Relationship between heterogeneity of source rocks and genetic mechanism of abnormally high pressure

• Published in: Science China. Earth sciences 2013-11, Vol.56 (11), p.1971-1976
• Main Authors: Zhang, XueJun, Xu, XingYou, Wang, YongShi, Song, GuoQi, Guo, ChunQing, Liu, Qing, Li, Ping
• Format: Article
• Language: English
• Subjects: Abundance; Earth and Environmental Science; Earth Sciences; Fluid dynamics; Fluid flow; Fluids; Geological time; Geophysics; Heterogeneity; High pressure; Organic matter; Overburden; Petrology; Research Paper; Rocks; Spatial distribution; Wettability; Wetting; 上覆岩层压力; 孔隙流体; 异常高压; 成因机制; 润湿性; 烃源岩; 空间分布; 非均质性
• ISSN: 1674-7313; 1869-1897
• DOI: 10.1007/s11430-013-4662-x

Based on the micro-fluorescence observation of polished sections of source rocks, two types of micro-layers with different wetting properties formed in thermal evolution, i.e., oil-wetting and water-wetting micro-layers, are distinguished. The wetting property is found closely related to the abundance of organic matter and its occurrences with inorganic minerals. The alternat- ing distribution and intercrossing of two types of micro-layers formed many separated spaces with different wettabilities. The strong capillary forces in these separated spaces with different wettibilities obstruct the cross flows of pore fluids and result in nearly independent and closed fluid systems. As a consequence, these spatially superposed spaces in source rocks bear the overburden pressure and then abnormally high pressures have developed in the whole source rock unit. Therefore, the abun- dance and occurrences of organic matter are the main inner factors influencing the formation of abnormally high pressures, whereas the formation, distribution and development of micro-layers with different wettabilities during the evolution of source rock determine the intensity and spatial distribution of abnormally high pressures.