基于核磁共振测井的束缚水饱和度评价方法：以中东地区M层组的孔隙型碳酸盐岩储层为例

束缚水饱和度是储层流体性质识别和油气藏储层评价的关键参数。利用地球物理测井资料进行储层束缚水饱和度评价是目前广泛使用的方法，其中核磁共振测井一般通过确定横向弛豫时间截止值来计算储层束缚水饱和度，而在中东H油田M层组核磁共振实验研究中发现，部分实验样品出现了“扩散耦合”现象，导致通过T₂截止值难以准确求取储层束缚水饱和度。通过提取核磁共振T₂谱中反映孔隙结构与流体赋存状态信息的特征参数，并结合铸体薄片等资料探讨这些参数与束缚水饱和度之间的相关关系，规避T₂截止值从而避免“扩散耦合”现象对模型的影响。实验结果表明，束缚水饱和度与核磁孔隙度、区间孔隙分量及T₂几何均值之间具有相关性，并基于上述参数建立了束缚水饱和度预测模型，在中东H油田M层组中对预测模型进行实际井验证，取得良好应用效果，为后续判别储层流体性质与水淹层识别打下坚实基础。

Evaluation method of irreducible water saturation of porous carbonate rock based on nuclear magnetic resonance logging data- Taking M Formation of H Oilfield in Middle East as an Example

Irreducible water saturation is a key parameter for reservoir fluid property identification and reservoir evaluation. Using geophysical logging data to evaluate reservoir irreducible water saturation is a commonly used method. Nuclear magnetic resonance logging generally calculates the irreducible water saturation of the reservoir by determining the cutoff value of the transverse relaxation time. In the nuclear magnetic resonance experimental study of the M layer group in H oilfield in the Middle East, it is found that some experimental samples have the phenomenon of '' diffusion coupling '', which makes it difficult to accurately calculate the irreducible water saturation of the reservoir through cutoff. By extracting the characteristic parameters reflecting the pore structure and fluid occurrence state information in the nuclear magnetic resonance spectrum, and combining with the data of casting thin sections, the correlation between these parameters and irreducible water saturation is discussed, and the cut-off is avoided to avoid the influence of '' diffusion coupling '' on the model. The experimental results show that there is a correlation between irreducible water saturation and nuclear magnetic porosity, interval pore component and geometric mean. Based on the above parameters, a prediction model of irreducible water saturation is established. The prediction model is verified by actual wells in the M layer group of H oilfield in the Middle East, and good application results are obtained, which lays a solid foundation for the subsequent identification of reservoir fluid properties and water flooded layer identification.