珠江口盆地恩平凹陷油气沿断层走向运移模式

Mode of oil-gas migration along fault strike in Enping Sag of Pearl River Mouth Basin

勘探思路的转变往往会带来新的勘探突破。通过对珠江口盆地恩平凹陷断层研究发现,在恩平凹陷陡坡带北部凸起区发育1种具备以下4点特征的断层:与控洼断层呈大角度相交;断陷湖盆发育中期开始活动,并形成向湖盆输砂的物源通道;成藏期切开断陷中期沿断层输入的砂体和烃源岩;沿断层走向形成往凸起区方向因地层逐渐抬升而形成的断裂内部输导脊。这种断层在区域厚层泥岩盖层的顶侧封作用下,油气沿断裂内部输导脊发生走向运移。基于此研究,在传统认为较难运移成藏的恩平凹陷陡坡带北部凸起区获得了勘探突破,并在该区获得一系列勘探发现。珠江口盆地恩平凹陷油气沿断层走向运移模式可供类似地区借鉴。

The transformation in philosophy of oil-gas exploration often brings new exploration breakthroughs.Based on the study of the faults in Enping Sag of the Pearl River Mouth Basin,we recognized a new type of fault that is developed in the northern uplift of the steep slope zone of Enping Sag with the following four characterist-ics:1)it intersected with the major fault of the sag at a large angle;2)it became active at the middle stage of the development of faulted lacustrine basin,forming the sedimentary sources channel for sand transport to the lacus-trine basin;3)at the accumulation stage,it cut the source rocks and sand bodies that were input along the faults in the middle faulting period;4)the internal transport ridge of the fault were formed along the fault strike due to gradual uplifting of strata toward the uplifting area.Under the sealing effect of the regional thick mudstone cover layer,oil and gas migrated along the fault strike.In this study,exploration breakthroughs were made in the north-ern uplift of the steep slope zone of Enping Sag that is traditionally considered difficult for oi-gas migration and reservoir formation,and now a series of exploration discoveries have been made in this area.The migration mode of oil and gas along fault strike in the Enping Sag of Pearl River Mouth basin can be used as a reference for prac-tice in similar areas.