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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 |
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