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提出了一种可以提高核磁共振测井测量速度的新型测量脉冲序列 ,它基于对原有CPMG测量脉冲序列的改进 .在原有的测量序列中 ,在一个CPMG脉冲序列结束之后 ,直接进行等待 (T1延时 ) ,以使磁化强度矢量能够完全恢复到平衡位置 ,然后再进行下一个CPMG脉冲序列的测量 .由于测井仪器的连续运动 ,在测量含有长T1成分的地层时 ,等待时间需要取得较长 ,使得测井速度很低 .但在实际地层中 ,恰恰又是油气的T1较长 ,这无疑给核磁共振测井带来了麻烦 .作者发现 ,如果在一个CPMG脉冲序列结束之后在 -x方向先施加一个 90°脉冲 (或在x方向施加一个 2 70°脉冲 ) ,再进行等待 ,就能更好地使长T1成分得到极化 ,从而缩短等待时间、提高测量速度 .文中对这种改进后的脉冲序列进行了计算和分析 ,证明它确实具有一定的优越性 .
A new type of measuring pulse sequence, which can improve the measuring speed of nuclear magnetic resonance logging, is proposed based on the improvement of the pulse sequence measured by the original CPMG. In the original measuring sequence, after a CPMG pulse sequence is completed, Delay) so that the magnetization vector can be fully restored to the equilibrium position before the next CPMG pulse sequence is measured.Because of the continuous motion of the logging tool, when measuring the formation with long T1 components, the waiting time needs to be compared Long, making the logging speed is very low, but in the actual formation, it is precisely the T1 of oil and gas is longer, which undoubtedly caused NMR logging trouble.The authors found that if a CPMG pulse sequence after the end of -x Applying a 90 ° pulse (or applying a 2 70 ° pulse in the x direction) in the first direction gives better polarization of the long T1 component, resulting in shorter latency and higher measurement speed. The improved pulse sequence is calculated and analyzed to prove that it does have some advantages.