成岩作用对生储盖层的影响与成岩史模拟——以北部湾盆地福山凹陷为例

Influence of diagenesis on source,reservoir,cap rocks and diagenetic history simulation:A case study of Fushan Depression in Beibuwan Basin

为了研究油气藏形成的动力学过程,以北部湾盆地福山凹陷为例,划分了该凹陷碎屑岩的成岩阶段,探讨了成岩作用对生、储、盖层的影响与控制,模拟了成岩史和生、储、盖层发育史。研究结果表明,福山凹陷的成岩作用控制、影响了有机质热演化和储集层的物性,早成岩阶段A期、B期,中成岩阶段A1亚期及中成岩阶段A21和A22微期,对应着有机质未成熟、半成熟、低熟和成熟阶段,并分别主要发育高-特高孔隙度、中-高孔隙度、低-中孔隙度、特低-低孔隙度储集层;在碎屑岩成岩演化过程中,盖层的封闭性能发生规律性的变化,从早成岩阶段A期到中成岩阶段A21微期,盖层的封堵性能逐渐增强,在A21微期达到最大,之后开始减小。模拟结果表明,在古近纪涠洲组沉积早期,流沙港组烃源岩就开始生油,但直到新近纪中新世,才进入主成藏期。

To study the dynamic process of hydrocarbon reservoir formation,taking Fushan Depression in Beibuwan Basin as an example,the diagenetic stages of clastic rocks in Fushan Depression were divided,the influence and control of diagensis on source,reservoir,cap rocks were discussed,and diagenetic history and the development history of source,reservoir,cap rocks were simulated.The results show that the diagenesis of Fushan Depression controls and affects the thermal evolution of organic matter and the physical properties of the reservoir.A and B periods of eogenetic stage,A1 substage and A21 and A22 microstages of mesogenetic stage correspond to immature,semi-mature,low-mature and mature stages of organic matter,and mainly develop high-extra-high porosity,medium-high porosity,low-medium porosity and ultra-low-low porosity reservoirs respectively.During the diagenetic evolution of clastic rocks,the sealing capability of cap rock changes regularly.From A period of eogenetic stage to A21 microstage of mesogenetic stage,the sealing capability of cap rock gradually increases,reaches the maximum in the A21 microstage,and then decreases.The simulation results show that the hydrocarbon source rocks of Liushagang Formation began to generate oil in the early stage of Paleogene Weizhou Formation deposition,but it did not enter the main accumulation period until the Neogene Miocene.