南堡凹陷油气运移特征及成藏动力学系统划分

Characteristics of hydrocarbon migration and kinetic system classification of p ool forming in Nanpu sag.

详细分析南堡凹陷油气运聚特征 ,划分出下第三系的成藏动力学系统。研究区油气初次运移的排烃门限较深 ,处于成油门限之下的第一个高异常孔隙流体压力值骤减的深度即为本区油气大量初次运移的主排烃门限。对于二次运移 ,油源和正向构造带展布控制了油气侧向运移的区域指向 ;断裂活动和生储盖组合控制了油气的垂向运移和纵向分布 ;供油断层的活动性与烃源层主排烃期的配合 ,是控制油气在各正向构造带富集程度的重要因素。根据孔隙流体压力分布和油气运移聚集特征 ,该区纵向上可划分出 3个成藏动力学系统 :下部自源高压原生封闭—半封闭成藏动力学系统、中部自源—它源高压—常压半封闭—封闭成藏动力学系统、上部它源常压次生开放型成藏动力学系统。

Characteristics of hydrocarbon migration and accumulation in Nanpu sag are analyzed in detail and kinetic system of pool forming in Lower T ertiary are classified. Threshold depth of hydrocarbon expulsion for primary mig ration in this study area is rather deep, which is at place where the 1st abnorm al pore fluid pressure is lowered below the threshold of hydrocarbon generation and just at the main hydrocarbon expulsion threshold for the migration of large amount of hydrocarbons generated in this area. In secondary migration, oil sourc e and distribution of positive structural belt controlled the regional direction of lateral migration, while faulting and source reservoir seal combination co ntrolled vertical migration and longitudinal distribution of hydrocarbon. The ac tivity of oil supplying fault coordinating with the period of main hydrocarbon e xpulsion period is an important factor controlling the enrichment of hydrocarbon in all three positive structural belts. Based on the characteristics of hydroca rbon migration of accumulation and distribution of pore fluid pressure. 3 kineti c systems for pool forming can be vertically classified in this region: ①self source, high pressure, closed semi closed pool forming kinetic system in the lower part; ②self source to other source, higher pressure to ordinary pressur e,closed semi closed, pool forming kinetic system in the middle part; and ③o ther source, ordinary pressure, secondary opening pool forming kinetic system i n the upper part.