基于数值模拟的四川盆地二叠系火山岩地震响应特征分析

Seismic response characteristics of volcanic rocks in Tianfu 2 well area of Sichuan province based on numerical simulation

天府2井证实了四川盆地二叠系火山岩较发育,但其钻遇的火山岩地层岩性较复杂、且火山岩岩相具有多样化的地震反射特征,增加了火山岩地层识别及储层预测的难度。这里开展研究区火山岩的地质建模和模型正演分析研究,首先基于火山岩纵向岩性变化规律及地震波场响应分析,提出了研究区火山岩的三期喷发模式;再结合喷发模式建立了研究区典型的火山岩地质模型;最后采用波动方程数值模拟方法获得了火山岩地层的地震响应特征。综合火山岩地质模型的模拟记录和实际的地震响应特征发现,火山岩顶界由于火山岩与龙潭组地层物性差异较大呈现为中强波峰反射特征,火山岩底界由于粒玄岩与茅口组地层物性差异小呈现为断续弱反射特征,而火山岩内部由于发育爆发相的角砾熔岩呈现出丘状杂乱或断续反射特征。基于火山岩喷发模式分析建立的火山岩地质模型和基于数值模拟分析得到的火山岩地层的地震响应特征,有助于研究区后续的火山岩岩相分析与储层预测研究。

Tianfu 2 well confirmed the permian volcanic rocks in Sichuan basin is development,but its drill in volcanic rock formation lithology is complex.And volcanic lithofacies and seismic reflection characteristics of diversified,increase the difficulty of volcanic rock strata identification and reservoir prediction.This paper carried out volcanic geological modeling of the forward analysis in the study region.First of all,based on the volcanic rock vertical lithologic change rule,the seismic wave field response analysis is put forward the three periods of eruption pattern of volcanic rocks in the study area;combining eruption pattern study area is a typical volcanic rock,and then geology model is established.The wave equation numerical simulation method is then used to obtain the seismic response characteristics of the volcanic rock formation.Integrated volcanic geological model simulation records and actual seismic response characteristics,it is found that the volcanic rocks in the top boundary appears as the strong wave reflection characteristics of volcanic rocks in the bottom because of its high volcanic rocks and the longtan formation physical property difference.Because the dolerite and MAO group strata property differences small present for intermittent weak reflection characteristics,and volcanic breccia lava of internal explosion due to the development phase shows the characteristics of hummocky mixed and disorderly or intermittent reflection.In this paper,based on the analysis of model of volcanic eruption of volcanic geological model and the numerical simulation based on the analysis of seismic response of the volcanic rock strata characteristics helps the follow-up volcanic lithofacies analysis and reservoir prediction research in the study area.