巴西桑托斯盆地油气田形成的关键条件与勘探方向

Key conditions and exploration direction of oil-gas fields of Santos Basin in Brazil

巴西桑托斯盆地是全球著名的油气田富集的深水含油气盆地,盐下裂谷沉积体系规模巨大,发育世界级的烃源岩和规模优质的湖相碳酸盐岩储层,巨厚盐岩形成高效区域盖层,盐下油气成藏条件优越。通过对桑托斯盆地构造沉积演化及油气成藏特征分析的基础上,系统剖析了盐下大油气田形成的关键条件,并指出勘探方向。研究表明储层发育程度是决定能否形成大油气田的关键,烃源岩成熟度差异控制了大油气田的油气类型,盐层的连续性和厚度控制了盐下大油气田的形成与保存,盐下继承性古隆起构造控制了大油气田的分布,幔源CO2晚期充注可能改造大油气田。盐下裂谷层系是桑托斯盆地最重要的勘探领域,东部隆起带与中央坳陷带东北部为有利勘探潜力区带,且南大西洋两岸还有数个深水含盐盆地具有与桑托斯盆地相似的盐下沉积体系与成藏组合,勘探前景广阔。

The Santos basin has become a world-famous deep-water petroliferous basin with giant oil-gas fields gathering. There are favorable conditions of hydrocarbon reservoir forming with world class source rocks,large scale of lacustrine carbonate reservoirs and excellent thick salt sealing in the huge pre-salt rift system of Santos basin. Based on the analysis of tectonic-sedimentary evolution and characteristics of hydrocarbon reservoir forming in Santos basin,we systematically analyzed the key conditions of pre-salt giant oil-gas fields forming and pointed out exploration direction. The results show that: ①the degree of reservoir development is the key factor of controlling giant oil-gas fields forming.②the maturity of source rock defines the hydrocarbon type of giant oil-gas fields.③the thickness and continuity of salt layer determines the forming and preservation of pre-salt giant oil-gas fields.④the pre-salt inherited palaeo-uplift structures controlled the distribution of giant oil-gas fields.⑤The late CO2 influx from mantle probably transformed the giant oil-gas fields. The pre-salt rift strata have become the most important exploration field and the eastern uplift zone and northeast part of central depression are the favorable exploration potential areas in Santos basin. Moreover,there are several deep-water salt-bearing basins with the pre-salt depositional system and hydrocarbon plays similar to Santos basin,which show vast exploring prospect in South Atlantic.