东海陆架盆地西湖凹陷平北地区含煤地层岩性圈闭识别

Identification of lithologic trap in coal⁃bearing stratum of Pingbei area,Xihu Sag,East China Sea Shelf Basin

东海陆架盆地西湖凹陷平北地区主要目的层始新统平湖组沉积受潮汐作用影响较大,薄砂体多层叠置、横向变化快,煤层发育。目的层埋深普遍超过3500 m,储层物性相对较差。现有地震资料深层信噪比低、能量弱,砂泥阻抗特征差异小,储层预测及刻画难度大。在深层保幅宽频处理资料的基础上,按照明确岩性圈闭发育类型、精细砂体描述、落实岩性圈闭目标的整体思路开展研究,明确了古地貌背景、砂体模式及岩性圈闭发育类型,在这一格架约束下开展精细的砂体描述工作,应用地震波形、地震反射结构特征、叠前反演弹性属性相结合预测砂体,并利用叠后统计学反演预测煤层分布,提高了砂体描述的精度和可靠性。

In the Pingbei area of Xihu Sag,East China Sea Shelf Basin,the sedimentation of the main target Eocene Pinghu Formation,is significantly affected by tidal action.Thin sand bodies are stacked on top of each other,the lateral changes are fast,and coal seams are developed.The target layer has a depth of bury generally deeper than 3500 m,and the physical properties of reservoir are relatively poor.The existing seismic data have low signal⁃to⁃noise ratio,weak energy,small impedance difference of sand and shale in the deep,and it is difficult for the reservoir prediction and description.Based on deep amplitude⁃preserved and broadband processing,this paper studied the type of lithologic trap development,characterization of sand reservoir,and implementation of lithologic trap targets.The paleogeomorphic background,sand development pattern and the type of litho⁃logic trap are defined.Under the constraints of this framework,accurate sandstone description is carried out.The sand reservoir is predicted by comprehensive analysis of seismic waveform,seismic reflection characteristics and the elastic properties of pre⁃stack inversion,the coal seam distribution is predicted by post⁃stack statistical inversion,and the accuracy and reliability of sand description are improved.