渤海海域中生界火山岩岩相特征及其识别方法

Lithofacies characteristics and identification methods of Mesozoic volcanic rocks in Bohai Sea

火山岩储层受岩相控制作用明显,因此,进行岩相识别可以有效降低火山岩油气藏的勘探风险。以渤海海域为例,首先利用地质及钻井(岩心)资料落实区内发育的主要火山岩岩相类型,再通过测井相识别、地震相识别及地震属性分析等手段,对渤海海域中生界火山岩的岩相特征进行系统总结,探索不同岩相的识别方法。结果表明:渤海海域以中基性火山喷发为主,主要发育爆发相、溢流相、火山通道相及火山沉积相等火山岩岩相,其中溢流相在区内发育最广。溢流相具有高电阻率、低声波时差的测井特征,基性溢流相的自然伽马低于中性溢流相;爆发相具有高声波时差、低电阻率的测井特征,火山角砾岩密度大于凝灰岩。三维地震资料上,爆发相与火山通道相均以杂乱反射为主,具有低频中等振幅的反射特征;溢流相具有连续的低频强振幅反射特征;火山沉积相为连续的中频弱振幅反射特征。爆发相与中性溢流相均为渤海海域优质储集岩相。

With great control effects on volcanic reservoir forming, volcanic facies identification is an effective way to reduce the exploratory risk. Based on the geologic and drilling data, the types of volcanic facies were defined, and the lithofacies characteristics of Mesozoic volcanic rocks in Bohai Sea were analyzed through electrofacies analysis, seismic facies identification and seismic attribute analysis, and the identification methods for different types of lithofacies were studied. The results show that the Bohai Sea area is dominated by intermediate basic vol- canic eruption, and the volcanic facies include eruptive thcies, effusive facies, volcanic vent facies and volcanic sedimentary facies, dominated by effusive facies. The effusive facies has the characteristics of high resistance^low acoustic time difference, and the basic effusive facies has lower gamma ray value compared with neutral effusive facies. The eruptive facies is characterized by high acoustic time difference and low resistance, and the density of volcanic breccia is greater than that of tuff. From 3D seismic data, the eruptive facies and volcanic vent facies are mainly clutter reflection, with low frequency and medium amplitude, while Effusive facies are characterized by continuous and strong amplitude and low frequency, and volcanic sedimentary facies has the characteristics of continuous medium frequency and weak amplitude reflection. The eruptive facies and neutral effusive facies are favorable reservoir rocks in the study area.