沉积盆地超压体系划分及其与油气运聚关系

以生成油气的烃源岩为线索,依据超压成因的主控因素,将沉积盆地中超压体系划分为两类:即深部超压体系及浅部超压体系。前者具有成熟至过成熟的烃源岩,超压分布广,尤其是在中新生代盆地;而后者缺乏成熟的烃源岩,且分布局限,一般仅见于前陆盆地,也就是在前陆盆地存在双超压体系。深部超压体系的形成与生烃作用密切相关,其他因素只是促使压力的进一步增大,而上部超压体系的形成则是后期构造侧向挤压的结果。正确区分两类超压体系,对于探讨油气生成、运移及聚集成藏有着至关重要的作用。从油气勘探的角度分析,深部超压体系显得尤为重要,它是油气生成的化学反应炉,油气运移的原动力,并决定油气的运移相态、方式及成藏特征等。深部超压体系一般难以成藏,但构造抬升或断裂作用使原有的温压平衡系统遭受破坏时也可以成藏。

Classification of overpressure systems in sedimentary basins and their relationship with hydrocarbon migration and accumulation

Based on locations of source rock and key factors controlling genesis of overpressure systems,overpressure systems in sedimentary basins can be classified into deep overpressure system and shallow overpressure system.The former have mature to overmature source rocks,and overpressure is widely distributed,especially in Meso-Cenozoic basins;while the later lack of mature source rock,and the distribution of overpressure zone is generally limited in foreland basins,i.e.dual overpressure system occurs in foreland basins.Based on the analyses of generation and sealing of hydrocarbons in deep overpressure system,it is believed that hydrocarbon generation would be the primary factor controlling overpressure systems,while others are only secondary factors that further increase formation pressure.The upper overpressure system has been formed as the result of late tectonic compression on the basis of early normal pressure reservoirs.Correct discrimination of the two types of overpressure systems is essential to the study of hydrocarbon generation,migration and accumulation.Deep overpressure system is especially important to petroleum exploration, as it is the"chemical reaction furnace"of hydrocarbon generation,provides the original power for hydrocarbon migration,and determines the phase state and mode of migration and characteristics of accumulation.Generally,hydrocarbons would be difficult to accumulate in deep overpressure system.However,hydrocarbon accumulations can be formed in overpressure system when the original balance of temperature and pressure is broken due to structural uplifting or faulting.