四川盆地永探1井火山岩地质建模及数值模拟

Geological modeling and numerical simulation of volcanic rocks in Well Yongtan 1,Sichuan Basin,China

研究四川盆地永探1井区火山岩岩相,为火山岩岩相分析提供参考。永探1井火山岩具有多期次喷发、岩性多样化的特征,且火山岩内幕反射较杂乱。基于永探1井的火山岩喷发模式分析,综合多源信息(喷发模式、岩相地震反演和裂缝预测)的火山岩建模和波动方程数值模拟,总结分析火山岩地震响应特征。基于钻井岩性数据分析,建立了永探1井火山岩4期喷发模式;再采用波形指示反演进行火山岩地层的不同喷发期次的岩性反演,并通过最大似然方法进行火山岩地层的(断层)裂缝预测;然后综合火山岩的喷发模式、岩性反演剖面和裂缝发育特征等多源信息,建立永探1井火山岩的典型地质模型;最后采用波动方程数值模拟方法分析火山岩地层的地震响应特征。数值模拟结果表明永探1井火山岩内幕的杂乱反射主要来源于爆发相的角砾熔岩(具有强非均质性),短段弱连续性反射主要来源于爆发相与侵入相的界面。

Volcanic rocks in Well Yongtan 1 in the Sichuan Basin are characterized by multiple eruptions and diversified lithology with disorderly internal reflection.Emphasis of this study is mainly put on the research of lithofacies of volcanic rocks from Well Yongtan 1 in order to provide reference for volcanic lithofacies analysis in the area.Based on the volcanic eruption mode analysis of Well Yongtan 1,volcanic modeling and wave equation numerical simulation with multi-source information(eruption mode,lithofacies seismic inversion and fracture prediction)are used to summarize and analyze the volcanic seismic response characteristics.A four-stage eruption model of Well Yongtan 1 is established on the basis of the analysis of drilling lithology data.Then waveform indication inversion is used to retrieve lithology of volcanic strata in different eruptive periods,and maximum likelihood method is used to predict(fault)fractures of volcanic strata.Subsequently,a typical geological model of Well Yongtan 1 is established based on the multi-source information of volcanic eruption pattern,lithologic inversion profile and fracture development characteristics.Finally,the wave equation numerical simulation method is utilized to analyze the seismic response characteristics of volcanic rock layers.The numerical simulation results show that the chaotic reflection in the volcanic rocks of Well Yongtan 1 mainly comes from the breccia lava of the explosive phase(which has strong heterogeneity),and the weak continuous reflection in the short section mainly comes from the interface between the explosive phase and the intrusive phase.