中非Melut盆地与我国东部裂谷盆地的类比及意义

Analogy between Melut Basin of Central Africa and Rift Basins of East China and Implication

Melut盆地为中非地区重要的含油气裂谷盆地,具被动裂谷成盆特征,处于区域构造勘探向"三新领域"勘探的转型阶段,油气富集规律尚不十分清楚,通过开展Melut盆地与我国东部主动裂谷盆地的类比分析,有助于深化盆地成藏认识,推进勘探转型.研究表明,Melut盆地北部具被动裂谷成盆特征,发育大型富油凹陷,形成以古近系跨时代成藏组合为主,近源白垩系成藏组合为辅的油气富集特点,古近系Yabus组上段跨时代岩性油藏与近源白垩系Galhak组断块油藏是北部深化勘探的重要领域;盆地中南部具被动裂谷与主动裂谷的叠加演化过程,与海拉尔盆地相似,具小型断陷沉积充填与成藏特征,近源成藏组合是有利的勘探对象,继承性洼槽内低凸起、凹陷间断裂隆起带及缓坡断层坡折带是有利的成藏构造带.该研究深化了Melut盆地成藏认识,明确了盆地南北具有不同的成盆机制与成藏特征,对推动北部成熟探区深化勘探与中南部低探区勘探突破具有重要意义.

Melut Basin is an important petroliferous passive rift basin of Central Africa,and now it is in the midst of transformation from negional structure exploration to new formations,new domains and new areas exploration without very clear understandings of hydrocarbon accumulation.By analogy between Melut passive rift basin and active rift basins of East China,the geological understandings of hydrocarbon accumulation in Melut Basin are deepened,and the exploration transformation will be promoted.The analogy shows that,the North Melut Sub-basin has typical passive rift basin character,and developed large oilrich sag with the primary"far-source"play of Paleogene and secondary"near-source"play of Cretaceous.The"far-source"lithological reservoir of Upper Yabus Fm.in Paleogene and Cretaceous faulted block reservoirs of Galhak Fm.near source rock are two important domains of fine exploration in North Melut Sub-basin.The Central-South Melut Sub-basins experienced overlapping tectonic evolution process of passive and active rift basin,with the sediments filling and play features of small faulted depression,which is similar with the Hailar Basin,and the"near-source"reservoir-caprock assemblages are favorable exploration targets,inherited low uplifts in sags,faulted uplifts between sags,and faulted slope break belts in gentle slope are favorable hydrocarbon accumulation structural zones.The study deepens the understandings of hydrocarbon accumulation in MelutBasin,and it is suggested that the North and Central-South Melut Sub-basins have different basin forming mechanisms and hydrocarbon accumulation characteristics,which is of great importance to promote the fine exploration in mature exploration areas of North Melut Sub-basin and exploration breakthrough in low exploration areas of Central-South Melut Sub-basins.