CT技术在致密砂岩微观孔隙结构研究中的应用——以鄂尔多斯盆地延长组长7段为例

为揭示致密砂岩复杂的孔隙结构特征，应用高分辨率CT技术,对鄂尔多斯盆地延长组长7段致密砂岩样品开展了定量研究。利用CT阈值差异识别样品中的孔隙和喉道，从而获得致密砂岩高精度二维及三维孔喉图像；应用数字岩心方法建立致密砂岩孔隙网络模型，并根据模型中的定量参数分析，获得孔隙及喉道的半径分布及其对储集空间的贡献率、孔喉连通性等特征，实现了长7段致密砂岩微观孔隙结构特征定量表征：长7段致密砂岩微米级孔喉连续分布；半径大于2 μm 的孔隙是长7段致密砂岩的主要储集空间；孔隙、喉道间具有一定的连通性，配位数主要为1~3. 应用高分辨率CT技术可定量表征致密砂岩孔隙结构特征。

Application of CT Scanning System to Study of MicroPore Structure of Tight Sandstone: A Case Study of Chang7 Member of Yanchang Formation in Ordos Basin

In order to reveal the complicated pore structure characterisitcs of tight sandstone, this paper made a quantitative study of the tight sandstone sample from the Chang?7 member of Yanchang formation in Ordos basin by high?resolution CT scanning system, obtained the high?accuracy 2D and 3D pore throad images of it by using CT threshold differences, developed the tigh sandstone pore network model using digital core method, and conducted quantitative parameter statistics and analysis from this model, obtaining the radius distribution of pores and throats and their contributions and pore throat connectivity characterisitcs to the tight sandstone storage spaces, hence realizing the quantitative characterization of micro?pore structures of the tight sandstone. The results show that the tight sandstone of Chang?7 member of Yanchang formation in Ordos basin is characterized by continued distribution of micron pore throats, different contributions of different radius pores to the storage spaces, of which the pores with radius over 2 μm are the main storage spaces of it, and a certain connectivity between pores and throats, with coordination number from 1 to 3