东营凹陷北带西段花岗岩风化壳地震相特征及地质成因分析

东营凹陷北带西段花岗岩风化壳各层结构在地震上呈现出不同反射特征, 风化壳地震相地质成因及对应储层物性和含油性特征尚不明确。针对上述问题, 采用地质和地震相结合的思路, 研究了花岗岩风化壳地震相类型和分布特征, 分析了地震相地质成因, 建立了风化壳顶部地震相分布模式, 并明确了各类地震相对应储层的含油性和勘探意义。结果表明: ①花岗岩风化壳地震相划分为低频连续强振幅相、中频低连续中振幅相和弱振幅-空白相3种类型, 低频连续强振幅相分布在邻近构造高部位缓坡上, 中频低连续中振幅相分布在构造中低部位, 弱振幅-空白相广泛分布; ②低频连续强振幅相对应高度风化的残积层, 中频低连续中振幅相对应演化程度中等的溶蚀层, 弱振幅-空白相对应风化程度较低的崩解层; 风化壳各层结构处于不同的演化阶段, 经历的风化程度不同, 岩石结构存在差异, 从而在地震上呈现出不同反射特征; ③不同类型地震相对应的储层物性、保存条件和含油性存在差异, 指示的油气勘探意义也有所不同。研究成果为研究区花岗岩风化壳有效储层的识别和进一步的储层勘探指明了方向。

The structures of granite weathering crust in the western segment of the northern belt of Dongying Sag show different seismic reflection characteristics, and the geological origin of seismic facies of weathering crust and the reservoir's physical properties and oil-bearing characteristics are unclear.Research ideas combining geology and seismic were pursued to address the issues mentioned above.The types and distribution characteristics of seismic facies in granite weathering crust were investigated, the geological genesis of seismic facies was analyzed, the distribution model of seismic facies on top of the weathering crust was established, and the oil-bearing properties and exploration significance of reservoirs were defined.The results show that ①the seismic facies of granite weathering crust can be divided into three types: low frequency continuous strong amplitude facies, medium frequency low continuous and medium amplitude facies, and weak amplitude-blank facies.The low frequency continuous, strong amplitude facies are mainly distributed in the gentle slope near the top of the structure, while the medium frequency low continuous and medium amplitude facies are distributed in the middle and bottom of the structure, and the weak amplitude-blank facies are widely distributed.②Low frequency, continuous, strong amplitude facies correspond to highly weathered eluvium, medium frequency, low continuous and medium amplitude facies correspond to medium evolution dissolution layer, and weak amplitude-blank facies correspond to low weathering disintegration layer.As the layers of granite weathering crust are in different evolutionary stages and have experienced different degrees of weathering, the rock structure is different, which leads to different seismic reflection characteristics.③The physical properties, preservation conditions, and oil-bearing properties of different types of seismic facies reservoirs are different, as are the implications for oil and gas exploration..The research results indicate the direction for identifying effective reservoirs of granite weathering crust and recommend further reservoir exploration in the study area.