本文对具有特定横向弛豫时间（T2）的硫酸铜溶液进行了多回波间隔（TE）的核磁共振（NMR）实验，并利用数值模拟对32组具有不同弛豫分量的模型进行了变TE模拟实验，定量研究了TE对致密油气、页岩气等低孔低渗储层NMR孔隙度的影响规律.实验结果表明，随着TE的增大，各T2弛豫组分NMR孔隙度先维持在100%左右，然后迅速衰减，当TE增加到一定数值时，趋近于0；不同T2弛豫组分NMR孔隙度开始迅速衰减及最后变为0的TE值存在显著差异.根据不同T2弛豫组分NMR孔隙度与TE的关系，将整个NMR测量分为无损测量区、快速衰减区、无效参数区和仪器盲区4个区域.对特定弛豫组分而言，在快速衰减区弛豫组分损失量与TE呈对数关系，本文还给出了该区域NMR孔隙度的校正公式及方法.
In order to study the effect of echo time (TE) on nuclear magnetic resonance (NMR) porosity in tight oil (gas) and shale reservoir, multi-TE NMR experiments and NMR numerical simulations were performed on CuSO4 solutions with specific transversal relaxation time (T2). The results showed that the normalization NMR porosity of different T2 relaxation components remained 100% in the low TE region, and rapidly decreased with increasing TE. When TE was greater than certain value, the normalization NMR porosity dropped to zero. However, the TE value at which the normalization NMR porosity began to decrease and the TE value at which the normalization NMR porosity dropped to zero were different for different NMR relaxation component. Moreover, the whole NMR measurement was divided into lossless zone, fast decay zone, invalid parameter zone and instrument blind zone, based on the relationships between the normalization NMR porosity of different relaxation component and TE. For each specific relaxation component, a logarithmic relationship was demonstrated between the loss of relaxation component and TE in the fast decay zone. A method for NMR porosity correction was given.
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