论油气地表化探烯烃异常成因机制及其意义：以塔里木盆地库车坳陷米斯布拉克地区为例

摘要

在塔里木盆地库车坳陷米斯布拉克地区化探工作中发现了高强度烯烃异常。由于烯烃的不稳定性，在地表形成高强度烯烃异常是很少见的。通过对米斯布拉克地区高强度烯烃异常来源及成因机制的分析，发现该区烯烃异常在一定程度上反映了深部油气组成特征；烃源岩热演化程度、盆地沉降特征、输导动力及输导空间发育特征等因素都对高强度烯烃异常的形成起到一定控制作用。在此基础上提出了烯烃生成的地质模式，认为本区烯烃是在高过成熟演化阶段氢来源匮乏的情况下由干酪根或其他有机分子裂解生成的。地表高强度烯烃异常的存在指示了地下高温、高压环境以及由烃源到地表的高速运移通道的存在。%A high-intensity olefin anomaly had been found during the geochemical exploration in the Meath Braque area of Kuqa Depression, Tarim Basin. Due to the instability of olefin, it is rare to form a high-intensity olefin anomaly in the surface. By analyzing source of the olefins and mechanism of the olefin anomaly formation in the Meath Braque area, it is showed that the olefin anomaly can reflect composition characteristics of underground oil and gas, and various factors, such as, thermal maturity of source rocks, basin subsidence, migration power and transportation space, play a controlling role in the generation of high-intensity olefin anomaly. A geological model of olefin generation is suggested based on the study of high-intensity olefin anomaly in the Meath Braque, in which the olefins in this area are considered to be generated from the pyrolysis of kerogen or other large organic molecules under the condition of shortage of hydrogen source at high-over mature stages. The existence of high-intensity olefin anomaly in the surface indicates a subsurface environment of high temperature and high pressure, and a high-speed hydrocarbon migration pathway from hydrocarbon source to the surface.