北部湾盆地构造迁移特征及对油气成藏的影响

Tectonic transport characteristics and their influences on hydrocarbon accumulation in Beibuwan Basin

综合利用各种地质、测井、录井等资料,在对盆地内4个凹陷范围内的三维地震资料地质解释基础上,通过分析各凹陷边界主控断裂的空间展布特征和不同时期的断裂落差以及盆地内不同时期沉积中心和沉降中心的变化特征,分别从单个凹陷的角度和整体的角度探讨了盆地的构造迁移特征,最后从油气勘探的指导意义上简要探讨了构造迁移对油气成藏的影响。研究认为:北部湾盆地的构造迁移具有波浪式定向性、汇聚型偏对称性等特征;构造迁移造就了盆地现今的构造格局,控制了盆地内的生储盖组合、造成了温压场的改变,促进了烃源岩的成熟演化以及油气的运移、聚集成藏等,影响了油气成藏的各个环节;受构造迁移的影响,研究区四个凹陷的富烃情况有所不同,涠西南凹陷是主要的富生烃凹陷,乌石凹陷次之,海中凹陷次于乌石凹陷,迈陈凹陷次于海中凹陷。

Geological data and various logging data were integrated to perform geologic interpretation of 3D seis- mic data of 4 sags in Beibuwan Basin. Characteristics of tectonic transport in this basin were discussed based on analyses of spatial distribution of the major boundary faults of each sag, fault throw at different stages and the transport of depocenter and subsidence center in the basin at different stages. The influences of tectonic transport on hydrocarbon accumulation was also discussed. The tectonic transport of Beibuwan Basin is characterized by wave-like directivity and convergent bias-symmetry. Tectonic transport resulted in present tectonic framework of the basin,controled the souree-reservoir-caproek assemblages within the basin, changed temperature and pressure fields, accelerated source rock maturation and evolution, and hydrocarbon migration and accumulation. Because of the influence of tectonic transport, the source rock richness are different from sag to sag in the basin, the Weixinan sag has the richest source rock followed by the Wushi sag, Haizhong sag and Maichen sag.