中国南海地区电缆工具与随钻工具在泥岩电阻率测量中的差异现象及原因探讨

The Difference of Shale Resistivity Measurement Between the Wireline Tool and LWD Tool in the South China Sea

在中国南海地区普遍存在泥岩中随钻电阻率低于电缆电阻率的现象。研究发现,介电影响和工具原理的差异是导致两类工具对泥岩电阻率测量差异的原因。首先,研究区深、浅层黏土矿物类型和地层水矿化度的差异导致该区深、浅层泥岩介电特征的差异,同时,随钻电阻率工具的介电校正只针对砂岩校正,未考虑泥岩及区域介电特征的差异,泥岩的介电影响校正不足,是造成随钻工具和电缆工具电阻率测量差异的主要因素;其次,电缆工具和随钻工具测量原理上的差异也是导致该现象的另一个因素。即便是同为随钻电阻率工具,不同服务公司工具采用的收发系统、频率不同,也会造成测量结果的差异。

In the south China Sea,there was a common phenomenon that the shale resistivity of LWD was lower than that of wireline logging in relatively deeper zones of the same well.It was discovered in the study that there were two reasons for the shale resistivity difference between wireline logging and LWD.Firstly,the difference of dielectric property in the deep and shallow mudstones was induced by the type of clay minerals and salinity of formation water.At the same time,the dielectric calibration of the LWD tool was only appropriate for sandstone,the difference of dielectric calibration of mudstone and between areas was not taken into consideration,the insufficient dielectric calibration of mudstone was the major factor inducing the difference of resistivity of LWD and wireline logging tools.Secondly the difference between the wireline and LWD logging tools was the other major factor in principle.Although the same LWD resistivity tool is used by each service company,the receive and dispatch system and frequency are different,which would result in a difference in resistivity measurement.