Mechanical properties of mudstone caprock and influencing factors: implications for evaluation of caprock integrity
Mechanical properties of mudstone caprock and influencing factors: implications for evaluation of caprock integrity
复制标题
DOI：
10.3389/feart.2023.1229851
复制
发表时间：
2023-07
影响因子：
2.9
通讯作者：
Ru Jia;Xiaofei Fu;Ye-Jun Jin;Tong Wu;Sheng Wang;Huijie Cheng
中科院分区：
文献类型：
--
作者：
Ru Jia;Xiaofei Fu;Ye-Jun Jin;Tong Wu;Sheng Wang;Huijie Cheng
泥岩是含油气盆地中最常见的盖层。不同地区、不同埋深的泥岩力学性质差异明显，直接影响盖层的脆韧性及其变形特征。对3个盆地的6组泥岩样品进行了X射线衍射（XRD）岩石矿物成分分析、矿物结构特征显微观察和不同条件下的岩石力学三轴压缩试验。在此基础上，建立数值模型，模拟地质条件下泥岩的破裂变形，阐明不同因素对泥岩岩石力学的影响。对比分析试验后泥岩试样的断裂特征和应力-应变曲线表明，在油气富集深度范围内，围压是影响泥岩力学性质和变形机制的最直接因素。地层温度虽然对岩石变形有一定的影响，但作用十分有限，没有围压的作用很难对岩石变形产生本质性的影响。泥岩的矿物成分也是影响岩石力学变形的主要因素之一。主要矿物含量与岩石力学参数的对比表明，岩石的力学性质和泥岩脆韧性的转化与粘土矿物的相关性最明显。数值模拟表明，孔隙流体压力是影响超压盖层的一个不可忽视的重要因素。较高的孔隙流体压力能显著抑制岩石脆性和韧性的转变过程，同时影响泥岩的破裂方式，对盖层完整性评价具有重要意义。
Mudstone is the most common cap rock in petroliferous basins. The mechanical properties of mudstone in different areas and buried depths are obviously different, which directly affects the brittleness and ductileness of caprock and its deformation characteristic. This research carried out X ray diffraction (XRD) rock mineral composition analysis, microscopic observation of mineral structural characteristics and rock mechanics triaxial compression tests under different conditions on six groups of mudstone samples from three basins. On this basis, establish numerical model to simulate the fracture deformation of mudstone under geological conditions, and to clarify the influence of different factors on the rock mechanics of mudstone. Compare and analyze the fracture characteristics and stress-strain curves of mudstone samples after the test show that, the confining pressure is the most direct factor affecting the mechanical properties and deformation mechanism of mudstone in the range of oil and gas enrichment depth. Although the formation temperature has a certain influence on the rock deformation, the effect is very limited, and it is difficult to have an essential influence on the rock deformation without the action of confining pressure. The mineral composition of mudstone is also one of the main factors affecting the mechanical deformation of rock. The comparison between the content of main minerals and the mechanical parameters of rock shows that the mechanical properties of rock and the transformation of brittleness and ductileness of mudstone have the most obvious correlation with clay minerals. Numerical simulations show that, pore fluid pressure is an important factor that cannot be ignored in overpressured caprocks. Higher pore fluid pressure can significantly inhibit the transition process of rock brittleness and ductileness, and at the same time affect the fracture mode of mudstone, which is of great significance for the evaluation of caprock integrity.