Nuclear magnetic resonance(NMR)imaging is an advanced technology for core-scale heterogeneity analysis.Affected by rock complexity and encoding technology,existing methods are not really effective.2D/3D nuclear magnetic resonance technology based on gradient fields is easy to image but has a low signal-to-noise ratio.The traditional T2 method(frequency coding/phase coding)without gradient field is in low efficiency.This study proposes a tomography method based on constant gradient coded 1D T2 spectrum,which can achieve small imaging data volume,high signal-to-noise ratio and more complete signal.Tomographic T2 spectrum images and their heat distribution can effectively characterize the effects of capillary force and diagenesis on the non-uniform distribution of fluids.In the oil-saturated state,the difference between T2 spectrum layers reflects the influence of diagenesis.The heat change of the image in the high saturation stage mainly reflects the displace pattern of low capillary force controlled free oil.After complete displacement,the capillary force enters a stable state,and the axial heat reflects the difference of micro-pore content that filled with adsorbed oil.The new technology has achieved good results in gas displacement experiments of cemented sandstone,and is expected to play an important role in the analysis of seepage laws of strong heterogeneous rocks.
关键词
岩心核磁共振/T2谱成像/梯度编码/毛细管压力/非均质性
Key words
core nuclear magnetic resonance/T2 spectrum imaging/gradient coded/capillary pressure/heterogeneity
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