The Study Of Logging Response Characteristics And Mechanism Of Ultra-long Borehole Cores Based On The Scientific Drilling In Songliao Basin

After many years of exploration and extensive research in petrology,sequence stratigraphy,petroleum geology,logging geology and other fields,we achieved plentiful achievements in the Songliao Basin.However,due to the lack of ultra-long borehole cores,the geologic phenomenon could not be accurately correlated with the logging response,which brought troubles to the study of logging geology in Songliao Basin.The continuous ultra-long borehole cores information of SK2,from the top of lower cretaceous Denglouku formation to basement,provides unprecedented basic geological data for the study of log response characteristics in Songliao Basin.In this thesis,we take the core information of SK2,logging information and thin section identification as the research object.With the application of logging geology,sedimentology,volcanic stratigraphy and other methods and principles,we study the logging response characteristics of lithology,stratigraphic interface and the influence of burial depth and get the following understanding:1.Lithology logging response characteristicsAccording to the results of actual data read from logging curve,the lithology types can be classified by the numerical value of spontaneous potential(SP)and natural gamma ray(GR),which the natural potential range of volcanic rock is 50-100 mv,and the range of sedimentary rock is 0-50 mv.By analyzing the anomalous amplitude,smoothness,curve shape and the contact relation between the top and bottom of log curves,the change characteristics of lithology,particle size and others are reflected.Five sedimentary rocks and six volcanic rocks are identified by analyzing the response characteristics of common logging and electric imaging logging.ECS element logging data of the volcanic rocks of Yingcheng formation in SK2 were analyzed by using graphic method of TAS,which the results show that the rock is mainly composed of rhyolitic volcanic rocks,a small amount of trachytic,trachydacitic,and dacitic volcanic rocks and andesitic pyroclastic lava.2.Logging response characteristics of stratigraphic boundariesBy analyzing the core and logging data of SK2,the stratigraphic boundaries in the well can be divided into three types according to the lithological classification: contact boundaries between sedimentary rocks and volcanic rocks,interior boundaries of volcanic rocks and interior boundaries of sedimentary rocks.Contact boundaries between sedimentary rocks and volcanic rocks mainly consists boundaries between rhyolitic pyroclastic rocks and conglomerate;contact boundaries between andesitic pyroclastic lava and glutenite.Interior boundaries of volcanic rocks mainly consists of two main types: eruptive boundaries and eruptive interval boundaries.Interior boundary of sedimentary rock mainly includes weathering crust,scouring surface,lithological composite boundaries and thin layer of special lithology.3.The influence of burial depth on logging responseAccording to the changes of logging curve,when the depth of burial increases,the rocks will become denser due to the increase of formation pressure.The deeper the burial depth,the greater the density of rock and the smaller porosity,the logging curves show that compensated density increases,neutron porosity and acoustic travel times decreases.When mineral compositions of rocks,oil and gas saturation and other influencing factors do not change significantly,the increase of buried depth lead to rock porosity and content of formation water decrease,so as to make the rock resistivity increase obviously.According to statistic results we found that data read from logging curve of physical properties and resistivity of rocks showed obviously linear relationship with buried depth,and the corresponding linear formula was fitted to describe the change rate of physical property and resistivity of rocks.The logging response characteristics of physical properties and resistivity changing with buried depth are compared.Due to the differences in mineral composition,consolidation pattern,structure and other aspects,the logging data of sedimentary rocks increases linearly with increase of burial depth,but volcanic rocks increases without regularity.