Application of Multi-Exponential Inversion Method to NMR Measurements

A new multi-exponential inversion method for NMR relaxation signals is presented and tested, which is based on a solid iteration rebuild technique (SIRT). The T2 spectra inversed by the new method are compared with MAP-II results. The T1 and T2 inversion results with different pre-assigned relaxation times and different SNR show that 16 to 64 logarithm equal spaced time constants is better obviously than MAP-II. And in particular, it can ensure the relaxation time distribution when the SNR of the measured signal is very low. The new algorithm has been applied in rock core NMR analysis and NMR logging data process and interpretation.

A new method for multi-exponential inversion of NMR relaxation measurements

A new method for multi-exponential inversion to NMR T1 and T2 relaxation time distributions is suggested and tested. Inversion results are compared with MAP-II which is based on SVD algorithm and widely accepted in the industry. Inversed NMR relaxation spectra that have different pre-assigned relaxation times from echo trains with different SNR confirm that the new method with 16 to 64 equally spaced time constants in logarithm scale will ensure the relaxation distribution. Testing results show that the new inversion algorithm is a valuable tool for rock core NMR experimental analysis and NMR logging data process and interpretation.

Multi-exponential inversions of nuclear magnetic resonance relaxation signal

Beginning from the first kind of integral equation, two kinds of methods, i. e. Singular Value Decomposition (SVD) and transform that are fit for the inversion calculation of NMR multi-relaxation data from rock, have been derived. The mathematical processing was discussed in detail. The advantage and disadvantage of the two methods have been compared in theory and application. From the view of the degree of freedom of the inversion solution, we discussed the resolution of the solution of NMR relaxation inversion and the selection of optimal inversion modeling. Results showed that SVD method is fit for the inversion of NMR relaxation data with a higher signal to noise ratio and transform inversion method is more flexible and can be used in NMR data with a lower signal to noise ratio. It is advisable that transform inversion method be selected for the multi-relaxation inversion of rock NMR data. SVD method can be used when the signal to noise ratio is better than 80. In order to ensure the accuracy, the number of T2 points should be varied from 30 to 50. The results of the research are useful for NMR core analysis and the interpretation of NMR logging data.

泥页岩储层孔隙度测量方法分析与评价

泥页岩属于非常规储层,孔隙度普遍小于10%,渗透率普遍低于1 mD。低孔低渗的特征致使常规实验方法和测井解释方法难以准确获取其孔隙度值。这里选取沧东凹陷孔二段泥页岩样品,对其孔隙度分别进行压汞法、气测法、液测法以及核磁共振法的测量,并将核磁共振实验与核磁共振测井的孔隙度值进行对比。结果表明,核磁共振技术是获取泥页岩孔隙度相对适用的方法,高精度核磁共振仪器在选择较小回波间隔(T_(E)=0.1 ms)的条件下,可测得更为全面的泥页岩孔隙度值。在有机质含量较高(TOC≥9%)的泥页岩层段,核磁共振测井信噪比呈现出一定的相关性,低信噪比可能是造成核磁共振测井获取孔隙度值偏高的原因。因此在实际测井评价过程中,要考虑信噪比的影响。

核磁测井在火成岩储层解释评价中的应用研究

常规测井资料在辽河油田火成岩储层评价中存在储层识别率不高、储层参数计算精度低等问题.利用一种适用于低信噪比核磁测井弛豫信号的多指数反演方法,提高火成岩地层核磁测井处理解释精度,并在岩心实验分析基础上研究建立了火成岩核磁测井储层参数计算解释模型.应用结果表明,在16～64点对数均匀布点时,多指数反演方法明显优于传统算法,特别是在信噪比较低的情况下,该方法反演的弛豫谱连续性好,具有较好的谱分辨能力,能保证实际岩石、流体弛豫谱的真实性.利用核磁测井资料能较好地识别火成岩储层,划分火成岩的储层类型,提高孔、渗、饱储层参数计算精度及储层流体性质解释符合率.核磁测井在辽河油田火成岩储层测井解释评价中发挥了较好的应用效果.

核磁共振测井移谱差谱法影响因素实验分析

针对实际生产中利用核磁共振的移谱、差谱法识别油气所遇到的疑难问题,选取了29块岩心样品和12种不同粘度的原油样品,进行了室内核磁共振特性的测试和分析。根据实验数据,分析了不同粘度的原油在相同测试条件下的T2谱,不同粘度的原油饱和到不同孔隙的岩样中的T2谱,不同岩样饱和盐水后的移谱、差谱,不同岩样饱和不同粘度原油后的移谱、差谱;通过分析发现移谱、差谱法在识别储层油气水的应用过程中的一些影响因素,寻求解决方法,以指导实际生产。

一种新的核磁共振弛豫谱反演算法

提出了一种新的基于整体迭代修正的核磁共振弛豫信号的多指数反演算法 ,对算法的具体实现过程进行了详细的论述 ,并通过算法实例处理与基于奇异值分解法的MAPⅡ算法的反演结果进行了对比 ,对比总结了不同信噪比下、不同布点方式下核磁共振弛豫谱的反演结果 ,表明在 16～ 64点对数均匀布点时SIRT反演结果能保证岩石、流体弛豫谱的真实性 ,该算法对岩心核磁共振实验分析以及核磁共振测井资料解释分析具有重要的参考价值。