华庆地区长6致密油储层微观孔喉结构特征

针对鄂尔多斯盆地华庆地区三叠系延长组长6段致密油储层，应用恒速压汞和微、纳米CT扫描分析等技术手段和方法，开展了微观孔喉结构特征研究。研究结果表明，长6致密油储层孔隙以微米级孔隙为主，纳米级孔隙分布频率较低，主流喉道半径为1.07 μm，平均喉道半径为0.84 μm；平均孔隙半径为140.12 μm，平均孔喉比为281.03，微纳米孔喉特征明显。喉道半径、孔喉比与孔渗关系表明，孔喉特征是影响和制约储层物性的关键因素，孔喉特征参数对渗透率的影响和制约要明显高于其对孔隙度的影响。致密油储层微纳米CT实验表明，致密油储层发育孔喉网络复杂的纳米微米级孔喉系统，且具连通性；微纳米孔隙结构三维重构显示，纳米孔隙一般呈椭圆形、长条形和不规则形，微米级孔隙呈现圆形、椭圆形、三角形和不规则形，石油赋存在较大孔隙的团块状、球形斑点状孔隙结构和微裂缝中。

Microscopic Characteristics of Pore-throat Structures of the Chang 6 Member Tight Oil Layer in the Huaqing Region

Structural characteristics of microscopic pore-throats of the Chang 6 Member tight oil layer of the Triassic Yanchang Formation in the Huaqing Region, Ordos Basin were studied using techniques including constant-speed pumping and microand nano-CT scanning. Results show that the pore spaces in the Chang 6 Member were predominantly microscopic, while nanoscopic pore spaces were less dominant. The mainstream throat radius was 1.07 μm, average throat radius was 0.84 μm, and pore radius was 140.12 μm. The average pore-to-throat ratio was 281.03, representing significant micro/nanoscopic porethroat characteristics. The relationships of pore infiltration with throat radius and pore-to-throat ratio show that pore-throat characteristics are the key factors that influence the physical properties of the tight oil layer. The effects and limitations of porethroat parameters on infiltration rate are more significant than those of porosity. Micro/nano-CT scans on tight oil layers indicate the presence of complex and interconnected micro/nanoscopic pore-throat networks. The three-dimensional reconstruction of micro/nanoscopic pore space reveals that nanoscopic pores are mainly oval, elongated, or irregular, whereas their microscopic counterparts are circular, oval, triangular, and irregular. Tight oil is located in micro-cracks and in the clustered and spherical pore-throat structures with relatively larger pore spaces.