Sequence Stratigraphic Division and Recognition Based on Wavelet Analysis: Example from the Upper Permian Longtan Formation in Eastern Sichuan Basin

Taking the upper Permian Longtan Formation in eastern Sichuan Basin as an example, GR logging data from the well of Longtan Formation in eastern Sichuan Basin have been analyzed by IDL wavelet toolkit of Matlab through using wavelet transform and frequency spectrum, which will provide a geological basis for the exploration and development of Longtan Formation in eastern Sichuan Basin. Results show that the Longtan Formation in eastern Sichuan can be divided into three third-order sequences, that is SQ1 divided into LST, TST, HST, while SQ2 and SQ3 both divided into TST and HST, respectively. Fischer plots based on wavelet transform of GR logging curve has a good display for accommodation, showing a good corresponding relationship with third-order sequence. Results of frequency spectrum indicates that the Longtan Formation has a more complete record of Milankovich cycles, with 15 eccentricity long cycles developed in eastern Sichuan Basin, but the eccentricity short cycle and slope cycle are different, which was influenced by sedimentary environment.