mineralogical properties of volcanic rocks has been the subject of a range of studies (e.g., Björnsson, ; Browning et al, ; Kitao et al, ; Siratovich, Villeneuve, et al, ,Siratovich, von Aulock, et al, ), but the range of scenarios (e.g., heating vs. cooling), conditions (e.g., magnitude of temperature fluctuations), and reservoir rock types (e.g., unaltered versus altered) has prevented the generalization of the impact on the resultant reservoir rock permeability. For instance, cooling results in contraction, which may generate macroscopic thermal cracks to promote fluid flow (Lamur et al, ), yet it may also precipitate secondary mineralization that can, through time, block otherwise permeable pathways (Heap et al, ). In contrast, the impact of temperature increase (e.g., from magma intrusion) on the resultant rock permeability remains poorly constrained (Gaunt et al, ; Kushnir et al, ) as it has received noticeably less attention than the influence of changes in pressures on permeability (e.g., Cant et al, ; Eggertsson et al, ; Gudmundsson, , ; Heap, Baud, et al, ; Heap et al, ; Lamur et al, ).…”

Section: Introductionmentioning

confidence: 99%

“…For instance, cooling results in contraction, which may generate macroscopic thermal cracks to promote fluid flow (Lamur et al, ), yet it may also precipitate secondary mineralization that can, through time, block otherwise permeable pathways (Heap et al, ). In contrast, the impact of temperature increase (e.g., from magma intrusion) on the resultant rock permeability remains poorly constrained (Gaunt et al, ; Kushnir et al, ) as it has received noticeably less attention than the influence of changes in pressures on permeability (e.g., Cant et al, ; Eggertsson et al, ; Gudmundsson, , ; Heap, Baud, et al, ; Heap et al, ; Lamur et al, ). Understanding how the permeability of reservoir rock changes in response to thermal fluctuation is critical to elaborate solutions to maintain the economic potential of hydrothermal resources.…”

Section: Introductionmentioning

confidence: 99%

“…Hydrothermal fluids and heat input may also dissolve or break down rock-forming minerals, thus creating additional permeable porous pathways for fluid flow (e.g., Cant et al, 2018;Farquharson et al, 2019;Heap et al, 2012;Kanakiya et al, 2017;Nemčok et al, 2007). Alternatively, hydrothermal fluids may induce the precipitation of minerals (e.g., clays, salts, carbonates, and silica polymorphs) within the pores and cracks (e.g., Rowland & Sibson, 2004;Griffiths et al, 2017;Kanakiya et al, 2017) and thereby decrease permeability (e.g., Heap et al, 2017). The permeability evolution of the reservoir rock is ultimately governed by the temperature, stress field, and chemistry of the system (fluids and solids), which control fluid convection (Fournier, 1985, and references therein).…”

Section: Introductionmentioning

confidence: 99%

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Increasing the Permeability of Hydrothermally Altered Andesite by Transitory Heating

Mordensky

Kennedy

Villeneuve

et al. 2019

Geochem Geophys Geosyst

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Changes in permeability can impact geological processes, geohazards, and geothermal energy production. In hydrothermal systems, high‐temperature heat sources drive fluid convection through the pore network of reservoir rocks. Additionally, thermal fluctuations may induce microfracturing and affect the mineralogical stability of the reservoir rock, thus modifying the fluid pathways and affecting permeability and strength. This study describes the results of thermal heating events lasting several hours on a “moderately altered” plagioclase‐clinochlore‐calcite‐quartz andesite and a “highly altered” plagioclase‐clinozoisite‐quartz‐clinochlore andesite from the Rotokawa Geothermal Field, New Zealand. We use a low thermal gradient (~1.2 °C/min) in an H2O‐saturated, 20‐MPa pressure environment to constrain changes in petrophysical properties associated with transitory thermal phenomena between 350 and 739 °C. As the treatment temperature increases, the mass reduces, while porosity and permeability increase. These effects were greater in the “moderately altered” andesite than in the “highly altered” andesite. Microfracturing is responsible for these changes at lower temperatures (e.g., ≤400 °C). At higher temperatures (e.g., >400 °C), microfracturing remains partially responsible for these rock property changes (e.g., higher permeability); however, these changes are also a product of clinochlore, quartz, and (when present) calcite reacting out of the altered andesite, and increasing porosity. We propose that at temperatures >400 °C, volumetric phase changes associated with heat‐driven reactions in a wet environment can contribute to microcracking and porosity/permeability changes. Our data support observations where high‐temperature conditions at the margins of magma bodies can be associated with substantial increased permeability and decreased strength.

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Evolution of a small hydrothermal eruption episode through a mud pool of varying depth and rheology, White Island, NZ

et al. 2017

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A multidisciplinary approach to quantify the permeability of the Whakaari/White Island volcanic hydrothermal system (Taupo Volcanic Zone, New Zealand)

Cited by 107 publications

References 85 publications

Matrix permeability of reservoir rocks, Ngatamariki geothermal field, Taupo Volcanic Zone, New Zealand

Matrix permeability of reservoir rocks, Ngatamariki geothermal field, Taupo Volcanic Zone, New Zealand

Increasing the Permeability of Hydrothermally Altered Andesite by Transitory Heating

Evolution of a small hydrothermal eruption episode through a mud pool of varying depth and rheology, White Island, NZ

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