澳洲西北及南部被动陆缘油气差异分布

澳洲西北陆架和南部被动陆缘盆地群是澳大利亚主要的油气富集区带,西北陆架与南部陆缘2个地区在构造演化背景、裂谷发育期次、发育时间、油气分布特征等方面存在异同之处.从构造演化对盆地结构的控制、区域构造对烃源岩分布的控制和断裂系统对成藏区带的控制3个方面分析两者的差异.研究结果表明:(1)西北陆架多期裂陷,盆地结构复杂,表现出“上油下气”的垂向分层式结构,各盆地内裂陷期的构造活动强弱与发育期次不同造成了整个西北陆架平面上油气分布的不均匀性,南部被动陆缘构造活动简单,裂陷期发育晚,时间短,均为单一的产油型盆地:(2)区域构造控制生烃中心的分布,西北陆架盆地烃源岩在整个中生代部有发育,南部地区晚白垩世和新生代发育烃源岩:(3)断裂系统的差异导致2个地区圈闭类型的差异,西北陆架早期圈闭受破坏,以断块性圈闭成藏为主,南部多为背斜圈闭和掀斜断块圈闭.澳洲2个地区的被动大陆边缘发育特点与中国南海北部准被动陆缘具有相似性,因此,这2个地区的油气分布特点对南海北部陆架有重要的参考意义.

Differences in hydrocarbon distribution of two passive continental margins of Australia:North West Shelf and Southern margin

The Australian North West Shelf(NWS) and Southern passive continental margin are both main hydrocarbon accumulation areas in Australia.Similarities and differences exist in tectonic evolution history,fracture system,development time,hydrocarbon distribution,etc.Study on the differences from three respects: tectonic evolution controlling basin framework,source-controlling regional structure and trap-controlling fault.The results show that:(1) The NWS develops multi-period rifting,completed structures,and there appears oil lies upon gas vertical layered structure.The intensity of tectonic activity and differences of development period causes hydrocarbon distribution heterogeneity.The Southern margin develops rifting late and short duration.Basins in this area are all produce oil only.(2) Regional structure controls distribution of hydrocarbon generation center.The NWS develops source rock in all Mesozoic.The Southern margin develops in late Cretaceous and Cenozoic.(3) Differences of fracture system cause the differences of trap types.In the NWS,early-trap is destroyed by late faults,developed fault block traps.The Southern margin develops anticline traps and tilted fault block traps.The developed features of the two passive continental margins are similar to the South China Sea passive continental margin.The hydrocarbon distributions of the two areas have the guiding significance for the South China Sea passive continental margin.