基于压汞实验研究低渗储层孔隙结构及其对渗透率的影响——以鄂尔多斯盆地西南部三叠系延长组长7储层为例

Pore Structure Characteristics and Its Effect on Permeability by Mercury Injection Measurement: An Example from Triassic Chang-7 Reservoir,Southwest Ordos Basin

压汞是研究孔隙结构的有效岩石物理学方法,毛管压力曲线能为我们提供多孔介质孔隙结构的大量信息。本文对鄂尔多斯盆地西南部三叠系延长组长7低渗储层的20个样品进行了压汞测试。主要从毛管压力曲线形态特征、孔喉分布特征、孔隙结构分形特征三个方面对储层的微观孔隙结构进行了深入研究。在此基础上,运用逐步回归法分析了孔喉参数对储层渗透率的影响。结果表明最大渗透率贡献半径对储层渗透率的影响最为显著,分选系数、孔喉均值和歪度也是影响储层渗透率的重要因素。并且发现,对于同一岩样,由双曲线顶点确定的半径值总是接近于但略小于对渗透率贡献最大的半径值。最后,讨论了运用逐步回归法优选出的四个孔喉参数对储层渗透率的影响,并对其它可能影响渗透率的因素作了有益探讨。

mercury injection measurement is an effective petrophysical method to study pore structure of reservoir. Information about pore structure of porous materials can be obtained from capillary pressure curves. Based on the capillary—pressure data, this article studied the Pore structure characteristics and its effect of on permeability of Triassic Chang 7 reservoir in the southwestern Ordos basin. In order to understand the characteristics of pore structure, the mercury injection curves, pore throat distribution and the fractal of pore structure were studied. Moreover, we studied the influence of pore throat parameters on permeability by stepwise regression. The results reveal that the radius which makes the greatest contributions to the permeability is the most important factor affecting permeability. Sorting, sorting coefficient, mean size and skewness also have significantly effect on reservoir permeability. Besides, the radius which makes the greatest contributions to the permeability is close to but a little coarser than the radius corresponding the apex of hyperbola. At last, we discussed the influence of pore throat parameters sorted by stepwise regression on permeability. Meanwhile, other factors that might have impact on permeability were also constructively discussed.