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孔喉大小是评价储层质量的重要因素,而致密砂岩储层孔喉分布较强的非均质性使其表征难度较大。在分析目前孔喉表征方法的基础上,通过场发射扫描电镜、高压压汞和恒速压汞等实验,研究了鄂尔多斯盆地陇东地区延长组7段致密砂岩储层孔喉大小分布特征及其对储层物性的控制作用。结果表明:储层孔隙类型主要为剩余粒间孔、溶蚀孔、微孔和少量微裂缝;高压压汞表征孔喉的大小分布在0.014 8~40μm,大于1μm的孔喉分布较少;恒速压汞测试表明对于不同物性的样品其孔隙半径分布相对集中,主要分布在80~350μm;喉道半径则表现出较强的非均质性,分布在0.12~30μm;高压压汞和恒速压汞结合有效地表征了致密砂岩储层整个孔喉分布特征,孔径分布在0.0148~350μm。储层渗透率主要由比例较小的大孔喉(大于R_(50))所控制,对于渗透率大于0.1 mD的致密砂岩,其渗透率主要由微孔和中孔所控制,而小于0.1 mD的致密砂岩则主要由纳米孔和微孔所控制;此外,小孔喉的比例随着渗透率的减小而增加,虽然其对渗透率影响较小,但对储层储集性的影响却十分重要。
Pore throat size is an important factor to evaluate reservoir quality. The strong heterogeneity of pore throats in tight sandstone reservoirs makes it difficult to characterize the reservoir quality. Based on the analysis of current pore-throat characterization methods, the pore-throat size distribution characteristics of tight sandstone reservoirs in the Member 7 of Yanchang Formation in the Longdong area of Ordos Basin were studied by means of field emission scanning electron microscopy, high pressure mercury intrusion and constant pressure mercury injection Control of reservoir physical properties. The results show that the pore types of reservoirs are mainly residual intergranular pores, dissolution pores, micropores and a few micro-fractures. High-pressure mercury intrusion characterizes the size distribution of pore throats from 0.014 8 to 40 μm, less pore throats than 1 μm, The mercury intrusion tests showed that the distribution of pore radius is relatively concentrated for samples with different physical properties, mainly distributed in the range of 80 ~ 350μm; the throat radius shows strong heterogeneity in the range of 0.12 ~ 30μm; Mercury binding effectively characterizes the pore-throat distribution of tight sandstone reservoirs with a pore size distribution of 0.0148 ~ 350μm. The permeability of the reservoir is mainly controlled by the smaller proportion of large pore throats (greater than R 50). For tight sandstone with permeability greater than 0.1 mD, the permeability is mainly controlled by micropores and mesopores and less than 0.1 mD Of tight sandstone are mainly controlled by nanopores and micropores. In addition, the proportion of micropore and throat increases with the decrease of permeability. Although it has little effect on permeability, the effect on reservoir reservoir Very important.