合肥盆地东部朱巷组X射线衍射分析及其油气意义

Analysis of the Zhuxiang Formation in the eastern part of Hefei Basin by XRD and significance of the results in the light of oil and gas

对取自合肥盆地大桥凹陷内下白垩统朱巷组(K1Z)21个泥岩样粘土矿物进行X射线衍射分析,定量研究表明,伊利石结晶度值均大于0.42,一般为0.42～0.75。伊利石/蒙皂石混层比有5个样品小于50.00%,其余为50.20%～70.10%,蒙皂石转化从无序间层到部分有序间层,反映地表处朱巷组处于成岩作用中-早期阶段,有机质成熟度处于成熟-未成熟阶段,没有进入埋藏变质。结合钻井Ro资料及地球物理资料,揭示朱巷组埋深大于3000m,预测深埋地下的朱巷组烃源岩已进入生油门限。

Based on the XRD data of clay minerals of 21 mudstone samples from the Zhuxiang Formation of lower Cretaceous in the Daqiao depression of Hefei Basin,it is found that all of the values of illite crystalline degree are over 0.42,generally the values are from 0.42 to 0.75;and only 5 values of smectite percentage(I/S) are lower than 50.00%,the others are from 50.20% to 70.10% . And the smectite transition occurs from random interlaying to partly ordered interlaying. The results indicate that the Zhuxiang Formation came up to the mediumtoearly stage of diagenesis,the organic maturation degree was at the stage of being matured to immature, and the Formation had not undergone the burial metamorphism.The data from drilling wells and geophysical exploration reveal that the Zhuxiang Formation was buried at the depth of over 3 000 m,thus it can be predicted that the source rock buried deeply has been matured.