渤海湾盆地沾化凹陷页岩微观孔隙特征实验研究

Micro-pore characteristics of shale in Zhanhua Sag,Bohai Bay Basin

页岩的微观孔隙结构是影响页岩油气富集与渗流机理的关键。利用氩离子抛光扫描电镜、低温CO_2吸附、低温N_2吸附、高压压汞及核磁共振等实验方法,对沾化凹陷沙河街组陆相页岩的微观孔隙特征进行了研究。页岩主要发育有机孔、粒间孔、粒内孔、晶间孔、溶蚀孔和微裂缝等6类孔隙。其中微孔、中孔和宏孔均有发育,微孔比表面积约占总比表面积的61.52%,提供了页岩油气吸附的主要空间,而中孔和宏孔则提供了大部分孔体积,分别占比49.99%和41.19%,对页岩油气的储集和运移起主要作用;页岩孔隙度为4.08%～7.04%,有效孔隙度为0.11%～0.64%,孔隙连通性差。

The micro-pore structure of shale is a key contol of shale oil and gas accumulation and seepage.The micro-pore structure of the continental shale in the Shahejie Formation in the Zhanhua Sag was analyzed by using argon-ion polishing SEM,CO2 adsorption,N2 adsorption,MIP and NMR.The shale displays six kinds of pores,including organic,intergranular,intragranular,intercrystalline,dissolution pores and micro-cracks.Micropores,mesopores and macropores are all developed.The micropore specific surface area accounts for about 61.52% of the total specific surface area,providing the main space for shale oil and gas adsorption.The mesopores and macropores provide most pore volume,accounting for 49.99% and 41.19%,respectively,which play a major role in the storage and migration of shale oil and gas.The shale porosity is 4.08%-7.04% and the effective porosity is 0.11%-0.64%,which means that pore connectivity is poor.