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沧东凹陷孔二段的孔二~1、孔二~2和孔二~3段,因利用常规测井难以识别,一直被认为是只具生烃能力的生油岩。其中孔二~1油组底部高自然伽马段一直认为是泥质含量高造成的,通过自然伽马能谱测井可以看出,高自然伽马主要是该层段放射性铀元素高造成的,可为该区地层划分的标志性特征,同时也是油气聚集的一种指示。而孔二~2油组顶部高自然伽马砂岩段也一直认为是泥质含量高造成的,又有较低的电阻率,与常规砂岩油层测井特征截然不同,过去常常被忽略,因此也使该层段的油气勘探步伐止步不前;通过自然伽马能谱测井,结合钻井取芯、核磁测井可以看出,高自然伽马主要是该层段放射性钍元素高造成的,本层段是较好的砂岩油层段(核磁孔隙度可达17%);并且该层段厚度较大、分布广泛,为下步油气勘探部署提供了良好的评价依据。
Holes 2 ~ 1, Holes 2 ~ 2 and Holes 2 ~ 3 of Kong 2 Member in Cangdong Depression have been considered as hydrocarbon generation rocks with hydrocarbon generation ability only because they are difficult to identify by conventional logging. Among them, the high natural gamma ray at the bottom of Well No.2 ~ 1 has been thought to be caused by the high clay content. By means of natural gamma ray spectrometry, it can be seen that high natural gamma ray is mainly caused by the high level of radioactive uranium in this interval , Which can be the hallmark feature of the stratigraphic division of the area and an indication of hydrocarbon accumulation. The high natural gamma ray sandstone at the top of Kong II-2 oil group has also been considered to be caused by the high clay content and low resistivity, which is very different from the logging characteristics of conventional sandstone reservoirs and was used to be neglected. Therefore, So that this interval of oil and gas exploration pace halted; by natural gamma ray spectroscopy logging, combined with drilling coring, NMR logging can be seen that the high natural gamma ray is mainly caused by the high radioactive thorium of this interval, the The intervals are good sandstone reservoirs (nuclear magnetic porosity up to 17%); and the thick and widely distributed intervals provide a good basis for further exploration and deployment.