东营凹陷永北地区古近系顶部不整合结构及其物性响应

Architectures and responses of physical properties of the unconformity in the uppermost part of the Palaeogene strata in the Yongbei region, Dongying depression

关键词:  风化作用  物性响应  不整合  地层不整合圈闭  沙三段  永北地区

Key words:  weathering  physical response  unconformity  stratigraphic trap  third member of the Shahejie Formation  Yongbei region

摘要:

综合三维地震、钻井岩心、测录井、物性分析、薄片鉴定资料,通过宏观描述与微观镜下分析相结合的方法,系统分析了东营凹陷永北地区古近系顶部不整合结构体岩石学特征、测井曲线特征、物性响应特征及其与圈闭的关系。研究表明,不整合可划分为3层结构:水进砂层、风化粘土层和半风化淋滤层。每个结构层具有不同的岩石学和测井响应特征。水进砂层孔隙度高;风化粘土层风化作用最强,泥质含量高,孔隙度低;半风化淋滤层溶蚀作用强,次生溶孔发育,孔隙度较高;未风化层未受风化作用改造,孔隙发育差。永北地区沙三上段发育断块掀斜型和盆缘型两种地层不整合圈闭模式:断块掀斜型模式受到不整合与二级或二级以下序级断层的共同控制,圈团发育规模较小;盆缘模式多出现在抬升强烈的湖盆边缘,主要受控盆断层的控制,圈闭发育规模较大。

Abstract:

The architectures and responses of physical properties of the unconformity are discussed according to the 3-D seismic data, thin section examination, well logs and physical properties of the unconformity at the uppermost part of the Palaeogene strata in the Yongbei region, Dongying depression. The three-layer architectures are discriminated for the unconformity, including the transgressive sand layer with high porosity, weathered clay layer with higher mud contents and lower porosity, and semi-weathered leached layer with developed secondary opening solutions and higher porosity. There occur two types of stratigraphic traps such as the block-tilting and basin-margin types developed in the upper part of the third member of the Shahejie Formation in the Yongbei region. The blocktilting model is controlled by the unconformity and second-order or lower-order faults, and thus displays relatively small scales of traps. The basin-margin model often appears on the highly-uplifted basin margins constrained by the faults, and thus display relatively larger scales of traps.