松辽盆地徐家围子断陷深层异常高孔带分布特征与成因分析

Distribution and origin of anomalously high porosity zones of the Xujiaweizi Fault Depression in Songliao Basin

为了解松辽盆地低孔低渗背景下优质储集层的形成和分布,文中应用岩心实测孔隙度、测井孔隙度以及铸体薄片等资料,研究了松辽盆地徐家围子断陷异常高孔带的分布特征及其成因。结果表明,松辽盆地北部纵向上发育3个异常高孔带(ⅰ—ⅲ),其深度分布范围分别为600～2350m、2500～3500m、3600～4400,m,对应的孔隙度分别为12%～35%,6%～28%,5%～20%。第ⅰ高孔带主要发育在中浅层,主要由Ⅰ、Ⅱ型干酪根形成的有机酸溶蚀砂岩储集层形成;第ⅱ、ⅲ异常高孔带发育在深层,主要由Ⅲ型干酪根产生的大量有机酸溶蚀砂砾岩储集层和火山岩储集层形成,大气水淋滤作用也有一定贡献。此外,裂缝和岩相对徐家围子断陷深层异常高孔带的形成具有特别重要的意义。

In order to identify the formation and distribution of high-quality reservoir under the conditions of low porosity and low permeability reservoirs,the distributions and origins of the anomalously high porosity zones of the Xujiaweizi Fault Depression in the northern Songliao Basin were studied by using the data of measured porosity,logging porosity,thin sections,blue epoxy resin-impregnated thin sections and SEM.As the results show,there are three anomalously high porosity zones at depths of 600～2350,m,2500～3500,m,3600～4000,m respectively,with porosity ranges of 12%～35%,6%～28%,5%～20% correspondingly in the northern Songliao Basin.The first anomalously high porosity zone is distributed in the middle-shallow horizon,mainly formed by organic acids generated from kerogen Ⅰ and Ⅱ dissolving sandstone reservoirs.The second and the third ones are distributed in the deep horizons,formed by organic acid generated from kerogen Ⅲ dissolving volcanic reservoirs and conglomerate reservoirs,and meteoric water leaching is important too.Moreover,fracture,lithology and lithofacies are of great significance to the formation of the anomalously high porosity in the deep horizons.