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Poster EGU 2010

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Paulo Maciel Amaral
Paulo Maciel Amaral

The document summarizes measurements of thermal conductivity and thermal diffusivity taken from core samples extracted from two boreholes on Livingston Island, Antarctica. Thermal conductivity and diffusivity measurements were taken from cores stored in boxes, with depth estimated to within 20cm. Measurements were made in three orientations and showed average thermal conductivity of 3.14 W/mK for CALM site cores and 3.17 W/mK for PAPAGAL site cores, with CALM site having the highest average thermal diffusivity. Values varied some between boreholes and by core depth and orientation. The study provides a starting database of physical property measurements of the island's metamorphic rocks.

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INTRODUCTION AND OBJECTIVES: The thermal conductivity and thermal diffusivity are two physical properties of rock materials that are related to how thermal energy is transmitted through them, and so they also fundamental to describe and understand energy transfer in soil and, in particular, in perma- frost areas. Thermal conductivity is a measure of the efficiency with which materials conduct heat energy; thermal diffusivity measures the efficiency with which materials lose or absorb energy. For isotropic and homogeneous materials thermal conductivity (?) can be de- fined by the quotient between the rate at which heat is conducted through the unit area (q) and the temperature gradient or the change in the temperature with depth (?T). The thermal diffusivity () depends on the thermal conductivity (?) according to the following expression: where is the density and Cp is the specific heat. Thermal conductivity of rocks depends on several factors among which are mineralogy, chemical composition, porosity and fluid type in the pores, pressure, temperature, texture, structure, degree of consolidation, alteration, etc. Under the framework of the program New generation of polar scientists of Caixa Geral de Depsitos, the project Petrophysical char- acterization of rock and soil samples in relation to permafrost and climate change in Antarctica was granted a scholarship to me meas- ure thermal conductivities and thermal diffusivities of cores from boreholes drilled in the Island of Livingston in Maritime Antarctica. Here the results of the first measurements performed in cores collected from boreholes drilled in January and February, 2008, are pre- sented. The two boreholes are 5 and 6 meters deep and are located near the Bulgarian Antarctica Base (BAB) of St. Kliment Ohridski, on northwest of Hurd Peninsula of Livingston Island (Figures 1, 2, 3 and 4). The boreholes were drilled with continuous coring to col- lect as many samples as possible for laboratory studies. One of the boreholes is located in a CALM site with coordinates 60?2144.3W 62?38?48.5S (Figures 1 and 3) and the other is located in a place called PAPAGAL, with coordinates 60?2149.3W 62?3854.2S (Figure 2 and 3). PHYSICAL PROPERTIES OF ROCKS COLLECTED IN TWO BOREHOLES DRILLED IN LIVINGSTON ISLAND, MARITIME ANTARCTICA: A STARTING DATA BASE Antnio Correia (1), Paulo Amaral (2), Gon?alo Vieira (3), Miguel Ramos (4), and Alexandre Trindade (5) (1) Department of Physics and Geophysical Centre of Evora, University of Evora, Evora, Portugal (correia@uevora.pt), (2) Geophysical Centre of Evora, University of Evora, Evora, Portugal (amaral.paulomaciel@gmail.com), (3) Centre for Geographical Studies, University of Lisbon, Lisbon, Portugal (vieira@campus.ul.pt), (4) Department of Physics, University of Alcal, Madrid, Spain (miguel.ramos@uah.es), (5) Centre for Geographical Studies, University of Lisbon, Lisbon, Portugal (alexandretn@gmail.com) THERMAL CONDUCTIVITY AND THERMAL DIFFUSIVITY MEASUREMENTS: The cores obtained in the boreholes are identified using the following code (see Table 1): the first letter and digit refers to the box where the cores are stored; after the dot, the second number refers to the order location in the box. According to the drilling process the depth of the cores are estimated with an error of about 20 cm. The determination of the thermal conductivity and the thermal diffusivity of the cores from the two boreholes were made us- ing a TCS Lippmann & Rauen GbR equipment. The measurements were made in three orthogonal directions (a, b, and c), as shown in Figure 5, with the cores dry. RESULTS AND ANALYSIS: Table 1 shows the values of the thermal conductivity, the thermal diffusivity, and the heat production for cores obtained in the boreholes drilled in January, 2008, in the CALM site (Figure 1 and 3) and the PAPAGAL site (Figure 2 and 3). CONCLUSIONS: The thermal conductivity and thermal diffusivity values measured in cores from two boreholes drilled in the Island of Livingston confirm that the area where the boreholes were drilled correspond to outcrops of metamorphic rocks (Sch?n, 1996), which is consistent with local geology. The highest values of thermal conductivity were measured in the cores from the PAPAGAL site; the CALM site has the highest thermal diffusivity value and the lowest thermal conductivity value. The results presented here are preliminary and are far from been completed. There are porosity estimations being done to calculate the thermal conductivity values for the cores with the pores filled with water and ice, which correspond to the climatic environment of the area where the boreholes were drilled. Sch?n, J. H. (1996). Physical properties of rocks: fundamentals and principals of petrophysics (Vols. Handbook of geophysical exploration. Section I, Seismic exploration. v. 18). Oxford, Pergamon, 583. REFERENCE: The values of thermal conductivity measured in the cores of the CALM site (Table 1) vary between 2.78 W/mK and 3.36 W/mK and in PAPAGAL site vary between 2.95 W/ mK and 3.57 W/mK. The thermal conductivity average for the CALM site is 3.14 0.15 W/mK and in PAPAGAL site is 3.17 0.17 W/mK. The values of thermal diffusivity measured in the CALM site (Table 1) vary between 1.49 x 10-6 m2 /s and 1.67 x 10-6 m2 /s and in the PAPAGAL site between 1.34 x 10-6 m2 /s and 1.64 x 10-6 m2 /s. The thermal diffusivity average for the CALM site is 1.58 x 10-6 0.04 x 10-6 m2 /s and for the PAPAGAL site is 1.52 x 10-6 0.05 x 10-6 m2 /s. Table 1 also shows the values of the heat production for the two boreholes. A SILENA gamma-ray spectrometer was used to determine the contents in uranium, thorium and potassium from bits of the cores from the two boreholes. For each borehole those values are presented as well as the heat production values which are 1.30 ?W/m3 for the borehole in the CALM site and 0.70 ?W/m3 for the borehole in the PAPAGAL site. The boreholes distance from each other coarse 187 metres. The variations on thermal conductivity on booth boreholes according to the cores deep are shown on Figures 6 and 7. The different colours represent the boreholes and the shapes represent the measures realized according to the axis. Figure 1: General view of the CALM site. Figure 2: General view of the Papagal site. Figure 3: Location of the CALM and Papagal sites. Figure 5: Directions of measurement of the ther- mal conductivity and the thermal diffusivity. Table 1: Thermal conductivity, thermal diffusivity (dry samples), and heat production values for the cores collected in the CALM and Papagal sites boreholes, Livingston Island. TCa, TCb, and TCc, and, TDa, TDb, and TDc refer to the measurement directions of thermal con- ductivity and thermal diffusivity, respectively, along (a), (b), and (c) directions of Figure 5. Figure 4: Drilling in Livingston Island. ACKNOWLEDGEMENTS: The authors thank the Funda??o para a Cincia e a Tecnologia for funding the project PERMANTAR which allowed to collect the cores used in the presentation and process the data. One of the authors (PMA) acknowledges the grant of Caixa Geral de Depsitos. Figure 7: Average Thermal conductivity and average thermal diffusivity values for the CALM and PAPAGAL sites ac- cording to core depth. Figure 6: Thermal conductivity values for the CALM and PA- PAGAL sites according to core depth. D A B C

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Poster EGU 2010

  • 1. INTRODUCTION AND OBJECTIVES: The thermal conductivity and thermal diffusivity are two physical properties of rock materials that are related to how thermal energy is transmitted through them, and so they also fundamental to describe and understand energy transfer in soil and, in particular, in perma- frost areas. Thermal conductivity is a measure of the efficiency with which materials conduct heat energy; thermal diffusivity measures the efficiency with which materials lose or absorb energy. For isotropic and homogeneous materials thermal conductivity (?) can be de- fined by the quotient between the rate at which heat is conducted through the unit area (q) and the temperature gradient or the change in the temperature with depth (?T). The thermal diffusivity () depends on the thermal conductivity (?) according to the following expression: where is the density and Cp is the specific heat. Thermal conductivity of rocks depends on several factors among which are mineralogy, chemical composition, porosity and fluid type in the pores, pressure, temperature, texture, structure, degree of consolidation, alteration, etc. Under the framework of the program New generation of polar scientists of Caixa Geral de Depsitos, the project Petrophysical char- acterization of rock and soil samples in relation to permafrost and climate change in Antarctica was granted a scholarship to me meas- ure thermal conductivities and thermal diffusivities of cores from boreholes drilled in the Island of Livingston in Maritime Antarctica. Here the results of the first measurements performed in cores collected from boreholes drilled in January and February, 2008, are pre- sented. The two boreholes are 5 and 6 meters deep and are located near the Bulgarian Antarctica Base (BAB) of St. Kliment Ohridski, on northwest of Hurd Peninsula of Livingston Island (Figures 1, 2, 3 and 4). The boreholes were drilled with continuous coring to col- lect as many samples as possible for laboratory studies. One of the boreholes is located in a CALM site with coordinates 60?2144.3W 62?38?48.5S (Figures 1 and 3) and the other is located in a place called PAPAGAL, with coordinates 60?2149.3W 62?3854.2S (Figure 2 and 3). PHYSICAL PROPERTIES OF ROCKS COLLECTED IN TWO BOREHOLES DRILLED IN LIVINGSTON ISLAND, MARITIME ANTARCTICA: A STARTING DATA BASE Antnio Correia (1), Paulo Amaral (2), Gon?alo Vieira (3), Miguel Ramos (4), and Alexandre Trindade (5) (1) Department of Physics and Geophysical Centre of Evora, University of Evora, Evora, Portugal (correia@uevora.pt), (2) Geophysical Centre of Evora, University of Evora, Evora, Portugal (amaral.paulomaciel@gmail.com), (3) Centre for Geographical Studies, University of Lisbon, Lisbon, Portugal (vieira@campus.ul.pt), (4) Department of Physics, University of Alcal, Madrid, Spain (miguel.ramos@uah.es), (5) Centre for Geographical Studies, University of Lisbon, Lisbon, Portugal (alexandretn@gmail.com) THERMAL CONDUCTIVITY AND THERMAL DIFFUSIVITY MEASUREMENTS: The cores obtained in the boreholes are identified using the following code (see Table 1): the first letter and digit refers to the box where the cores are stored; after the dot, the second number refers to the order location in the box. According to the drilling process the depth of the cores are estimated with an error of about 20 cm. The determination of the thermal conductivity and the thermal diffusivity of the cores from the two boreholes were made us- ing a TCS Lippmann & Rauen GbR equipment. The measurements were made in three orthogonal directions (a, b, and c), as shown in Figure 5, with the cores dry. RESULTS AND ANALYSIS: Table 1 shows the values of the thermal conductivity, the thermal diffusivity, and the heat production for cores obtained in the boreholes drilled in January, 2008, in the CALM site (Figure 1 and 3) and the PAPAGAL site (Figure 2 and 3). CONCLUSIONS: The thermal conductivity and thermal diffusivity values measured in cores from two boreholes drilled in the Island of Livingston confirm that the area where the boreholes were drilled correspond to outcrops of metamorphic rocks (Sch?n, 1996), which is consistent with local geology. The highest values of thermal conductivity were measured in the cores from the PAPAGAL site; the CALM site has the highest thermal diffusivity value and the lowest thermal conductivity value. The results presented here are preliminary and are far from been completed. There are porosity estimations being done to calculate the thermal conductivity values for the cores with the pores filled with water and ice, which correspond to the climatic environment of the area where the boreholes were drilled. Sch?n, J. H. (1996). Physical properties of rocks: fundamentals and principals of petrophysics (Vols. Handbook of geophysical exploration. Section I, Seismic exploration. v. 18). Oxford, Pergamon, 583. REFERENCE: The values of thermal conductivity measured in the cores of the CALM site (Table 1) vary between 2.78 W/mK and 3.36 W/mK and in PAPAGAL site vary between 2.95 W/ mK and 3.57 W/mK. The thermal conductivity average for the CALM site is 3.14 0.15 W/mK and in PAPAGAL site is 3.17 0.17 W/mK. The values of thermal diffusivity measured in the CALM site (Table 1) vary between 1.49 x 10-6 m2 /s and 1.67 x 10-6 m2 /s and in the PAPAGAL site between 1.34 x 10-6 m2 /s and 1.64 x 10-6 m2 /s. The thermal diffusivity average for the CALM site is 1.58 x 10-6 0.04 x 10-6 m2 /s and for the PAPAGAL site is 1.52 x 10-6 0.05 x 10-6 m2 /s. Table 1 also shows the values of the heat production for the two boreholes. A SILENA gamma-ray spectrometer was used to determine the contents in uranium, thorium and potassium from bits of the cores from the two boreholes. For each borehole those values are presented as well as the heat production values which are 1.30 ?W/m3 for the borehole in the CALM site and 0.70 ?W/m3 for the borehole in the PAPAGAL site. The boreholes distance from each other coarse 187 metres. The variations on thermal conductivity on booth boreholes according to the cores deep are shown on Figures 6 and 7. The different colours represent the boreholes and the shapes represent the measures realized according to the axis. Figure 1: General view of the CALM site. Figure 2: General view of the Papagal site. Figure 3: Location of the CALM and Papagal sites. Figure 5: Directions of measurement of the ther- mal conductivity and the thermal diffusivity. Table 1: Thermal conductivity, thermal diffusivity (dry samples), and heat production values for the cores collected in the CALM and Papagal sites boreholes, Livingston Island. TCa, TCb, and TCc, and, TDa, TDb, and TDc refer to the measurement directions of thermal con- ductivity and thermal diffusivity, respectively, along (a), (b), and (c) directions of Figure 5. Figure 4: Drilling in Livingston Island. ACKNOWLEDGEMENTS: The authors thank the Funda??o para a Cincia e a Tecnologia for funding the project PERMANTAR which allowed to collect the cores used in the presentation and process the data. One of the authors (PMA) acknowledges the grant of Caixa Geral de Depsitos. Figure 7: Average Thermal conductivity and average thermal diffusivity values for the CALM and PAPAGAL sites ac- cording to core depth. Figure 6: Thermal conductivity values for the CALM and PA- PAGAL sites according to core depth. D A B C