K.A. Snellink
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1
Image Analysis of Granular Materials
Understanding the Effects of High Temperatures and Pressures
Understanding the behaviour of rocks subjected to high temperatures and pressures is essential for a wide range of subsurface applications. This thesis aims to develop an image analysis methodology to measure the porosities and permeabilities of rock samples. These samples were created as part of the doctoral thesis of K.H.A.A. Wolf by compacting rock rubble in a copper tube and subjecting it to various high temperatures and pressures. Despite earlier image analysis on these samples, there was an opportunity for improvement using higher-resolution imaging and more advanced processing techniques. UsingaDSLRcameraand2typesoflight (normal and UV), 33 samples were photographed and then analysed using Adobe Photoshop and ImageJ. Additionally, three samples were selected to be scanned using a µCT scanner. The image processing included the conversion to greyscale, binarisation and the use of the morphological ”open” operation. Porosity was directly measured, while permeability was estimated using a modified Kozeny-Carman equation. The quality of the impregnation of the sample with UV dye differed, yet for 28 out of the 33 samples, imaging with UV light worked better than with normal light. Using temperature data from when the samples were formed, a clear trend emerged showing that the higher the temperature, the lower the porosity and permeability become. This trend was also visible in the work by Wolf (2006) and the values were generally in agreement, except for the samples with extremely low porosities and permeabilities. While CT and image analysis gave similar porosity values, permeability results differed, highlighting the need for simulation-based permeability estimates from CT data. Further research into impregnation techniques is also recommended to enhance future image analysis workflows.
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Understanding the behaviour of rocks subjected to high temperatures and pressures is essential for a wide range of subsurface applications. This thesis aims to develop an image analysis methodology to measure the porosities and permeabilities of rock samples. These samples were created as part of the doctoral thesis of K.H.A.A. Wolf by compacting rock rubble in a copper tube and subjecting it to various high temperatures and pressures. Despite earlier image analysis on these samples, there was an opportunity for improvement using higher-resolution imaging and more advanced processing techniques. UsingaDSLRcameraand2typesoflight (normal and UV), 33 samples were photographed and then analysed using Adobe Photoshop and ImageJ. Additionally, three samples were selected to be scanned using a µCT scanner. The image processing included the conversion to greyscale, binarisation and the use of the morphological ”open” operation. Porosity was directly measured, while permeability was estimated using a modified Kozeny-Carman equation. The quality of the impregnation of the sample with UV dye differed, yet for 28 out of the 33 samples, imaging with UV light worked better than with normal light. Using temperature data from when the samples were formed, a clear trend emerged showing that the higher the temperature, the lower the porosity and permeability become. This trend was also visible in the work by Wolf (2006) and the values were generally in agreement, except for the samples with extremely low porosities and permeabilities. While CT and image analysis gave similar porosity values, permeability results differed, highlighting the need for simulation-based permeability estimates from CT data. Further research into impregnation techniques is also recommended to enhance future image analysis workflows.
The following report investigates the land ice height decrease of the Fleming Glacier between 2019 and 2022 using ICESat-2 satellite data. This glacier is located on the Antarctic Peninsula, an area that has been severely impacted by global warming. Using data from the Advanced Topographic Laser Altimeter System (ATLAS) on board ICESat-2, more specifically its ATL06 product, the average land ice heights in 2019 and 2022 could be compared. This was done with the aid of Python and the icepyx library, which allows for an easy extraction of the desired data from the NASA Eathdata website. The raw data had to be processed and filtered to eliminate the NaN values and reduce the noise. The resulting height measurements were then plotted and an average rate of land ice height decrease of 4.40 metres over the 3-year period was found, which corresponds to a 1.47 m/year decrease. The findings of this study indicate a slightly lower value compared to the results reported by Friedl et al. in their 1994-2016 study. However, this discrepancy is plausible, particularly considering the episode of increased ice melting observed in the Fleming Glacier after 2008, which can be attributed to the disintegration of the Wordie Ice Shelf. Crucially though, due to an issue with the Reference Ground Track overlap the amount of common data points found was just 27. This is insufficient to draw definitive conclusions regarding the overall melting of the entire Fleming Glacier. Future research, especially involving the use of the ATL11 product, is therefore recommended for this region.
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The following report investigates the land ice height decrease of the Fleming Glacier between 2019 and 2022 using ICESat-2 satellite data. This glacier is located on the Antarctic Peninsula, an area that has been severely impacted by global warming. Using data from the Advanced Topographic Laser Altimeter System (ATLAS) on board ICESat-2, more specifically its ATL06 product, the average land ice heights in 2019 and 2022 could be compared. This was done with the aid of Python and the icepyx library, which allows for an easy extraction of the desired data from the NASA Eathdata website. The raw data had to be processed and filtered to eliminate the NaN values and reduce the noise. The resulting height measurements were then plotted and an average rate of land ice height decrease of 4.40 metres over the 3-year period was found, which corresponds to a 1.47 m/year decrease. The findings of this study indicate a slightly lower value compared to the results reported by Friedl et al. in their 1994-2016 study. However, this discrepancy is plausible, particularly considering the episode of increased ice melting observed in the Fleming Glacier after 2008, which can be attributed to the disintegration of the Wordie Ice Shelf. Crucially though, due to an issue with the Reference Ground Track overlap the amount of common data points found was just 27. This is insufficient to draw definitive conclusions regarding the overall melting of the entire Fleming Glacier. Future research, especially involving the use of the ATL11 product, is therefore recommended for this region.