Wellbore stability has been considered as a major issue in troubled shale, salt, poorly consolidated sandstone and fractured formations. Thermally induced stresses may be detrimental to a well integrity or enhance the stability depending on if the temperature rises or declines near a wellbore. A cooler fluid is normally injected through a well into a hot formation for thermal energy extraction. A tangential stress reduction is expected near a wellbore due to a temperature decrease and such a reduction is also associated to a hydraulic fracturing process. This seems to suggest a low risk of wellbore stability should expected in the aforementioned situations. A hydraulic fracturing process, however, corresponds to a higher principal stress difference near a wellbore if we express the principal stresses in terms of Mohr stress circles, and such a stress circle however is under a low shear stress limit region at the same time. This stressing states impose a so-called passive loading mode near a wellbore during fracturing, and a stability problem can be expected after fracturing during production.
How would Injection and hydraulic fracturing process affect wellbore integrity during EGS in HDR formations?
Wang, Y., and D. Li. "How would Injection and hydraulic fracturing process affect wellbore integrity during EGS in HDR formations?." Paper presented at the ARMA-CUPB Geothermal International Conference, Beijing, China, August 2019.
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