基于界面沉积特征的薄互层盐岩储气库群矿柱失稳机理

Due to the scarcity of salt dome, the undergound gas storages of China can only be constructed in thin interbedded salt formations with multiple interlayers and interfaces. The failure risk of the strata surrounding the salt cavern increases, because the existence of multiple interfaces, whose deformation and failure characteristics determine the pillar stability of salt caverns in the thin interbedded salt formations. However, it is not enough to determine the mechanical properties of the interfaces and the thin interbedded salt formations just according to the indoor mechanical experiments of the cores, because the stress state of cores varies and man-made damage occurs in the coring process, especially to the interfaces. Therefore, it is particularly necessary to distinguish the types and mechanical characteristics of the multiple interfaces and the thin interbedded salt formations, by thoroughly investigating the sedimentary rhythm of the whole salt formations. Based on the project of Yingcheng underground gas storages, starting from the sedimentary characteristics of salt formation, combing with core experiment and model material experiment, further researches are carried out on two key scientific problems: 1) damage and failure mechanism of thin interbedded salt formations under the interfaces with different sedimentary characteristics; 2) pillar instability criterion of underground gas storages in thin interbedded salt formations under the construction and operation period. Finally, the relationship between the sedimentary characteristics and failure characteristics of the thin interbedding rock salt will be developed; a core protection scheme will be put forward during coring; then a more reliable failure criterion of the thin interbedded salt formations with different can be acquired; and then a more reasonable instability mechanism of the pillar can be revealed. This project can be expected to provide the theoretical basis to pillar design of underground gas storages in thin interbedded salt formations.

由于盐丘型矿床稀缺，我国盐穴储气库只能建设于夹层和界面更多的薄互层盐岩中。界面的存在，增加了储气库围岩破损的风险，其变形破损特性决定了储气库群矿柱的稳定性。然而，由于钻井取心造成了人为破坏及岩心应力状态的改变，仅仅依靠岩心力学实验，难以准确描述界面及薄互层盐岩的破损特性，从而不能合理判定储气库群矿柱的稳定性。本项目依托湖北应城盐穴储气库工程，从盐岩层的沉积特征出发，利用岩心实验和模型材料实验相结合的方法对关键科学问题：①不同界面沉积特征条件下薄互层盐岩的破损机理；②薄互层盐岩储气库建设与运营过程中群间矿柱失稳判据进行深入研究。通过研究，探明薄互层盐岩和界面破损特性与其沉积特征之间的关系，提出现场取心时薄互层盐岩岩心的保护方案，获得具有不同界面沉积特征下薄互层盐岩的强度准则，揭示适合于薄互层盐岩体的储气库群矿柱的失稳机理，为薄互层盐岩内储气库群安全矿柱优化设计提供理论依据。

我国的盐岩地层具有夹层多、厚度薄的特点，相对于大型能源地下储备库，盐岩围岩可视为薄互层盐岩，其力学特性研究是储备库安全评价的基础。本项目首先调研了盐岩地层的沉积韵律及界面特性；然后，开展了岩心试验、模型材料试验和理论分析，研究了夹层和界面对薄互层盐岩变形、强度和破损的影响；继而，结合数值模拟对压气蓄能储气库群矿柱的稳定性进行了分析。主要研究内容和结论如下：. 1、薄互层盐岩沉积韵律和界面研究：开展了现场地质调查，获取了地层岩心，揭示了盐岩地层的沉积韵律特性，对盐岩地层中的界面进行了命名和分类，并结合扫描电镜，指出了弱界面的潜在位置。. 2、岩心室内力学试验研究：在将各分层归类为盐岩和夹层的基础上，开展了含夹层盐岩岩心单轴压缩、三轴压缩和蠕变试验，分析了夹层对含夹层盐岩变形、强度和破损的影响；开展了直接剪切和抗拉强度试验，分析了夹层和界面对含夹层盐岩岩心变形、强度和破损的影响；提出了一种渐变界面强度模型以及一种突变界面强度的模型。. 3、模型材料压缩破坏试验研究：利用模拟试样开展了室内试单轴和三轴试验研究，分析了倾角、界面粘结状态、夹层力学特性等对薄互层盐岩变形、强度和破损的影响，归纳了不同倾角条件下薄互层盐岩变形破损的主控因素。. 4、考虑界面和夹层效应的薄互层盐岩变形破损理论研究：借鉴横观各向同性岩体的Jaeger强度准则及节理岩体单弱面破坏准则，分析了模拟试验中观察到的试样破损具有不同主控因素的原因，提出了基于界面沉积特性的薄互层盐岩体破坏准则，指出了其在储库稳定性分析中的应用。. 5、薄互层盐岩储气库矿柱稳定性研究：利用数值模拟的手段，分析了物理模拟实验和理论分析结论的适用条件，研究了夹层为软弱和坚硬条件下薄互层盐岩中储气库矿柱的稳定性。. 共发表SCI论文5篇，EI论文2篇，出版专著1部，授权专利1项，正在申请专利2项，获得省级科研奖励1项，参加国际国内学术会议3次。研究成果为薄互层盐岩内储库群安全矿柱的优化设计提供了理论依据。