新西兰Taranaki盆地深水新探区油气成藏条件

    OIL AND GAS ACCUMULATION CONDITIONS IN THE NEW FRONTIER DEEP WATER AREA OF TARANAKI BASIN, NEW ZEALAND

    • 摘要: Taranaki盆地是新西兰国家唯一在产油气的盆地。其勘探活动和油气发现主要在陆上和浅水区,深水区目前勘探程度极低,是近年来全球深水油气勘探关注的重要新领域之一,但存在构造沉积演化不清、勘探潜力不明的问题。从盆地的构造-沉积演化背景入手,追溯新西兰板块漂离冈瓦纳古陆东缘之前的沉积环境及特征,结合地震地层层序的识别,划分深水区地层层序;同时运用地质类比评价方法和地球物理技术相结合,分析研究了深水区烃源岩生烃潜力、储盖组合类型、圈闭条件以及可能的油气运聚成藏模式及其勘探方向。指出:①盆地深水构造-沉积演化与目前研究认识程度较高的陆上及浅水区有差异,其地层系统及地层沉积充填格架可划分为4个层序;②深水区存在比盆地陆上及浅水区更老的新含油气系统,其沉积充填了裂谷期陆相煤系和裂后期海侵泥岩2套烃源层系,且具有“裂谷期生气、裂后期生油”的成烃特点,生烃潜力较大;③深水油气藏主要勘探目的层为三角洲砂岩及晚白垩世浅海相滨岸砂岩,而东部隆起之上的火山披覆构造圈闭为该区的主要勘探目标。

       

      Abstract: The Taranaki Basin is the only oil and gas producing basin in New Zealand. However, exploration activities and oil and gas discoveries are mainly concentrated in the land and shallow water areas, but deficient in the deep water area. There are some basic problems to be solved, such as, the tectonic and sedimentary evolution of the basin, the resource potential of oil and gas in the deep water area of the basin and so on. This paper is devoted the deep water hydrocarbon potential. It starts from the tectonic background and sedimentary evolution of the basin before the New Zealand plate drifted away from the eastern margin of Gondwana paleo-continent. The deep water stratigraphy is established based on seismic stratigraphic sequences. At the same time, combining geological together with geophysical methods, the potential of source rocks, reservoir-cap assemblages, traps, possible hydrocarbon accumulation models and exploration directions in the deep water area are studied. It is concluded that:①The tectonic and sedimentary evolution of the deep water area of the basin is different with that in the land and shallow water areas which are well known at present, and the deep water area depositional sequences and the filling history of the basin can be divided into four sequences; ②There exists a new petroleum-bearing system in the deep water area which is older than those found on the land and in the shallow water areas of the basin. There are two sets of hydrocarbon source beds of continental coal measures in the rifting stage and covered by transgressive mudstone in post-rifting stage. Gas generated in rifting period and oil in post rifting period, and the hydrocarbon-generating potential is high.③The main exploration targets of the deep water oil and gas reservoirs are delta sandstone and shallow marine littoral sandstone of Late Cretaceous. However, the volcanic drape structural traps could be the main exploration targets in the eastern uplift area.

       

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