测井图上曲线的第一个可靠读数的深度。
The depth of the first reliable reading of a curve on a log.
由于孔隙空间存在着气体，同一地层的中子孔隙度测井和密度孔隙度读数不同。
Different porosity reading on the neutron porosity log for the same formation due to gas in the pore space.
对于常规的上提测井，最后读数出现在仪器刚进入套管的时候。
For the normal bottom-to-top survey, the last reliable reading often occurs just before the logging tool enters the casing.
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