基于核磁共振实验的低渗透砂岩岩电参数分类及应用——以东营凹陷南坡沙四段为例

低渗透砂岩储层孔隙结构复杂，储层有效性识别及饱和度准确计算难度较大.笔者以东营凹陷南坡沙四段（Es₄）低渗透砂岩为研究对象，根据压汞、物性、薄片及核磁等资料，将研究区孔隙结构分为三大类、五小类.在岩样孔隙结构分类基础上，明确了孔隙结构类型与岩电参数之间存在确定的关系，而核磁共振T₂谱定量特征参数在一定程度上能够表征孔隙结构类型及其细节信息，通过提取T₂谱中T₂几何平均值（T_2g）、T₂均值（T₂）、峰度（K_G）、可动流体分量（S_mf）及区间孔隙分量等孔隙结构参数，建立了基于核磁T₂谱特征参数的孔隙结构识别图版，显示核磁T₂谱孔隙结构参数对不同类型的储层有较好的识别效果，进而探讨核磁孔隙结构参数和岩电参数之间的关系，结果表明，T₂谱峰度值与孔隙胶结指数（m）值相关性较高，进一步确定了岩电参数m的核磁计算公式.最终，将该套方法应用于研究区井筒剖面中，有效地提高了饱和度计算精度，也为东营凹陷南坡低渗透砂岩油藏储量估算与高效开发提供了依据.

Classification of rock-electro parameters of low-permeability sandstone based on nuclear magnetic resonance log and its appication: An example of Es4 in south slope of the Dongying depression

Comlpex pore structure makes it difficult to identify the reservoir validity and calculate the saturation accurately of low permeability sandstone. This work attempted to address this issue taking the forth member of the Eocene Shahejie Formation (Es₄) of the south slope in Dongying Depression as an example. Based on data of mercury injection, physical properties, thin sections and nuclear magnetism, the pore structure of low permeability sandstone in this area was divide into to 3 main types and 5 branch types, which permitted to determine the relationship between pore structure types and rock-electro parameters. Quantitative parameters of NMR T₂ spectrum can characterize the pore structure types and its detailed information to some extent. By extracting the parameters of pore structure, such as T₂ geometric mean (T_2g) and T₂ mean (T₂), kurtosis (K_G), mobile fluid ratio (S_mf) and interval pore component in T₂ spectrum, the identification chart of pore structure based on the characteristic parameters of T₂ spectrum of NMR was established, which can help indentify reservoirs of varied types. Further more, the relationship between rock-electro parameters and T₂ characteristic parameters were discussed. The results show that the K_G is highly correlated with the cement exponent (m), and the calculation formula of m was further determined. Finally, this method was applied to the logging profile in the study area, which effectively improved the accuracy of saturation calculation and provided a basis for the reserves estimation and efficient development of low permeability sandstone reservoirs in the south slope of Dongying Depression.