弧后盆地控凹断层带反转作用与油气差异聚集的耦合效应——以东海盆地西湖凹陷平湖地区为例

Coupling effect between tectonic inversion of sag-controlling fault zone and differential hydrocarbon accumulation in back-arc basin: a case study of Pinghu area, Xihu Sag, East China Sea Basin

  • 摘要: 平湖油气田作为东海盆地增储上产的核心区域,对保障我国能源安全具有重要战略意义。该油气田不同油气藏的油气富集层位和聚集规模存在显著差异,而目前对控制油气差异聚集与分布的关键因素尚不明确。基于最新采集的三维高分辨率地震数据,结合钻井与录井资料,系统分析了断层类型与组合关系、构造反转与伸展构造的叠加演化过程,以及油气成藏的主控因素,进而探讨了构造分层分带特征对油气差异聚集的控制机理。结果表明,Ⅰ级控凹断层与Ⅲ级伴生断层共同构成了平湖边界断裂带,多条Ⅱ级板状断层组合形成了平湖断阶构造带;始新世末至中新世期间发生的构造反转作用与平湖边界断裂带叠加复合,形成了一系列与边界断层近平行的串珠状断背斜,这类断背斜规模小、油气成藏差异显著,且油气主要富集于始新统平湖组中、下段;构造反转与断阶构造带叠合形成了下部以断背斜为主、上部以背斜为主的双层结构,油气集中分布于下部的断褶构造层。典型油气藏解剖进一步揭示,断层的开启与封闭特征是控制油气成藏的关键。综合认为,裂陷期断层的伸展与裂后期构造反转的叠合,改变了油气成藏要素之间的配置关系,从而控制了烃类流体的输导、封存和差异聚集。

     

    Abstract: The Pinghu Oil and Gas Field, as a core area for reserve increase and production enhancement in the East China Sea Basin, has important strategic significance for ensuring China's energy security. Significant differences in hydrocarbon enrichment layers and accumulation scales exist among different reservoirs in this oil and gas field, but the key factors controlling this differential hydrocarbon accumulation and distribution are still unclear. Utilizing newly acquired 3D high-resolution seismic, drilling, and logging data, the study systematically analyzed fault types and combinations, the superposition and evolution process of tectonic inversion and extensional structures, and the main controlling factors of hydrocarbon accumulation. Furthermore, it investigated the controlling mechanism of tectonic stratification and zonation on differential hydrocarbon accumulation. The results showed that the class Ⅰ sag-controlling fault and class Ⅲ associated faults together formed the Pinghu boundary fault zone, and multiple class Ⅱ plate-like faults formed the Pinghu fault-step structural zone. Tectonic inversion from the late Eocene to Miocene superimposed and compounded with the boundary fault zone, forming a series of bead-like faulted anticlines nearly parallel to the boundary faults. These faulted anticlines were small in scale and exhibited significant differences in hydrocarbon accumulation, with hydrocarbon enrichment mainly occurring in the middle and lower sections of the Eocene Pinghu Formation. The superposition of tectonic inversion onto the fault-step structural zone formed a dual-layer structure with faulted anticlines dominant in the lower part and anticlines dominant in the upper part. Hydrocarbons were concentrated in the lower fault-fold structural layer. The anatomy of typical oil and gas reservoirs further revealed that the opening and sealing characteristics of faults were critical in controlling hydrocarbon accumulation. It is comprehensively concluded that the superposition of fault extension in the rift period and post-rift tectonic inversion alters the configuration of hydrocarbon accumulation elements, thereby controlling the migration, storage, and differential accumulation of hydrocarbon fluids.

     

/

返回文章
返回