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

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.