某些油气田地表土壤的磁性与烃运移相互关系研究

A STUDY FOR RELATIONSHIP BETWEEN HYDROCARBON MIGRATION AND SOIL MAGNETISM ABOVE OIL AND GAS FIELDS IN CHINA

根据鄂尔多斯盆地靖边气田上方的ＭＩ０２线、江苏储家楼油田与江汉盆地花园油田地表十字剖面土壤磁性的测量结果，研究地表是否存在与深部油气藏中烃类垂向运移相关磁性蚀变带的可能性及其分布形式．结果表明，ＭＩ０２线样品显示了明显的高磁性异常特征，并与酸解烃之间呈很强的正相关．磁滞回线形态与参量显示出明显的亚铁磁性特征．电子探针分析结果表明，样品中主要磁性矿物（磁铁矿）中高温杂质元素含量很低．江汉盆地花园油田十字剖面磁滞回线参量（饱和磁化强度Ｊｓ与饱和等温剩磁Ｊｒ）的高异常位于油田周边，油田顶部土壤呈典型顺磁性特征．储家楼油田地表土壤的高磁性异常主要位于油田上方，它们均与盖层中的断裂构造对应，储家楼油田的高磁性样品中发现的典型球粒状磁铁矿为次生低温磁铁矿，它与烃运移之间存在成因关系．

This paper presents the measurements of soil magnetism from profile MI02 above Jingbian gas field,Ordos Basin and cross profiles from Chujialou oil field,Jiangshu Province and Huayuan oil field,Jianghan Basin,in order to identify existence of magnetic alteration zones in the surface, related to vertical migration of hydrocarbonin oil reservoirs. The results show that profile MI02 has a strong magnetic anomaly and positively correlated cleared with content of gas hydrocarbon(linearity correlation coefficients get up 0.95).The shape and parameters(saturation magnetization Js,saturation isothermal remanent Jr and coercivity) Of magnetic hysteresis loops expressobviouly ferrimagnetic characteristics.Electronprobe analysis results indicate that hightemperature foreign substance elements content is very low of magnetite in soil andso,we inferd that it probably is low temperature magnetie related with hydrocarbon microseepage.High magnetic anomalies(Js,Jr)of soil are located on margin of oil field from cross profile of Huayuan oil field, Jianghan Basin and presented paramagnetic characteristics above oil field,then high magnetic anomalies situated aboveoil field in Chujialou and they are corresponding to faults within cap strata. The spherical magnetite grains in soil from high magnetic anomalies of Chujialou oil field are secondary low temperature magnetite and have genetic relation with hydrocarbon migration.