页岩油储层孔隙发育特征及表征方法

Pore structure and characterization methods of shale oil reservoir

页岩油是非常规油气资源重要的组成部分,主要赋存于泥页岩不同类型的孔隙和裂缝中。与产生页岩气的高成熟阶段泥页岩不同,处于生油窗的富有机质泥页岩中的油气储集空间往往被早期生烃产物完全或部分充填,影响对页岩油储集空间的结构表征和形态描述。通过镜下观察发现,页岩油储层中发育的孔隙总体上可以划分为矿物颗粒间孔隙、矿物颗粒内孔隙和有机质孔隙,其中前两者主要的孔隙类型包括不同矿物颗粒间的粒间孔隙、溶蚀孔隙和黏土矿物片层间孔隙等,有机质孔隙包括有机质颗粒边缘收缩孔(缝)和少量的热解孔隙。从页岩油储层孔隙表征方法的要求出发,对页岩油储层样品进行溶剂抽提处理,探讨分别适用于碎状样品和块状样品的孔隙表征方法。不同页岩油储层孔隙表征方法的原理和应用具有差异性,也存在局限性,可以综合多种表征方法,通过对比分析和统一量纲的方式提高页岩油储层孔隙表征结果的准确性。

Shale oil is an important component of unconventional hydrocarbon.It mainly exists in different types of pores and fractures of shale.Unlike the shale at high maturity stage which generate shale gas,hydrocarbon pore space in organic shale at oil-generating window is often filled completely or partially by early hydrocarbon-generating materials,thus affecting the structure characterization and geometry description of shale oil pore spaces.Through the microscopic observation of a large number of shale samples,the pores of shale oil reservoir could be divided totally into intergranular mineral pore,intragranular mineral pore and organic pore.The former two types of pores include intergranular pore among different mineral particles,dissolution pore,clay mineral interlaminar pore,etc.The organic pores are composed by marginal shrinkage pore(fracture)and a small amount of pyrolysis pore.Based on the requirement for characterization of shale oil pores,solvent extraction was carried out on the samples,and the suitable pore characterization techniques for crushed and blocked samples were discussed respectively.Different shale oil characterization methods have certain differences in principle and application,and have certain limitations as well.In order to avoid the influence of this factor on pore characterization,a variety of characterization methods could be combined to characterize pore through comparative analysis and unified dimension,so as to improve the accuracy of pore characterization results of shale oil reservoir.