珠江口盆地文昌B凹陷输导层非均质性及油气运移路径模拟

Heterogeneity of carrier and simulation of hydrocarbon migration path in Wenchang B Sag,Pearl River Mouth Basin

碎屑岩地层普遍具有非均质性,在剖析文昌B凹陷基础地质资料的基础上,通过对研究区岩心-微观-测井等多尺度分析,认识输导层非均质性特征,查明输导层内有效储集岩类型,以文昌B凹陷恩平组二段输导层为例,构建非均质性输导层三维地质模型,实施油气运移路径定量模拟,探究非均质性输导层中油气运移路径的展布特征.研究结果表明:根据砂岩岩心相、岩石学特征、物性、孔隙类型及成岩作用等方面的差异性,非均质性砂岩输导层可划分为贫塑性颗粒砂岩、富塑性颗粒砂岩、钙质砂岩3类岩石相,其中贫塑性颗粒砂岩因具有相对较好的孔隙结构、物性、含油气性等为输导层中的有效储集岩.在此基础上,建立了考虑输导层非均质性的三维地质模型,结合流体动力条件、烃源岩条件和成藏期古构造,开展关键成藏期油气运移过程模拟,揭示了文昌B凹陷恩平组二段烃类自凹陷中心向北西向和北东向的构造高部位发生侧向运移的过程中,在北部斜坡区发生局部聚集,形成整体呈现弥散状的小型油气聚集.

Clastic strata are generally heterogeneous.Based on the analysis of basic geological data of Wenchang B Sag,through multi-scale analysis of core-micro-logging in the study area,the heterogeneous characteristics of the carrier beds are understood and the types of effective reservoir rocks in the carrier beds are identified.Taking the carrier bed of the second member of Enping Formation in Wenchang B Sag as an example,a three-dimensional geological model of the heterogeneous carrier bed was constructed.Quantitative simulation of hydrocarbon mi-gration path was carried out to explore the distribution of hydrocarbon migration path in the heterogeneous carrier bed.The results show that:According to the differences of sandstone core facies,petrography characteristics,petrophysical properties,pore types and diagenesis,the heterogeneous sandstone carrier bed can be divided into three types of petrofacies:ductile-lean sandstone,ductile-rich sandstone and calcite-cemented sandstone,among which ductile-lean sandstone is the effective reservoir rock in the carrier bed because of its relatively good pore structure,petrophysical properties and hydrocarbon bearing property.On this basis,a three-dimensional geological model considering the heterogeneity of the carrier bed was estab-lished.Combining the hydrodynamic conditions,source rock and paleostructure of the accumu-lation period,the hydrocarbon migration process of the key accumulation period was simulated,and the lateral migration of hydrocarbons from the center of the sag to the NW and NE of the second member of Enping Formation in Wenchang B sag is revealed.Local accumu-lation occurs in the Northern Slope area,forming a small dispersed hydrocarbon accumulation.