漠河盆地上侏罗统额木尔河组陆相泥页岩孔隙结构特征

Pore Structure Characteristics of Upper Jurassic Emuerhe Formation Continental Shale in Mohe Basin

通过氩离子抛光-扫描电镜、低温N_2和CO_2气体吸附、覆压孔-渗、X-射线衍射和有机地化等分析测试,对漠河盆地上侏罗统额木尔河组陆相泥页岩孔隙结构特征开展了系统研究。研究表明:额木尔河组泥页岩孔隙类型以长石溶蚀孔、黏土矿物晶间孔和粒间孔为主,整体上由介孔和宏孔构成;泥页岩孔、渗性较差,氦气孔隙度为0.167%~5.69%、覆压渗透率为0.000 513×10^(-3)~0.050 38×10^(-3)μm^2;有机质成熟度未达到热裂解干气阶段,限制了有机质孔隙的发育;长石溶蚀孔普遍发育,长石含量与介孔孔容呈负相关,表明部分介孔的形成可能与长石溶蚀作用有关;伊利石晶间孔主要提供微孔体积,而伊蒙混层相关孔隙则可能是介孔的主要贡献者;张性和剪切构造裂缝的普遍发育,有利于改善泥页岩储层的孔隙结构和渗流能力。综合分析表明,分布于滨黑龙江隆起中东部、埋藏较深的(约800m以下)高成熟页岩更适合开展进一步的页岩气评价和勘探工作。

This study investigated the characteristics of pore structure in Upper Jurassic Emuerhe Formation continental shale in Mohe Basin by using field emission scanning electron microscopy,low temperature N_2 and CO_2 isotherm analysis,porosity and permeability under overburden pressure（Poro PDP）,X-ray diffraction and organic geochemistry analysis.Results show that the dominate pore types of the Emuerhe Formation shale are the intraparticle dissolution pores within feldspar grains,the interparticle pores within clay mineral crystals and interparticle pores.Its porosity and permeability is poor.Helium porosity ranges from 0.167%to 5.69%,and permeability（under overburden pressure）from 0.000 513×10^（-3）μm^2 to0.050 38×10^（-3）μm^2.The limited development of organic matter pores is due to the relatively low thermal maturity.The widespread dissolution pores within feldspar grains combined with the negative correlation between the feldspar content and the pore volume of mesoporous may indicate that the formation of mesopores is partly related with the feldspar dissolution.The illite intergranular pores might contribute to most micropores,and the illite/smectite is the major contributor to the mesopores.The general development of structural fractures,which mainly include tensional crack and shearing crack,is favorable to improve its pore structure and potential for gas flow in the Emuerhe Formation shale.It is assumed that the shale distributed in mid-eastern of shore Heilongjiang uplift,and buried deep（about 800 mor more）,with high maturity,is more suitable for further evaluation and exploration.