碎屑储集岩磁化率与含油性的关系

Relationship between Susceptibility and Oil-bearing Property of the Clastic Reservoir Rocks

对采自渤海湾盆地济阳坳陷孤南洼陷9口探井的430块古近系碎屑储集岩标本进行了细致的体积磁化率、频率磁化率和非磁滞磁化率测试,研究了不同含油级别的储集岩磁化率响应规律。结果表明:岩性是控制磁化率信号强弱的首要地质因素,泥质含量指示磁化率十分灵敏。碎屑储集岩磁化率与含油性关系密切,以岩性为约束,除去泥质成分的影响,储集岩含油程度越高,磁化率越低,两者呈负相关;油浸碎屑岩中极有可能存在与烃类流体运移聚集作用密切相关的超顺磁(SP)-单畴(SD)-假单畴(PSD)粒级的自生磁铁矿。在常规地球物理测井基础上,针对有石油地质意义的层段开展磁化率测井,砂岩段中的磁化率低值区是可疑的油气层,泥岩段中的磁化率异常高值区可能是优质的烃源岩层。

A total of 430specimens were collected from the Cenozoic clastic reservoir rocks in Gunan Sag for testing volumetric susceptibility and frequency susceptibility and non-magnetic susceptibility.The magnetic response rules of different clastic reservoir rocks were studied.The result showed that the lithologic property was the first geologic factor controlling the strong or weak of signals.Clay content indicating susceptibility was very sensitive.The susceptibility of clastic reservoir rocks was closely related with oil-bearing property.Constrained by lithologic property,after the effect of clay content was deducted,the higher the oil content of reservoir rocks was,the lower the susceptibility would be, its oil-bearing property and susceptibility are negatively correlated.There possibly existed SP-SD-PSD authigene magnetite in the oil-immersed clastic rocks induced by migration and accumulation of hydrocarbon fluid.Based on the conventional geophysical well logging,a susceptibility logging is carried out on the special stratigraphic units with the petroleum geological significance.The low-magnitude area of the magnetic susceptibility in the sandstone sections is probably suspected oil and gas layers.The high-magnitude area of the susceptibility in the mudstone sections is probably the high-quality source rocks.