渤海海域中生界火成岩岩性测井识别技术及应用

Well-Logging Identification Technique and Its Application in Mesozoic Igneous Rocks in Bohai Sea Aera

渤海海域中生界火成岩具有岩石类型多样,岩石结构复杂的特点,识别难度较大。钻井统计表明,研究区中生界以中基性喷出岩和酸性侵入岩为主,综合地质学分类以及测井响应特征,建立了研究区火成岩"成分-结构-构造"三端元分类方案,并提出了岩石成分、结构、构造单因素并行识别,综合命名的识别思路:成分上,由基性岩到酸性岩,元素测井上表现为由高铁低硅向高硅低铁变化,伽马能谱上铀、钍、钾以及总的自然伽马均不断升高,常规测井上酸性岩具有高伽马低密度的特点,基性岩与之相反;结构上,常规测井资料可初步判别岩石结构,成像测井可对熔岩结构、角砾结构、凝灰结构以及岩石蚀变结构进行精细识别;成像测井上可识别出块状构造、似流动构造以及气孔、杏仁构造,对有效判别侵入岩与喷出岩具有重要指示意义。利用该方法对重点井进行了分析,识别结果与壁心薄片鉴定结果一致,说明效果可靠。

With complex lithologic characters and structures,the Mesozoic igneous rocks of Bohai Sea area are difficult to identify.The result of drilling shows that middle and basic volcanic rocks and acid intrusive rocks are the main rock types of the study area.With reference to the geologic classification and well-logging response characteristics,the classification scheme of ＂composition-texture-structure＂ was built and a parallel recognition of single factor and comprehensive naming was put forward.From basic rocks to acid rocks,total silicon content rises and total iron content reduces in the data of elemental logging,while the U,Th,K and the total natural gamma all increase in the data of gamma ray spectrometry log.In contrast,the density rises and the gamma reduces in the data of conventional logging.Hence,the texture of the rocks can be identified by conventional logging,lava structure,brecciated structure,tuff structure and alteration structure and can be identified accurately by the data of imaging logging.The block structure,flow structure,vesicular structure and amygdaloidal structure identified by the data of imaging logging can be used to divide the vocalic rocks and the intrusive rocks.The key wells were analyzed with the method and the identified results were in accordance with the data of rock section.This shows the identification is effective and reliable.