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| 内部磁场梯度对火山岩核磁共振特性的 影响及其探测方法 |
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廖广志1,2,肖立志1,2,谢然红1,2,付娟娟1,3
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(1.中国石油大学资源与信息学院，北京102249 ;2.中国石油大学油气资源与探测国家重点实验室，北京100249 ;3.中石油华北油田分公司勘探斤发研究院，河北任丘062552)
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| 摘要: |
| 在常规岩心测量和核磁共振(NMR)试验的基础上,分析顺磁性矿物对火山岩NMR测量的影响,并对部分样品 进行2D NMR测童，探测到基于内部磁场梯度-横向弛豫时间的信号分布、视内部磁场梯度分布和视T2弛豫时间谱。 结果表明:顺磁性矿物会在火山岩样品中产生很强的内部磁场;在磁旋动力和分子扩散的作用下，NMR测得的信号 信噪比很低,计算到的孔隙度偏低，对于磁铁矿、黄铁矿含量较多的岩心差别最大;用20 NMR方法可探测这种 内部磁场梯度的分布,并用于流体的扩散分析。 |
| 关键词: 火山岩 核磁共振 岩心分析 顺磁性矿物 内部磁场梯度 |
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| 基金项目:国家“863”技术导向课题(2006AA06Z215);国家自然科学基金项目(40674075) |
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| Influence of internal magnetic field gradient on nuclear magnetic resonance of volcanic rocks and its detection method |
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LIAO Guang-zhi1,2,XIAO Li-zhi1,2,XIE Ran-hong1,2,FU Juan-juan1,3
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(1. School of Resource and Information Technology in China University of Petroleum, Beijing 102249, Chirm ;2. State Key Laboratory of Petroleum Resource and Prospecting in China University of Petroleum，Beijing 102249, China ;3. Exploration & Development Research Institute of Huabei Oilfield Company , PetroChina, Rertqiu 062552, China)
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| Abstract: |
| Some volcanic core samples were measured by conventional petrophysics method and nuclear magnetic resonance (NMR) core analysis method Through the two dimensional NMR core analysis experiments, the signal distributions based on internal field gradients and transverse relaxation time, apparent internal field gradients and apparent transverse relaxation distribution were probed. The results show that there is an internal gradient field caused by some paramagnetic minerals (magnetite, pyrite or chlorite) in core matrix. The signal-to-noise ratio of NMR single is very low because of the effects of fluid diffusion and spin dynamic. The porosity measured by NMR is much lower than that by conventional measurement, especially for the core which contains magnetite or pyrite. The T2-G 2D NMR method can be used to detect internal magnetic field gradient distribution and for fluid diffusion analysis. |
| Key words: volcanic rocks nuclear magnetic resonance (NMR) core analysis paramagnetic minerals internal magnetic field gradient |
