轮南低凸起三叠系烃类聚集模式及控藏要素分析

应用现代油气成藏理论,结合钻井、地震以及地球化学资料对轮南低凸起三叠系烃类聚集模式及控藏要素进行了研究。轮南低凸起是以奥陶系岩溶缝洞型油气藏为主、垂向上多套含油气层系叠置的复式油气聚集带。虽然喜山早期运动诱发了区域性断裂活化,但在石炭系弱超压型隔挡层及潜山顶面断裂体系发育特征的联合约束下,下伏的奥陶系油气资源仅能沿着断垒带地区的深大断裂向浅部的三叠系圈闭发生限制型垂向输导调整。同时,虽然三叠系发育的3套砂体(对应3套油组)的孔渗及横向输导性能优越,但探井油气显示的统计分析发现中部斜坡带地区发育无油气显示带,表明轮南断垒带及桑塔木断垒带地区三叠系的油藏并无沟通;即使是在晚期构造反转作用下,由于三叠系圈闭的充满度较低、油气无法突破圈闭溢出点,导致三叠系的原油也从未发生过有效的南北向的层间运移。因此,三叠系油气藏的分布仅受深大断裂的控制,断穿潜山面与三叠系底面的断裂发育区是三叠系油气藏勘探的潜在靶区。

Research of Hydrocarbon Accumulation Mode and Key Factors Controlling Reservoir Formation in Lunnan Uplift

The Triassic hydrocarbon accumulation mode and the factors controlling reservoir formation Lunnan uplift were studied by using modern hydrocarbon accumulation theory and in combination wirn well drilling and seismic data.In Lunnan uplift,karst reservoir in Ordovician was dominated and oil-bearing strata were superimposed vertically.Oils in the Ordovician were migrated into the Triassic traps by fault and then redistributed,which was triggered by the fault revivification in the early Himalaya event.However,Carboniferous was an effective seal as it was developed in slight overpressure.What’s more,the characters of the fault were developed near the burial hill determined as the discordogenic faults of horst block for conducting the hydrocarbon.On the other hand,the analysis of the SG&O in the exploration well shows that though there are three sand beds with excellent reservoir characteristics and effective conduction performance of Triassic,there is a non-SG&O belt developed on the middle of platform,which determines that there is no connectivity between two horst blocks and Triassic oils never have an effective interlamination migration,because the amount of hydrocarbon adjusted from Ordovician to Triassic is too small to breakthrough the restrain of every single trap.Therefore,the distribution of the Triassic accumulation is obviously controlled by the discordogenic faults,and the area where the buried hill and fault fractures develop is the profitable target zone of Triassic and Ordovician.