澳大利亚西北陆架油气分布规律与主控因素研究

Hydrocarbon Distribution Patterns and Controlling Factors in North West Shelf,Australia

澳大利亚西北陆架油气资源,特别是天然气资源富集,是全球液化天然气的主要供应地之一。西北陆架不仅是澳洲油气勘探潜力最大的地区,而且也是中国油公司拓展海外油气业务的重要地区。以多方面收集的数据资料为基础,探讨澳大利亚西北陆架油气分布规律,揭示油气分布主控因素,进而优选有利勘探区。区域上,已发现的油气储量主要分布于西北陆架最西南端的北卡那封盆地;层系上,油气主要富集于下白垩统泥页岩区域盖层之下的上三叠统、侏罗系或下白垩统碎屑岩储集层。油气分布整体表现为"内油外气、下气上油、以气为主"的特征,油田多局限于侏罗纪裂谷作用控制的发育有成熟生油岩的次盆地。腐殖型干酪根类型和烃源岩的高成熟度决定了西北陆架的富气特征,侏罗纪发育的裂谷控制了石油的区域分布。基于油气地质综合研究和油气发现过程,优选出了埃克斯茅斯高地、埃克斯茅斯次盆、巴科次盆、卡斯韦尔次盆、萨胡尔台地、卡尔德尔地堑和武尔坎次盆7个有利勘探区。

Australia＇s North West Shelf is rich in oil and gas resources,particularly gas,and is one of the key bases for supplying LNG in the world.The shelf not only has the highest petroleum exploration potential in Aus-tralia,but it is also one of the important regions targeted by Chinese oil companies for expanding international petroleum exploration and production.Based on data collected from various sources,this paper discusses the oil and gas distribution patterns,documents the factors controlling such distributions and optimizes the favorable exploration areas.Regionally,the discovered oil and gas reserves are largely confined to the North Carnarvon Basin.Stratigraphically,they are mostly reservoired in clastic reservoirs in the Upper Triassic,Jurassic or Lower Cretaceous,which are sealed by the extensive Lower Cretaceous mudstones and shales.The distribution is characterized by patterns of oil in the inner fairway and gas in the outer fairway,gas in the lower reservoirs and oil in the upper reservoirs,and dominance of gas over oil.Oil fields mainly occur in sub-basins,which were developed during Jurassic rifting and contain effective oil source rocks.The humic kerogen type and high maturity of source rocks determine that the petroleum resources are dominated by gas in the North West Shelf. The Jurassic rift controlled the areal distribution of oil.On basis of integrated studies of petroleum geology and discovery process of oil and gas fields,this study selected 7 favorable exploration areas：Exmouth Plateau,Ex-mouth Sub-basin,Barcoo Sub-basin,Caswell Sub-basin,Sahul Platform,Calder Graben and Vulcan Sub-basin.