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在CPMG序列中，回波個(gè)數(shù)和回波間隔TE是可編程的采集參數(shù)。這兩個(gè)參數(shù)都根據(jù)測(cè)井目標(biāo)和預(yù)測(cè)的地層和流體性質(zhì)進(jìn)行選取。典型的NMR測(cè)井中，在大約1 S的時(shí)間內(nèi)要采集幾千個(gè)回波�；夭ǖ膫�(gè)數(shù)取決于預(yù)計(jì)的地層弛豫時(shí)間。在具有長(zhǎng) 時(shí)間的地層(如含輕質(zhì)油和大孔隙或孔洞巖石的地層)中，需要更多的回波以準(zhǔn)確測(cè)量分布中的大值。實(shí)際上，在儀器磁場(chǎng)梯度中，分子的擴(kuò)散會(huì)造成額外的T 擴(kuò)散衰減，可以測(cè)到最長(zhǎng)T2的上限。縱向弛豫時(shí)間T1不受擴(kuò)散影響。
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