随钻核磁共振测井仪探测特性研究

Characteristics of NMR Logging While Drilling Tools

随钻核磁共振测井是继电缆核磁共振测井之后的重要进步,具有直接探测原状地层孔隙度、束缚水、渗透率和流体饱和度等特点,受到广泛关注.随钻核磁共振测井需要在更加恶劣的环境下作业,对探头尤其是对磁体有更高的要求.该文研究随钻核磁共振测井的探测特性.基于测量环境和工作方式,分析了随钻核磁共振测井静磁场设计中的特殊问题;利用有限元方法,分别模拟了MRIL-WD(哈里伯顿)、proVISION(斯伦贝谢)和MagTrak(贝克休斯)3种随钻核磁共振测井仪的静磁场分布;根据数值模拟结果,提出可以抑制仪器随钻具运动(轴向转动、纵向钻进和径向振动)对测量的影响的随钻核磁共振测井静磁场方案,为自主随钻核磁共振测井仪器的设计、实现和优化提供了思路和注意事项.

NMR logging while drilling（LWD） has the advantage of detecting formation in-situ,and is a big progress in NMR logging.Compared with wireline NMR,NMR LWD is often performed in more hostile environment.In this paper,the magnet structures of typical NMR LWD tools,such as MRIL-WD（Halliburton）,proVISION（Schlumberger） and MagTrak（Baker Hughes）,were simulated and analyzed.Finite element method was employed to calculate the magnetic field distribution.The results were shown to be in good agreement with the typical tools＇ nominal features.Based on the results of simulation,we proposed schemes to suppress or eliminate the effects of tool motion during drilling.This work provided insights for NMR LWD tools design,implement and optimization.