In deep geothermal reservoirs,a multitude of sealed rock fractures are prevalent.Utilizing hydraulic stimulation to induce shear along these fractures can significantly enhance the permeability and convective heat transfer performance of geothermal reservoirs.To investigate this mechanism,a series of shear tests were conducted on granite fractures at different temperatures(25 ℃ to 300 ℃),and the evolution of permeability and convective heat transfer coefficient during the shear were measured concurrently.Through quantitatively characterizing the changes in surface morphology and the damage to surface asperities caused by shear slip,the mechanism of high temperature and shear induced damage effects on the permeability and heat transfer characteristics of fractured granite was revealed.The results show that:(1)the permeability and convective heat transfer coefficient of granite during shear slip exhibit three stages,which are closely related to shear-induced changes such as shrinkage,dilatancy,asperity damage,and gouge production;(2)The permeability K1 in the stable stage exhibits minimal correlation with temperature.However,as the temperature increases from 25 ℃ to 300 ℃,the rate of permeability increase K2/K0 during the growth stage gradually decreases from 159.75 to 30.58,and during the attenuation stage,it decreases from 148.68 to 3.03.(3)There is a positive correlation between the convective heat transfer coefficient and permeability.Higher temperatures in granite are associated with higher convective heat transfer coefficients.(4)Higer temperatures exacerbate shear damage to surface asperities.As the temperature increases from 25 ℃ to 300 ℃,the damage volume increases from 508.1 mm3 to 729.3 mm3.The production of smaller particles from shearing contributes to the enhanced attenuation effect of gouge blockage on permeability and convective heat transfer coefficients during shear slip.This research provides valuable insights for the efficient extraction of heat energy from dry hot rocks.
关键词
岩石力学/高温花岗岩/动态剪切-渗流/对流换热特性/剪切损伤/地热开采
Key words
rock mechanics/high-temperature granite/dynamic shearing-flow/heat transfer characteristics/shear damage/geothermal exploitation
维普
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