定量多维核磁共振测井的理论基础与方法研究

After more than 20 years, 1D and 2D NMR logging method is become more and more popular. Multidimensional NMR method has been attracted considerable attention and has achieved initial progress of inversion method, but the quantitative multidimensional NMR method is still under investigation. From the previous research of our group, we found that the internal magnetic field gradients and restricted diffusion of fluid molecules are the key problems for the reservoirs evaluation with NMR method. Quantificational multi-dimensional NMR theory makes it possible to construct integral response models with the internal magnetic field gradient, fluid molecules diffusion and other NMR relaxation, which can provide more information about the distribution of pores size and fluid types than 1D and 2D NMR. Here, we want to study the basic theory and method of multi-dimensional NMR to identify the fluids typing quantificationally in complex reservoirs, especially when the organic, oil, gas and water occurred with mixed phase in porous media with high internal magnetic field gradients. The forward modeling will be built for numerical simulation to study the interface effect between the solid and liquid or between the solid and gas. Magnetization transfer occurred between hydrogen nuclear in bound state and free state will be estimated quantificationally, the fast T1-DG2-T2 3D pulse sequence and Laplace inversion algorithm are employed, which will be proved with core analysis experiments, to build a quantitative evaluation model. The research is important for the development of new methods and new technology of quantitative formation evaluation with NMR logging.

经过二十多年发展，一维和二维核磁共振测井方法日渐成熟。多维NMR方法一直广受关注并且在反演方法方面已经取得了初步进展，但定量化的问题一直没有得到解决。申请人在前期研究中发现岩石的内部非均匀磁场和流体分子的受限扩散是多维NMR测井定量评价的关键基础科学问题。定量多维NMR理论能够使得内部磁场梯度、流体分子扩散与NMR弛豫特性建立统一的响应模型，提供更加精细的孔隙结构与流体饱和度信息。研究定量多维NMR测井的基础理论与方法，特别是针对致密储层，分析有机质、油、气、水在多维空间上的混相赋存特征与响应机制，研究固-液、固-气界面效应，量化束缚状态下的氢核与自由状态下的氢核之间发生的磁化传递，设计快速T1-DG2-T2多维脉冲序列，开发稳定高效的逆Laplace反演算法，最终建立定量多维NMR流体识别方法及评价模型，并进行实验验证，对发展NMR测井新方法、新技术具有重要意义。

储层流体识别与定量评价是长期困扰油气勘探开发的重要疑难问题，多维NMR方法识别流体一直广受关注并且在反演方法方面取得了初步进展，但定量化的问题一直没有得到解决。本项目在前期研究基础上，利用高精细数字岩石成像技术建立三维岩石孔隙网络模型，通过数值模拟和岩石测试研究岩石内部非均匀磁场、表面弛豫和流体分子的受限扩散对多维核磁共振测量的响应机理；利用不同浓度的纳米材料改变多孔介质固/液界面的表面弛豫率，并设计多维脉冲序列定量定表面弛豫率与顺磁性纳米颗粒吸附量的关系，从而量化表面弛豫。在此基础上分析BE-CPMG脉冲序列对页岩等致密岩石样品的测量机理，提出了一种快速、高对比度T1-T2多维脉冲序列的观测模式；提出了一种结合压缩感知的三维核磁共振数据实时在线处理方法，在不影响反演质量的前提下减少所需的数据采集量，使得数据处理与数据采集同时进行并且能动态调整采集参数。以人造砂岩样品和页岩样品进行实验验证。研究工作对发展定量多维核磁共振测井新方法、新技术具有重要意义。