论文详情
川西广汉地区在二叠系钻遇厚层火山岩,因钻井少、埋藏深、地震资料品质低、岩相变化及地层接触关系复杂多变等原因,现有地震资料无法准确识别火山岩内部地层结构、火山通道及火山岩与围岩的边界,影响该地区的火山岩油气勘探。根据研究区实钻井资料建立中心式和裂隙式两种火山机构正演模型,模拟不同火山岩岩性、岩相及厚度变化引起的地震反射特征变化情况。正演模拟研究结果表明:①火山机构厚度增厚,外部呈丘状;②不同喷发方式火山岩相边界均呈斜交反射,但连续性不同;③不同岩性、岩相、厚度及波阻抗差值均影响成像,厚度大于60m时火山岩内部结构清晰,玄武岩最易识别;④火山通道位置成像中断、空白、弱反射,宽度越宽越易识别;⑤火山机构影响下伏地层成像,出现相位上拉、能量屏蔽和假构造现象。正演模拟结果有效识别了川西广汉地区二叠系火山岩复杂内部反射结构特征,结合地震相和多种表征火山岩特征的地震属性预测厚大爆发相和喷溢相火山岩主要分布在A井区和研究区中部,研究结果可指导火山岩储层预测和下一步井位部署。
The Permian strata in the Guanghan area of western Sichuan feature thick volcanic rock layers.Due to the lack of drilling,large burial depth,low quality seismic data,complex lithofacies changes,and complicated stratigraphic contact relations,the existing seismic data cannot accurately identify the internal stratigraphic structure of the volcanic rocks,volcanic channels,and the boundary between the volcanic rocks and surrounding rocks,affecting the oil and gas exploration in these volcanic rocks.Based on the actual drilling data from the study area,two forward models of central and fractured volcanic institutions were established to simulate the changes in seismic reflection characteristics caused by changes in lithology,lithofacies,and thickness of different volcanic rocks.The forward simulation results indicate that①The thickness of the volcanic body is thickened and the outside is in a mound shape.②The boundary of the volcanic facies between different eruptions was characterized by an oblique reflection with a variable continuity.③Differences in lithology,lithofacies,thickness,and wave impedance all affected the imaging results.If the thickness was greater than 60m,the internal structure of the volcanic rocks could be clearly imaged (in particular,basalt was the easiest to identify).④The imaging of the volcanic channel showed interruptions,blanks,and weak features,but wider portions were easier to identify.⑤Volcanic bodies affected the imaging of the underlying strata,resulting in phase pull-up,energy shielding,and false structures.Nonetheless,the modeling results led to a clear identification of the complex structural characteristics of the Permian volcanic rocks in Guanghan area,western Sichuan.On the basis of the seismic facies and various seismic attributes representing the characteristics of volcanic rocks,it is predicted that thick and large explosive facies and effusive facies volcanic rocks are mainly distributed in well A and in the central part of the study area.The results of this research could be used to guide the prediction of volcanic reservoirs and the deployment of well locations in the next step of development.
中国石化科技部项目(P20059-3)资助。