伽马-伽马密度测井的密度校正方法及应用

Correction Method and Application of Gamma-gamma Density Logging

针对天然放射性引起的伽马-伽马密度测井解析地层密度值偏低的问题,文章提出一种利用天然伽马探测器计数率与长、短源探测器计数率比值(RGGFR/NGR,RGGNR/NGR)系数,对长、短源探测器计数率进行修正的方法,进而利用常规刻度系数进行密度值解算。分别利用现场核查模型和钻孔实测数据进行密度解算与修正,结果表明该方法是一种有效的密度校正方法,满足密度测井对精度的要求。

To solve the problem of negative deviation of derived rock density caused by natural radioactive interference in gamma-gamma density logging,this paper introduced a count rate ratio method which assume the detector count rate was of linear proportion to uranium concentration in formation rocks.Ratio of count rates of natural gamma detector to that of long distance detector was derived through calibration pits.Field calibration model verification and borehole density measurement showed that the above mentioned count rate ratio technique was an effective density correction method,which can reduce rig time and improve derived density accuracy.