澳大利亚北卡那封盆地中上三叠统Mungaroo组油气勘探潜力分析

Exploration Potential of Triassic Mungaroo Formation,North Carnarvon Basin,Australia

对澳大利亚北卡那封盆地三叠系古构造、古气候及古沉积等的系统分析表明,北卡那封盆地三叠纪时期位于环特提斯洋季风影响的海洋性潮湿气候带,地形宽缓,构造稳定,物源供给充足,发育了独具特色的大型浅水辫状河三角洲——Mungaroo三角洲。三角洲发育广阔的三角洲平原相带,平原相带上煤层、碳质泥岩广泛发育,暗色泥岩中陆源有机质含量高,季风影响下洪泛作用频繁,使得中粗砂岩与富含陆源有机质泥岩频繁互层。大型浅水辫状河三角洲为北卡那封盆地天然气富集提供了优质的气源岩、良好的生储盖组合,同生断层的发育为天然气提供运移通道同时也形成大量的构造圈闭。综合研究表明盆地中Exmouth高地北部构造带是三叠系下一步重点勘探领域。

Based on the analyses of paleostructure,palaeoclimatology and paleogeography,it is concluded that the climate of North Carnarvon Basin was warm and humid in Triassic.North Carnarvon Basin developed a unique large shallow braided river delta in Late Triassic because of the environment of Mungaroo deposition provided with gentle basement,strong power and shallow water,abundant source and oceanic humid climate.The plane facies belt of the shallow-water delta was wide.The thin coal seam with a high abundance of organic material was widely developed in delta plane facies.The alternation of distributaries sandstone and dark inter-distributaries bay mudstone was frequently because of monsoon and flooding.The large scale delta provided high quality source rocks and good source-reservoir-cap assemblages for gas enrichment in Triassic of North Carnarvon Basin.At the same time,the development of contemporaneous fault provided the oil-gas migration channel and large structural traps.According to this study,we believe that the northern belt of Exmouth Plateau in the North Carnarvon Basin is the next exploration focus.