页岩多维核磁共振探测及微观响应研究

发布时间：2018-05-05 22:53

本文选题：数字岩心 + 核磁共振　；参考：《中国地质大学(北京)》2017年硕士论文

【摘要】：核磁共振(NMR)技术是一种能够评价岩石空间内孔隙流体分布的新型技术,在常规砂岩和碳酸盐岩地层中,核磁共振的不仅可以得到岩心的孔隙度、渗透率等常规参数,还可以实现孔隙流体的识别和储层评价。但是在页岩储层的NMR探测中,由于页岩具有孔隙多为纳米尺度、矿物构成十分复杂、有机质较高以及测量时存在的内部磁场等原因,导致页岩核磁共振探测面临着分辨率太低和模型在页岩储层不适用等问题。因此开展页岩多维核磁共振探测及微观响应的研究,对页岩核磁共振的测井评价有着重要的意义。本文以数字岩心的核磁共振数值模拟为基础,开展了基于成岩过程法重构数字岩心模型和X射线CT扫描的页岩数字岩心模型的核磁共振微观响应研究。首先,依据沉积岩石的沉积机理,模拟沉积岩石的沉积过程并重构三维数字岩心,生成不同孔隙度大小的理想数字岩心模型。其次,对理想模型的三维数字岩心开展核磁共振数值模拟研究,通过改变压实程度和填充不同的含水饱和度开展核磁共振的一维、二维微观响应研究,并研究其受限扩散特征。然后,采用X射线CT扫描技术,开展高分辨率的CT扫描实验,生成了 3块纳米尺度的三维页岩数字岩心,并通过AVIZO软件重构页岩CT图像,划分其矿物成分。最后,基于页岩三维数字岩心,开展页岩数字岩心的核磁共振一维、二维数值模拟研究,并探究其微观响应。研究表明,对于不同分辨率的数字岩心,其受限扩散程度随着分辨率的提高越来越大。在模拟成岩过程中,随着压实程度的加大,理想数字岩心的孔隙度会变小,其T2谱的幅度会有明显的降低,T2分布会向短弛豫方向移动。通过对含有不同润湿相饱和流体的数字岩心进行核磁共振数值模拟发现,随着润湿相饱和度的减小,其T2-D分布中润湿流体的信号会偏离其自由扩散系数线。在对页岩进行核磁共振微观数值模拟研究的过程中,随着回波间隔的增大,其T2分布的形态有了明显的变化,并向右方向偏移,页岩核磁共振仪器实验结果一致。同时由于页岩数字岩心分辨率较高,所以其润湿流体的受限扩散现象明显,并随着孔隙度的减小,其受限扩散更加的明显。这对于我们构建页岩核磁共振解释模型提供了理论基础。
[Abstract]:Nuclear magnetic resonance (NMR) is a new technique that can evaluate the distribution of pore fluid in rock space. In conventional sandstone and carbonate strata, nuclear magnetic resonance (NMR) can not only obtain the core porosity, permeability and other conventional parameters. It can also realize the identification of pore fluid and reservoir evaluation. However, in the NMR exploration of shale reservoir, the shale has many nano-scale pores, complex mineral composition, high organic matter and the internal magnetic field in measurement, and so on. Therefore, nuclear magnetic resonance (NMR) detection of shale is faced with problems such as low resolution and inapplicability of model in shale reservoir. Therefore, it is of great significance for logging evaluation of shale nuclear magnetic resonance to carry out multi-dimensional nuclear magnetic resonance detection and microcosmic response research. Based on the nuclear magnetic resonance numerical simulation of digital cores, the nuclear magnetic resonance microscopic response of shale digital core models based on diagenetic process reconstruction and X-ray CT scanning has been studied in this paper. Firstly, according to the sedimentary mechanism of sedimentary rock, the sedimentary process of sedimentary rock is simulated and 3D digital core is reconstructed to form an ideal digital core model with different porosity. Secondly, nuclear magnetic resonance (NMR) numerical simulation is carried out for 3D digital cores of ideal model. 1D and 2-D microscopic responses of NMR are studied by changing compaction degree and filling different water saturation, and its confined diffusion characteristics are studied. Then, by using X-ray CT scanning technology and high resolution CT scanning experiment, three nanoscale 3D shale digital cores were generated, and the shale CT images were reconstructed by AVIZO software, and their mineral compositions were classified. Finally, the 1D and 2D NMR numerical simulation of shale digital core is carried out based on the 3D digital core of shale, and its microscopic response is explored. The results show that the limited diffusion degree of digital cores with different resolution increases with the increase of resolution. In the process of simulating diagenesis, with the increase of compaction degree, the porosity of ideal digital core will become smaller, and the amplitude of T2 spectrum will obviously decrease and the distribution of T2 will move to the direction of short relaxation. The numerical simulation of digital cores with different wetting phase saturation fluid shows that with the decrease of wetting phase saturation, the signal of wetting fluid deviates from its free diffusion coefficient line in T2-D distribution. In the process of nuclear magnetic resonance microscopic numerical simulation of shale, with the increase of echo interval, the shape of T _ 2 distribution changed obviously and shifted to the right. The experimental results of shale nuclear magnetic resonance instrument were consistent. At the same time, because of the high resolution of shale digital core, the limited diffusion of wetting fluid is obvious, and with the decrease of porosity, the limited diffusion is more obvious. This provides a theoretical basis for the construction of shale NMR interpretation model.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P618.13

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