【摘要】 采用核磁共振实验的方法研究鄂尔多斯盆地陇东地区延长组主力含油层段岩心样品的T₂分布,并结合离心实验的结果,确定岩心有效渗流喉道半径的下限值,并标定了每块岩心的可动流体与束缚流体的T_2cutoff。研究结果表明:可动流体对应的下限离心力为2.07 MPa,根据气水离心Washburn方程确定出岩心对应储层的有效渗流喉道半径下限为0.07μm。对长6和长8不同储层类型岩心的核磁共振结果分析可知:T_2cutoff与孔隙度和渗透率都没有较好的相关性,也就是孔隙度相近或渗透率相近的岩心T_2cutoff有可能差异很大。不同储层类型岩心的T_2cutoff差异较大:整体上,超低渗砂岩储层岩心的T_2cutoff分布范围较致密砂岩储层岩心的小;超低渗砂岩岩心分布在9.64ms¹6.68ms之间,致密砂岩岩心分布在9.64ms²4.04ms之间。分析造成这种差异的主要原因是T_{2 cutoff}除与孔隙度、渗透率有关以外,也受孔隙结构、矿物成分和黏土类型的影响。除此之外,束缚水饱和度与孔隙度和渗透率之间都有较好的相关性,随着孔隙度和渗透率的增加,岩心束缚水饱和度有减小的趋势。同时也分析了T_2cutoff与T₂谱的位置关系,总结出4个基本规律。最后,根据国内外油气田开发生产经验,并结合陇东地区延长组实际,以可动流体饱和度高低为标准,对岩心对应的储层进行分类,结果表明:致密岩心对应的储层都属于Ⅲ类储层（可动流体饱和度介于35%⁵0%之间）,超低渗岩心对应的储层有Ⅱ类储层（可动流体饱和度介于50%⁶5%之间）也有Ⅲ类储层。更多还原

【Abstract】 Ihe T₂ distribution of drilling core samples from oil-bearing formation of Yanchang Formation in the Longdong area is studied by use of nuclear magnetic resonance method,and the low limit of throat radius of the cores is determined on the basis of centrifuge tests and the T2 cutoff value of the movable fluid and irreducible fluid is calibrated.It shows that the low limit of centrifugal force for the movable fluid is 2.07 MPa,the low limit of throat radius for movable fluid is0.07μm,which is defined by gas water centrifugal Washbum equation.The NMR analysis for different reservoir types of Chang 6 and Chang 8 indicates that the T_2cutoff hardly has correlation with porosity and permeability,even its porosity or permeability is similar,and the core T_2cutoff may vary greatly.The difference of T_2cutoff is apparent in different reservoir cores.On the whole,the range of T_2cutoff distribution of ultra-low permeability reservoir is smaller than that of tight reservoir.In fact,the T_2cutoff distribution of ultra-low permeability reservoir is 9.64 ms¹6.68 ms while the T_2cutoff distribution of tight reservoir is 9.64 ms²4.04 ms.The main reason for this difference is that T_2cutoff is not only related to porosity and permeability,but also affected by pore structure,mineral composition and clay types.In addition,the irreducible water saturation has a good correlation with porosity and permeability,with the increase of porosity and permeability,the irreducible water saturation of core is decreased.Meanwhile,the relationship between T_2cutoff and T₂ spectra is analyzed,and 4 basic rules are summarized.According to the domestic and international oil and gas field development and production experience,combined with the practical situation of Longdong area Yanchang formation,the reservoir in the area is classified by level of movable fluid saturation.It shows that the tight reservoir belongs to class Ⅲ reservoir（movable fluid saturation is in the range of 35%⁵0%）,the ultra low permeability reservoir is the class Ⅱ reservoir（movable fluid saturation is in the range of 50%⁶5%） and part of the class Ⅲ reservoir.更多还原