致密油储层可动流体分布特征及主控因素分析——以鄂尔多斯盆地长7储层为例

Distribution characteristics and controlling factors of movable fluid in tight oil reservoir:A case study of Chang 7 reservoir in Ordos Basin

致密油储层微观孔隙结构复杂,流体分布特征不同于低渗储层,主要利用核磁共振对鄂尔多斯盆地延长组长7储层可动流体进行定量评价,辅助以铸体薄片、电镜扫描、高压压汞、高分辨率X-CT等技术分析可动流体差异性的主控因素。研究表明:致密油储层T2谱形态主要表现为6种类型,中大孔隙内束缚流体量较高,导致致密油储层可动流体参数偏低,且不同样品之间可动流体参数变化幅度较大、差异性较强;储层渗透率与可动流体参数相关性较强,储层物性越好,可动流体参数变化幅度越大;孔喉半径大小、次生孔隙发育程度及所对应的孔喉连通性,裂缝的发育程度及有效性,黏土矿物含量、赋存形式及充填孔喉程度等储层特征是致密油储层可动流体差异性的主要控制因素。

The micro-porosity structure of tight oil reservoir is complex,and distribution characteristics of the fluid in tight oil reservoir are very different from that of low permeability reservoir.The movable fluid evaluation of the Chang 7reservoir in the Ordos Basin was conducted by using nuclear magnetic resonance（NMR）technology,and the controlling factors of the differences in the movable fluid were analyzed by cast thin section,scanning electron microscopy,high pressure mercury injection,high-resolution computed tomography.The results show that T2 pattern of the tight oil reservoir displays six modes,the content of the immovable fluid is high in middle and large pore,which lead to the parameters of movable fluid being low,and the amplitude of variation and the differences in tight oil reservoir are large among different samples.The relationships are higher between the reservoir permeability and the parameters of movable fluid.The physical properties of the reservoir are better,and the change of the movable fluid parameters is greater.The microstructure characteristics of the tight oil reservoir,such as the distribution of pore and throat radius,development degree of induced porosity and connectivity between pore and throat radius,development degree and availability of micro-fracture,the content,the occurrence states,and the filling degree,are the main controlling factors to cause deviation of movable fluid parameters.