Well Log Methodological Research In Sequence Stratigraphy

Well logging data are the actual reflection of geological information of subsurface. It contains formation lithology, sedimentary cycle and other rich geological information, with enormous advantage in far more method, high accuracy and resolution, continued measurement. It will display significant contribution in sequence stratigraphy research.The thesis studied the logging method of identifying the boundary surface, condensed sequence and the overlay mode of parasequence set, restricted by seismic data, based on the core analysis and paleontology information. It discussed the principle, application result, applying condition and drawback of the logging methods in sequence stratigraphy research. It will obtain the optimal application result by associating qualitative analysis and quantitative calculation. Illustrated by Eogene of Linnan Sag, the thesis used the logging method to delimit the sequence, and analyzed the deposit character of each sequence, made preliminary research about the relation between the sequence and source, reservoir, cap formation.It may cause multiple solutions when using single well logging to identify the sequence interface. Combined logging data can reduce ambiguity, thus highlighting the differences between the sequences. It further concluded four patterns in R-AC overlap curve and its value in sequence stratigraphy research. Based on the logging response features, the sequence interface can be divided into"abrupt interface"and"gradational interface", corresponding to different features. For the position of the cycle, condensed section are often at the top in the normal cycle or the bottom in the abnormal cycle. For the superimpose mode, the condensed section often at the transition zone from retrogradation to progradation.Based on the well logging methodological study, the eogene of Linnan Sag can be divided to one first-order sequence, three second-order sequences and seven third-order sequences. Majority sequence interface is abrupt interface, and minority is gradational interface. Majority para-sequence is progradation with obvious features, followed by retrogradation para-sequence. Condensed section is vegetal in sequence S1 and S2, is the main source. Sequence S1, S2, S3, S4 are the main purposes of oil and gas production.