鄂尔多斯盆地姬塬地区长8低渗透砂岩储层微观孔隙结构特征研究

Study of Pore Structure Characteristics of Chang 8 Low-permeability Sandstone Reservoirs in the Jiyuan Area, Ordos Basin

以常规压汞、铸体图像、扫描电镜和薄片观察为基础,结合恒速压汞测试,对鄂尔多斯盆地姬塬地区长8低渗透砂岩储层微观孔隙结构特征进行研究。结果表明,姬塬地区长8储层孔隙类型多样,以残余粒间孔为主,孔隙结构可划分为4种类型。恒速压汞测试表明,姬塬长8储层为大孔细喉型。与特低渗透储层相比,超低渗透储层喉道分布范围更集中,小喉道所占比例更大,孔喉半径比分布范围更宽。特低、超低渗透储层差异主要体现在喉道的大小和分布上,喉道控制储层品质及渗流能力。在低渗透砂岩储层的开发中应尤其注重孔喉间的配置关系。

The microscopic pore structure of Chang 8 low-permeability sandstone reservoirs of the Yanchang Formation in the Ordos Basin Jiyuan Area is thoroughly analyzed and investigated by using constant-speed mercury intrusion technology,combined with conventional constant- pressure mercury injection,cast image,scanning electron microscopy and slice observation.The result shows Chang 8 reservoirs has various pore type and the main type is residual intergranular pore, the pore structure is divided into four categories. The reservoirs type of Chang 8 in Jiyuan Area is mainly large scale pore with thin throat.Compared with ultra-low permeability reservoirs,the throat distribution of super-low permeable reservoirs is more concentrated,it has more narrow throat, the rang of pore-throat ratio is wider. The differences of pore throat characteristics between ultra- low and super- low permeable reservoirs mainly lay in throats, throats control the quality of reservoirs and its percolation capacity.In the process of low- permeability sandstone reservoirs development, we should pay more attention to the allocation relation between pore and throat.