环印度洋地区被动陆缘盆地构造沉积演化及其对成藏要素的控制作用

环印度洋周缘被动陆缘盆地油气资源潜力巨大，是当前世界油气勘探的热点地区之一。本文基于IHS商业数据库和前人研究成果等资料，厘定了环印度洋地区被动陆缘盆地构造演化史，分析了构造演化对盆地充填结构和成藏要素的影响，并利用蒙特卡洛模拟法评估了盆地油气资源潜力，优选了有利勘探区带。研究结果表明，环印度洋地区被动陆缘盆地经历了3期构造演化阶段，依次为裂前期、同裂谷期和被动陆缘期。根据盆地演化的主导阶段，研究区内被动陆缘盆地可分为拉张边缘裂前发育型、拉张边缘断坳叠置型、拉张边缘坳陷发育型和转换边缘断坳叠置型。盆地内烃源岩主要发育于裂前期—被动陆缘早期，不同地区的主力烃源岩层系不同；储集岩主要发育于裂前期—被动陆缘晚期；区域盖层则主要发育于被动陆缘期。资源评价结果显示，研究区内重点被动陆缘盆地待发现石油、天然气和凝析油可采资源量（均值）分别为4.49×108 t，15.86×1012 m3和5.23×108 t，折合成油当量137.69×108 t。澳大利亚西北陆架北卡那封盆地裂前中—上三叠统区带、东非地区鲁伍马盆地北部和坦桑尼亚盆地南部中白垩统—新近系三角洲-深水扇区带是最有潜力的勘探区带。

Structural and sedimentary evolution of passive continental margin basins around the Indian Ocean and its effects on hydrocarbon accumulation

The passive continental margin basins around the Indian Ocean have huge exploration potential for oil and gas resources, and they are becoming hotspots for current global oil and gas exploration. With IHS commercial data and previous research results, this study defined the tectonic evolution history of passive continental margin basins around the Indian Ocean, analyzed the influence of tectonic evolution on filling structure and hydrocarbon accumulation in the basins, evaluated the resource potential by Monte Carlo statistical methodology and predicted favorable exploration zones. The results show that the passive continental margin basins around the Indian Ocean have experienced three stages of tectonic evolution, which are pre-rift, syn-rift, and passive continental margin stages. According to the dominant stage of evolution, the passive continental margin basins can be divided into four types: extensional marginal pre-rift, extensional marginal fault depression superimposition, extensional marginal depression and transform marginal fault depression superimposition. The source rocks in the passive continental margin basins are mainly developed from the pre-rift to the early passive continental margin stages, and the main source rocks vary by region. Reservoirs are mainly developed between the pre-rift and late passive continental margin stages; regional seals were mainly developed in the passive continental margin stage. The resource evaluation indicates that the undiscovered oil and gas resources (mean value) in the main passive continental margin basins around the Indian Ocean are 4.49×108 t of oil, 15.86×1012 m3 of natural gas, and 5.23×108 t of condensate, amounting to 137.69×108 t. The pre-rift Middle-Upper Triassic zone in North Carnarvon Basin, Northwest Shelf of Australia, the Middle Cretaceous-Neogene delta-deep water fan zone in northern Ruvuma Basin and southern Tanzania Basin, East Africa, are the most promising exploration zones.