断陷盆地构造枢纽部位油气富集规律

Hydrocarbon enrichment rules at structural pivot position in rift basin

以十屋断陷为例,根据其构造演化、主要断层特征及油气成藏条件分析,揭示多旋回断陷盆地构造枢纽带与油气富集关系。结果表明:十屋断陷枢纽部位经历了断陷期、断拗过渡期、拗陷期、萎缩隆升期等复杂的构造演化,多期差异构造变形及断裂活动导致了小宽枢纽带南段和北段具有相似性及差异性,后期构造反转发育部位多为早期断层发育部位,且主要集中在主干断层上,构造运动产生位移被断裂和褶皱吸收;不同阶段的隆起部位相叠加,使枢纽部位与构造高点相对位置发生变化,枢纽部位相对位置由原来的古隆起演变为斜坡部位;枢纽部位早期为油气的有利指向区,晚期具有良好的保存条件,同时发育多类型圈闭、有利沉积相组合及生储盖组合,围绕枢纽带可形成复式油气聚集带。

Shiwu fault depression was taken as an example to discuss the relationship between hydrocarbon enrichment and pivot zone in superimposed basin according to its tectonic evolution,the characteristics of main faults and the conditions of hydrocarbon accumulation.The results show that Shiwu fault depression has experienced four stages of the tectonic evolution including extension and compression as faulted period,transition period,depression period,uplift period.Multistage differential structural deformations and fault activity made the south and the north section of Xiaokuan pivot zone different.Tectonic inversion took place in the position where the early faults developed,and the position mainly concentrated in the main fault.Displacement of tectonic movement was absorbed by faults and folds.Superposition of paleouplift at different period caused the high point of the structure migrated,which made the relative position of the structural pivot and high point change.The pivot position being paleouplift in early stage became slope belt,and it was a favorable area for hydrocarbon accumulation in early stage and preservation in late stage.The pivot zone developed various traps,favorable facies assemblage and source-reservoir-cap assemblage,and the multiple hydrocarbon accumulation zones can be formed around the pivot zone.