火山岩岩相多方法逐级识别技术

Volcanic rock lithofacies identification step-by-step with multi-methods

火山岩岩相复杂且变化快,目前单一的识别技术存在多解性。为此,综合运用地质、地球物理资料,结合不同的研究思路和技术方法,探索了一套火山岩岩相多方法逐级识别技术,该方法以三维地层模型和敏感参数岩性模型作为约束,能很好地区分爆发相火山角砾岩、溢流相安山岩和火山沉积相凝灰岩,有效降低了岩相预测的多解性。准噶尔盆地XQ地区火山岩岩相识别结果表明:GR-RT、AC-DEN交会图板能区分溢流相溶岩、爆发相火山角砾岩、火山沉积相,而爆发相火山角砾岩和火山沉积相在电性上不易区分;分析沿石炭系顶面向下70ms最大波峰振幅属性可知,火山角砾岩以爆发相为主,安山岩、玄武岩、英安岩以溢流相为主,凝灰岩、凝灰质砂砾岩、凝灰质砂岩、凝灰质泥岩以火山沉积相为主。

Volcanic rock lithology and lithofacies are very complex.Volcanic rock lithofacies identification with a single method usually leads to multiple solutions.Therefore we propose an approach to volcanic rock lithofacies identification with multi-methods.Based on multi-disciplines(cores,well logging,and seismic)data,we conduct the identification step-by-step with multi-methods such as rock-electricity crossplot,seismic facies recognition,horizon seismic attributes,isochronous stratigraphic model,and geological model.With the constraints of 3D geological model and sensitiveparameter lithologic model,this approach distinguishes eruption facies volcanic breccia,effusion facies andesite,and volcanic sedimentary facies tuff based on drilling,logging and seismic data.The following understandings are obtained on our volcanic lithofacies identification in the XQ Area,Junggar Basin:(1)On GRRT and AC-DEN crossplots,effusive facies lava,eruption facies volcanic breccias,and volcanic sedimentary facies can be properly identified,but eruption facies volcanic breccia and volcanic sedimentary facies cannot be identified;(2) With optimal attribute analysis of drilling information and seismic data,volcanic breccia belongs to eruption facies,andesites,basalt,and dacite belong to effusive facies,and tuff,tuffaceous glutenite,tuffaceous sandstone,and tuffaceous shale belong to volcanic sedimentary facies.