Thermal shock-induced damage can significantly enhance the connectivity of the rock's fracture network. Thermal Enhanced Recovery (TER) technology holds promising potential for application in shale gas production. Nevertheless, there is still a lack of direct experimental studies focusing on the evolution of shale's gas-flow channels and the mechanism of thermal fracturing in shale under the influence of thermal shock. In this study, we initially investigated the impact of thermal shock on various minerals in shale through X-ray diffraction (XRD) analysis and scanning electron microscope (SEM) imaging, and examined the mass and heat variation with temperature using Thermogravimetry-Differential Scanning Calorimetry (TG-DSC) testing. Subsequently, we assessed the alterations in shale's internal structure due to thermal shock through low-temperature gas (N) adsorption (LTGA) analysis, and observed the distribution and expansion patterns of shale fractures under thermal shock using computed tomography (CT). Finally, we evaluated the changes in shale permeability before and after thermal shock. The findings indicate that quartz, feldspar, and clay exhibit relatively stable behavior in shale under thermal shock, whereas carbonate and pyrite are prone to crack. Under the combined influence of mineral cracking and thermal stress, the internal pore structure of shale tends to enlarge in size while reducing in surface area. The substantial decrease in pore specific surface area highlights the considerable reduction in gas adsorption capacity. Furthermore, fractures expand along the bedding planes as surface fractures. The expansion of pores and fractures promotes the formation of primary gas-flow channels. In addition, the aforementioned test results demonstrate a high level of consistency, specifically highlighting a distinct threshold temperature (500 °C) for the alteration of various physical parameters of shale during thermal shock. This study is anticipated to offer insights into the implementation of TER technology in the oil and gas industry.

中文翻译：

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热冲击下页岩矿物热行为及其对气流通道演化的影响

热震引起的损伤可以显着增强岩石裂缝网络的连通性。热强化采收（TER）技术在页岩气生产中具有广阔的应用潜力。然而，目前还缺乏针对热冲击影响下页岩气流通道演化和页岩热压裂机理的直接实验研究。在本研究中，我们首先通过 X 射线衍射 (XRD) 分析和扫描电子显微镜 (SEM) 成像研究了热冲击对页岩中各种矿物的影响，并使用热重-差示扫描量热法检查了质量和热量随温度的变化。 (TG-DSC) 测试。随后，我们通过低温气体（N）吸附（LTGA）分析评估了热冲击引起的页岩内部结构的变化，并利用计算机断层扫描（CT）观察了热冲击下页岩裂缝的分布和扩展模式。最后，我们评估了热震前后页岩渗透率的变化。研究结果表明，页岩中的石英、长石和粘土在热冲击下表现出相对稳定的行为，而碳酸盐和黄铁矿则容易破裂。在矿物裂解和热应力的共同影响下，页岩内部孔隙结构趋于增大，表面积减小。孔比表面积的大幅下降凸显了气体吸附能力的大幅下降。此外，裂缝沿层理​​面扩展为表面裂缝。孔隙和裂缝的扩张促进了原生气流通道的形成。此外，上述测试结果表现出高度的一致性，特别强调了热冲击期间页岩各种物理参数变化的明显阈值温度（500℃）。这项研究预计将为 TER 技术在石油和天然气行业的实施提供见解。