松辽盆地长垣地区白垩系青山口组一段有机质含量对超压分析的影响及校正方法

The impact of organic matter content on overpressure analysis and its correction method in the first member of Cretaceous Qingshankou Formation,Placanticline area, Songliao Basin

应用测井参数对烃源岩超压进行实证性分析时,往往会受到有机质的影响。文中将富有机质泥页岩划分为非有机质泥岩骨架、固体有机质及孔隙流体3部分,以有机质含量为基础推导出了一套针对烃源岩超压成因判别的测井参数校正方法。在以松辽盆地长垣地区葡532井青山口组一段泥页岩为例进行研究时发现,经有机质含量校正后无论是孔隙度对比法还是速度-密度交会图法皆否定了过去超压是不均衡压实所致的认识。此外,文中强调在预测埋藏深度非历史最大埋深的地质体压力时,应根据古最大埋深与现今埋深差值对正常压实趋势做相应校正。根据校正后的测井参数,对典型井进行压力预测,其精度可达95%以上。

The organic-rich shale is composed of three parts:non-organic mudstone system,solid organic matter and pore fluid.Given that the empirical analysis of source rock overpressure by logging parameters tends to be influenced by orga-nic matter,we proposed a set of logging parameter correction methods based on the content of organic matter for the identification of source rock overpressure origin.A case study of the shale in the first member of Qingshankou Formation(K1qn1) in Well Pu532 in Placanticline area,Songliao Basin shows that the knowledge of overpressure caused by disequilibrium compaction has been proven wrong by both porosity comparison and velocity-density cross plot under the effect of organic-matter correction.Furthermore,when measuring the pressure of a research target with its predicted buried depth less than the largest buried depth in history,it is necessary to correct the normal compaction trend by the difference between the maximum palaeoburied depth and the current one.Subsequently the prediction precision of typical wells’ pressure will be better than 95% in line with corrected logging parameters.