柴达木盆地北缘侏罗系大煤沟组7段油页岩低放射性控制因素

以探讨柴达木盆地北缘侏罗系大煤沟组7段(J2d7)油页岩低放射性的控制因素为目的，选取鱼卡地区典型井目的层段的油页岩和暗色页岩为研究对象，结合测井资料及含油率、有机地球化学、X射线衍射、元素地球化学等岩心测试分析资料，对二者的组构、水体介质条件、放射性物质供给特征及其与岩石放射性的关系进行详细对比分析。结果表明：与暗色页岩段相比，油页岩整体具有低的自然GR值，具有高的含油率、有机质丰度及沉积期还原性较强水体介质条件，具有较低的黏土矿物含量及沉积期母岩区较弱的风化程度。初步分析得出，有机质富集及贫氧水体介质条件对于区内油页岩的低放射性无明显影响，而古气候条件由温湿到逐步干热，导致陆源黏土矿物及放射性物质输入有限是油页岩低放射性形成的关键。

Factors Controlling the Low Radioactivity of Oil Shale in the 7th Section of Dameigou Formation of Jurassic in Northern Qaidam Basin

The factors controlling the low radioactivity of oil shales in the 7th Section of Dameigou Formation of Jurassic in Northern Qaidam Basin were primarily discussed.Taking oil shales and dark shales in typical wells in Yuqia area as the research objects,the constituent, water medium condition, radioactivity source supply and their relation with radioactivity were analyzed in detail combined with logging data, oil yield test and the analysis of organic geochemistry, X ray diffraction and element geochemistry.The results show that, compared with dark shales, oil shales are generally characterized by the following attributes, lower GR, higher oil yield and organic matter content,stronger reducing sedimentary water, lower clay mineral content and weaker source weathering.Therefore, it can be inferred that the enrichment of organic matters and the condition of anoxic water medium hardly influence the radioactivity of oil shales, however, the limited input of terrestrial clay minerals and radioactive substances, caused by the semiarid climate, may dominate the low radioactivity of oil shales in the study area.