北非NK地区上白垩统灰岩裂缝油藏成藏因素

北非Pelagian盆地是一个重要的含油气盆地,在North Kairouan地区已经取得了一些积极的勘探成果,但仍存在油藏成藏条件复杂,主控因素不清、勘探难度大、勘探成效低等问题。以地震、钻井及分析化验资料为基础,对研究区上白垩统灰岩裂缝储层成藏条件进行了综合分析,认为该区油气成藏主要受裂缝的走向及发育程度、有效输导层以及盖层的分布共同控制,北西向断层及裂缝发育、具备复式输导层和厚层盖层的构造发育区为有利油气聚集区,指出NK地区中部复杂背斜带和东部鼻状隆起带为两个有利油气勘探带,对该区碳酸盐岩油藏勘探具有指导意义。

Controlling Factors of Fractured Limestone Reservoir-forming of Upper Cretaceous in North Kairouan Region,Pelagian Basin,North Africa

The Pelagian Basin in North Africa is one of the important oil and gas basins.Based on the seismic,drilling,analytic and testing data,the comprehensive analysis of the forming conditions of the Upper Cretaceous fractured limestone reservoirrevealsthefollowingpoints:theformationoftheoilandgasreservoirinthisregionismainlycontrolledbyoilresource conditions,thestrikeandabundanceofthefractureandfault,aswellasthedistributionofeffectivetransportlayerandthickcap rock;the structural areas developed northwest faults and fractures,composite passage system and thick cap rock are favorable areasofhydrocarbonmigrationandaccumulation.Thefaultsandfracturesdevelopinginthedirectionofnortheastareunsealed,which is beneficial for the lateral and vertical migration of the hydrocarbon and for the improvement of the limestone reservoir property.ThemovementofsaltinthelatePalaeocenemakesthemudstoneoftheHariaformation,whichistheregionalcovering strata,partially eroded,resulting in the maldistribution and the change of the thickness of the cap rock in the region,which can greatly influence the height of hydrocarbon column of reservoir that can be sealed.As a result,it is pointed out that the complex anticline belt in central NK and the nosing belt in Eastern NK are two favorable areas of oil and gas accumulation,which provide guidelines for the exploration of carbonate reservoir in this region.