LABORATORY INVESTIGATION OF CRYOFRACTURING POTENTIAL TO STIMULATE GEOTHERMAL RESERVOIRS IN KAZAKHSTAN
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Date
2024-04-19
Authors
Begaliyev, Dastan
Journal Title
Journal ISSN
Volume Title
Publisher
Nazarbayev University School of Mining and Geosciences
Abstract
Following the adoption of the Concept of Transition to Green Economy, Kazakhstan's renewable energy sector continues to expand. Shift to renewable energy is of key importance since it will help lower the amount of greenhouse gases which are emitted. The geothermal energy, including the HDR (Hot Dry Rocks), is a renewable source of power, though the low permeability is a challenge. EGS (Enhanced Geothermal Systems) are a promising technology which can widen geothermal energy use by creating reservoirs through stimulation practices, solving permeability problems in HDR formations. Methods like hydraulic fracturing and thermal stimulation have been suggested by researchers to enhance the productivity of hot dry rock reservoirs, however, these can cause environmental pollution and formation damage and not applicable in dry countries like Kazakhstan because of water scarcity. One way of solving the problem of water-related issues in Enhanced Geothermal Systems (EGS) is to use cryogenic fracturing, which with liquid nitrogen is not only efficient, but also environmentally friendly. This research project entails investigation of influence of elevated temperature with LN2 cooling on granite strength as a destructive and non-destructive experiments.
There were selected 2 different granites from the outskirts of Akmola region to make comparative analysis. The analysis was made through 16 destructive experiments with unconfined compression and Brazilian tests, as well as by 2 non-destructive measurements with the help of XRD (X-ray diffraction) and CT Scan. The tests were conducted to identify the structural modifications and the mechanical behaviour of the granites affected by the thermal shock process performed in the cryogenic environment. The variable temperatures with LN2 treatment during the compression and Brazilian tests were applied.
The analysis revealed several key findings. A compression and Brazilian tests showed that the breaking strength gradually diminished with the rise of temperature and LN2 cooling while the granite was heated, leading to the conclusion that the granite's strength is reduced. It was shown that Young's modulus decreased with increasing thermal shock, while there is a positive correlation between Poisson's ratio and thermal shock. Even though both granites showed similar incrementing trends regarding damage factor curves, granite 1 exhibited a more affected response after heating and LN2 fracturing, and it was more damaged compared to granite 2 in both the compressive and Brazilian tests. Therefore, it can be inferred that granite 1 achieved superior results compared to granite 2.
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Keywords
Type of access: Open Access, Geothermal energy, Enhanced Geothermal Systems (EGS), Hot dry rock (HDR), liquid nitrogen, cryofracturing, Kazakhstan
Citation
Begaliyev, D. (2024). Laboratory investigation of cryofracturing potential to stimulate geothermal reservoirs in Kazakhstan. Nazarbayev University School of Mining and Geosciences