东营凹陷古近系砂岩次生孔隙成因与纵向分布规律

东营凹陷古近系砂岩储集层的次生孔隙主要为不同期次的碳酸盐胶结物溶蚀成因,其次为长石溶蚀产生的次生孔隙,黏土矿物脱水促使这些溶蚀作用发生。早期方解石溶蚀作用为有机质成熟产生的有机酸所致,产生的次生孔隙分布深度较浅;晚期的含铁方解石和含铁白云石溶蚀作用与有机酸脱羧和有机质裂解产生的CO2有关,产生的次生孔隙主要分布于2500m以下深度。图3表1参22

Origin of secondary porosity of Paleogene sandstone in the Dongying Sag

The secondary porosity of Paleogene sandstone in the Dongying Sag mainly originated from the dissolutions of different stages carbonate cements, secondarily, from the feldspar dissolution. The secondary porosity from calcite dissolution is distributed in the shallow section, which is generated by the organic acids during organic mater maturation and the later secondary porosity from Fe calcite and Fe dolomite dissolution is distributed below 2500m,which related to the CO_(2) from the decarboxylation of organic acids and the thermal cracking of organic mater. The secondary porosity is mainly distributed in the interval below 2500m.