烃源岩地质色层效应的模拟实验

Simulation experiment of geochromatographic effect during hydrocarbon expulsion

利用未混油或混油源岩样品在低温、加压条件下分别对纹层状泥岩、暗色块状泥岩及灰质块状泥岩样品进行排烃模拟实验,其中块状泥岩及灰质块状泥岩被研碎后混入同层原油,而纹层状泥岩不被研碎(也未混油),以保持其层理结构的完整性。实验结果显示,排烃过程造成轻烃相对富集,色谱图中主峰碳前移,正构烷烃分布及部分甾、萜烷参数值在排烃过程中产生明显变化,萜烷对运移的敏感性没有甾烷强。在排烃过程中纹层状泥岩与块状泥岩及灰质块状泥岩的地质色层效应有着显著的差异,相对而言,块状泥岩与块状灰质泥岩的排烃效率低,但排烃过程造成了它们出现较为明显的地质色层效应,而纹层状泥岩排烃效率高,但在排烃过程中地质色层效应不明显。分析认为源岩的物理结构是造成这种地质色层效应的差异的主要原因之一。

The simulation experiments have been conducted at low temperature （150℃ for massive mudstone and massive lime mudstone and 300℃ for laminar mudstone） and 68 MPa to study the geochromatographic effect differences among laminar mudstone, massive mudstone and massive lime mudstone during hydrocarbon expulsion. In the experiments the samples of massive mudstone and massive lime mudstone were triturated and intermingled with crude oil of the same layers, while the laminar mudstone sample was not triturated in order to preserve the integrality of stratification. The results show that hydrocarbon expulsion has influenced the distribution of steranes and terpanes in all the samples. The hydrocarbon expulsion of the laminar mudstone sample is of the highest efficiency of the three samples, while the efficiency of massive mud and massive lime mudstone are much lower. The geochromatographic effect of the laminar mudstone sample is obviously different from that in the mudstone and lime mudstone samples and is the weakest. The differences of the geochromatographic effect between the laminar mudstone sample and the mudstone and lime mudstone samples may be mainly derived from the physical structure of the source rocks. For the laminar mudstone, the hydrocarbon migration is along the plane stratification with high efficiency and the resistance to the hydrocarbon migration is very low. While for the massive mudstone and massive lime mudstone, the resistance to the hydrocarbon migration is strong due to their massive structure, therefore, their geochromatographic effect are strong. There are obvious changes for distribution of normal alkane and the values of some parameters of steranes and terpanes during hydrocarbon expulsion. The geochromatographic effect of steranes is stronger than that of teroanes.