鄂尔多斯盆地三叠系延长组富有机质泥页岩储层特征

富有机质泥页岩储层特征研究对认识页岩油气勘探潜力具有重要意义。为确定延长组富有机质泥页岩储层特征,开展了岩石薄片、扫描电镜、X-射线衍射、物性、比表面积孔径分析和有机碳含量等分析测试工作,揭示了泥页岩岩相、矿物含量、成岩作用、孔隙类型、物性和孔隙结构等特征。延长组泥页岩可划分为泥岩岩相、含粉砂泥岩岩相和粉砂质泥岩岩相3种岩相类型。泥岩岩相的有机碳含量最高,粘土矿物含量高(>50%),成岩作用较弱;粒间孔和粒内孔是中生界泥页岩储层主要的孔隙类型;微孔主要集中在0.4~1 nm,中孔主要集中在3~5 nm,中孔对孔隙体积和比表面积的贡献好于微孔。根据现有资料认为,延长组富有机质泥页岩塑性矿物含量高,成岩作用弱,对储层后期改造提出了严峻挑战。

Reservoir characteristics of the organic-rich shales of the Triassic Yanchang Formation in Ordos Basin

Reservoir characteristics study is very important to understand the hydrocarbon potential of organic-rich shales.A series of analyses and tests,including thin sections,SEM,XRD,physical property,total organic carbon(TOC),specific surface area and pore size distribution,were made to reveal the reservoir characteristics of the organic-rich shales of the Triassic Yanchang Formation(Fm)in Ordos Basin.This paper also defined the lithofacies,mineral types,diagenesis,pore types and physical properties.Three types of lithofacies are identified in the organic-rich shales,including muddy shale,silt-bearing shale and silty shale.The muddy shale has the highest TOC content,clay content of more than 50% and relatively weak diagenesis.The dominant pore types of the organinc-rich shales in the Yanchang Fm are intragranular and intergranular pores.The pore sizes of micropores are mainly within 0.4 to 1 nm and those of mesopores are mainly within 3 to 5 nm.The contribution of the mesopores to pore volume and specific surface area is larger than that of the micropores.The high content of ductile minerals and weak diagenesis of the organic shales in the the Yanchang Fm make the reservoir stimulation more challenging.