核磁共振与压汞法的孔隙结构一致性研究

实验研究表明，核磁共振横向弛豫时间（T₂）与压汞法都能很好地反映地层岩石的孔隙结构，二者之间存在着必然的相关性。即由毛细管压力曲线可以计算出相应的T₂分布；反之亦可。这一物理理论的获证为利用核磁共振测井资料研究储层孔隙结构提供了理论依据。因此，从理论入手，分析了核磁共振T₂分布与毛细管压力曲线得到的孔喉半径分布之间的关系，找到它们之间的相互转换关系式。以岩心压汞资料为基础，同相应岩心的T₂几何平均值进行拟合，建立了适合鄂尔多斯盆地塔巴庙地区上古生界盒3段致密砂岩气层的核磁共振测井中的T₂几何平均值与孔隙结构参数之间的关系，还建立了应用核磁共振测井资料确定储层微观孔隙结构参数的方法，对于指导盒3段致密砂岩气层的生产具有重要的意义。

CONSISTENCY OF PORE STRUCTURES BETWEEN NMR AND MERCURY INTRUSION METHOD

Experimental study shows that both transverse relaxation time T_2 of NMR and mercury intrusion method can well reflect the pore structure of rocks, thus inexorable correlation exists between them. Namely, corresponding T_2 relaxation time distribution can be obtained by using capillary pressure curve, and vice versa. It provides a theoretical basis for studying pore structure with NMR logging data. This paper analyzes the relationship between T_2 relaxation time and the distribution of pore-throat radius obtained from capillary pressure curve and presents the relational expression of their conversion. Based on core mercury intrusion data and through fitting with the T_2 geometric average value of core, the relationship between T_2 geometric average value of NMR and pore structure parameters is established, which is suitable for the third member of Shihezi Formation of Upper Paleozoic in Tabamiao area of the Ordos Basin. In addition, methods of defining microscopic pore structure parameters with NMR logging data are also presented, and they are of great significance to guide production of tight sand gas in the third member of Shihezi Formation.