核磁共振T2截止值与毛细管压力的关系

核磁共振测井的独特之处在于它能将不动流体孔隙率与可动流体孔隙率分开，提供较可靠的束缚水饱和度。用核磁共振测井资料求取束缚水饱和度时，T2截止值是关键参数，该参数可通过实验确定。本文通过莺歌海盆地岩石样品核磁共振实验，研究了T2截止值与毛细管压力的关系。研究表明，随驱替压力的增大，T2截止值按指数规律下降，因此T2截止值与气柱高度有关。在核磁共振测井资料处理中，应根据气柱高度确定T2截止值的大小，尤其是在束缚水饱和度大的地层中，更要注意T2截止值的选取。

Relationship between NMR T_2 cutoff and capillary pressure.

The particular advantage of Nuclear Magnetic Resonance (NMR) log is that it can distinguish the irreducible fluid porosity from the free fluid porosity,provided more reliable irreducible brine saturation.T 2 cutoff is the key parameter when using nuclear magnetic resonance logging data to calculate irreducible brine saturation.T 2 cutoff is determined by NMR experiment.Through the NMR experiment of core samples from Yingge sea Basin,the paper studied the relationship between NMR T 2 cutoff and capillary pressure.The studied results showed that T 2 cutoff decreased exponentially when displacement pressure increased.Therefore,T 2 cutoff is related to the height of gas column.The size of T 2 cutoff needs to be determined by gas column in process of NMR logging data,especially when the reservoir has high irreducible brine saturation,the selection of T 2 cutoff needs to be more careful.