火山岩波动方程正演模拟研究

Wave equation forward modeling for volcanic rock

(1.中国石油化工股份有限公司西南油气分公司勘探开发研究院海相所，贵州贵阳550004；2.大庆石油学院地球科学学院，黑龙江大庆163318；3.中国石油大庆油田有限责任公司勘探开发研究院，黑龙江大庆163712）

Marine Facies Academy of Exploration and Development Research Institute, Southwest Oil & Gas Branch Company, SINOPEC, Guiyang 550004, China

松辽盆地火山岩埋藏较深，下伏地层成像精度极低，对构造解释造成了一定的影响。为了了解火山岩体对下伏地层的影响程度，采用波动方程正演模拟技术，研究了9种波阻抗组合和两类岩性组合情况下火山岩理论模型的地震响应特征，其波场快照能直观地展现地震波在火山岩体中的传播过程。对正演模拟结果进行了分析，认为火山岩体的底界面反射不清晰是火山岩体对下伏地层屏蔽作用所致；火山岩体厚度增大时，下伏连续地层的反射中断现象更明显，以致出现假断层和假构造现象。

The deeply buried volcanics in Songliao basin leads to very low imaging accuracy for underlying formation, which has some negative effect on the structure interpretation. In order to research the effect degree of volcanics on underlying formation, the forward modeling based on wave equation was used to analyze the seismic response characteristics of different theoretical volcanics models according to nine kinds of wave impedance association and two kinds of lithological association. The propagation process of seismic wave can be shown illustratively on snapshots, which is beneficial to analyze the effect of volcanics on underlying formation imaging. The forward modeling shows that the unclear reflection of bottom boundary in volcanics is for the shielding effect caused by particular wave impedances between the volcanics and the underlying formation. The discontinuity reflectance signature of underlying continuous formation will become more obvious when the volcanics is thick, resulting in forming pseudo- faults and structures. The modeling results show that the forward modeling based on wave equation can be used to accurately simulate the propagation process of seismic wave in volcanic rock, discover the shielding effect of volcanic to the underlying formation, find out the pseudo- faults and structures caused by the difference of volcanics thickness and its wave impedances, and eliminate the impact on structure interpretation eventually.