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Quartz Stressing and Fracturing by Pore Pressure Dropping Down to Negative Pressure
ACS Earth and Space Chemistry ( IF 3.4 ) Pub Date : 2021-02-04 , DOI: 10.1021/acsearthspacechem.0c00224
Lionel Mercury 1 , Emmanuel de Bilbao 2 , Patrick Simon 2 , Hugues Raimbourg 1 , Isabelle Bergonzi 1 , Claudie Hulin 1 , Aurélien Canizarès 2 , Kirill I. Shmulovich 3
Affiliation  

In water-bearing porous rocks, pore pressure variations play a major role in deformation, through dissolution–precipitation and fracturing processes. An often-overlooked variation where pressure falls to negative pressure or tension can operate whenever aquifer formations dry out, for instance, in deep storage (nuclear or industrial wastes, long-term CO2 mitigation, short-term energetic resources, etc.). This can generate capillary tension within the aquifers. This study investigates the mechanical effect of such in-pore tension in the surrounding crystal field, through laboratory experiments at the one-pore scale. Microthermometric procedures were carried out on synthetic fluid inclusions to generate large tensile stress and were combined with Raman microspectrometry to visualize the resulting stress fields in the host quartz. For comparison, we numerically modeled the stress field by linear elasticity theory. The experiments demonstrate that significant damage is produced in crystalline materials by the pore tension. Despite the induced stress measured by micro-Raman spectrometry to remain moderate, it is able to fracture the quartz. The volume of the cavity is a prominent controlling parameter for the stress amplitude. The crystalline heterogeneities of the solid are another major parameter for localizing the mean weak stress and accumulating overstress. Our results call for bringing pore-scale micromechanics into the safety assessment of the geological storage of various wastes inside depleted aquifers. They also show the magnifying effect of heterogeneities on propagating stress and localizing it along certain directions, promoting the final failure of water-bearing minerals, rocks, or pore networks.

中文翻译:

孔隙压力下降至负压引起的石英应力和压裂

在含水多孔岩石中,孔隙压力变化通过溶解-沉淀和压裂过程在变形中起主要作用。每当含水层变干时,例如在深层存储(核废料或工业废料,长期的CO 2缓解,短期精力充沛的资源等)。这会在含水层内产生毛细管张力。本研究通过单孔规模的实验室实验研究了这种孔内张力在周围晶体场中的机械效应。对合成流体夹杂物进行了微热测量程序,以产生较大的拉应力,并与拉曼光谱法结合使用,以可视化在主体石英中产生的应力场。为了进行比较,我们使用线性弹性理论对应力场进行了数值建模。实验表明,孔隙张力会在结晶材料中产生明显的破坏。尽管通过微拉曼光谱法测得的诱导应力保持中等水平,但它能够使石英破裂。空腔的体积是应力振幅的重要控制参数。固体的结晶异质性是确定平均弱应力和累积超应力的另一个主要参数。我们的研究结果要求将孔隙尺度的微力学纳入对枯竭含水层内部各种废物的地质存储的安全性评估。它们还显示了异质性对传播应力的放大作用,并将其沿某些方向局部化,从而促进了含水矿物,岩石或孔隙网络的最终破坏。我们的研究结果要求将孔隙尺度的微力学纳入对枯竭含水层内部各种废物的地质存储的安全性评估。它们还显示了异质性对传播应力的放大作用,并将其沿某些方向局部化,从而促进了含水矿物,岩石或孔隙网络的最终破坏。我们的研究结果要求将孔隙尺度的微力学纳入对枯竭含水层内部各种废物的地质存储的安全性评估。它们还显示了异质性对传播应力的放大作用,并将其沿某些方向局部化,从而促进了含水矿物,岩石或孔隙网络的最终破坏。
更新日期:2021-02-18
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