正演和反演法综合厘定珠一坳陷油气成藏期

目前基于地化分析的反演方法厘定的珠一坳陷成藏期,存在不少疑惑,难以解决。文中在前人地球化学方法研究成果的基础上,从正演角度出发,通过恢复埋藏史和排烃史,综合厘定油气的成藏期次。研究结果表明:珠一坳陷不同地区洼陷排烃序列不同,显示了油气成藏期存在差异,其中,对古近系油藏而言,位于恩平中半地堑表现出2期成藏;惠西半地堑油藏表现出3期成藏;西江南半地堑、惠北半地堑、陆丰南半地堑和陆丰北半地堑古近系油藏存在1期成藏;新近系油藏,成藏期主要分布在10.0~0 Ma。另外,烃源岩的主排烃期与圈闭的形成期和晚期构造活动相匹配,具有持续充注的特点。以上研究表明,含油气盆地不存在统一不变的成藏期,它们随着烃源岩生排油气条件和构造演化条件不同而改变。

Identifying hydrocarbon accumulation stages in Zhu 1 Depression by geological process modeling and experimental modeling

At present,it is difficult to solve the problem by the geochemical inversion method to determine the accumulation period.In this paper,based on the geochemical research results,we restore the burial history and hydrocarbon generation history by the forward modeling to determine the hydrocarbon accumulation period.The results show that the hydrocarbon expulsion sequences are different in different sags,Zhu 1 Depression,and it leads to different hydrocarbon accumulation periods.In the Paleogene reservoir,Enping half graben experienced two-period accumulation;Huixi half graben reservoir experienced 3 phases of accumulation;these reservoirs,located in the south of Xijiang half graben,Huibei half graben,south of Lufeng and north of Lufeng half graben,experienced 1 phase of accumulation.For the Neogene reservoir,accumulation periods are mainly distributed in 10.0-0 Ma.For example,the fault activation of the late Dongsha movement constructed an important large-scale hydrocarbon accumulation period for Neogene reservoir,the very matching period of hydrocarbon expulsion phase with the trap formation and the late tectonic activity has the characteristic of continuous filling.All these results show that the oil and gas basin has different accumulation periods,whose variation depends on source rock hydrocarbon generation and expulsion condition and structural evolution condition ofoil and gas.