Magnetic susceptibility registration in ICDP boreholes - test of a new logging tool

磁化率是最常测量的岩石物性之一。该参数在岩心或井眼上的测井为岩性剖面的构建和井眼间的对比提供了支持。记录磁化率的仪器通常使用固定的交流磁场振幅来构造。然而，正如最近的研究表明的那样，磁黄铁矿和钛磁铁矿等重要铁磁矿物的磁化率强烈依赖于交流磁场的振幅。这对敏感性测井曲线的解释和对比具有重要意义。GFZ-OSG新开发的小井眼探空仪MS2H是第一个考虑油田依赖影响的敏感性测井工具。在这个项目的框架内，我们计划测试新的探空仪在ICDP钻孔中的应用。初步的案例研究表明，依赖于现场的磁化率测量可以提供有关熔岩流组成变化的信息，并可能使含磁铁矿和磁黄铁矿的岩石得以区分。这类测试的结果被认为对敏感性测井曲线的有效解释至关重要。

Magnetic susceptibility is one of the most commonly measured rock physical property. The logging of this parameter on drillcores or in boreholes supports the construction of lithological profiles and correlation between drilling holes. Instruments, recording the magnetic susceptibility are commonly constructed using a fixed field amplitude for the applied ac magnetic field. However, as has been shown in recent work, the susceptibility of important ferrimagnetic minerals as pyrrhotite and titanomagnetite strongly depends on the ac-field amplitude. This has important implications for the interpretation and correlation of susceptibility logs. The newly developed slim-hole sonde MS2H of GFZ-OSG is the first susceptibility logging tool that considers the effect of field dependency. In the framework of this project we plan to test the application of the new sonde in ICDP drillholes. Preliminary case studies have shown that field dependent susceptibility measurements can provide information concering variations in the composition of lava flows and may enable magnetite and pyrrhotite-bearing rocks to be distinguised. The results of such tests are considered to be critical for the effective interpretation of susceptibility logs.