利用气体吸附法和压汞法研究烃源岩孔隙分布特征——以松辽盆地白垩系青山口组一段为例

Pore Distribution of Source Rocks as Reavealed by Gas Adsorption and Mercury Injection Methods:A Case Study on the First Member of the Cretaceous Qingshankou Formation in the Songliao Basin

烃源岩中微观孔隙空间是油气初次运移的重要通道,同时也是残留烃主要的储集空间。本文对烃源岩中不同尺度的孔隙分别使用气体吸附法和压汞法进行测定,进而对孔隙分布进行系统分析。实验结果表明,青山口组一段烃源岩孔隙度较低,分布于1.2%～3.87%之间,平均为2.17%,主要以微孔和介孔为主,孔容分布于1.8～30mL/mg之间,平均为9.49mL/mg;比表面积分布于0.91～31.02m2/g之间,平均为7.02m2/g。同时本文探讨了不同岩石组成对烃源岩内孔隙发育与分布的影响,发现有机质、伊利石及黄铁矿含量与孔容之间具有较好的正相关关系,孔隙的大小及数量随其含量的增高而增加,而粘土矿物中的绿泥石以及非粘土矿物中石英、方解石、斜长石含量与孔容之间呈负相关关系,烃源岩中的孔隙可能会随其含量的增高而减少,高岭石含量与孔容之间相关性较差,表明烃源岩孔隙可能不受其影响。此外,烃源岩中孔隙发育及分布还受有机质类型、丰度、热演化程度、粘土矿物排列形式、非粘土矿物的次生变化等因素的影响。

The micro pore system in source rocks is an important pathway for the primary migration of petroleum, and it is also an important storage space for the residual petroleum. In this paper we try to measure the micropores with different diameters by using gas adsorption and mercury injection methods, and analysis the distribution of micropores systemly. Experiment results indicate that the pore types in the source rocks of the first member of the Qingshankou Formation are mainly micro pores and meso pores. The distribution of pore volumes ranges from 1.8mL/mg to 30 mL/mg with a mean value of 9.49 mL/mg. The specific surface area rangs from 0.91m2/g to 31.02m2/g with a mean value of 7.02 m2/g. The source rock porosity is low, ranging from 1.2% to 3.87% with an average value of 2.17%. The content of organic matters （OM）, illite and pyrite and pore volume shows positive correlation. It is believed that the diameters and abundance of micro pores will increase with the increasing content of the three minerals mentioned above; but the content of chlorite in clay minerals and quartz, calcite and anorthose in non clay minerals and pore volume shows negative correlations. The data shows that the diameters and abundance of micro pores decrease with these three minerals＇ contents. The content of kaolinite and pore volume show a negative correlation, it means that the micro pore in source rocks may be not affected by kaolinite. In addition, the development and distribution of micro pores in source rocks are also affected by the types, abundance, thermal evolution degree of organic matters, arrangement of clay minerals, secondary change of non clay minerals.